My 2002 Honda Civic has lost its coolant reservoir cap for the second time.. the first time it over heated, and I had to replace the radiator, the thermostat, the engine covers, and the water pump. This time its not over heated, but its making a "Putting" sound like a standard does, and feels like its going to shut off. I covered the spot where the cap is supposed to be with a thick piece of plastic, and a hair tie to try and get it to my mechanic, but I can't figure out why the cap keeps falling off.. I do need to get the head gasket done as well... but could that really be the reason for the cap popping off?.. This is so frustrating :/... I'm about ready to give up on honda completely and switch to another brand if this keeps happening.

 

Okay so its not your radiator cap thats coming off, its the overflow reservoir cap?

Replace the entire overflow container. If that doesn't work, maybe replace the radiator cap. Sounds like you have you extra pressure building up, I can't think of any reason why the overflow reservoir cap would pop off like that unless its just really worn out.

It is imperative that you have an overflow reservoir. Did you by chance happen to tape the rubber hose that runs from your rad cap to the overflow because it is absolutely necessary that your coolant be able to escape the radiator when it heats up and expands, otherwise you will blow your radiator, all your hoses, and rupture your HG.

 

Bad head gasket-- buildup of gas under pressure in the cooling system-- gas has to go somewhere-- cap blows off.

If you keep driving like that it will ruin your engine if it's not already.