Hey guys, some quick questions on my daughter's 2.5 Iron Duke engine.
We've been driving it around lately, but the temperature gauge on the gauge cluster is totally crazy. It shows the car as overheating extremely... like at all times.
When I start it up, the temperature gauge almost immediately goes to the middle, and then sits well past the red into the black area. It freaked me out at first, so I bought a laser-temperature reader. I tested it on my forehead which gave me a perfect 98.6 degrees.
After thrashing the car... and driving it pretty harsh... here are the temperatures:
All temperatures are in Fahrenheit. I just want to make sure I'm not crazy, and that it's just the gauge (I think it's the gauge).
- Starting from the left (the thermostat housing), the temperature is anywhere from 185-199 degrees. I am running a Stant 195 degree thermostat. - At the intake manifold, it's typically around 155 degrees, sometimes gets up to 160 degrees. - In the middle, RIGHT where the exhaust manifold bolts to the cyl head, it's typically anywhere from 235 (coldest after warmed up) to 265 at the hottest. Just a little further back, directly on the manifold, it's around 325 degrees. - Below the Oil Fill on the passenger side of the cyl head, when I point the laser directly at the freeze plug, I'm getting usually anywhere from 200-220 (usually closer to 220).
These temperatures seem pretty decent. I do not know the condition of the radiator, other than it's not leaking. But everything from the middle of the car back has been replaced... so I still need to change the front heater core hoses, the two radiator lines, and probably flush the radiator. I used some cheap green anti-freeze in this engine while I'm attempting to break it in (doesn't even have 10 miles on it yet).
My guess is that the temperature gauge is completely broken... but I'm not sure WHY... so I'm trying to diagnose that. My tachometer is also messed up... but the oil pressure and speedometer are both working well.
Thank you!!!
[This message has been edited by 82-T/A [At Work] (edited 11-11-2024).]
Also... can you guys confirm that the coolant comes in FROM the drivers side (thermostat side). I would hope so, since that coolant appears to be much cooler... while the passenger side (exit at the water pump) appears to be hotter. I don't even know what to think if you guys tell me it's the other way around...
Of all the gauges, I have found the temp gauge the most inaccurate, I had similar readings, until I fixed the "bulb test" wiring, and cycled it a few times by grounding the wire at the sensor to the engine. With the early gauges, it seems the "operating range" can get shifted left or right from frequent/very quick cycles, so basically gauge is supposed to read between 0-100 (fictitious numbers) but instead reads between 50 and 150, the needle is still attached as normal, but seems to have "moved". Be careful when grounding the plug, as if you ground it a few times in quick succession (wire slips on the block, something like that) the gauge will pin itself way up at the top (operating range has changed to 250-350 in our fictitious scale, aka all the way up).
Of all the gauges, I have found the temp gauge the most inaccurate, I had similar readings, until I fixed the "bulb test" wiring, and cycled it a few times by grounding the wire at the sensor to the engine. With the early gauges, it seems the "operating range" can get shifted left or right from frequent/very quick cycles, so basically gauge is supposed to read between 0-100 (fictitious numbers) but instead reads between 50 and 150, the needle is still attached as normal, but seems to have "moved". Be careful when grounding the plug, as if you ground it a few times in quick succession (wire slips on the block, something like that) the gauge will pin itself way up at the top (operating range has changed to 250-350 in our fictitious scale, aka all the way up).
Interesting... thanks 85. I noticed just today though when I turned it to the on position, it was drop-dead in the far left, right at the first mark (100 degrees I guess)... it then climbs really fast to 220... which just seems imposible. Like, I start it, and within seconds it's already at the half-way point.
Insofar as the actual temperatures I recorded with the laser temperature reader... does those temperatures look OK to you?
Originally posted by 82-T/A [At Work]: Interesting... thanks 85. I noticed just today though when I turned it to the on position, it was drop-dead in the far left, right at the first mark (100 degrees I guess)... it then climbs really fast to 220... which just seems imposible. Like, I start it, and within seconds it's already at the half-way point.
Insofar as the actual temperatures I recorded with the laser temperature reader... does those temperatures look OK to you?
Yeah, perhaps the sender is bad, or a different ohms range or something, definitely something unusual there, I don't know what the temps should be, but seems pretty much normal.
Also... can you guys confirm that the coolant comes in FROM the drivers side (thermostat side). I would hope so, since that coolant appears to be much cooler... while the passenger side (exit at the water pump) appears to be hotter. I don't even know what to think if you guys tell me it's the other way around...
I don't understand your description... but from what I understand, coolant flows up through the thermostat and out of the thermostat housing.
I don't understand your description... but from what I understand, coolant flows up through the thermostat and out of the thermostat housing.
I'm very confused then... because the temperature of the coolant LEAVING my engine (out the drives side) is cooler than that which is coming INTO the engine from the radiator via the passenger side.
Can you look at the image above... does this look normal to you? These were the temperatures that I took with my laser temperature reader... thank you.
Let's get some more opinions on which way the coolant is supposed to be flowing at the thermostat housing.
Is there any way that your belt/pulley modifications have now resulted in your water pump being spun in the reverse direction? (I can't refer back to your photos at the moment.)
Let's get some more opinions on which way the coolant is supposed to be flowing at the thermostat housing.
Is there any way that your belt/pulley modifications have now resulted in your water pump being spun in the reverse direction? (I can't refer back to your photos at the moment.)
No, the rotation is completely stock to an 87-88 Iron Duke, it's just missing the belt tensioner... which just loops it around the tensioner, otherwise exactly the same. It hasn't slipped once either, even when I really beat on it. Of course, it's a new belt, so I'm not leaving it like this. I'll eventually install a solid idler pulley in the same place as were the factory belt tensioner would be, I just haven't done it yet.
I'm going to grab the service manual and see if it shows the direction of flow.
Ok, so here’s what I found. You are correct Patrick that the coolant goes from the passenger side, to the driver’s side of the engine… I.E., “up through the thermostat and out the water neck.” It flows out to the radiator from the driver’s side, at the top of the radiator, and then the cooled water leaves through the bottom of the radiator, and goes in through the water pump . This is for convection.
Including a picture of a radiator from 16 years ago who was restoring my V6:
Why the coolant is cooler on the other side might be because the thermostat is holding the hot coolant back.
I haven’t replaced the radiator yet… but I don’t even know if it’s overheating. Those temperatures look reasonable, but I just don’t know.
Todd the coolant goes out the thermostat housing and returns through the waterpump back into the block. should be hottest at the thermostat housing outlet. I have see where on smallblock chev where someone put on a newer serpentine type waterpump on a vbelt system and that had overheating problems because the pump was running in reverse. sleek
Todd the coolant goes out the thermostat housing and returns through the waterpump back into the block. should be hottest at the thermostat housing outlet. I have see where on smallblock chev where someone put on a newer serpentine type waterpump on a vbelt system and that had overheating problems because the pump was running in reverse. sleek
Thanks Sleek, I can absolutely assure you guys that I am following the factory belt routing that was on 1987-1988 Fieros. Everything I'm using is from a 1987-1988 Fiero. The only thing is that I don't have the belt tenssioner, and instead went from a fixed alternator bracket (87-88), to an adjustable one (84-86). It's all stock stuff, and is most definitely going in the right direction. Unless by some chance the waterpump impellar itself is different and going in the wrong direction (it's for an 85, but I put an 88 pulley on it). What I can figure though is that I'm measuring temperature (right side) on the exposed freeze plug on the cyl head (right next to an exhaust port), compared with the outside water neck after the thermostat, where I'm getting some flow past the thermostat.
Thing I really want to know though is if those temperatures seem normal.
EDIT: Thanks Patrick, those are good diagrams. I found something similar, and I guess they do this because of convection, so since heat rises, it at least helps reduce the temperature's a little bit by ensuring the water at the bottom will always be a bit cooler (as your diagram shows).
Here are some things I'm going to try to figure out. For one, I'm not sure these temperatures are BAD... but I may have screwed up:
1 - I think I have almost exclusively concentrate anti-freeze in the car, with almost no water whatsoever... dumb on my part, but I think I have at least 80% antifreeze or more in there, with the rest being distilled water. So, I'll fix that.
2 - I have the fan switch and temperature sensor in the wrong slots. They're nearly next to each other anyway, so I don't know if that affects the temperature gauge... but I'll try to move them back.
3 - I'll try to verify the temperature I'm getting from the ALDL connector via the OTHER temperature sensor that goes to the ECM (the one on the water neck).
4 - I'll double-check my timing... because I don't think I have... I think it's likely off a little anyway.
Anything else I should check or do? Maybe pull the thermostat just to see if the temperature changes?
I'll also take new temperature readings and post them to a newer image. Thanks!!!
[This message has been edited by 82-T/A [At Work] (edited 11-13-2024).]
Those temperature seem okay, but on the high side of okay, however, I would seriously investigate this reverse flow problem. Coolant MUST flow in from the passenger side which you will find connect to the lower (read cooler) side of the radiator. Coolant flows through the engine and holds at the thermostat, pressure is relieved through the heater loop (this is what gets you heat quick in the winter) then the slug facing the block expands enabling flow. If for some reason flow was reversed that slug would not heat correctly, expanding too late and you would face overheating
Those temperature seem okay, but on the high side of okay, however, I would seriously investigate this reverse flow problem. Coolant MUST flow in from the passenger side which you will find connect to the lower (read cooler) side of the radiator. Coolant flows through the engine and holds at the thermostat, pressure is relieved through the heater loop (this is what gets you heat quick in the winter) then the slug facing the block expands enabling flow. If for some reason flow was reversed that slug would not heat correctly, expanding too late and you would face overheating
Thank you... just to be clear though, I'm not aware that there is a reverse-flow going on. I think it's just where I measured everything (on the block, versus on the metal outlet).
I would love to know if there's an easy way for me to check this though...
Easy way to check is to pop the cap, pull the thermostat and have your daughter quickly start and the kill the engine. Youll see which side it comes out of
Easy way to check is to pop the cap, pull the thermostat and have your daughter quickly start and the kill the engine. Youll see which side it comes out of
Ok, I spent some time working on the car today with my daughter, and we tried to diagnose a few other things. I hope you guys can help me figure this out again.
Okay, so some things I discovered:
1 - I definitely have the fan switch and the temperature sensor locations reversed. 2 - It's almost entirely coolant. I have almost no water in there. I literally put 2.5 gallons of concentrate anti-freeze and maybe half a gallon of distilled water (don't ask, I know I need to fix it) 3 - I removed the thermostat cap, and the 195 degree thermostat is a MotoRad "fail-open" thermostat. It was "clipped" fully open... which means I assume it had likely overheated. 4 - I verified that the water pump IS moving the coolant in the correct direction. 5 - I also verified that the coolant leaving the thermostat housing is HOT (and going into the radiator is HOT), and the coolant leaving the radiator (and going into the engine) is quite a bit cooler. 6 - Timing is set to 8 degrees.
So here's what I did. I started the car, let it run and idle... it ran pretty cool... slowly warmed up to the 1/4 mark... and then gradually moved between the 1/3rd to 1/2 mark, and mostly sat there the entire time it was idling (which was about 10-15 minutes). It would flirt with higher than the 1/2 mark, so I'd stab the throttle a little, and the temperature would go back down to the 1/2 mark. We let it idle again... and then after a couple of minutes, the temperature started to climb and started to slowly go up, and we shut it off just before it got to the red area, as I didn't want it to overheat again.
Couple of other things: - Coolant is VERY clean, bright-ass green, like it's brand new (cause it is). - Oil is VERY clean, it's still the break-in oil, also mixed in with the assembly lube. Looks almost totally clear. - Everything is new, except the front radiator hoses, the front heater core hoses, and the original radiator. - Radiator fan has been wired permanently on, I did not do this, but will eventually fix it... I'm working from back of the car to the front.
The car has maybe 5 miles on it total, and maybe 1 hour of idle time. Twice I've overheated it (early on) way past the red into the black... but the engine idles and runs really smoothly... and I have not allowed it to overheat since.
I plan to eventually replace all the hoses in the front (I already have them), and may replace the radiator, if you guys think I need to... but we've been doing some other things on the car in the mean time.
Any ideas? I don't remember the car overheating previously when we first got it... the car had over 200k miles on the original Iron Duke, and the car was tired, to say the least. If you've followed my other posts, we totally rebuilt the motor and everything in the back is totally new. Thoughts? Really appreciate any advice. Could it just be that I have too much antifreeze and not enough water for it to actually cool?
...gradually moved between the 1/3rd to 1/2 mark, and mostly sat there the entire time it was idling (which was about 10-15 minutes). It would flirt with higher than the 1/2 mark, so I'd stab the throttle a little, and the temperature would go back down to the 1/2 mark.
I'm just curious to hear what your explanation might be for the coolant temp dropping when you "stab the throttle a little".
I'm just curious to hear what your explanation might be for the coolant temp dropping when you "stab the throttle a little".
I mean, more water pump flow? That sounds like what I've heard a slipping impellor to do, if it were starting to slip, a change in rpm might make it grip again, if only for a second, and would explain it being fine until it isn't, and then heading up pretty fast.
More than 50% coolant in your system will cause higher system temperatures. Glycol doesn't cool as efficiently as water so I use 40% coolant and 60% distilled water. Also make sure the cooling fan is turning in the right direction. Try running without the thermostat. If the engine runs cool then it may be a defective stat.
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Originally posted by 82-T/A [At Work]: My assumption is that it's spinning the waterpump faster, and then drawing in more coolant, more quickly?
I should say, "blip" the throttle... not like FLOOR it... so like... I'd have it go from 800 rpms / idle to 1,400 rpms is what I meant.
Do you have any thoughts? Kinda sucks...
Yeah I think slipping impellor, although I have no experience with that, and haven't researched much, so yeah, maybe look into that, that's the only reason more throttle would cool out down, as there's always water flowing, and the difference a blip of throttle makes shouldn't appear on the gauge, unless said blip moves a slipping impellor more than it was.
More than 50% coolant in your system will cause higher system temperatures. Glycol doesn't cool as efficiently as water so I use 40% coolant and 60% distilled water. Also make sure the cooling fan is turning in the right direction. Try running without the thermostat. If the engine runs cool then it may be a defective stat.
I'm hoping that's the problem... I used cheap stuff just because I wanted to get the car running and figured I'd have to dump it out anyway when we worked on the front / radiator area. But ... to be clear... man, I'm not using 50% coolant. I'm using like 85% coolant, and MAYBE 15% water, if I'm lucky. Do you think that could have a significant impact on the temperature? Thank you...
(Note, I realize it's ridiculous, I'd intended to change it out, I just didn't know how much needed to go in there, haha).
quote
Originally posted by 1985 Fiero GT: Yeah I think slipping impellor, although I have no experience with that, and haven't researched much, so yeah, maybe look into that, that's the only reason more throttle would cool out down, as there's always water flowing, and the difference a blip of throttle makes shouldn't appear on the gauge, unless said blip moves a slipping impellor more than it was.
Man, how could that even be possible? It's literally a brand new water pump... have these been known to be DOA?
My assumption is that it's spinning the waterpump faster, and then drawing in more coolant, more quickly?
In the old days, revving the engine in a stationary vehicle would help cool it down due to the directly connected rad fan spinning faster and drawing more air through the rad. Of course, that obviously isn't the case with a Fiero. A possible slipping (plastic) water pump impeller has been mentioned... but is that even an issue with dukes (as it is with the 2.8)?
I suspect you've got a restriction in the cooling system somewhere that's impeding the flow of coolant. Maybe a blockage in the rad, or a half-stuck thermostat, or a partially crushed coolant pipe along the side(s) of the car?
[This message has been edited by Patrick (edited 11-26-2024).]
In the old days, revving the engine in a stationary vehicle would help cool it down due to the directly connected rad fan spinning faster and drawing more air through the rad. Of course, that obviously isn't the case with a Fiero. A possible slipping (plastic) water pump impeller has been mentioned... but is that even an issue with dukes (as it is with the 2.8)?
I suspect you've got a restriction in the cooling system somewhere that's impeding the flow of coolant. Maybe a blockage in the rad, or a half-stuck thermostat, or a partially crushed coolant pipe along the side(s) of the car?
I didn't actually look at the impeller. When I purchased the water pump, it was already attached to the waterpump housing (came from Bosch), so I didn't bother to separate them, but in my usual fashion, I ordered two others by accident, thinking they would come with a pulley, and they were all steel impellers. So I definitely don't think it's plastic.
I'm hoping your wrong Patrick... on the restrictions. I'm going to change out some of the coolant when I replace the front cooling tubes. I MAY replace the radiator. I mean, I'm replacing everything else, and I don't know the condition of it, so I might as well.
The only other thing I can think of is the cooling pipe that connects the water pump to the lower cooling tube. It was hell getting that on, and it's a sharp 180 degree curve practically. It's not pinched or anything like that, but it's a very frustrating angle... and they only have generic replacements for that hose that "should fit" which are listed for the Fiero... but "cut to fit."
Anyway... I should probably do it all at the same time... including changing out to the correct ratio of coolant. Ugh...
Ok, so... I bit the bullet as they say, and I just bought a new replacement radiator. it's one of the new high performance ones that has additional cores (more capacity). It's way more than a Duke needs of course, but since I'm going to be re-doing the front, I wanted to take care of everything up there anyway. I don't know the condition of the radiator (I know it doesn't leak), but if I can rule that out, I might as well since I know I need to deal with that anyway.
I'll have my daughter replace both front hoses and the heater core hoses as well before putting it all back and testing it out.
Ok, I just wanted to post a quick update... because I've done a little bit more testing and want to make sure I understand what's going on here.
I started the car a few minutes ago... sat at the 1/4 mark for a bit.. and then the temperature gauge slowly climbed towards the red area (I didn't let it get there).
I immediately shut off the car, and then immediately (a few seconds after), turn the ignition back to the ON position (but don't start the car). The temperature gauge immediately goes to the 1/4 mark.
So I let it sit... I start the car, and then the temperature gauge starts to climb back to the red area... so I immediately shut it off, and then instantly turn it back to the on position (i.e., powering the gauges), and the temperature gauge immediately goes back to the 1/4 mark.
Thoughts? I am doubting the car can immediately cool itself off ~50 degrees within seconds?
Maybe there's a head gasket leak? It's possible we didn't do it right... but I know we torqued it down to 90 foot pounds. (25ft-lbs, then 45, then 75, then 90... new bolts, new head gasket, block and head machined flat).
Engine runs fine. Only a quick puff of smoke on start-up... which I'm assuming (hoping) that the rings have yet to properly seat. Car has like... maybe 3 miles or 30 minutes on the engine rebuild... it idles and runs fantastic... tons of power (within reason, I haven't floored it).
(I can't refer back to your photos at the moment.)
