Overheating problems. 7M-GTE

[7mSupra]

As a few of the people on here, im having heating problems as well.
It a MA70 supra with a fresh built motor.
Car runs fine for the first 30 min. then the temp starts rising really high.
All my timing on the engine is fine and a brand new water pump.
I took out my thermostat thinking it was sticking but the same results.
Any idea guys?
Cheers!

[Yian]

Have you had your radiator reconditioned? Or at least cleaned? It's amazing how clogged they can get over time.

With a freshly built motor, new water pump and you've ruled out the thermostat, that's the only thing I can think of.

Unless of course, the head wasn't torqued down properly and you've suffered the dreaded BHG.

Yian

[7mgte mx73]

Only other thing I can think of (besides what Yian said) is whether there are any air "pockets" not purged from the cooling system?

[Jackel]

i think his radiator is brand new and from what i saw the head was torqued down properly

[Joorsh]

Are you losing coolant? Is it feeding back from the overflow bottle properly?

Either way and BHG's aside, make sure you're running a propper thermostat. Running no thermostat is a bad idea, and I have heard of that leading to erratic temperatures. Get your hands on a TRD one ideally.

Next, check your radiator cap. The spring in it might be gone. I'd recommend upgrading to a 15-16 psi cap anyway.

And lastly, bleed the coolant system properly. You will need coolant and a garden hose. A mate to help you is handy, but not vital.

1) Park on an upwards incline (radiator filler as high as possible)

2) Take off the radiator cap (you'll be wanting the car to be cool at this point)

3) Turn on the heater inside the car.

4) Start the car up, giving a little bit of a rev until it gets up to temperature - or at least close to temperature.

5) Remove the inlet hose for the rear heater core - make sure there is no air trapped back there. You might need a screwdriver to jimmy under it because the little bugger sticks. Here's a pic to help - you'll want to be removing this hose:


6) Put the hose back one once you're sure there is no more air back there - try to avoid trapping big air pockets when you re-attach the hose. You can get your mate to use the garden hose and douse it all in water as your re-attach it, to help stop any air getting back there.

7) Top up overflow bottle to about 80% full with coolant.

8) Top up radiator with coolant if required.

9) Continue to run for about 10 more minutes while revving. Check for air bubbles or oil in the radiator filler neck. If bubbles continue to rise indefinitely through the filler neck, or if oil continues to collect, you may have a BHG.

10) Put the rad cap back in and you're done.

[7mSupra]

Thanks for that advise guys. Ill put in a new thermostat in and bleed the cooling system as soon as i can. My Radiator in fairly new along with my radiator cap. Unless theres some mudd and other crap in my radiator left over from the previous engine.
Would my car start overheating if there were any issues with my intercooler or inlet piping?
Im also running in the motor so its not like im thrashing it.
Thanks!

[Joorsh]

Are you running an aftermarket ECU/tune?
Sometimes a bad tune can cause overheating too.

[ed]

my money is on air pockets - fricken 7m seems to have the temp sender in the worst place for these things

[7mSupra]

I dont have any sensors on the heater hose attachment. Mine is Black and says denso on it. I am running standard tune and standard computer. Car had just been at the efi shop been checked over for all the sensors and all the timing. Ill try bleeding the system again tommorow. Its just weird how its running normal temperature for about 30-40 minutes then it starts overheating.

[leso]

Do you have the correct radiator cap for your system...does your car have a overflow bottle..if it does the radiator cap should have two seals.........

leso

[RyleyMA61]

when the temp sensor reads high, is the engine actually getting hot? other than perhaps bleeding the system? you've probably heard all this before...

my 7mgte with metal head gasket had minor heating issues- turned out to be it's 2nd BHG... hopefully you do not suffer the same fate!

good luck

[doobs]

ryley, Did you blow a metal headgasket? I'm looking at getting a mz20 soarer very soon, with a 7m-gte, while I have budgeted to replace the head gasket with a metal one if it goes, It would be damn annyoing to blow a metal HG

[cressida_1jz]

Im going for a blocked radiator or crap between the a/c condenser and radiator.

Even though its a new radiator,this can happen within a month or so.

Maybe the motor wasn't washed out properly when the radiator was replaced last.

[Hydra]

Air pockets are a pain... they are the reason I hate playing with the cooling system on my car!

As soon as I can i'm going to get my radiator reconditioned since it has developed a pinhole leak in the top tank, and it is probably all clogged up from years of use.

[RyleyMA61]

ryley, Did you blow a metal headgasket? I'm looking at getting a mz20 soarer very soon, with a 7m-gte, while I have budgeted to replace the head gasket with a metal one if it goes, It would be damn annyoing to blow a metal HG

yeah. the previous owner blew a headgasket, which he got fixed, then it blew again, so he put in a metal headgasket.

car has no mods bar a full 3" exhaust, dump and hi flow cat.

i drove the car home (adelaide to ballarat, around 700kms) last feburuary and it temperature spiked about 100km from home. it then slowly blew the metal headgasket.

took the car to my mechanic down here, and he said there was a bit of dirt between the head and metal gasket, which contributed to it blowing... the stock bolts had also been re-used. :S

i've since had it replaced with a stock gasket, aftermarket bolts and reconditioned head, and it's been good as gold. boosting around like mad, never even thinks about getting hot.

as always, just make sure you get the head polished and finished dead smooth, and checked for cracks etc. Also get the block machined dead smooth, and get aftermarket head bolts (arp etc. torqued to 72ft./lbs.) if i had my time again i'd spend the extra $500 i didn't have and get another metal one.

i also had a 'running in' period on my headgasket- no boost for 500kms, then in for a retorque, then no more than a little boost for 500kms, retorque, then good to go. a nice saftey precaution. my mechanic also thinks my new headgasket should be good for about 11-12psi, and thats a 'safe' limit....

we shall see soon!

good luck with the 7m mate.

[doobs]

yeah. the previous owner blew a headgasket, which he got fixed, then it blew again, so he put in a metal headgasket.

car has no mods bar a full 3" exhaust, dump and hi flow cat.

i drove the car home (adelaide to ballarat, around 700kms) last feburuary and it temperature spiked about 100km from home. it then slowly blew the metal headgasket.

took the car to my mechanic down here, and he said there was a bit of dirt between the head and metal gasket, which contributed to it blowing... the stock bolts had also been re-used. :S

i've since had it replaced with a stock gasket, aftermarket bolts and reconditioned head, and it's been good as gold. boosting around like mad, never even thinks about getting hot.

as always, just make sure you get the head polished and finished dead smooth, and checked for cracks etc. Also get the block machined dead smooth, and get aftermarket head bolts (arp etc. torqued to 72ft./lbs.) if i had my time again i'd spend the extra $500 i didn't have and get another metal one.

i also had a 'running in' period on my headgasket- no boost for 500kms, then in for a retorque, then no more than a little boost for 500kms, retorque, then good to go. a nice saftey precaution. my mechanic also thinks my new headgasket should be good for about 11-12psi, and thats a 'safe' limit....

we shall see soon!

good luck with the 7m mate.

Thanx for that dude, very informative

[RyleyMA61]

no worries, hope it helps

[7mSupra]

Thanks for the help guys i took it down the radiator shop and it was in fact my radiator that was 30% blocked. Runs good now.
I have one more question about retorquing my head.
Since the rebuild i have done about 850km of sensible driving. When is it time to retorque the head? I have APR bolts ect.?

[Yian]

Thanks for the help guys i took it down the radiator shop and it was in fact my radiator that was 30% blocked. Runs good now.

Woo... I was right

[RyleyMA61]

i'm pretty sure if you want to use new bolts you'll need to pull the head off again, so you'll need a new gasket and machining etc.

perhaps you could retorque the stock bolts whilst leaving the head on, and see how you go? if/when it blows next you could put the aftermarket bolts in...

but i'm sure someone more knowledgeable will help you out...