85 2m4 SE / 2.5 Temperature Issues (Page 3/7)
1985 Fiero GT NOV 26, 06:28 PM

quote
Originally posted by Patrick:

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.
Dennis LaGrua NOV 26, 06:30 PM
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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1985 Fiero GT NOV 26, 06:31 PM

quote
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.
82-T/A [At Work] NOV 26, 06:34 PM

quote
Originally posted by Dennis LaGrua:

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?
Patrick NOV 26, 08:23 PM

quote
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?



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).]

82-T/A [At Work] NOV 27, 11:03 AM

quote
Originally posted by Patrick:

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...
82-T/A [At Work] NOV 28, 11:42 AM
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.


Thanks!
82-T/A [At Work] NOV 30, 01:12 PM
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).
82-T/A [At Work] DEC 23, 06:27 PM
Ok, update... we spent most of our time working on the interior, cleaning, repairing, painting and re-installing all the interior pieces. My daughter was getting frustrated and asks literally every day if we can go drive the Fiero (she only has her learners, and the Fiero isn't registered yet).

I finally say yes, but tell her that the car is massively overheating... so we should replace the radiator first. I bought off Rock Auto an aftermarket radiator that fits the Fiero's front, and has an additional core on it... so it's larger, has more capacity, etc. We take off the hood, remove the two front hoses and the radiator and install the new one.

We get everything back together, get cleaned up, sit in our new Mr. Mikes seats with the immaculate interior, and start the car. It starts up fine (as always), and runs great. The temperature gauge... within a minute, is going insane... like... 300+ degrees. I call bull **** , and I pop the trunk, use my temperature laser gauge, and the thermostat housing isn't even 120 degrees. I can put my hand on it... no problem at all. It's like, not even uncomfortable. I put the laser temperature gauge right on the literal sensor that's feeding the gauge, and it says ~125 degrees. I even put my finger on it... and it's like... barely warm... like I can easily wrap my finger around it and keep my had on the cyl head, and it's not even hot.

Couple of things,

- I'm not running a thermostat (I took it out because I thought the car was overheating, but I'll put one back in the coming days).
- With the new radiator, I did 50/50 coolant / antifreeze with Redline Water Wetter
- Fan runs 24/7... no idea why, it comes on with the key on, so I'll need to figure that out.
- I had my gauges professionally checked and adjusted by Jack Gunsett... he fixed a bunch of things, and confirmed the temperature gauge is correct.
- Car still has the break-in oil in it... which is still really, really clean... and the car doesn't even have like 10 mile on it, obviously because we haven't been driving it.


So... after checking everything one last time with the laser gauge (and it's warmed up now to something like 160 degrees... but with the temperature gauge showing some insane temperature like 400 degrees), I decide to take the car for a spin. We drive the car around the neighborhood, going through all the gears except 5th, for like 30 minutes. We drive it everywhere... accelerating slowly... accelerating moderately hard, you name it... for like 30 minutes straight.

I finally come back to the house and use the laser temperature reader on the engine... Outgoing (thermostat housing) is like 190 degrees, incoming side of the engine block shows like 175 degrees. The hood is off, so I put my hand on the radiator in (top hose) and it's warm... but not even that hot, and then put my hand on the lower radiator hose, and it's significantly cooler.


Temperature gauge is like... the world is about to end.


What on Earth could I have done wrong? It's VERY obvious to me that the car is NOT overheating, like... at all. The car drove amazing, I mean... that engine... an Iron Duke, is insanely smooth, I can't even tell you guys. I've never owned an Iron Duke in all my years that ran this smooth. It's sounds amazing... revs really well, no clattering, nothing. It idles like a dream, and drives fantastic... it even pulls really hard, which impresses me immensely because we built it more or less to stock specifications.


So what's the deal, what on earth could be causing this temperature gauge to be reacting this way? It shoots up almost immediately. Could I possibly be using the wrong temperature sensor? Did I screw up the wiring somewhere? Everything else is amazing... no check engine codes or anything... I mean, the car just runs so totally fantastic.
Riney DEC 26, 07:13 PM
Any updates on what you have found with this?

My guess is wiring to temperature sending unit or the sending unit itself. Something grounding our or touching one of the wires?
You said you temperature gage is correct. I do not think this has anything to do with the 70/30 mix of antifreeze.

Also, you said the tach was messed up. Is it bouncing around like the tach filter is bad or just reading incorrectly?

My tach started reading abnormally high, i actually had a conversion chart to compare it to the correct engine RPM. I had an extra gauge set I picked up years ago so i pulled the tach out and put the other one in and tRMP's are reading correctly now. There is a write up on this forum somewhere about fixing the issue with the tach, sounds like it is a common problem. I resisted the urge of rolling back the odometer to zero when i had it open, I did roll the spare one back just because.