Hello, im new here. I've bought a 1998 civic 1.5 vtec-e, today i opened the radiator cap and noticed some weird looking sludges, might this be just old coolant or something more seriuos like head gasket??? Car starts and runs fine, no overheating (at least from the temp gauge), no smoke, oil cap and oil dip stick looks fine.

Im posting pictures below:











any help?

 

that could be sludge, but looks like coolant mix. go buy/rent a block tester and find out.

 

I had the same thing happen with my D16. My head gasket went bad but it was only leaking oil into the coolant. My overflow would be full of an oil/coolant mix. I would also lose about a quart of oil maybe every week or every other week. I ended up having my engine rebuilt and head gasket replaced and problem fixed. I flushed my radiator but still had oil residue finding it's way into my coolant overflow a month after the build. Another flush fixed that.

Edit: I never had overheating problems or anything either while it was like that. I drove it for a good month or two before I had the rebuild and never had any issues. The sludge had actually jammed my vtec pin shut so it never engaged.