Hey guys, I recenty came across a problem with my car I think. I openned the rad cap with the car flow yesterday just to check the level and look of the fluid, and fluid RUSHED up my overflow tank out sprouted out of the overflow cap threads. I closed the rad cap and the flow stopped.
Tried again today, same thing with the car cold, and again fluid rushed up the overflow.
WHat would cause this?? I dont wanna cause a big mess on my driveway but Id love to know why its doing this as I know Im now a bit low on coolant.
Thanks
Why does my overflow explode when my rad cap is openned??
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Pwnin O'Brien
- Posts: 1612
- Joined: Wed Jun 24, 2009 1:10 pm
Re: Why does my overflow explode when my rad cap is openned?
After your car is cooled down and you squeeze the upper radiator hose, is it stiff (like when the car is running)?
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Densetsu
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- Joined: Wed Mar 12, 2008 5:50 am
- Car: 2004 Nissan Pathfinder Chinook
Prev: 2003 Nissan Pathfinder Chilkoot - Location: Edmonton, AB
Re: Why does my overflow explode when my rad cap is openned?
Were there bubbles in the coolant that rushed into the overflow tank?
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Chuck Tribolet
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- Car: '01 Nissan Pathfinder
'87 Chevy Corvette
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Re: Why does my overflow explode when my rad cap is openned?
The radiator cap is the pressure release valve for the cooling system. When the pressure exceeds some value (typ. 15ish PSI), the spring-loaded gasket in
the rad cap is pushed open by the pressure, and the pressure is vented into the overflow. When you partially release the cap, the relief pressure is reduced a bit.
I suspect that you were very close to relief pressure when you loosened the cap.
NEVER EVER remove the cap hot.
I think what you need to do is to start with a cold engine. Top up the coolant. Burp the system. On an '01 PF there's a burp vent just in front of the firewall, top
dead center. It has a rubber cap. Be careful not to loose the jesus clip that holds it on. Pull the cap and let the level stabilize. And the FSM shows another at the
front of the engine, but my stick shift '01 sure doesn't have it. Top up the coolant and put the burp cap(s) back on. Leave the rad cap off. Run the engine until
you can see coolant start to flow through to rad cap hole. Do you see gas bubbles in the coolant after more than a minute or so (gas bubbles in the first minute or so
may just be trapped air getting passed out). If you do see gas bubbles past a minute or so, go have several beers, you have a blown head gasket.
the rad cap is pushed open by the pressure, and the pressure is vented into the overflow. When you partially release the cap, the relief pressure is reduced a bit.
I suspect that you were very close to relief pressure when you loosened the cap.
NEVER EVER remove the cap hot.
I think what you need to do is to start with a cold engine. Top up the coolant. Burp the system. On an '01 PF there's a burp vent just in front of the firewall, top
dead center. It has a rubber cap. Be careful not to loose the jesus clip that holds it on. Pull the cap and let the level stabilize. And the FSM shows another at the
front of the engine, but my stick shift '01 sure doesn't have it. Top up the coolant and put the burp cap(s) back on. Leave the rad cap off. Run the engine until
you can see coolant start to flow through to rad cap hole. Do you see gas bubbles in the coolant after more than a minute or so (gas bubbles in the first minute or so
may just be trapped air getting passed out). If you do see gas bubbles past a minute or so, go have several beers, you have a blown head gasket.