Hello, I looked at my oil filler cap tonight to find a light brown sludge on the inside of the cap. What is wrong with my car?

EDIT: The car also has 155k on the OD.

 

Bump diggity

 

Are you losing coolant? The sludge you are noticing is a combination of combustion by products, rust and possibly water (coolant). Look down the filler pipe itself. Are the inside surfaces of the pipe rusty? They should not be rusty at all. If they are then you have a problem with water or coolant in your oil system. This could be anything from a leaking seal to a corroded water pump housing.

If you suspect your cooling system is leaking into the engine internals then a pressure test is the only way to know for sure if you indeed have a problem.

I had the same problem and it turned out to be caused by the expansion plugs on the front end housing leaking coolant into the oil pan. There are three plugs there. Two of them are behind the front engine cover and the third is on the outside, kind of below the crank angle sensor.

 

sometimes **** just collects up on or underneath oil filler caps after a long time, but the oil itself is not necessarily sludgy. is the oil sludgy on the dipstick? if you put oil from the stick on your fingernail can you see through it? i cant really imagine a rotor motor lasting too long if the oil has turned to sludge. i worked at a lube place and some cars oil would actually be nothing but a thick tar type ****. if the oil stays clean on the stick thats all i would care about.

 

Read this http://mrmazda.members.atlantic.net/...t.html#OILFOAM and bookmark the home site. Lots of tid bits.