Hi everyone,
I'm aware this topic has been covered to death in the past but I'm hoping someone can help or offer some advice. I'm a retired diesel mechanic with over 17 years experience of the trade and still carry out small jobs for family and friends. I had a friend contact me 2-3 weeks ago regarding poor performance, lumpy idle and an intermittent engine management light on his 2004 Audi A4 1.8T (BFB engine) which has covered approximately 93k miles. I carried out some diagnosis with my handheld tester and found several DTC's stored mostly detailing misfires on cylinders 3 and 4, plus some other sporadic faults regarding pressures and air flow. Upon quick inspection of the coil packs, plugs etc, I immediately found the spark plug holes of cylinders 2, 3 and 4 were almost entirely full of fresh oil so I advised my friend the cam cover gasket would need to be replaced first before any further diagnosis could take place as the presence of oil wouldn't be helping matters! I also noticed several vacuum and breather hoses were loose/incorrectly clamped plus there seemed to be an air leak from the control valve housing at the rear of the cylinder head. After replacing the cam cover and spark plug gaskets plus all the clips on the breather/vacuum hoses, I road tested the vehicle but to my horror the red oil pressure warning lamp illuminated literally within 300 yards of driving. After returning from the road test, I immediately checked the oil level which was fine.
I run the engine again at idle but noticed the top end was slightly rattling so I attempted to remove the oil filler cap during idle to check for oil feed to the cylinder head but found the cap was impossible to remove which I found bizarre. I then searched online for answers and almost every post I read pointed to a faulty PCV valve which was causing high pressure in the breather circuit which also had the potential to affect the oil pressure. I then replaced the PCV valve under the intake manifold and sure enough the old valve was broken internally and allowing crankcase pressure to pass straight through it unregulated. I started the engine again and the new PCV valve had cured the pressure issues and I found I was now able to remove the oil filler cap with no resistance. The engine was running smoothly with no warnings or rattles so once again I road tested the vehicle, but within 30 seconds of driving the oil pressure warning light illuminated once again. I have since purchased a very cheap mechanical oil pressure gauge and plumbed it in to the sender outlet at the filter housing. Rather worryingly the gauge is reading very little pressure at idle (needle barely moving!) and does not rise at all with increased engine revs. I've read on forums these engines are prone to blocked oil pump pick ups and the oil pumps also failing. The car is now abandoned on my driveway and I'm currently trying to explain to my friend why it's not repaired. He informed me he had no issues with oil pressure before I started any work so I'm now worried it's something I've caused when replacing the cam cover gaskets? I did apply a thin bead of RTV silicone to both sides of the new gaskets before assembly to ensure a good seal and this is something I've always done in the past with no issues. I'm worried I've possibly blocked an oil chamber in the head but on reflection there are no chambers/feeds near the gaskets that I could've blocked plus it doesn't explain the lack of oil pressure down at the switch end. May I also add that I've tested the oil pressure switch and this is working correctly.
I have no idea of the service history on this vehicle so unsure when the filter was last replaced and also if the correct grade of oil was used? I'm now tempted to put an oil flush through the engine and replace the oil and filter to see if that helps? Failing that the sump will have to come off to check the pick up for blockage but this is something I don't want to commit to straight away if possible plus it will incur even more cost to my friend plus my own time. This vehicle is now becoming a bit of a nightmare and any help would be greatly appreciated!
Many thanks,
Bruce
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