Why does my coolant reservior fill up and overflow when I turn off my 1988 Camaro?

Question

My fan comes on and my thermostat opens, but when I turn off the car all my coolant flows into the reservior and starts overflowing. When it stops, it recedes and the reservior ends up empty and bone dry.

Answer 1

He's right on about the radiator cap.It needs a higher pressure version to contain the heat when the engine shuts down and the coolant starts to boil.

Answer 2

Eventually it will burp out the air pocket in the engine but you have to watch the resv. and add coolant when the engine cools . But because the air is starting a boiling to blow the coolant into the bottle it might not be good to the motor. With cold motor remove the highest heater hose cork or have some one hold there finger over the heater outlet with there other hand raise the heater hose up a little. find a tight fitting funnel or have the front end on ramps fill the radatior until water/coolant runs out that heater hose and from the firewall heater core connection the n replace the hose quickly reclamp try again. Air pocket in my 2006 gto would do exactly the same thing when I turned the motor off.

Answer 3

everyone is close to right

yes buy a new cap with the factory psi.

the overflow container is designed to GIVE water and RECEIVE water.

it will balance out in a trip or two someplace between FULL HOT & FULL COLD in the middle of the reservior.

if its overflowing it has to much coolant.


you should never remove the radiator cap so as to keep the pressure. You can feel it by squeezing the upper hose.

the reservior should never be empty!!!!!!!!
if needed fill the colant in the reservior.

Answer 4

Your valve is stuck open and closed and or partially stuck. The resorvoir is designed to enlarge your radiator's capacity to match a stress condition, and should not do anything but help and not be the radiator part, a supplemental help, by emptying on command. I do not know how to fix it, but your motor should be checked for some type of malfunction, includeing the fan and the line's to and fro, the coolant plastic, that is either drained from malfunction or leak.

Answer 5

Bad Radiator Cap. While engine is cold, fill radiator with 50/50 coolant and use a new
radiator cap rated at 13 lbs. Then fill reservoir to cold line on tank.
Without testing for other issues, I believe this should alleviate troubles.

Answer 6

I would change the thermostat a new cap would'nt hurt neitherand flush your radiator and make sure the cooling vains on the outside of you radiator and ac is dirt free and bug free but a cap keeps pressure inside like a pressure cooker it lowers the boiling point of water so don't rule that out good luck