Head gasket fear
 

So my first "problem" post: my 95 SL1 has a paste-like substance in the coolant expansion tank. I have read that black spots indicate oil, but I cannot see any. It smells like coolant and the car doesn't bleed either coolant or oil. I am doing a compression test this weekend but wanted to see if anyone here ever seen this before, or if it's norm (my first Saturn). Advice welcome, and if it is head gasket, easy for the weekend mechanic? Thanks!

Does the stuff in the coolant reservoir look like a chocolate milkshake? That usually means oil is entering the cooling system. This problem is more common on the DOHC engines from 95-97 due to porous head issues. The problem is, it usually wont be confirmed by a compression test.

hos -- I thought that was more common for the SOHCs

plus I want you to be wrong because I own a 95 and 97 SC2 (DOHCs)

May be so, Derf, but I've only replaced twin cam engines with those symptoms. Not all go bad-maybe it was just a bad batch of heads. Also, there are probably a lot more twin cam cars out there, with the majority having no issues. The only problems I've had with the single cam engines are intake manifold gaskets.

I haven't done the compression yet, but a buddy of mine (better mechanic than I) looked at it and knew instantly: mixed coolants. There is no "chocolate" color, and that's what had me perplexed. He says that sometimes blokes mix coolants that aren't compatible, and they react and create this milky paste. So I'm flushing the system completely tomorrow and hopefully that's the end of that!!

Good luck with that.

There was a tech bulletin put out a few years back about mixing coolants (don't do it) ... too bad it didn't filter out to the general public