Need help with a overheating issue. out of ideas...

[Subcept]

Hello, just got my first supra last weekend, I'm extremely excited, lots of big plans.

so it overheats. according to the previous owner this started shortly after he installed a new HG, then he parked it. its the 2nd 7M GTE engine in the car, came from japan with about 60k on it, and about another 20 since the swap. it also has a new radiator, new radiator cap, new water pump, and a previously removed thermostat.

here is what happens. car can start, warm up, and idle and the temp stays in the middle of the gauge. the birdcage and engine check lights are on at all times. radiator and overflow both show full / normal fluids. fan clutch seems fine. I bypassed the VSV valve that stops coolant from going to the heater core when AC is on, and now the heater blows hot.

after the bypass today, I took it for some hot laps around our facility, seemed fine, temp gauge stayed in the middle. parked and let it idle for 10 min while playing with some other stuff, went for 2 more hot laps and the temp gauge shot up to red in about 30 seconds, and heater stopped blowing hot air. it was definitely overheating, not a gauge malfunction. I stopped and let it idle and in a couple min it was back in the middle. Also when I pinch the hose going to the radiator, I can feel coolant moving through it (didn't try to do this after it started to overheat however, it was hot)

I'm out of guesses as to what it is. I want to try and flush the system tomorrow, and am about to go read up on the best way to do that.

its also only making about 4lbs of boost, with a newer factory turbo, but thats probably not related, and I have new turbo goodies on the way.


Any help or ideas would be greatly appreciated, I'm starting to get frustrated.


thanks in advance!
~Steve

 

[87CandyBlueT]

First of all do not run the 7m without a thermostat.

 

[Subcept]

First of all do not run the 7m without a thermostat.

its on my parts store list. car came that way, and my first priority is to fix the overheating.

I'm trying to learn as much as I can about this engine, (have only had the car 3 days) could the lack of thermostat be contributing to this? previous owner said he removed it and ran it that way for a while, before this issue started.


one more thing. I tried to purge any air out of the system, however, with the radiator cap off, when I started the car, it just started steadily flowing coolant out of the top of the radiator (due to lack of thermostat?) I'm praying that the new HG wasn't improperly installed, however oil and coolant look fine.

 

[jdub]

Simple things 1st

- Get a thermostat in there...Toyota or Stant SuperStat.

- Check/change your rad cap

- Get the air out of the system...fill the rad every time it goes through a heat cycle (heat up, cool down)...do it from the rad cap not the coolant bottle. Keep the coolant bottle half full.

- Check your fan clutch...it should howl for about 33-45 sec when the car is 1st cranked, then quiet down. If it does not do this, the clutch is bad.

- Get the coolant system pressure tested for leaks.

 

[jetjock]

A fine example of false hope if I ever saw one

 

[Idealsupra]

why not just bite the bullet instead of throwing parts at it....and just do a compression test FIRST. its not hard to do and will give you a lot of information.

 

[IJ.]

10,9,8,7,6........

 

[jdub]

Yeah, but for $20 + Pressure test cost you know it's not the cooling system. A Napa Block test just might be on the agenda as well
Needs a thermostat anyway.

 

[jetjock]

"However I still stand by my statement that 99 times out of 100, the weak link in the MKIII is the previous owner."

Fixed

 

[jdub]

LOL!!!

:runaway:

 

[PROJECT N00b]

Or you can just change your radiator, maybe the thing is clogged up.

 

[jdub]

Said it has a new rad...at least that's what the previous owner told him

 

[Subcept]

rad cap is new, fan works fine.

getting thermostat tomorrow, then I'll jack the front of the car up and try to burp the system.

its not visibly leaking, so what would the pressure test tell me?

engine compression is fine, I've tested that.

90% of my automotive knowledge is water cooled VW, so bear with me as I adjust to the supra and ask some dumb questions

 

[PROJECT N00b]

ok nvm about the radiator change.

 

[Subcept]

Said it has a new rad...at least that's what the previous owner told him

previous owner is a co-worker I've known for years. he may not be the smartest guy, but he's honest.

 

[jdub]

Well...what Ideal is getting at and what I was trying to avoid jumping on right away is a BHG...it has the attributes :3d_frown:
Don't mean to bash your co-worker, but there's been too many insistences of people selling Mk III's knowing there is a likely BHG...why do you think it has a new rad and no thermostat?

A coolant pressure test will tell you if you have air leaks in the system...these may not be apparent. The Mk III does not tolerate air in the coolant system well at all. But it also seems that most of the common problems are covered...a coolant pressure test will confirm that. Ideal's suggestion is a good one...do a compression test on each cylinder and it will tell you if you have a major problem.

 

[Subcept]

I've compression tested the engine, and its 150-155 on all cyl.

the overheating began after he put in a new HG. the thermostat was removed for some dumb reason long before all this.

there isn't much for automotive shops near my shop, with the overheating and old tabs I'm limited to how far I can take it. hopefully a new thermostat and a good burping will fix it tomorrow, if not I'll figure out a place to test it.


thanx for all the info, any other ideas?

I'll update tomorrow

 

[MDCmotorsports]

Im wondering if the block & head surface was ever redone and or if the bolts were retorqued over stock ft-lbs.

If not, then Id say you may have a BHG already.

 

[Subcept]

Im wondering if the block & head surface was ever redone and or if the bolts were retorqued over stock ft-lbs.

If not, then Id say you may have a BHG already.

to re-cap, the consensus is that my overheating is caused by air in the cooling system, and not from another issue? and the air could just be stuck in there, or it could be continually coming from either a system leak or a BHG? since it flows well, blows heat initially, I thought there may be something in the system thats intermittently clogging, but the air makes more sense.

 

[jetjock]

I'll cut to the chase: You have a BHG. I guarantee it. Compression testing often won't reveal a leak at this stage. You can either get a coolant test kit or try injecting each cylinder at TDC with shop air while listening at the radiator. Pay particular attention to number 6. It isn't going to change anything though...someone will be taking the head off.