My 85 golf decided to start leaking fluid out coolant expansion tank cap today. Do these caps normally go bad after 34 years or do you think I have bigger problems? Any way to test the cap?
No overheating. Car only went up to 1/2 temp on the gauge before I noticed the constant drip. Coolant lines felt pretty firm as well.
Well I took the cap off and noticed the inside was covered in a black sludge. Actually there seems to be globs of black floating around the coolant system. I took a rubber glove and an elastic band and put it on the expansion tank. The glove did not inflate after a few minutes so Im going to say the coolant is not getting pressurized by combustion gasses. I cleaned out the inside of the cap with soap and water and the car went up to temperature with no leaks. So the next question is how the hell did black sludge get into the coolant system? Is it possible that an external oil leak could seep into a coolant hose?