zogster

I can see signs of some water in oil... that slightly emulsion-y look to oil at the top of the filler tube.

Did a quick compression test, results: 120/120/135/132 (cold, no added oil in cylinders, 4-5 seconds of cranking, not at full throttle which I gather is recommended as a better test)

Firstly, what do those numbers reveal, if anything? (I know that ideally they'd be the same, and higher, but the engine does have over 210,000 miles on it)

Secondly... I am in the process of changing the clutch, and did the test just before I started, so unfortunately I can't do any more engine tests until everything's back together, but is there anything I should look at while access to all engine bits is a little easier to help track down or fix the source of that leak?

(I think I replaced both the head gasket and oil cooler seals about 4 years ago)

MAGK944

The emulsion on the top of the oil filler tube is normal and nothing to worry about. Totally unrelated to any water/oil mixing, compression numbers vary from car to car but should be about even across all cylinders. Your numbers tell you very little apart from that you have lower compression on two cylinders. To determine the cause you should do them again wet and then perform a leakdown test. With all three tests you can make an educated guess if it's the rings, guides or elsewhere. Personally I think you are fine for the mileage, stop worrying and just enjoy it.

V2Rocket

if you are seeing yellow/green/brown goo on the inside of the oil filler cap or the AOS tube when the engine hasn't warmed up very much, but the goo and stuff is gone after a hard, hot drive, you're ok..

zogster

Thanks, that sounds pretty reassuring - I'll have the my local mechanic do a leak down test after I get the clutch finished, which is of course proving to be so much easier than I could possibly have imagined ;-)