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Guest Marck

coolant overflowing into over flow tank.

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Guest Marck

This is the second time in a row that my 87 subaru turbo coupe has shot out coolant into the overflow tank. It shoots enough coolant out to fill up the overflow tank to the cap. Both trips were about 30 miles in length. Weather has been around 80 degrees. Is this normal? Is there something clogged in my cooling system? Could it be the thermostat or radiator cap? There is no oil in the coolant or coolant in the oil. I have no coolant leaks. I drained the coolant and added fresh 50/50 mix two weeks ago. Could it be that I did not do a good job of bleeding the air out? Everything in the cooling system except the heater core is no more than half a year old; I replaced the radiator, radiator cap, waterpump, hoses, thermostat, etc. After my drives I would lift my over flow tank above the radiator so that the coolant goes back into the radiator. The temperature gauge would be at half way on the highway (normal), but when I get off the high way and let the car idle the temp goes up to about 3/4 ways (still far enough from the redzone). This makes sense since much of the coolant is in the overflow tank at this time instead of flowing through the engine or radiator.

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Guest GeneralDisorder

If the temp gets high enough, this is normal. When the temp goes back down, it will suck the coolant back into the system. If it does this too often, you might pressure test your radiator cap - or just buy a new one for the $5.00 they cost.

 

GD

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Guest Marck

On monday I forced the coolant to drain back into the radiator by raising the overflow tank above the radiator.

 

Today, I just let the car sit after running it for 30 miles and then checked it a few hours later. When I checked it the coolant had drained back into the the radiator. So at least it is draining back.

 

I have a spare new radiator cap, so I will try replacing that first.

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Guest GeneralDisorder

yeah - I replaced mine a couple weeks ago - took a sharp turn into a parking spot (going WAY to fast :D ), and there was coolant everywhere. No overflow tanks on EA81's (I think the turbo's had em tho).

 

GD

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Guest ShawnW

Turbo ea81's didnt have em either...at least I havent seen one. Mine will have one though.

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Guest GeneralDisorder

yeah - pretty easy to add one - at the drag strips we used to use beer cans.

 

GD

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Guest EmmCeeBee

Could very well be your radiator cap -- as long as you have the new spare, I'd try that first.

 

After all the coolant loss problems I had in the past year, I should have replaced the radiator cap first. Fiddled around with flushes, head gasket leak tests, etc etc and after 4 months got down to "change the radiator cap". That was it. I've since tested the old cap, and sure enough, it wasn't sealing to 13 psi.

 

The 13 psi is the pressure release point. The cap is built with a vacuum release point, too, but I don't know what value that is. The system will hold a very slight vacuum; above that limit it will suck in from the overflow tube. That is, if the cap is working right.

 

So what I'm curious about is when you say "raising the overflow tank lets coolant flow back into the radiator". If this happens when it's cold, then for sure it's the cap. In other words, after the system cools the vacuum should already be equalized (actually holding a slight vacuum). You couldn't force coolant back through the cap at that point unless the cap just wasn't sealing.

 

On the other hand, if you mean you raise the overflow tank when it's hot and wait till things cool -- then OK. As the system cools the vacuum pulls in overflow coolant (or air.....) bit by bit.

 

In any case, air in the system could be causing the expansion. It can take a dozen or more times of squeezing hoses and burping the radiator to get it done.

 

-- Mark

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Guest Marck

I still have the same problem-even though I replaced the radiator cap. I also parked my subaru facing up a hill while reving the engine in order to get the air bubles out. This isn't normal is it? Should I have a radiator shop pressure test my cooling system? I have no coolant leaks. It only happens when I drive on the highway for at least 15 minutes. Then as the engine cools, the pressure decreases, and so the coolant drains back into the radiator.

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Guest GeneralDisorder

Sounds normal to me - engine gets hot, and the coolant expands, so it has to go somewhere. Maybe you just have an overheating problem - probably time for a new radiator. Maybe an aluminium double-row type.

 

GD

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Guest Marck

Dual row radiator was installed in November. It doesn't overheat. This has only been happening for a week now. Coolant is to over flow tank full mark before I run the car, and if I drive long enough coolant will reach the cap when I stop driving. It makes sense for the coolant level to fluctuate a little, but I think too much coolant is getting pumped into the overflow tank.

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