Radiator cap?
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Melting Slicks
Joined: Jun 2011
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Radiator cap?
I can drive my car for miles and the radiator does not build any pressure?? Temp gauge is fine but I can get home and squeeze the top rad hose with no problem. Does that mean I have a bad rad. cap?
Thread Starter
Melting Slicks
Joined: Jun 2011
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Pro
Joined: May 2011
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From: BC
On a system using a coolant recovery tank connected to the overflow line (not a pressurized reserve tank) when you remove the rad cap it should always be full to overflowing (provided there's fluid in the recovery tank). If there is any air space in the top of the rad that's indicating that the recovery system is not working. Still doesn't tell you if it's cap or leak, but tells you something is wrong.
Steve g
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Melting Slicks
Joined: Jun 2011
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It doesn't take much of a leak to prevent it from building pressure, and if the leak is high in the system you won't necessarily even see anti freeze dripping.
On a system using a coolant recovery tank connected to the overflow line (not a pressurized reserve tank) when you remove the rad cap it should always be full to overflowing (provided there's fluid in the recovery tank). If there is any air space in the top of the rad that's indicating that the recovery system is not working. Still doesn't tell you if it's cap or leak, but tells you something is wrong.
Steve g
On a system using a coolant recovery tank connected to the overflow line (not a pressurized reserve tank) when you remove the rad cap it should always be full to overflowing (provided there's fluid in the recovery tank). If there is any air space in the top of the rad that's indicating that the recovery system is not working. Still doesn't tell you if it's cap or leak, but tells you something is wrong.
Steve g
Race Director
Joined: May 2006
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sounds like you have a leak. On a completely cold engine remove radiator cap and completely fill. Add coolant to tank up to cold line. Start looking for the leak. If you had a bad cap it would either leak out the cap or overflow the coolant tank.
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Pro
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From: BC
Why would it overflow the coolant tank?
Steve g
Race Director
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Why it would overflow.
On a cap with a coolant tank either the outter rubber ring will fail causing a leak at the cap or if the cap no longer holds pressure do to a failed spring or a bad inner rubber ring the fluid will expand in the radiator go to the coolant tank and eventually cause it to overllow.
Burning Brakes
Joined: Dec 2002
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From: STANTON CA
you have a leak somwhere.have you checked your oil for water.
Thread Starter
Melting Slicks
Joined: Jun 2011
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Actually when I bought it it didn't have any heat, the heater valve was corroded shut. But when replacing it I looked in the reservoir and it was like it is now, just traced of brown sludge. I'm gonna replace the reservoir, cap and rad. cap and see what happens. Oil looks and smells fine. I think this car might have sat awhile, not for sure though.
Pro
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From: BC
On a cap with a coolant tank either the outter rubber ring will fail causing a leak at the cap or if the cap no longer holds pressure do to a failed spring or a bad inner rubber ring the fluid will expand in the radiator go to the coolant tank and eventually cause it to overllow.
Steve g
Pro
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From: BC
Not when you first mentioned a bad cap.
"On a cap with a coolant tank either the outter rubber ring will fail causing a leak at the cap or if the cap no longer holds pressure do to a failed spring or a bad inner rubber ring the fluid will expand in the radiator go to the coolant tank and eventually cause it to overllow. "
Where I have seen someone overflow the tank is when they opened the rad and found the level low so they topped it up, not considering that there was still af in the overflow. Checked it again, rad low again, level up in the tank. Add more to the rad. Keep doing that until you overflow the tank. What it is doing is pushing the amount you keep addint to the rad into the tank.
If there is sufficient fluid in the tank to cover the pickup hose and you remove the rad cap and find an airspace, you have a problem. Fluid is expanding into the tank when it warms, but when it cools and contracts it's pulling air somewhere. Can be from the upper seal in the cap, but more often it's a small leak.
Steve g
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Melting Slicks
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