[Taff]

went wheelin on sunday morning... drove a pretty cool hill, lula saw it scary stuff... my passenger was crapping himself.

opened my bonnet to day to find a place to mount my new air compressor and found oil all around my radiator overflow and it had blown the lid off and sprayed a fair bit over the inside of the bonnet/engine bay. i checked my oil and its at minimum but its still clean, no water in there! i did a fairly extreme and steep hill climb yesterday and i assume it happened then. i know i should have had a look there but i was in a massive hurry to get to work (and was still 30min late; being late for work on Christmas eve in a bottle shop is NOT GOOD)

so is the oil there from something wrong with my head or is it just from the extreme angles/high revs/hot engine ...

it has never happened before. its a 91 sierra 1.3

[Taff]

well i drained my radiator overflow and there wasn't as much oil in there as i first expected. alot of brown gunk though, more like mud. im going to get my radiator flushed out and refill it all then see if it happens again.

im pretty sure now it wasnt actually oil getting in but more of a build up over time that has been pushed out all together. my radiator water is still green and the car is running fine, no heating problems and it idles very smooth.

[royce]

sounds like you have it all sussed and I'd reckon maybe the overflow on your overflow bottle may of been blocked and the extra pressure of a hot day built up in the bottle and popped the top off

some coolants also contain an oily substance in them that tends to seperate over time and float to the top like that

if your not getting any bubbles in the coolant or anything I would go with a flush out and some new QUALITY coolant (alloy engine remember) so your prepared for the summer ahead, maybe look at a new cap for good measure

oh and if you take the overflow bottle out, make sure it clips in firmly, they have a habit of dissapearing on rough tracks