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Cooling systems are always under pressure. Even when cooled off. It's the pressure that raises the boiling point of water. Without a proper Rad Cap, things would begin to boil at 212*.
Reading your opening paragraph Kjande, I don't see anything wrong. Rad Caps pressure specs run from 14 - 18 lbs of pressure. Beyond their maximum, the relief valve built into the cap releases and the coolant discharges into an overflow tank epoxy flooring greenville sc. Then in most cases, the coolant returns to the Rad when cold via the small hose on top of the Rad.
You never stated and no one asked, but what does your temp gauge show?
I am having an interesting problem with a2001 xc70 i5. Cooling system is pumping air and pressure is high. No sign of head gasket issue. CO test shows no exhaust in the coolant. No water in oil, no exhaust steam. Can a turbo pump air into the coolant? The water temp is not to boiling point, but it acts like it is .. like it's boiling over, but from pressure. The radiator has a hairline crack in the plastic, below the upper hose, which will be replaced. But I don't see how that would contribute to this problem. I looked at other posts on the site, but have not found a resolution.... has anyone faced this before??? Thanks in advance.
I am having an interesting problem with a2001 xc70 i5. Cooling system is pumping air and pressure is high. No sign of head gasket issue. CO test shows no exhaust in the coolant. No water in oil, no exhaust steam. Can a turbo pump air into the coolant? The water temp is not to boiling point, but it acts like it is .. like it's boiling over, but from pressure. The radiator has a hairline crack in the plastic, below the upper hose, which will be replaced. But I don't see how that would contribute to this problem. I looked at other posts on the site, but have not found a resolution.... has anyone faced this before??? Thanks in advance.
Replace the cracked radiator. Every night when your engine cools down it's sucking air back in through that crack. Every day when it's hot its expelling coolant.
Nothing's gonna work until you seal the system.
Last edited by wadenelson; Oct 6, 2023 at 02:28 PM.