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NTRA08

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A BHG!!! Okay... My car doesn't overheat with the thermostat out. (obviously) But when I install the thermostat it starts to overheat. But only when I'm driving it. Its fine at idle. The radiator is full with 50/50. I can drive the car and it overheats. Well I figured out that if I get out and relieve the pressure in the radiator while the car is still running, it cools down. (quick) Dumb but it works. And thats it until next time I drive the car. The thermostat is new. There is no water in the oil and no oil in the water. ???????????? HELP
 
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NTRA08

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BTW its a 2.0mm Greddy MHG. About 12,000 miles on the motor. And yes Greg Sabin this is Jared.
 

fonz87

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................bhg ?


there might be bubbles in your system, try to flush it out and refill back in. See if that helps
 

Keros

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Try a new radiator cap and pressure test the whole system for leaks.

And stop letting it overheat or that will cause a BHG.
 

NTRA08

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Tested the thermostat yet?
(pot of water on the stove and watch it to see if it ever opens)
Yeah I tested the thermostat. Works fine. Its new. I had a fail safe one time those work great. No leaks. All hoses have been replaced. I did put a shorter hose on the bottom. But haven't changed the cap yet.
 

jdub

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Did you cut the jiggle valve off? I've had a new T-stat held closed by the pressure behind it. Removing the juggle valve fixed it.
 

jetjock

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My car doesn't overheat with the thermostat in. (obviously) But when I install the thermostat it starts to overheat.
What does that mean?

I'm assuming it means the car doesn't overheat with the thermostat out. If so what does the temperature gage show under those conditions. Lower than normal, normal, or higher?
 

NTRA08

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What does that mean?

I'm assuming it means the car doesn't overheat with the thermostat out. If so what does the temperature gage show under those conditions. Lower than normal, normal, or higher?
Sorry about that. I should have seen that.:nono:

With the thermostat out it runs lower than normal. Unless I'm sitting in traffic. With it in it starts to get past normal so I relieve the pressure and it goes down. The motor has never overheated. I just mean it starts to get above normal and keeps going until I relieve the pressure. But I fix it every time before it gets too hot.
 

Nick M

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On another note, do you have a belt on the waterpump?
 

Nick M

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Is the impeller still on the shaft? Is the radiator look ok on the inside? Is there dirt on the outside, between the intercooler and radiator? Does it flow good, even though it looks ok on the inside?

You must look at how it operates(the cooling system) to decide what is wrong.

After you determine it works as designed, and has no fault, then you move to what is causing excess heat in the engine.
 

NTRA08

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Is the impeller still on the shaft? Is the radiator look ok on the inside? Is there dirt on the outside, between the intercooler and radiator? Does it flow good, even though it looks ok on the inside?

You must look at how it operates(the cooling system) to decide what is wrong.

After you determine it works as designed, and has no fault, then you move to what is causing excess heat in the engine.
Its a new radiator. No condenser. So I have good air flow. No dirt or anything. Inside of the radiator looks like it should. And I don't know about the impeller shaft. I haven't checked it yet.
 

GrimJack

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Is anything missing from the cooling system? Fan shroud? Undertray? Turbo coolant lines / bypass? Have you switched to electric fans?

Ambient temps?

What ratio of water : antifreeze are you running?
 

NTRA08

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Is anything missing from the cooling system? Fan shroud? Undertray? Turbo coolant lines / bypass? Have you switched to electric fans?

Ambient temps?

What ratio of water : antifreeze are you running?
No undertray. The car didn't have one when I bought it. Bypass on the turbo coolant line. I have a t70 on the car. I used to have electric fans. I went back to all stock and new.

Edit: and I use 50/50 coolant.
 

jdub

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Its still there (edit: jiggle valve). But isn't it there for a reason.
No undertray. The car didn't have one when I bought it. Bypass on the turbo coolant line. I have a t70 on the car. I used to have electric fans. I went back to all stock and new.

Edit: and I use 50/50 coolant.

I highly suggest you remove the jiggle valve ;)
 

jetjock

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And put the hole at 12 o' clock ;)

I dunno though. Running without a T stat should have purged any air and with it in the turbo bypass should have done the same thing.

Coolant expelled out the expansion tank? If not how much does it rise over the cold level? Hoses feel rock hard or look ballooned? Does the gage creep or spike?

Lower temp sans thermostat shows reserve capacity which implies a healthy cooling system. How healthy we don't know since you didn't say how much lower. Temp drop with heater use implies the water pump is also OK. So far it's not looking good...
 

NTRA08

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And put the hole at 12 o' clock ;)

I dunno though. Running without a T stat should have purged any air and with it in the turbo bypass should have done the same thing.

Coolant expelled out the expansion tank? If not how much does it rise over the cold level? Hoses feel rock hard or look ballooned? Does the gage creep or spike?

Lower temp sans thermostat shows reserve capacity which implies a healthy cooling system. How healthy we don't know since you didn't say how much lower. Temp drop with heater use implies the water pump is also OK. So far it's not looking good...
I can recall one time the coolant expelled out the tank. Hoses are ballooned. And the gauge creeps up. The gauge is in between the cold and normal with the thermostat out. When I had my electric fans one fan went out and the car would start to get hot. So I would turn on the heater. That would cool it down alot. But it doesn't work like that since I went to the clutch fan.
 

NTRA08

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Um.. You have a bgh.
But there isn't any fluids where they shouldn't be. And it doesn't get hot anymore after I release the cap. I would say that me relieving the pressure in the cooling system allows the thermostat to open. Cooling the motor. I'm going to remove the jiggle valve like jdub said and see what happens.
 

tissimo

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If you're building up that much pressure (and having to release it) you're getting combustion gases injected into the coolant system via the cylinders. If your leave your radiator cap open and start the car you'll probably see an endless stream of small bubbles in the coolant.

MHGs dont blow in the same way as stock gaskets. They simply break the seal and leak instead of deforming and causing fluid mixtures.
 

jetjock

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Hmmm, your reserve isn't as good as it should be with a new rad. Do you feel any cold spots on it? Is there at least a 40 degree drop across the top and bottom hoses? Since the heater doesn't bring temp down like it used to the water pump impeller may be corroded or the belt slipping. That's reaching though. At this point I'm inclined to agree with tissimo. Time for a block test...
 

NTRA08

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Hmmm, your reserve isn't as good as it should be with a new rad. Do you feel any cold spots on it? Is there at least a 40 degree drop across the top and bottom hoses? Since the heater doesn't bring temp down like it used to the water pump impeller may be corroded or the belt slipping. That's reaching though. At this point I'm inclined to agree with tissimo. Time for a block test...
No cold spots. And i never really checked the hoses for temp change. Okay time for a block test.
 

jdub

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Was this a new or used fan clutch?

Are you sure it's a GTE clutch with a 10 blade fan?

Is the fan shroud in place and in good condition?

Does the fan make a howling noise for 30-45 sec after the car is started, then quiet down?


Unfortunately, I'm starting to think the same as tissimo and JJ :(
 

jetjock

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What's worrisome is the lower temp sans t-stat implies the system ought to handle a typical heat load but can't. His reserve isn't a good as I usually see but it should be enough for all but extreme operation in a very hot ambient. Not a good sign.

OP: It's best to do a test at this point even though overheating alone will cause pressurization up to the cap's rating. Or try looking for bubbles like he said. Or drain some coolant into a glass and hold it up to the light. Usually obvious if there's gas entrained in it...
 

NTRA08

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Just started the car. No bubbles in the coolant. The whole rad assembly is new. fan, clutch, shroud, rad, t-stat. I went for a drive too. It didn't get over normal temperature. But when the car warms up I get a metallic grinding noise by the water pump. But not when the car is cold.
 

B3AST

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Does your fan cut on? This happened to my civic, it would overheat so i put a new thermostat in it and it still overheated so i took it out and it ran cool. Turned out my fan switch took a shit so i wired up a switch directly to the radiator fan and installed the new thermostat and it ran at normal temp
 

Mk3runner

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Defective water pump?? What the grinding noise exactly?

Is the pump old? Check for play.
 

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bearings in the pump are shot, replace. kbye.