85 2m4 SE / 2.5 Temperature Issues (Page 2/7)
82-T/A [At Work] NOV 12, 09:00 PM
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.
sleek fiero NOV 12, 09:07 PM
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
82-T/A [At Work] NOV 13, 06:42 AM

quote
Originally posted by sleek fiero:

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).]

Dukesterpro NOV 13, 09:36 AM
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
82-T/A [At Work] NOV 13, 10:28 AM

quote
Originally posted by Dukesterpro:

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...
Dukesterpro NOV 13, 10:57 AM
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
82-T/A [At Work] NOV 13, 11:01 AM

quote
Originally posted by Dukesterpro:

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 will do that. Thanks!
82-T/A [At Work] NOV 26, 05:52 PM
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?
Patrick NOV 26, 06:17 PM

quote
Originally posted by 82-T/A [At Work]:

...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".
82-T/A [At Work] NOV 26, 06:25 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".




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...