hi, i have a mk4 1.6 8v astra and have recently discovered a beige coloured sludge under the oil cap. my girlfriends mum's bf is a mechanic and reckons my car will be fine, he smelt the coolant to see if he could smell petrol. not quite sure why you would smell petrol as oil doesn't smell but yeah.
i have a few schools of thought so would appreciate all opinions:
coolant level hasn't dramatically dropped and the sludge is only around the top of the oil cap and tip of oil dip stick, so could possibly be due to the cold weather and the fact i go on short journeys means engine not getting hot enough for vapor to evaporate.
sludge is a sure sign of head gasket on its way, so mine could be too however i haven't lot any power, coolant hasn't really dropped and around the gasket look fine. plus the head went in 2007 before i bought the car, so its a relatively new HG.
this is my dads opinion, he reckons the thermostat is stuck open hence the condensation. he checked the coolant pipes for leakages, checked around the HG, and looked in the breather pipes, which were completely covered in sludge. my dad thinks its the stat stuck open because it doesn't matter how long i run the car my temp gauge doesn't move at all, I'm always complaining about my crappy mpg, and my car is very punchy for a 1.6 8V. my dad said my car is probably running cold hence getting the condensation sludge and low temp gauge readings.
Sorry for the long essay, all comments appreciated as im completely unsure what it is.
although my dad said the thermostat is a big job to get to in these engines so might be better to add a second stat further in the pipe before the radiator.
Thanks for taking the time to read this, just looking at it make me think omg lol