Running too hot!!

richd · 03-30-2002, 02:12 AM

You mentioned that your overflow tank doesn't return fluid, only catches it?

If that is the case, you should get a new/used one that will return the coolant. What happens is the coolant expands as the engine warms up and pressurizes the system. After a certain point the rad cap releases some pressure to not stress the system. It does this by letting some coolant pass by. When the engine cools the coolant contracts, thus creating negative pressure in the system. The cap opens a reverse valve letting coolant get sucked in from the overflow bottle.

If the coolant can't return you will have less coolant in the system after the first drive cycle. Once this happens you will slowly lose coolant over time. This is from the coolant evaporating in the 'air space' in the radiator and being pushed out when the engine heats up and only air (without evaporated coolant) return when it cools.

I bet if you switch overflow tanks you'll see your temp stay where it should be much more often.

Good luck,

Rich D.

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03-30-2002, 02:12 AM	#1
richd Registered Member Join Date: Jul 2001 Location: Edison, NJ, USA Posts: 125	You mentioned that your overflow tank doesn't return fluid, only catches it? If that is the case, you should get a new/used one that will return the coolant. What happens is the coolant expands as the engine warms up and pressurizes the system. After a certain point the rad cap releases some pressure to not stress the system. It does this by letting some coolant pass by. When the engine cools the coolant contracts, thus creating negative pressure in the system. The cap opens a reverse valve letting coolant get sucked in from the overflow bottle. If the coolant can't return you will have less coolant in the system after the first drive cycle. Once this happens you will slowly lose coolant over time. This is from the coolant evaporating in the 'air space' in the radiator and being pushed out when the engine heats up and only air (without evaporated coolant) return when it cools. I bet if you switch overflow tanks you'll see your temp stay where it should be much more often. Good luck, Rich D.