Stupid question.

Does running at a higher boost level affect the coolant pressure in turn potentially causing the radiator cap to fail?

 

Unless you have an issue somewhere (i.e. blown head gasket) that is letting boost pressure into the coolant system, then no... Boost pressure should not effect coolant pressure

 

^^^ exactly.

The timing belt spins the water pump, which controls coolant pressure. The higher the rpm, the higher the flow of coolant throughout the motor, but it is very low pressure. If the car runs too hot, pressure increases as the liquid expands, or boils, but if high boost is making the cap fail, I would definitely start by doing a leakdown test, and looking for a bad head gasket.

--Mark

 

This...

Keep an eye on your reservoir tank. If its filling up after a semi hard drive, you might have a blown headgasket.

-Josh

 

Thanks for the info guys

 

The pressure cap determines the coolant pressure. This pressure may be the rated presssure on the cap or nothing depending on the condition of the cap. High temperatures do not cause cap failure, age causes the cap failure. If you have gone 30k on a cap you need a new one.

 

Checking the cap would be the simplest of tests. but if you're saying that the cap is only failing when you're putting some boost through the motor. I would look internally.

Leakdown is the way to go, just to add reinforcement to what neonglh said...

 

What if the opposite is happening, reservoir is empty after a week, I keep having to refill it. Engine temp is fine, no white smoke coming out of the exhaust.

 

Well, it is a simplest of tests if you have a tester. I bought one about 5 years ago and it was $120. Then I had to buy the adapters that fit the Evo - another 60 bux.

 

I didn't necessarily mean with a tester. a new OEM replacement rad cap is probably less than 10 bucks at pep boys. That's the cheapest way to test it...

 

Either you have a leak somewhere or the pressure cap is toast. I had to replace a cap a while back because it was dumping coolant on top of the radiator.

 

then it's leaking from somewhere...

the coolant tanks in these cars aren't that big so it wouldnt take much to empty it...

are you checking the Rad or just the coolant tank? If the rad is getting low as well as the tank being empty, then you've got a significant problem if you're losing that much coolant in a week.

 

Agree!

 

thats probably the only reason I havnt bought a cap tester yet... lol

 

I'm of of those guys that has to own weird equipment like this. The thing is, most people don't see the pressure cap as a maintenance item. BTW, this isn't the first pressure tester I've owned, I wore out another. In that time I've had occasion to test a lot of pressure caps, both on my cars and on others. While it has happened, it is rare enough that I am surprised when a cap with a little age on it holds rated pressure. So, a good many car owners are giving up part of the capacity of the cooling system. That is why I recommended above that we change out pressure caps at 30K.