Hopefully i can help..
There aren't may places oil can meet coolant - though if it does and the oil is seen to be floating around in the coolant system - then there are few places this could be coming from - the first could be the headgasket failure or the stages of failure depending where its failed usually if that's the case then it will be between the oil/coolant galleries - The next obvious cause could be an internal fault with the oil cooler not uncommon on the vauxhalls of that age/engine - this will be actually part of the oil filter housing which is cooled by engine coolant fluid - you'll likely see a couple of coolant hoses going to it "a square silver unit" - a feed and return hose - so first locate the oil filter housing and the observe the two coolant hoses going to it - that will be the cooler - The reason oil gets into the coolant is simply because the oil pressure is much higher than the coolant system, and when the engine is running, the crack through which the engine oil escapes into the water passage is forced open by the high oil pressure - thus the engine oil finds its way into the coolant system as opposed to the other way round with coolant in the oil..so those are likely the two places you need to have checked out anyway - then after which, you will need your coolant system flushed out completely and thoroughly and refilled with new antifreeze/water & oil and new filter.but bear in mind in most cases some of the hoses if not all may/recommend to have to be replaced..i do hope this helps..if you need to ask anything else or include anything further then just continue before you rate
Thanks for your reply
Could this have anything to do with the intermittent misfiring problem or would that be separate?
Also, if the headgasket is failing, does the same thing apply regarding the higher oil pressure forcing oil into the water system or would I see traces of oil water (white scum) in the oil?
Hi..there..thanks for your reply..
Its possible especially if one cylinder is acting up.loosing compression etc..its kind of harder to diagnose on a diesel "compression test wise" unlike on a petrol with sparkplug removed..on a diesel you would need to remove either injectors/glowplugs using the correct adapter in place of those then check compression that way..In regards XXXXX XXXXX last question..yes it can do..its depends how the gaskets gone..eventually it will show up in the oil/coolant mixing..One thing you should maybe check up on is if this is a old problem and who ever previously hasnt flushed the system out properly..You have no choice at this stage to have that system cleared out..oil in there will no doubt clog up the matrix.extra strain on the water pump trying to get that thick substance around the system and through the radiator.its a messy job and will take lots of flushing using detergents etc to get all that out..one test to see which is which..is to temp bypass the oil cooler in a way of joining both coolant hoses together..if the oil still shows up in the expension tank then you can asume the cooler isnt really at fault but as per the headgasket..if the oil doesnt appear during that test when the engines running - then the oil cooler is at fault..especially too if oil ior traces of which does start to leak out the ports where the coolant hoses where connected too on the cooler itself..i do hope this helps
Ah well..... here goes.....
Thanks for your help