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Engine temps all over the place by Cliff Pennock
Started on: 06-14-2022 03:07 AM
Replies: 82 (1234 views)
Last post by: Cliff Pennock on 01-23-2023 02:13 PM
Cliff Pennock
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Report this Post06-14-2022 03:07 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
Like the subject says, my engine temperatures are all over the place. "Normal" temperature seems to be between 175F and 195F but most of the time it shoots up to 230F in 20-30 seconds, stays there for a few minutes only to drop back to 175 within 10 seconds. Rinse. Repeat.

There seems to be enough coolant in the system. If I remove the thermostat cap, coolant is right up to the edge. Same thing with the radiator. If I remove the cap, coolant is up to the edge. I don't hear any air going through the system. I checked the overfill bottle after driving the car for about an hour and it was empty. So I filled it up and checked it after another hour of driving. The coolant inside the overflow bottle wasn't warm. I'd say around 75F so I'm guessing the radiator cap needs to be replaced.

I had already replaced the thermostat and the thermostat cap recently. But could a defective radiator cap cause the violent temperature swings?
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Report this Post06-14-2022 03:43 AM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

I checked the overfill bottle after driving the car for about an hour and it was empty.


When did you last check it? The coolant must be going somewhere.

 
quote
Originally posted by Cliff Pennock:

So I filled it up and checked it after another hour of driving. The coolant inside the overflow bottle wasn't warm. I'd say around 75F so I'm guessing the radiator cap needs to be replaced.


Why would the coolant reservoir be warm? The engine was already warmed up when you re-filled the reservoir, so there wouldn't be any hot coolant flowing into the reservoir. However, when the engine cools down, coolant would be drawn from the reservoir into the main system.

Unless you didn't fill the coolant system (including the reservoir) properly in the first place, your coolant is either leaking and/or is being burned.

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Report this Post06-14-2022 08:07 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
My reasoning for why the coolant in the overflow button should be hot is because the engine reaches temperatures of about 240F which should cause pressure to rise above 15/16 psi causing hot coolant to enter the overflow button (and sucked back into the radiator when temperature drops). Apparently, the radiator cap valve didn't open at all during the time I drove the car.

And yes, I do have a coolant leak somewhere. Just can't find where. Although it seems it´s has been a bit less lately.
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Report this Post06-14-2022 09:41 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

My reasoning for why the coolant in the overflow button should be hot is because the engine reaches temperatures of about 240F which should cause pressure to rise above 15/16 psi causing hot coolant to enter the overflow button (and sucked back into the radiator when temperature drops).


Reading this again, this sounds a bit condescending. It was in now way meant like that. You probably know how the coolant system works better than I do. 😄

But I just checked coolant levels with a cold engine and when I opened the thermostat cap, it was filled to the edge still. Checked at the radiator and saw the same thing. So it doesn't seem like it's loosing coolant (anymore).
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Report this Post06-14-2022 10:19 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Engine Temp Gauge "Bouncing" is often 100% Normal. More So w/ Standard Thermostat in Fiero and many others and "dumb" gauges.
Fiero has ~ 3 times the coolant the T-stat tries to handle and depending on weather and time engine runs and loads, may take a long time or never reach a stable temp w/ OE type T-stat.

Get Stant SuperStat
See my Cave, Thermostat

When you have open the system, can take hours to days for system to purge air out even assuming overflow tube and tank is working.
That even if you follow Burping crap methods used by many others.

Just replacing T-stat shouldn't let much air in so should purge easy. Open the radiator etc lets more air in and take longer to purge. more so if you don't drive enough to heat cycle the system.
See my Cave, Coolant Fill

------------------
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Doug85GT
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Report this Post06-14-2022 03:51 PM Click Here to See the Profile for Doug85GTSend a Private Message to Doug85GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
The last time I had coolant disappearing like that my water pump was leaking. The next time you get your car up to operating temperature, slide a flattened cardboard box under the engine and let it idle for 2 minutes. Pull the cardboard out and look for any fluid that dripped on it. The cardboard can be used to figure out where the leak is located too. It is also possible that something else is leaking when the system is up to pressure.
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Patrick
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Report this Post06-14-2022 04:48 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

But I just checked coolant levels with a cold engine and when I opened the thermostat cap, it was filled to the edge still. Checked at the radiator and saw the same thing. So it doesn't seem like it's loosing coolant (anymore).


Instead of removing either cap, especially the radiator cap, you should be able to determine coolant level by simply looking at the level in the reservoir. It should be at the lower mark when the engine is cold, and at the higher mark when the engine is at operating temperature. The reservoir should never be empty, and/or never be boiling out of the top.

 
quote
Originally posted by Cliff Pennock:

...my engine temperatures are all over the place. "Normal" temperature seems to be between 175F and 195F but most of the time it shoots up to 230F in 20-30 seconds, stays there for a few minutes only to drop back to 175 within 10 seconds. Rinse. Repeat.


Of the four Fieros that I've daily-driven and/or autocrossed (two 2.5s, two 2.8s), not one of them has ever had coolant temperature swings. I suspect you've got pockets of air within your GT's cooling system.

Yes, the Ogre scoffs at any sort of "crap methods used by many others" to burp the system ... but nevertheless, if you wish to try my method, Here it is.

[This message has been edited by Patrick (edited 06-15-2022).]

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Raydar
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Report this Post06-15-2022 01:30 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:
...
Yes, the Ogre scoffs at any sort of "crap methods used by many others" to burp the system ... but nevertheless, if you wish to try my method, Here it is.



I should add, that this is precisely how I burp my system.
With the added step of parking my car on an incline, with the back end higher than the front. Probably not necessary, but it certainly doesn't hurt.
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Report this Post06-15-2022 02:54 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:

With the added step of parking my car on an incline, with the back end higher than the front.


Raydar, that step was definitely implied. "Position rear end of Fiero higher than the front." I back my Fiero(s) up onto ramps if/when I needed to burp their cooling system.

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Report this Post06-15-2022 03:03 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:

Raydar, that step was definitely implied. "Position rear end of Fiero higher than the front."


Ah. I missed that. Must have "head-spaced".
You've "known" me a long time. This should not be a surprise.

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Patrick
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Report this Post06-15-2022 03:40 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:

Ah. I missed that. Must have "head-spaced".


No problem. It was a good opportunity to reiterate that point, as I feel having the thermostat housing well elevated above the radiator cap opening during the burping procedure to be critical. It allows pockets of air to naturally gravitate towards the rear of the car, and hopefully end up at the thermostat housing where they can be released into the atmosphere.

[This message has been edited by Patrick (edited 06-15-2022).]

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Cliff Pennock
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Report this Post06-15-2022 03:55 PM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:

I should add, that this is precisely how I burp my system.


Yes, that's how I do (did) it too.

Anyway, I checked the levels in the overflow bottle with a cold and hot engine. There was no difference.
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Report this Post06-15-2022 04:35 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

I checked the levels in the overflow bottle with a cold and hot engine. There was no difference.


Well, something's definitely funky. The coolant level in your reservoir should be going up and down during every heat cycle of your engine... but you already know that. I can't help but think that this is indeed related to the wild temperature fluctuations.

[This message has been edited by Patrick (edited 06-15-2022).]

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Report this Post06-16-2022 03:29 PM Click Here to See the Profile for IMSA GTClick Here to Email IMSA GTSend a Private Message to IMSA GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I guess my only question is in the morning when cold and you start the car, do you smell antifreeze from the exhaust?
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Report this Post06-16-2022 04:01 PM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
Will check tomorrow. 😁
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Patrick
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Report this Post06-16-2022 04:39 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by IMSA GT:

...when cold and you start the car, do you smell antifreeze from the exhaust?


...and/or is the crankcase oil starting to resemble a milkshake?

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Report this Post06-16-2022 05:34 PM Click Here to See the Profile for ArthurPealeClick Here to Email ArthurPealeSend a Private Message to ArthurPealeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:

Instead of removing either cap, especially the radiator cap, you should be able to determine coolant level by simply looking at the level in the reservoir. It should be at the lower mark when the engine is cold, and at the higher mark when the engine is at operating temperature. The reservoir should never be empty, and/or never be boiling out of the top.



Um...oh. Huh. I rarely have any liquid in there. Temps have almost always been fine, except when I had a heater core leak, and the fluid levels were down. Added more fluid and off we went.
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Report this Post06-16-2022 06:46 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by ArthurPeale:

Um...oh. Huh. I rarely have any liquid in there.


I've got one question for you.




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Report this Post06-17-2022 02:03 AM Click Here to See the Profile for ArthurPealeClick Here to Email ArthurPealeSend a Private Message to ArthurPealeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:

I've got one question for you.



Well, I guess I'll make sure there is, going forward
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Cliff Pennock
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Report this Post06-17-2022 02:58 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
I need to consider it's just an erratic temperature sending unit...

Yesterday, after having driven the car, I wiggled the wires from the temp sender a bit, just to see if it felt loose. It didn't. But then today, my temperature gauge wasn't reading anything at all. So I stopped the car and started wiggling the wires again and the temp gauge came back to live.
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Report this Post06-17-2022 02:03 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
Could use an infrered temp reader to measure temps at the head and radiator.
Losing coolant and erratic temps could be head gasket issues.
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Report this Post06-17-2022 02:19 PM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
Erratic temps seems to have gone now. Yes, it still fluctuates quite a bit but between 165F and 195F which doesn't seem all that out of the ordinary.

But a new problem developed in the last few days. Low transmission fluid. This isn't the first time I have low transmission fluid, but in the past this was a gradual process over a year or so. I would notice the car going into neutral in shapr turns which progressively gets worse. But like I said, in the past it took about a year before I thought it actually needed extra fluid.

Now this occured in a few days. In the beginning of the week, I had no problems and now it's so bad that even when I accelerate, it goes intro neutral.
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Report this Post06-17-2022 04:36 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

In the beginning of the week, I had no problems and now it's so bad that even when I accelerate, it goes intro neutral.


If your transmission fluid level is dropping, then there must be evidence under the car of a leak.

Is the fluid level actually low, or is the filter becoming plugged?
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Report this Post06-21-2022 09:36 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:


But a new problem developed in the last few days. Low transmission fluid. This isn't the first time I have low transmission fluid, but in the past this was a gradual process over a year or so. I would notice the car going into neutral in sharp turns which progressively gets worse. But like I said, in the past it took about a year before I thought it actually needed extra fluid.

Now this occurred in a few days. In the beginning of the week, I had no problems and now it's so bad that even when I accelerate, it goes intro neutral.


Automatic Transmission leaks can be a result of a pan gasket. Also the short hoses that connect the transmission to the hard lines can leak. If you have a stick that could be a shaft seal but you will surely see oil at the bottom of the bell housing. The input shaft seals are now 30+ years old and were not designed to last forever.

------------------
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Cliff Pennock
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Report this Post11-20-2022 05:04 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
The fluctuating temperature swings have come back - with a vengeance.

I start the car in the morning and within a few miles (2-3) temperature goes up to 230F. It then continues to rise to about 250F, stays there for a few minutes, then drops in seconds to 140. Again it stays there for a few minutes, then temp rises to 230F-250F again. This cycle repeats itself for about a half hour, after which temperature drops to 175F-195F at which it stays for the remainder of the trip.

Checked coolant levels and somehow it had lost almost 4 quarts since the last time I checked about 2 weeks ago.

Another thing that happened last week: I parked my car on a small incline and when I returned to the car, I saw a fluid coming from under the car, I couldn't really make out the color but it smelled and felt like transmission fluid. I then looked behind the car and saw a trace of the fluid. I followed the trace and it stopped after about 150 feet. So it hasn't been losing fluid all the time, just for the last 150 feet. When I started the car again, I didn't see anything dripping. Checked several times in the days after that but never saw it losing fluid again.
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Report this Post11-20-2022 07:36 AM Click Here to See the Profile for Fie RoClick Here to Email Fie RoSend a Private Message to Fie RoEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

I need to consider it's just an erratic temperature sending unit...

Yesterday, after having driven the car, I wiggled the wires from the temp sender a bit, just to see if it felt loose. It didn't. But then today, my temperature gauge wasn't reading anything at all. So I stopped the car and started wiggling the wires again and the temp gauge came back to live.


You could check and clean the connectors and ground. Have you tried reburping the system again? There may be air in the system causing fluctuating readings in temps and level. Also you could check below the waterpump (seephole) if it leaks the pump may be going out.

I think one sign of low transmission fluid is when you put it in reverse it may take longer before it "grabs"
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Report this Post11-20-2022 04:32 PM Click Here to See the Profile for Mike in SydneySend a Private Message to Mike in SydneyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

The fluctuating temperature swings have come back - with a vengeance.

I start the car in the morning and within a few miles (2-3) temperature goes up to 230F. It then continues to rise to about 250F, stays there for a few minutes, then drops in seconds to 140. Again it stays there for a few minutes, then temp rises to 230F-250F again. This cycle repeats itself for about a half hour, after which temperature drops to 175F-195F at which it stays for the remainder of the trip.

Checked coolant levels and somehow it had lost almost 4 quarts since the last time I checked about 2 weeks ago.

Another thing that happened last week: I parked my car on a small incline and when I returned to the car, I saw a fluid coming from under the car, I couldn't really make out the color but it smelled and felt like transmission fluid. I then looked behind the car and saw a trace of the fluid. I followed the trace and it stopped after about 150 feet. So it hasn't been losing fluid all the time, just for the last 150 feet. When I started the car again, I didn't see anything dripping. Checked several times in the days after that but never saw it losing fluid again.


Cliff, how old is the water pump? Just a suggestion, pull the thermostat and start the engine. You should be seeing a solid flow if the water pump is OK. Does your radiator fan and fan switch operate properly? You can turn on the A/C and the fan should start. Otherwise, it comes on when the fan switch reaches operating temperature. There's plenty in the archives about this. Also, if your transmission is slipping or low on fluid, could it be causing additional heat? This is just a WAG (wild arse guess) on my part. Patrick, Ogre, or some of the other members could probably shed light on this.
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Report this Post11-20-2022 04:57 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Mike in Sydney:

This is just a WAG (wild arse guess) on my part. Patrick, Ogre, or some of the other members could probably shed light on this.


Not that I know what the problem is, but due to what was discussed five months ago Here, I'm not surprised that Cliff is experiencing further issues.
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Report this Post11-21-2022 05:15 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Mike in Sydney:

Cliff, how old is the water pump?


I replaced the water pump two years ago. Thermostat was replaced recently

 
quote
Just a suggestion, pull the thermostat and start the engine. You should be seeing a solid flow if the water pump is OK. Does your radiator fan and fan switch operate properly?


I have no reason to believe they don't. I can't say for sure when the fan switches on so I don't know yet if there's any relation to the temps I'm seeing and when the fans switches on. The problem is, I live in a small village which only has two roads out. By the time I start seeing the high temperatures, I'm on a road where I can't stop. So I can't check if the fan is on or not. And by the time I'm at the end of that road, the engine would have reached "normal" operating temperature any way, so the fan is always on there. I'm thinking of hooking up an indicator light that lights up whenever the fan switches on. That way I can actually see when the fan comes on. So if I see 250F on my dash but the fan isn't on, then it's probably the temperature gauge sensor that's wacky.

On the other hand, I am loosing coolant.

 
quote
You can turn on the A/C and the fan should start.


Yeah, my car doesn't have A/C...

 
quote
Also, if your transmission is slipping or low on fluid, could it be causing additional heat?


Well, I do know that if I'm at a traffic light and I put the car in Neutral, temps drop but only with a few degrees. But that's normal. It has always done that.

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Report this Post11-21-2022 09:30 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Again... gauge bouncing maybe normal as posted above. You have cool to cold weather slugging the engine w/ cold coolant.
But may have other problems adding to that....

Nope.
When Coolant System is Working Right... Rad Fan, & aux blower for V6, Does Not turn on all the time even when Engine is @ operating temp.
See my Cave, Rad Fan

Even when GM made 87-88 Dukes ECM programing and aftermarket fad switches turn on @ ~ 220°F/105°C does Not turn on the fan in a lot of driving.
Isn't just Fiero. Most vehicles w/ E-fans for Radiator don't turn on all the time. Saves E-motor wear and power use by it. And many vehicles have 2 speed fans sim to 84 Fiero w/ AC and they don't turn on all the time at low speed.

If you have this turn on all the time then have crush pipe(s), crap in the system blocking flow, etc.

Run light from rad fan red wire and find a ground to turn on w/ fan on. Pull relay socket then pull red wire to rad fan and twist a bit of wire to a test light so don't need to cut/strip wire.
If you run a light to green wire controls it then light may turn on the relay even if doesn't light itself. Putting a light may cause other problems as well connected there.

Coolant from "overflow" tank or tube for it can be... most common...
iffy lower Rad Hose or Valve below in same area.
iffy tube or joint(s) to it is leaking. Good/bad Rad Cap doesn't matter here.
Damage Rad Fill Port causing cap problems.
Bad Rad Cap. Just worn and bad OR have wrong type.

Old caps can fail the top section and leak from the top rubber seal or when have "level locking" type can leak at lever "pin" going into the cap.
Wrong type... See my Cave, Radiator Caps

Many install overflow tube w/ worm clamps and related then crush the rad, tank or both ports then tube leaks or rad can't use the tank and pushes coolant out top of cap when hot. So if/when you pull to tube... check the ports for crushing/blocking.

[This message has been edited by theogre (edited 11-21-2022).]

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theogre
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Report this Post11-21-2022 05:00 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
And if is Slugging... Can't get Stant Super stat now thru most part sources to help the temp bouncing.
See Stant is Gone https://www.fiero.nl/forum/Forum2/HTML/146523.html
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Cliff Pennock
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Report this Post11-22-2022 02:02 PM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
I was finally able to check if the fan was running after driving the car for about 5 minutes, and temperature showing 230F. Fan wasn't running. So there was either a huge temperature difference between the temp gauge sender unit and the fan switch, or the temp gauge sender unit is defective. Assuming of course the fan switch isn't defective.
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Report this Post11-22-2022 02:56 PM Click Here to See the Profile for steve308Send a Private Message to steve308Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

I was finally able to check if the fan was running after driving the car for about 5 minutes, and temperature showing 230F. Fan wasn't running. So there was either a huge temperature difference between the temp gauge sender unit and the fan switch, or the temp gauge sender unit is defective. Assuming of course the fan switch isn't defective.


Fan could also be failing (as mine did). Fan motor replacement is easy assuming it's available. It is a generic GM part.
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Patrick
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Report this Post11-22-2022 03:57 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by steve308:

Fan could also be failing (as mine did).


That should be easy to determine by checking to see if the trunk blower is running, or by simply grounding the single wire to the fan switch.
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Mike in Sydney
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Report this Post11-22-2022 11:57 PM Click Here to See the Profile for Mike in SydneySend a Private Message to Mike in SydneyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Like Patrick said, ground the fan switch sensor to see if the fan is operating. It's located here (https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20110502-2-101002.html). Turn on the ignition and using a piece of wire, screwdriver, etc. ground the wire to the block. The fan should start. If it doesn't there is a problem with the wiring or the fan. If it runs, the likely culprit is the fan switch and the connector that gets brittle with age.

One other thing, it could be is low water in the system. After replacing a hose that Customs cut when I brought my GT into the country I would get occasional overheating. I pulled the T'stat to check for flow. Water was flowing but not much. (The mechanic who replace the damaged hoes was not familiar with the cooling system on the Fiero and tried to fill it from the radiator, not the engine.) I think there was an air bubble somewhere in the system so even filling from the block still left me with the problem. Here's how I resolved the problem:

1. I made sure the fan operated from the fan switch and the A/C.
2. parked the car on a hill with the nose and radiator considerably lower than the engine.
3. I removed the radiator cap completely.
4. I removed the pressure cap over the t'stat and the t'stat itself.
5. i added a 50-50 mix of antifreeze and distilled water and kept pouring it in until the mixture came out of the top of the radiator.
6. I replaced the radiator pressure cap on the radiator and made sure it was tightly closed.
7. I continued to fill the system from the block until the water overflowed the t'stat housing. I did not put the cap on the system.
8. I cranked the car and observed the water flow in the t'stat housing. I ran the car for a few minutes and watched the coolant level. It dropped a bit and I topped up the system again. I did this a couple of times and when the level stabilised, I replaced the t'stat and the pressure cap.

After I did this, I had no more problems with the car overheating. It sets rock-steady at 160°F which is what the T'stat is rated for.

I don't know if tis will work for you but it did for me.
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Report this Post11-23-2022 01:40 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm pretty sure the fan is working properly. After driving the car for about 5-10 minutes, it's always on unless it's really cold outside. Most of the time I can hear it switch on when it's idling like at a traffic light.
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Report this Post11-23-2022 02:01 AM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

I'm pretty sure the fan is working properly. After driving the car for about 5-10 minutes, it's always on unless it's really cold outside.


"Properly"? As Ogre has pointed out, it isn't normal (nor desirable) for the fan to "always" be running . Did you install an aftermarket extra-low temperature fan switch?

 
quote
Originally posted by theogre:

When Coolant System is Working Right... Rad Fan, & aux blower for V6, Does Not turn on all the time even when Engine is @ operating temp.
See my Cave, Rad Fan


[This message has been edited by Patrick (edited 11-23-2022).]

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Report this Post11-23-2022 02:46 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just now, the temperature gauge went up pretty fast again until it reached 260F (highest it can display) and it stayed there for quite some time before dropping off to slightly more sensible temperatures (still high, but not rediculously high).Since the ECM never threw a Code 14 (and the Check Engine Light is working), I'm pretty sure the temp gauge sender unit is not working properly. So that at least is part of the problem.

Still leaves the problem why it's losing coolant.
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Report this Post11-23-2022 02:57 AM Click Here to See the Profile for Cliff PennockClick Here to visit Cliff Pennock's HomePageClick Here to Email Cliff PennockSend a Private Message to Cliff PennockEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:

"Properly"? As Ogre has pointed out, it isn't normal (nor desirable) for the fan to "always" be running . Did you install an aftermarket extra-low temperature fan switch?



Let me rephrase that. It's running when I expect it to be running.

Every morning I drive the same 7 miles with an average speed of about 50-60mph. At the end of those 7 miles when I stop the car, the fan is running. Unless it's really cold outside. Then it isn't. When driving short distances where speed never gets above about 40 mph and I stop the car, the fan isn't running.

 
quote
Originally posted by Cliff Pennock:

After driving the car for about 5-10 minutes, it's always on unless it's really cold outside.


I meant 5-10 miles.
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Report this Post11-23-2022 06:10 PM Click Here to See the Profile for Mike in SydneySend a Private Message to Mike in SydneyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cliff Pennock:

Every morning I drive the same 7 miles with an average speed of about 50-60mph. At the end of those 7 miles when I stop the car, the fan is running. Unless it's really cold outside. Then it isn't. When driving short distances where speed never gets above about 40 mph and I stop the car, the fan isn't running.

I meant 5-10 miles.



Cliff, for comparison, I drove my '86 2.8 GT 30 km to work this morning at speeds of 80 - 100 kph. The temperature never went above 160°F. The outside air temperature was 9°C. My coolant fan never came on. My car has 107,000 miles on it.

 
quote
Originally posted by Cliff Pennock:


On the other hand, I am loosing coolant.


Where from? How much? Any strange puddles under the car? Like I said in a previous post, I had low coolant levels and I saw problems similar to what you are describing. I was able to identify the leak because of a big puddle of coolant.

Does your oil look like a chocolate milk shake? Got any sweet smelling exhaust (if you have antifreeze, anyway.)? What do your plugs look like? Do you have any that are really, really clean? These are usually indications of a faulty head gasket or something worse.

One other thing, when you replaced the water pump did the replacement have a plastic or metal impeller? I've heard that plastic impellers will sometimes slip on the shaft and nor move the coolant very well.

(edited for spelling)

[This message has been edited by Mike in Sydney (edited 11-23-2022).]

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