I am having an issue with my overflow tank. Seems to spit out coolant after I drive it pretty much anywhere. The cap itself screws on tight, the temp never goes over 190-200. It doesn't happen all the time, but has caused me to have to carry water with me just to go to work and back. All this started happening after I drained to replace the coolant temp switch under the intake exhaust manifold that sends signal to the computer. May just be the cap but was just wondering if anyone had had this issue since it didn't have it until after I changed the sensor.

 

Engines always puke coolant out when they are completely filled with coolant. Older cars with no recovery system just puke it out until the right level is reached. Ones with a recovery system allow the ejected coolant to be sucked back in when the engine cools.

Any cracks in the overflow bottle? In my 89 Cherokee The plastic bottle had cracks that would open up when heated and leaked alot.

You might be overfilling it but Its a cheap fix to start with a new cap, might have a leak or bad cap.

 

Maybe a bad gasket. You can use a Volvo coolant cap, the best one is a green one but even the black ones work good, have used them on a few of my Jeeps for 7 years now. You can even use the coolant bottle from a Volvo 240, it is a nearly a direct fit.

 

If your system is the original RENIX closed cooling system, there is no overflow provision.

You need to run it awhile at fast idle in your driveway with the heater on full blast, and the cap off. You may have some trapped air in there.

If coolant still comes out, you have a crack somewhere that may open up only under pressure. Replace the bottle.

Incidentally, only fill it up halfway. Leave some air space in it.