Overheating question, sort of.

[frank]

I got such good info on my last question I figured I'd try another!

1990 turbo supra, A/T, stock.
When the weather warmed up this summer overheating problems reared their heads.
What I did: New fan clutch, (tundra orange hub) rad re-core, new 180 thermostat, new 13psi cap, and while I was at it I replaced all hoses that looked funky, especially those ones you can't get at easily.
The rad I had re-cored was the one that was in the car when we got it, and it is not stock, it's a brass tanked two row job.
There is no auxillary trans cooler, just the one in the rad.
The air conditioning does not work, so there is no extra heat load there, and I've straightened fins/ cleaned core on the condenser and IC.
The head gasket does not leak, the car loses no coolant.
The fan shroud and engine undercover are there.

The above listed repairs dealt with the heat problems, mostly.
The reason I say mostly is because there is a hilly road I use for cooling system testing, and the car still fails on it. The road is two lane, very steep, long, and full of hair pins. So, lower speeds, on and off boost, but more on than off. After about ten minutes of this the temperature starts to climb.

It's a piss-off pulling over to cool while watching rusted out old chevys with V8's cruise by pulling hard with no issues. I'm considering getting the biggest aluminum rad I can stuff into the thing, but instinct tells me I'm missing something; the car should not overheat on an 80 degree day in stock configuration with stock cooling system.

What I'm looking for is someone's real world experience with a similar car in a similar situation.
In the owners manual they tell you to avoid long periods of boost or risk overheating, however I do not see how you can avoid long periods of boost on a road like the one I'm using as a testing ground.

 

[boost fiend]

how old is the coolant? did you burp the system well?

heres another option, stop by a advanced auto parts and pick up a bottle of water wetter. its a pink additive that drops temps really well. ive used it and it works great.

also, you mentioned a/c. ya still have the a/c fan installed? try running a toggle switch to it and use that to help with heat spikes.

 

[johnathan1]

My gut instinct tells me that your radiator isn't cooling properly...maybe it's too small? Anyway, a bigger radiator definitely wouldn't hurt.

Does the cooling system become pressurized when the engine is warm? Or is the upper radiator hose limp? (it should be firm)

That is very strange...My car is a stock 87T 5-Spd, with cheap $45 fan clutch, autozone radiator, Toyota cap and thermostat, with no undertray, and I was just out earlier driving around in stop and go traffic with the A/C on full blast and it's about 90 out... Guage didn't even fluctuate at all...

Also, I keep getting bubbles in my cooling system...and it still doesn't overheat at all...I would imagine that the amount of air in the system wuld have to be huge to cause overheating problems...

edit: Beware of that A/C fan mod...I did that to my car, and it caused an electrical fire when I had the fan switched on, with the A/C on at the same time...

 

[frank]

Sorry, should have mentioned coolant, flushed, new 50/50 coolant mix. The cooling system has no air in it. I do have the fans, and they seem to come on of their own accord when the temperature climbs slightly above half on the stock gauge.
I havn't seen an advanced auto parts in my part of Canada, but I'm sure that some of the local auto parts places sell water wetter.
Like I say, it's really only this one place (which I use for testing, because it's a workout) where the car has trouble.
It did heat up a bit once on the highway coming out of Kamloops, BC, in that case, 100+ degree day, and about 15 miles of steep upgrade, once again, lots of boost. In that case I was able to keep the temperature under control with the heater. It's as though the system is almost good enough, but not quite. I would have thought a two row brass rad would be a step up from stock, maybe not.
I'll track down some water wetter and give it a try.
I may pull the pump and check it out, although I doubt if that's the issue, it seems to be moving lots of coolant. (Good pressure surge if I squeeze the top hose.)

Perhaps I'm just not used to turbo charged cars. That's what I'm trying to determine really, is whether I'm just expecting too much, or whether I really have a problem.

My jeep has a much lower specific output, and is N/A, and I can run it at WOT as long as I want without the temperature climbing at all. It has a two row brass rad as well, and it holds about a gallon more coolant. I'm wondering if the supra cooling system is just a bit marginal to start with.

Edit, Jonathan1, you posted while I was posting. The car has no trouble with sitting still/stop and go, I think it could handle that all day long, the stock gauge needle sits just under half in that kind of situation, and under all normal driving, it's just when it's pushed hard for an extended period of time that it seems as if the cooling system just gets heat soaked and says "enough".
System holds pressure perfectly, tanks were boiled clean, new core installed. The rad is as good as it can be, it's effectively new. Size wise, it's a perfect duplicate in metal of the stocker, as far as I can tell.

 

[xarewhyayen]

The temperature shouldnt climb. Ive had problems with a bad hg putting exhaust in my system and i still ran well without any real fluctuation on a 45 mile trip to school each day in 90-100 degree heat. Maybe try a compression test to be sure you arent leaking any exhaust into your coolant. If not, id just get a stock radiator... its proven to work or else it wouldnt be oem. The stock cooling system works plenty fine as is if there are no other operating problems within the car itself.

 

[frank]

I think maybe I'm not making the problem clear.
The car passes compression test and shows no sign of BHG, though I havn't done a coolant system exhaust gas test. (There's a specific name for it, it escapes me at the moment.) It has a felpro head gasket tourqued to 72 lb/ft for whatever that's worth.
The temperature will sit steady as a rock just below half on the gauge all day long. I drove the car 1500 miles straight through (stopped for gas and meals)in 22 hours, hitting sustained speeds of 100 mph in places and the needle never moved.
However this sustained extremely steep winding grade for a couple of thousand feet near my home will make it heat up. It wouldn't make it heat up if it was at highway speed, there would be enough airflow to keep it cool then, and it won't make it heat up if I keep the boost down, but it heats up if I drive "spiritedly", boost hard, brake for the corners, boost again.

Other than that the only time I've had a problem after fixing the cooling system was, as I mentioned, on a very hot day on the Coquihalla highway leaving Kamloops, it's 12+% I believe, and goes on for miles and miles and miles. Lots of boost for many minutes.

I picked up some redline water wetter, they claim it will lower coolant temperature by as much as 8 degrees F. (50/50 mix, 20 degrees with straight water) Can't hurt to try. I'm thinking I might go and get a BHG coolant test kit as well, in case there's a small issue there. Seems unlikely with the miles I've put on with no worsening of the problem, but who knows...

 

[frank]

Unfortunately water wetter wasn't a mircle cure...
Took it for a run up the devil's hill and it did it's usual. As soon as the temp climbed over half I pulled over and popped the hood while it idled and cooled.
All three condensor fans running, clutch fan engaged, lots of pressure in the system.
Overflow/expansion tank filled about 2/3 full, no bubbling going on in there.
I have a hard time believing it's the rad, the rad is beautiful.

That leaves combustion chamber leakage or water pump problem.

I priced out the test kit at my local NAPA. $70 Canadian and they have to order it in. I told them to hold off a bit.

Can anyone tell me what the water pump impeller looks like? Is it a steel stamping or cast aluminum? I'm tempted to pull the damn thing off and confirm that it's all there, but then I'd have to come up with a gasket. I'll probably pull it anyway, this is pissing me off.

The PO rebuilt the engine, (about 25000 miles ago) and he gave me the old head with the car. The head had to be replaced because the water jackets were corroded. I'm starting to wonder if the damn pump is all eaten up inside and just doesn't pump enough when the going gets tough. I have bills from the PO for lots of stuff, 13 years worth of stuff, but not for a water pump.

 

[Yellow 13]

Take the water pump off then. You can use FIPG to seal it if you cant come across a gasket.

Check for debris between the AC condenser and radiator. Youd be surprised what a few leaves can do.

 

[frank]

Take the water pump off then. You can use FIPG to seal it if you cant come across a gasket.

Check for debris between the AC condenser and radiator. Youd be surprised what a few leaves can do.

Yah, that's a point about the FIPG, I just hate to do it because it makes cleanup harder next time, however... one does what one has to.

I cleaned what little debris there was out and straightened all the bent fins on the condenser when I had the rad out for it's recore.