Engine temps all over the place (Page 3/9)
2.5 JUN 17, 02:03 PM
Could use an infrered temp reader to measure temps at the head and radiator.
Losing coolant and erratic temps could be head gasket issues.
Cliff Pennock JUN 17, 02:19 PM
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.
Patrick JUN 17, 04:36 PM

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?
Dennis LaGrua JUN 21, 09:36 AM

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 NOV 20, 05:04 AM
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.
Fie Ro NOV 20, 07:36 AM

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"
Mike in Sydney NOV 20, 04:32 PM

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.
Patrick NOV 20, 04:57 PM

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.
Cliff Pennock NOV 21, 05:15 AM

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.
theogre NOV 21, 09:30 AM
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).]