overheating, I'm stumped. Options

[94GT]

and no, I can't blame toyota for my koyo radiator leaking, but I can blame toyota for my toyota radiator leaking which is why I bought the koyo radiator to begin with. on top of all the other things that have gone wrong with the car. I dunno. maybe just because the car is 13 years old with 154,000 miles on it...

13 years for a radiator that has plastic reservoirs is quite good. You're not going to find a domestic that has a radiator that lasts that long... You just have to remember that even with a car as superior as a Toyota, there are some parts (like timing belts and water pumps) that have a limited lifespan.

[Manny]

and no, I can't blame toyota for my koyo radiator leaking, but I can blame toyota for my toyota radiator leaking which is why I bought the koyo radiator to begin with. on top of all the other things that have gone wrong with the car. I dunno. maybe just because the car is 13 years old with 154,000 miles on it...

13 years for a radiator that has plastic reservoirs is quite good. You're not going to find a domestic that has a radiator that lasts that long... You just have to remember that even with a car as superior as a Toyota, there are some parts (like timing belts and water pumps) that have a limited lifespan.

+1

you did purchase a car with 140k+ miles on it..... depending on how well cared for it was before you got it... its about due for some of the wearable parts to start getting swapped out....

[alltracman78]

^
exactly

We had a guy come in with a Camry he bought new. Had 2x,xxx miles on it.
The engine had seized on him. He expected a warranty claim.

Until we found out he had NEVER changed his oil since the day he bought his car.

"It's a Toyota, I shouldn't have to change the oil"......

[hatchy_gt-s]

It sounds more like you have an air pocket somewhere in the coolant.
It certainly won't hurt to replace the therm just in case though.

After you replace the therm, put the front of your car up on jackstands SECURELY so it won't fall [this includes pulling the ebrake] and let it run with the rad cap off. Keep topping off the coolant if it drops. Keep your heat on full the whole time.


Also, just FYI for you guys, overheating doesn't actually damage the HG, what happens is it CAN warp the head. Which then doesn't allow the HG to seal properly. So you get a BHG. But the overheating itself doesn't damage the HG.

i dont know where to start with this an air pocket isnt going to do **** seeing as it always has air going threw it, the second is the second you start the car without a rad cap on it will spray out seeing as it needs presure to run the coolent, and yes overheating the engine will blow a head gasket because the gasket of course is made out of a rubber substance and the header is aluminum so heat from the engine will weaken the gasket and the preasure from the enclosed engine will blow the head gasket.

[Batman722]

lighten up guy and do some research, do you work for toyota ?

you should know that air and air bubbles could be found in the liquid that cools your engine. This may not be a big deal to you but remember that if this is the case, your engine could actually overheat. That is why it is important to remove any air in your coolant reservoir.

You just add to the radiator a mixture composed of half water and half antifreeze. Make sure you fill it right up until the top portion. Then, do the same to the overflow or coolant reservoir.

After doing such, just leave the cap of your radiator off and let the engine run. You would know that the radiator has already removed the bubbles because there would be a large air bubble come to the top or you would see the coolant go down. When this has been successful, refill the radiator with the right amount of coolant. And you can turn the cap of the radiator back on.

"Burping" the cooling system allows trapped pockets of air to escape: Air pockets can cause overheating because there will not be enough coolant in the cooling system, even if the radiator and coolant reservoir look full.
Instructions
STEP 1: Add a mixture of one-half water and one-half antifreeze to the radiator. Fill it right up to the top. STEP 2: Fill the overflow/coolant reservoir with the same 50/50 mixture. STEP 3: Leave the radiator cap off, turn the engine on and let it run until the radiator "burps": You will see the coolant level drop and may see or hear a large air bubble come to the top as the system burps. STEP 4: Keep an eye on the temperature gauge throughout this process. STEP 5: Refill the radiator to the top and coolant reservoir as needed. STEP 6: Put the radiator cap back on. STEP 7: Note that if the engine runs hot after this procedure there may have been another pocket of air that "burped." Let the engine cool down and then add more coolant to both the radiator and the coolant reservoir.

just 2 quick articles I found when I googled "air bubbles in coolant".

[alltracman78]

i dont know where to start with this

You obviously don't.....

You're not supposed to have ANY air in the coolant system. If "it always has air going threw it" then you have a problem.
An air pocket can cause a temp sensor to read incorrectly, and cause the heater core to not work right. As well as cavitation in the water pump, hot spots, ect, ect, ect.
Bottom line, you DON'T want them in your coolant.

The only pressure in your coolant system is from it heating up. When it gets hot, it expands. The rad cap controls how much pressure stays in the system.
So if you start it/run it cold, there will be NO pressure. Rad cap on or not.
And when it's cold the thermostat is closed, so the flow from the pump doesn't effect the radiator. Once it reaches temp it will slowly rise above the level of the rad, assuming it's full. When this happens you can put the cap on and let it pressurize. But it won't build ANY pressure until the cap is put on. It will just overflow.

A Head Gasket is NEVER rubber. It would melt.
A "header" is an exhaust manifold, so throw that term out the window when talking about a head gasket.
Yes the head is aluminum. Has nothing to do with overheating, other than it warps easier than cast iron. File that away for a minute.
Heat doesn't damage head gaskets. Normal coolant temp is 180 - 220*F [roughly] How hot do you thing your coolant is when you overheat? 280*F? 300*F? 500*F?
CONSTANT temps in your combustion chamber are WELL over 1500*F. It can spike to over four THOUSAND *F during combustion.
Do you honestly think even 500*F coolant temps [which you shouldn't ever see] are going to damage the gasket?
Now detonation/preignition CAN damage a HG. But not from the heat. From the pressure.
Back to the overheating/BHG.
When the coolant in the head/block can't get to the rad to cool itself off, your engine overheats. When this happens much of that extreme heat in the head cannot escape anymore. So the head gets hotter and hotter. When you heat something, it can change shape. Aluminum is much more susceptible to this than cast iron. Which is why you don't hear about old school cast iron head engines blowing HG from overheating very often...

When the aluminum warps, it no longer has a flat sealing surface with the block, it's now warped, or rippled.
Which means the HG no longer has flat pressure all over it. Without the pressure it can no longer hold in the pressures from the oil, coolant, and combustion. so it leaks.
Blown HG.


I wasn't trying to be a dick, just to help you out.
I've worked on cars for 8 years. I currently work for a Toyota dealer as a tech.
That doesn't mean I know everything, nor am I always right.
But what I posted is basic stuff. Which I have down pat.
Please do some research before you jump on my case next time.

Batman!!!!!!!

I'm working on an answer. I have most of it, just checking on one more thing.

Back to thread.

The reason I recommended you raise the front of the car up BTW, is to create more pressure for any air bubbles in the system to come to the top. This makes the "burping" more effective.

[hatchy_gt-s]

it will not hurt the engine to have air in it
example:
if i where to run water threw a closed system (with clear tubes) their would thousands of air bubles going by and if i wher to stop the flow the bubles would colect to make large bubles (or air pockets) and if i where to try to remove the bubles and then pump the water it would create more air via H2O consist of oxygen and where to stop it again it would creat bubles so no matter what you do it creats bubles (air pockets) and i didnt include the factor of extreme heat from the engine and evaporation

engineers think of these things and think hmm we need a substance between the header and the block that inkase an engine overheats it will break befor the header has extensive damage im not saying the the header does not warp it does but the gasket blows for that reason

[alltracman78]

Dude.
It's HEAD.

NO headER......

A header is an exhaust manifold, NOT an engine head.......

First off, water and coolant are 2 different things.
Second, there is a big difference between some small bubbles [Not that many, BTW. One of the products in antifreeze prevents them] in the system and large air pocket[s].

Do a little research on the subject.
I hardly think it would be mentioned in textbooks and all over online if it didn't matter.

The HG isn't there to blow before anything else. It's there to seal the gap between the head and block.
It does happen to be the weakest link, but once again, if the engine overheats, it's the head warping that causes the HG to leak.

[Manny]

soo uhh yea........

Hows the car comin along Nathan??

[6strngs]

hehe. sorry it's my fault this whole argument started. anyway! I finally got the thermostat housing off about 5 minutes ago when I finally resorted to a dremel to get the darn thing off. I pulled out the thermostat, compare it to the new one I have and the new one I have is totally the wrong size and it's about 9 PM and all the parts stores are closed now. so basically, since I have no school tomorrow I'm gonna run down to the parts store and either get a refund or find out if they just pulled the wrong one off the shelf and they do have a correct sized one. if not, I'm gonna make some phone calls to all the toyota dealers within reasonable driving distance and see if any of them have one. I want to get my car running by saturday for the nor cal meet!

[lagos]

definetely try to get a toyota one. they are worlds apart in quality then what normal parts stores sell.

[Batman722]

part # 90916-03046 for a 94 GT thermostat.

[alltracman78]

soo uhh yea........

Hows the car comin along Nathan??

Sorry guys.

I just didn't want the misinformation up there confusing someone that didn't know.....

Yeah, I would recommend an OEM therm as well. For some reason that is a big issue with Toyotas [aftermarket ones that don't fit].
Don't forget the Oring that goes around it.

[Manny]

soo uhh yea........

Hows the car comin along Nathan??

Sorry guys.

I just didn't want the misinformation up there confusing someone that didn't know.....

Yeah, I would recommend an OEM therm as well. For some reason that is a big issue with Toyotas [aftermarket ones that don't fit].
Don't forget the Oring that goes around it.

Completely understand...... and I also understand where hatchy was comin from.... 2 people just tryin to help.... Its like trying to get 2 engineers in a room to agree on how to do something.... not gonna happen....

But in this case.. I may not be an expert on toyotas... but I know a little on workin on cars.... and Id have to agree... Hatchy was a little misinformed.

[6strngs]

headed to the parts store for a refund now. I'll keep you all informed.

[6strngs]

alright! got my refund, headed to the closest toyo dealer and they had one in stock!!! sweet! I think the best part of the trip though was seeing a silver 96+ GT and an MKIV supra at the dealer. made my day. anyway, I'm gonna go install this thermostat now. I'll update afterwards.

[6strngs]

Good news! thermostat was replaced. coolant filled to the top with brand new coolant. and everything re-assembled. and now it runs fine without overheating! thanks for all the help guys.

Oh, one other thing. when I was putting my engine covers back on under my car right after I had burped the system, I found a small dribble of coolant on the bottom of my radiator. I wiped it away and more came... did that a couple times. I don't know if it was just the coolant that I spilled leaking down or if it was a leak from the bottom of my radiator. I'm gonna keep an eye on it. I might have to take my radiator in to my welding class and ask my instructor to help me weld it where it's leaking.

This post has been edited by 6strngs: Feb 16, 2007 - 5:28 PM

[alltracman78]

You can't really weld those rads. The flame will blow a hole in it.
You have to braze it. Your instructor might be able to do that.

[bindertch]

it will not hurt the engine to have air in it
example:
if i where to run water threw a closed system (with clear tubes) their would thousands of air bubles going by and if i wher to stop the flow the bubles would colect to make large bubles (or air pockets) and if i where to try to remove the bubles and then pump the water it would create more air via H2O consist of oxygen and where to stop it again it would creat bubles so no matter what you do it creats bubles (air pockets) and i didnt include the factor of extreme heat from the engine and evaporation

engineers think of these things and think hmm we need a substance between the header and the block that inkase an engine overheats it will break befor the header has extensive damage im not saying the the header does not warp it does but the gasket blows for that reason

Since the topic is over. I agree with Altracman78. I am currently in school. Air in the coolant can severely damage your water pump. Quote from Corinthian Colleges INC AKA Wyotech ‘Cavitation is the formation of low-pressure bubbles by the water pump blades. A pressurized system makes it difficult for these bubbles to form. Cavitation is undesirable because the bubbles collapse with enough power to blast small cavities in any metal surface they are near. Unchecked, cavitation will erode the water pump blades and housing.’ Also if the engine has a large enough air pocket it can cause uneven heating of the engine which can cause any part of it to warp not just the head.

[jcbass7]

Glad you got it all figured out