My cooling system is acting strangely, and I am running out of ideas. It all began when I noticed my temp gauge going up and causing my A/C to shut down.
(Earlier thread: https://www.yotatech.com/forums/f116...s-down-122042/ It has a new waterpump and recently installed Toyota thermostat)

After carefully observing in all driving situations, here is what it's doing:

Starting out cold, the engine warms up to normal temp after driving a couple of miles. By the time I've gone 5-6 miles (A/C is on -- it is August in SC), the temp gauge begins to go higher than norm, to about halfway between norm and hot. Next, one of two things happens.

First, if I continue driving it stays there between normal and hot for several miles. It doesn't go all the way to hot, and eventually after driving several miles it will begin to drop back to normal.

Or, if when I see it going toward hot I pull over, put it in Park and rev the engine to about 2K rpms, it drops back to normal within 30-45 seconds.

Note that either way, once it has gone through this cycle of going toward hot and dropping back to normal, it STAYS normal through the rest of my commute/drive. Also, this is happening whether the outside condition is 75 and raining or 95 and sunny. It happens with or without the A/C on, just happens quicker with the A/C on.

This is driving me crazy! But the consistency with which it does this has got to mean something -- maybe someone here can give me some new ideas.

 

[edit]

I re-read the post carefully..

22REs used to do that hot over shoot all the time.

There was a thermo mod to "correct" this problem.

 

Might try running without a thermostat and test that out. Since Toyota t-stat gaskets are part of the t-stat don't just remove it but do something like this:


Or try a cooler t-stat.

It does sound like something is closing your t-stat (like maybe your oil cooler flow or something).

It would still be nice to find out with a real gauge what your temps are. Are there any other signs of it getting too hot or are you just going by that factory temp gauge.

 

what does your radiator look like on the inside?

 

I'm going by the factory temp gauge. I'm not loosing any coolant, and the inside of the radiator looks fine.

Could the thermostat keep repeating this cycle so predictably? It's so weird how it will stay at normal, then go up, then come back down and stay normal.

If I remove the thermostat and run it, it should not get up to operating temp, right?

 

Is your fan clutch operating properly? Just my $.02.

 

Pretty certain it is. It was replaced when the head gaskets were done about 6 months ago.

 

That depends on how cold it is outside, in hot weather it will still get up to temp. But it will eleminate that as a possible source of the problem.

 

Sympathies, been there myself...

I know there's the mod to fix things, but I also remember doing all that, just to find out it was a partially plugged heater and radiator core.

Definitely make sure if you havn't within the last 5 years to first check out the cooling system, and make sure they're not filled up with deposits.

 

So you had a similar problem, and it was a partially plugged system?

What is the "mod?"

 

Have you checked the fins on the radiator? I've had the problem where there was just a ton of junk stuck in the fins and that was causing my over heating issues. I ended up having to blow it out from the back side. Just a thought? You should be able to see through the entire radiator.

 

Pull the radiator.
Take it to a Reputable radiator shop and have them rod it out.

Sediment in bottom tank, plugging up the coring. Maybe they can clean it out, maybe they won't be able to.

If they can't clean it out, buy a new radiator.

Flush the system, start over again with distilled water [from the grocery store ] and proper amount of anti freeze. 50/50 mix.

 

The "mod" is to drill a bleed hole into the thermstadt and adda "wiggle bar" so keep bubbles from blocking the bleed hole

Rodge Brown has pics of an OEM one that has the mod.

BTW - the thermostadt "pumps" as the car warms up.
I used to have a low temp autometer guage attached just next to the thermo and you could watch it cycle as the the car warmed up....

 

New Question:

Should the auxilliary fan (the electric fan in front of the radiator) come on ONLY when the A/C is on? I notice that mine is shutting off when the temp rises and the A/C shuts down.

 

I believe that's the way its wired, you could always rewire it to some kind of controller with a temp sensor too. (Like a Hayden 3647 controller)

 

I would definately go into that next. Radiator r&r, plus inspection/cleaning and/or replacement.

The a/c would put additional heat into the system to cause overheating to happen faster.

Missing or damaged fan shroud (even the plastic strip on the lower portion) would make things worse too.

If the rad and all check out fine after servicing, I'd try another (genuine toyota) thermostat and see what happens. I wouldn't try removing it, as the thermostat directs water flow thru the rad when it's open. A missing thermostat doesn't do that, and can contribute to localized overheating.

HTH.

 

Huh.... what???? You know the t-stat is on the return side of the radiator right?

 

I think its your thermostat. Relatively cheap to change out. Get one from the dealer. It may not be performing as it should but sill kind of works. If engine never cooled down you would have a radiator or fan problem. Temperature spike from ill performing thermostat is what is showing up on gage and shutting down AC. Go for the T-stat.

My $0.02