Engine Gasket?
 

I have a 98 Z28 with 138k miles on it. She has done very good for me. I noticed when filling oil that there is a some yellowish gunk on the bottom of the crankcase fill cap. I saw this on my old Lumina and it was coolant getting in the crankcase (lower intake manifold gasket). Anyone have this problem before? Any clue as to what is specifically wrong or how to proceed trouble shooting to find the issue? I haven't noticed a substantial drop in coolant or anything. She still runs strong. Help please!

I can post a picture if needed. No serious mods. replaced water pump, low temp thermostat, replaced clutch, K&N filter and SLP lid.

Sounds like something minor or nothing at all if you aren't combusting oil or coolant.

PCV valve intact?

Just inside the filler cap? Sounds like normal condensation from short trips.

I like what I'm hearing so far. I do mainly drive less than 20 miles/trip. I will check PVC.

Could even be the oil cap seal.

You need to get take that car for a long drive every once in a while. Get it nice and hot, and don't be afraid of 6000rpm. Your engine will thank you.