Hey guys, I was getting ready to embark on a 3000 mile trip, and I went to check the crucial fluids (Changed oil, brake fluid was done not long ago, power steering and tranny was fine), but when I got to my coolant level, I noticed it was at the low level, which typically isn't a concern for a cold engine, but being that I just drove for 2 hours straight, I knew something was wrong. I went looking and immediately noticed that my coolant overflow tank cap was broken

The part # is 19102-PM5-A00, and was under 2$ at my local Honda dealership.

EDIT: parts in parenthesis is me being wrong! (With a broken cap, the cooling system fails to pressurize, and the boiling temperature of the coolant is lowered, meaning it your coolant can be more prone to evaporating). No coolant makes engines pretty unhappy. Luckily, I caught this before anything began failing. The plastic on the part seems pretty durable new, but seemed a bit flimsy on the one I took off. I don't think the design was changed, but maybe over its life, it deteriorated.

 

Negative. Pressurization is controlled by the radiator cap, not the overflow lid.

 

Edited before anyone freaks out. For some reason I was under the impression that the overflow was pressurized as well. My step fathers jaguar s-type had a crack is his coolant reservoir (pretty common issue on those cars), and his car was overheating, even when full with coolant due to it not being able to pressurize. Once the tank was fixed, It stopped overheating. I was just going off that instance.

Anyways, I guess its still something to check.

Also, does this mean that im actually low on coolant. I was under the impression that once the car was warmed up and running for a while, the level should go up. Mine is sitting at the min level, regardless if it sat overnight or if I ran it for two hours.

 

you might be thinking about a pressurized coolant expansion tanks. BMWs and other makes have these and are known failure points.