Overheating Problems Continue - I'm out of ideas.

[TravisD62]

Hey guys,
I posted up not too long ago because my car was overheating badly. I just changed the rad hoses, and installed a new radiator + cap and I'm still having problems. The car doesn't have a BHG, I've tested the fluids for exhaust gasses, the compression is perfect, and it was recently rebuilt with an HKS MHG and ARP's. I've replaced the upper and lower rad hoses, rad cap, radiator, thermostat, coolant temp. sender, flushed the system, burped it, and installed a new fan clutch. None of this has had any effect whatsoever on the overheating. Things I've noticed about it -

- It seems to take quite a while to overheat : at least a good 30min. of driving
- The radiator is always low on coolant, the overflow tank is always full
- As soon as I fill the radiator back up, the overflow sprays coolant everywhere as soon as it heats up
- The upper rad hose can be squeezed HARD and it holds pressure
- System doesn't seem to be building vacuum pressure or pulling coolant back into the rad when it cools off
- Car runs, drives, boosts, and pulls great
- Overheats the worst when the engine is under load, even the slightest bit of acceleration will make it peg the red, even on the highway
- My heat has stopped working

I'm thinking there's a connection between the heat not working and the car overheating. I didn't realize this as I haven't even attempted to turn the heat on in the car since I've installed the new turbo, but I do remember the heat working perfect before, and the car didn't overheat at all. My big concerns right now are that I REALLY don't want the car to overheat again, it's pegged the temp. gauge too many times as it is and I don't want to kill my new motor. I'm really curious if this could be the heater core or something perhaps? I just hope there's an easier way to test this out before I rip the dash apart to pull it out, because I really, really, really don't want to do that if at all possible. If i were to connect the two lines running to and from the heater core together, this wouldn't harm anything, and would tell me if this is my problem right? Thinking I may try that tomorrow, but I'd like reassurance that this entire idea is even plausible. Any ideas, suggestions, or whatever would be greatly appreciated. Sorry for the essay,
thanks.

Travis

 

[CyFi6]

Are you sure the head and block were prepped properly? Were the studs torqued properly? Were they re torqued? When I had a bad BHG it didn't show on the block tester. As soon as I did a leakdown test, it was clear as day, radiator started to overflow water with the cap open and pressure in cylinder 5. Sure sounds like a BHG, but have you checked your hose that runs from the radiator to the overflow bottle? Even the hose from the overflow cap to the bottom of the bottle. Any leaks in this will cause the system to draw air back into the system when cooling off. Pressure test on the cooling system will tell you right away whether or not you have a leak somewhere.

 

[TravisD62]

From what I've been told, and from the receipts everything should have been done correctly. Studs were re-torqued before the overheating began, and both those little hoses are fine... I would like to do a leakdown test, but don't have access to a tester. If it were a BHG wouldn't the exhaust gas test come up positive? I don't really know how else to test anything right now, can I pressure test the cooling system some other diy/macgyver sort of way? If I really have no other option I'll go buy the testing kit myself but I'd rather not if possible because I'm waaaaaay over budget.

 

[mk3_7m]

are your radiator fans turning on? and hows the condition of your water pump? also is your over flow tank boiling when it sprays out coolant when it gets hot?

Usually (as a thumb rule) if you can't hold your upper radiator hose for more than 10 seconds from heat your fans should switch on. You might wanna check your thermostat again if it ain't stuck open. From my experience with my new engine as well when I replaced the water pump after all the other methods I attempted to do (thermo stat, radiator etc) Temp stopped spiking.

 

[TravisD62]

Water pump is new and oem Toyota, fans are all turning on and working properly, and from what I have seen the coolant in the overflow isn't boiling... I just did a leak down test on the car and these are the numbers I got, motor was cold when I did the test, but I don't have any other way.

1 - 25%
2 - 32%
3 - 22%
4 - 25%
5 - 23%
6 - 23%

I really don't know how to interpret these results... does this point to a bhg?

 

[mk3_7m]

Usually the results interprets the percetage of leakages.... an engine in great condition is about 5 to 10% leakage. more than 30% leakage indicates trouble.

 

[TravisD62]

A BHG would cause a pretty huge leak percentage though wouldn't it? i know my valve stem seals are shot, perhaps this is contributing? jfkdhsljkfd I really have no idea anymore, what else can I really do to confirm if the car has a blown gasket or not? It seems the only sure fire answer is to visually inspect it!

 

[mk3_7m]

It could be possible that your heatercore might play a role (but I wouldn't count on it)
You did mentioned about your heater not working anymore??
I think you have a possessed supra

If worst comes to worst I reckon ripping the head off would be the last resort.

 

[Devin LeBlanc]

It might not be a blown head gasket (pretty much impossible with a metal head gasket) Might be a leaking or not sealed properly.

I don't tell many people to do this much because I will get bashed by everyone but take your thermostat out and use RTV on the water neck, put the car in the driveway so the engine is the highest point and refill the coolant. To me it sounds like there is air in the system. If this fixes it, get a new thermostat and re burp the system. I have had tons of people have issues burping the 7M cooling system properly.

I personally don't run a thermostat, However everyone here will tell you to. However I have reasoning behind and a Mechanical and fluid engineer that will tell with the type of water pump the more flow the better. Ill have him write it out some time and maybe get it sticky'd!

Let me know if that fixes it. This is what a blown head gasket looks like. See how the fire ring around the cylinder is egg shaped instead of perfectly round. Pushed right over the cooling passage in the block and exhaust gases leak right through.

Is impossible for a MLS metal head gasket to do this

Im betting its a improperly burped system. Removing the thermostat will be a very easy way to tell as you don't have to burp the system.

 

[TravisD62]

That makes perfect sense, I guess I really couldn't properly burp it either considering my heater doesn't work. I unfortunately pulled the turbo out today, and have been tearing into the motor so I won't be able to check that.. I need to change my valve stem seals, so I'm just going to do it the hard way and pull the head off. I'll be sure to update this as soon as I know what's really going on!

 

[TravisD62]

Sorry for all the questions, but am I going to run into any issues removing and then reinstalling the head? I think so long as I make sure everything is clean, and i clean off the mhg, reusing it and my arp's won't pose any problems?

 

[Devin LeBlanc]

What order did you loosen the head studs in?

 

[mk1spyder]

It doesn't sound like a BHG, you need to burp the system properly. You have a huge pocket of air in your heater core and probably in the block too.

Park it facing up on a big hill so the radiator cap is the highest point in the system, fire it up and let it get hot with the heater on full blast. If it doesn't start blowing hot air by the time the engine gets hot shut it off and open the radiator cap with alot of rags between your hand and the cap. Very slowly crack it until you are just allowing pressure but not coolant out and hold it there until all the pressure/steam works its way out. Watch out the rags can get really hot and it isn't exactly the "correct" way to do it but it works. After you let all the pressure out you'll be left with a somewhat empty radiator, fill that beast up and ur ready to go. Fire it up again and the heat should blow hot.

 

[Poodles]

Sounds like a pinhole leak somewhere, and/or bad radiator cap.

 

[TravisD62]

I realllllllllly hope you guys are right. I just ordered a new coolant hose set, another rad cap, and the driftmotion 67mm turbo kit. I'll bolt all this up, run through EVERY coolant hose and change the coolant again. Hopefully this fixes it!

 

[toyotanos]

FYI, I lifted my head on the exhaust side and did a cold leakdown test- came up with 25-35% across the board. I knew there was a HG issue so I did a different type of leakdown test. I used a compression tester adapter and remove the schrader valve, rolled the engine to TDC on each piston, hooked the adapter to an air compressor, and looked to see if it bubbled out of the cooling system. Since it did on all 6 cyls, I knew I had completely blown the HG, but even if 1 bubbled it needed to be torn down.

 

[IBoughtASupra]

You should get one of these, turn the heat on, male sure the heater valve moves, fill the cap and put the front on jack stands.

These things work very well to bleed any system. Keep squeezing the upper and lower radiator hose. I used this many times without even jacking up the car.

First time a mechanic showed me this kit, I was like :O.

http://www.denlorstools.com/home/dt...funnel_kit_wext.html?rid=base&source=googleps

 

[caballo]

Hey guys, hows it going? I am having some similar problems too.. whenever I drive on the freeway for about 15 min the temperature gauge needle sits at a little less than half way. As soon as i exit the freeway the temperature gauge needle goes a little bit above half way. It eventually returns to a little below half way. It doesn't over heat though. I just don't know why the temperature gauge needle rises and lowers. Being a turbocharged vehicle is this normal? Or do i have some air bubbles trapped or something else? I have a brand new thermostat and radiator cap. I have yet to do a coolant flush.

 

[toyotanos]

You should get one of these, turn the heat on, male sure the heater valve moves, fill the cap and put the front on jack stands.

These things work very well to bleed any system. Keep squeezing the upper and lower radiator hose. I used this many times without even jacking up the car.

First time a mechanic showed me this kit, I was like :O.

http://www.denlorstools.com/home/dt...funnel_kit_wext.html?rid=base&source=googleps

I agree, an absolutely essential tool to have if you ever work on a car's cooling system. Works like a dream

 

[suprarx7nut]

So many things to say...

First off, as a mechanical engineer myself, I would love to see the rationale behind devins thermostat-less ideology. The thermostat is in charge of maintaining the correct engine temp. Without one, the engine could run too hot or too cold. If the radiator is too efficient it will keep the engine too cold. Running too cold is just as bad as running hot. Removing the thermostat entirely could potentially allow the system to pump to fast. The coolant may need more time to cool down in the radiator. Remove the thermostat and you could possibly run coolant too fast by the radiator to ever cool. Like I said, I'd love to see this engineer's rationale.

Second, you could certainly have a bad head gasket install. If it wasn't torqued right, or wasn't machined correctly that would certainly cause bhg symptoms. Devin: a "bhg" is simply used to denote a non-sealing head gasket. While a mhg may not "blow" like the composites do, you can most certainly have a non sealing mhg which acts just like the common bhg.

Op: if you install an mhg on anything but a freshly machined head, you're risking it. Mhgs are intended for fresh builds and nothing more. If you've put appreciable mileage on the head/block you may want to consider pulling the whole thing.

You'll also need to check if they machine the timing plate with the deck.

A bhg won't always throw a positive on the chemical exhaust gas test.

A leaking heater core may cause some of your issues, but you'd notice a bit of coolant collecting under your carpet behind the dash, in the cab.

I almost like devins idea of running without a thermostat just to check for overheat due to a stick thermostat. Better yet, take an old thermostat and remove the inner parts so it allows constant flow.

I'm sure there's more to add, but that's about all i'll add from my phone, lol.

I also thinks its hilarious you've ordered a bigger turbo kit while already "over-budget" on your build and still not having a solid, reliable motor with the stock turbo. Don't let the need for power overtake your common sense.

Oh! And a cooling system tester is available at most any parts store. Free rental, assuming you return it and it'll help a ton with your hunt for the problem.


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