Coolant System Problem - need help?

[MoonDog]

Hope you guys can help me.

Having a problem with my coolant system. I have an overflow tank setup on my expansion tank and sometimes after the vehicle is shut down it squirts coolant out of the breather hole on the overflow tank.

The car does not overheat when running generally 85-90 celcius.
The radiator cap is 16lb.

The overflow tank is empty when I start the vehicle so I don't think it can be an overflow problem???.,
It doesn't do it all of the time, but nowadays more regularly.

Any ideas?

[Mr.Fixit]

There is some normal heat expansion of the coolant. If you keep topping the system off while cold, it will keep blowing out that pint of coolant everytime it heats up to operating temps. Is the overflow tube on the expansion tank after the cap, requiring more than 16 psi to get coolant into the catch can. Or is it part of the pressurized system, making it a (non-pressurized) system with tiny hole way up high that some coolant can get out of.

[MoonDog]

Mr. Fixit.

Thanks for replying.

The overflow tube is after the cap. Connected to the normal overflow outlet on the expansion tank and not part of the pressurised system. Therefore it only works when the pressure is greater than 16lbs, is that correct?

The tiny hole is at the top of the recovery tank.

When the car is cold and I check the coolant level in the expansion tank i usually ensure that is is fully topped up. Maybe I am putting too much in?.. Should I leave the level lower?..

[chopper]

Not sure what type of expansion tank you're running on your Chevy but the Ford FE types have an internal horizontal baffle about halfway up the volume of the tank. The fluid level is brought up to the level of the baffle, leaving an empty space (called the "ullage", FWIW) into which the fluid can expand. Not trying to be cute, but that's why it's called an "expansion tank." It's supposed to have the empty space above the fluid. The expansion comes from thermal expansion of the fluid during normal operation, and also boiling of the coolant in the cylinder heads after shutdown. Most of us who have FEs and live in the warmer climates have some type of recovery tank added to the system to minimize the problems which you have. Make sure you have the later type of radiator cap which has the reverse check valve so that as the engine/coolant cool down, the resulting vacuum will draw the coolant back into the expansion tank.

[Whaler]

Originally posted by chopper


Not sure what type of expansion tank you're running on your Chevy but the Ford FE types have an internal horizontal baffle about halfway up the volume of the tank. The fluid level is brought up to the level of the baffle, leaving an empty space (called the "ullage", FWIW) into which the fluid can expand. Not trying to be cute, but that's why it's called an "expansion tank." It's supposed to have the empty space above the fluid. The expansion comes from thermal expansion of the fluid during normal operation, and also boiling of the coolant in the cylinder heads after shutdown. Most of us who have FEs and live in the warmer climates have some type of recovery tank added to the system to minimize the problems which you have. Make sure you have the later type of radiator cap which has the reverse check valve so that as the engine/coolant cool down, the resulting vacuum will draw the coolant back into the expansion tank.

Just want to confirm this for my self.....I am adding 50/50 coolant to a cold and yet to be flashed up FE with an expansion tank. I assume I am looking for this coolant level as well?

Just to the baffle or slightly above.

Also the thermostat has had a small hole drilled into the top of it, to help out with entrapped air etc. Does a closed thermostat on the cold engine make things any different for me adding coolant. Since I am looking to fill to the running level now?

Thanks

Tim