1997 audi a6 1.8 oil pressure problems

[Jeff Vision]

I have just bought a 1997 AUDI A6 Avant 1.8 which has oil circulation/pressure problems. The symptoms are that the car always runs cold until sitting in traffic and then when it gets hot (just before the radiator fans cut in) the oil pressure light comes on and the top end starts rattling, confirming that oil isn't circulating properly. When the engine is cold to lukewarm it runs OK with no oil warning lamp or rattling.
I have tried an engine flush, new filter and good quality Castrol Edge oil but it makes no difference.
The car has 140,000 miles on the clock with FSH and loads of bills, so it has been looked after so I doubt that sludging is the problem, though it is 10,000 miles since the last service and I don't know if the garage would have used the correct oil.
I bought the car off a trader/friend who bought it as a trade in, could the previous owner (a bit unscrouplously) have removed the thermostat to keep the car running cool (to avoid the oil problem) to get rid of it? I know it was not tampered with by the trader whom I bought it off!
So where does that leave us, oil pump failing? but why only when hot? Bearings shot? but there is no perceptable rumble, or maybe sludging but why problems only when hot?
Your help would be of great assistance!
Thanks, Jeff

[Peter D]

Fairly common at 10 plus years for the stat to fail and open too early. I suggest your oil problem is due to the oil pick up tube strainer is blocked up. The 1.8 is very prone to this, the strainer is small and very fine mesh. The sump need to come off. The engine flush will have made this worse as it probably has loosened debris in the sump which has not been sucked into the pick up. The flow is limited thus as the oil thins with heat the pressure drops. What engine code do you have. It is on the ID label in the spare wheel bay. Post up your email address and I'll send you a drawing of the problem area. Regards Peter

[tony_tan]

Hi Jeff,
I concur with Peter's comments too. I used to have a 2000 Audi A6 before my Audi A6 Avant (2009, DIS, Auto, Exective Model) which also had oil pressure problems. The audi technicians (and through posts on here) it was found that a debris had caused the oil pump to become blocked - a replacement soon resolved the issue.
I can remember after picking the car up from Kent being stuck on the side of the M25 awaiting recovery due to the oil warning light - not a memory I want to recall!!
Hope this helps.
Would be great to see a picture of it.
Thanks
Tony

[Jeff Vision]

Well the answer was a worn out oil pump. After replacement the car ran (and still does) run well!