71 lt1 vert coolant question

[woodhouse]

lately after a drive, i have been noticing a coolant overfill spill after the car has been parked for a few minutes. is this a sign of something gone wrong? seems to be about a cup of fluid each time. the thermostat seems to be operating properly, as the hoses are full and hot when warmed up.

any thoughts???

thanks in advance, w.

[JohnZ]

There are normally two causes for "puking" coolant during "hot-soak" after shutdown - a radiator cap that isn't sealing properly and thus won't hold its rated pressure (which reduces the boiling point of the coolant), or an over-filled cooling system, which doesn't leave adequate expansion space in the radiator or expansion tank.

The radiator (or expansion tank) is clearly marked "Cold Full" - don't top it off any higher than that, and it will stop "puking".

When you shut off the engine, heat continues to be absorbed by the coolant, but it isn't circulating through the radiator any more, so "hot spots" form and become steam; if the radiator cap doesn't hold rated pressure, it allows the coolant to boil, and it "pukes". A 50-50 mixture of anti-freeze and water with a 15# radiator cap won't boil until it reaches 265*F.

[72-LT1]

You don't have an overflow tank correct? I had a similar problem and was told that the tank will puke if you keep filling it up to the very top of the rad. Mine will not puke when I leave the fluid down about 2" from the top of rad.

[SR'71]

Keep the maximum height of you radiator return hose as low as possible. Loosen both ends of the hose and twist it to obtain the lowest profile possible. Any air captured in a high spot [higher than fluid level in your expansion tank] formed by the return hose, will allow steam to form. This steam will overpressurize your radiator cap and puke fluid on you garage floor.