Not your usual Oil pressure issues on an S3

[Omniquito]

Hi Folks,

Please, before you moan at me I really cant find the answers I am looking for and think that I have a "not that common" problem with my S3 oil pressure, in a way I hope I am wrong but we will see.

I recently bought my 2000 plate S3 from a one owner from new and full every bit of history that you can think of incl full audi service history using long life all the way up to its stratospheric 220k miles that it has.

I had the 3 beeps and it started to sound like an old fiesta so the story begins...

It only happens when warm, never when cold and the real unusual thing is it generally happens after a little squirt of acceleration (not even that hard) and on back off the throttle and the revs drop below 2000 RPM... once left overnight and cooled it is fine again until warm and the above happens.

I know that this sounds like the usual "below 2k rpm" but cant find anything about the "after acceleration and backing down the revs" bit or it just randomly happens.

I have had the pressure switch replaced and no joy

had the sump off and OMG the gauze was chock full "no exaggeration" so really thought that would help... but no, its worse!

What next guys? I have seen threads talking about PRVs, big ends, oil pumps etc etc but not sure what to try next...

The thing that concerns me is that it tends to only happen when warm, usually induced after some semi hard acceleration and then only when the revs drop below 2k but it also happens when I drive like a granny (most of the time) on straights and bends.

Sound like a return flow issue? when it cools and also when cold the oil flows well, the tappets fill and it is fine for a while.

One last thing, it is on long life oil and has been for its entire 220k life, could this cause this?

Sorry if it is going over old ground but really hope you guys are patient and have some good advice.

Thanks in advance, Neil.

 

[Omniquito]

A couple of things to add:

Its an APY engine

I have all of the oil breather system off and it was chockabloc full of crap, is the valve that takes a hose from under the manifold the oil PCV and should it be sprung loaded?

Mine opens and closes if I suck and blow but there doesnt feel like there is any resistance in either direction and thus makes me think that it is not sprung loaded... plus if I blow from the manifold direction it seals but I can get a little blow by... should this seal 110%?
I also have oil residue around filler cap...

Could the PCV/PRV cause my oil pressure issues?

 

[aragorn]

Its probably a worn out oil pump with that mileage.

Oil pressure is related to engine RPM, the faster the engine spins the more pressure is generated, so it makes sense the issue would appear at lower RPM's. As for only happening after a bit of accelleration, i guess it could be a slightly sticky relief valve in the pump.

Stick a new pump in and switch to 5w40 fully synthetic oil (most longlife is 5w30 which is a bit thin for a high mileage motor) and see how it goes.

Long life oil itself doesnt cause the problem, what does cause it is long life servicing, ie the huge service intervals that are employed.

 

[Omniquito]

Hi Aragorn,

Thank you, that makes a lot of sense and they arent massive money either. I may just get that sorted.

One other thing, do you think my PCV valves spring has "sprung" and needs replacing or are they usually that easy to open?

 

[aragorn]

i'm not familiar with the S3 breather pipes.

PCV is a fairly large round disk, and usually sits in the turbo intake hose.

The valves under the manifold are check valves, and should only allow air thru them in one direction. They're there to stop boost pressure reaching the breather system. Interestingly i noticed the other week that a brand new audi check valve for the breather on my A4 seemed to let a very small amount of air past when you tried to blow thru it in the wrong direction, whereas the check valve for the brake servo thats 12 years old let nothing past at all.

 

[Omniquito]

What I dont understand guys is why is it ok when warm for a while and then it triggers the light and sounds like a tractor? top end starvation...

Its as if it is ok for a while and then loses pressure and doesnt gain it back... until a lot later and its all cooled or the next day.

Its a little like a prv opening and then not closing, I would understand that when I give it a squirt and then the warning but that doesnt explain the warnings when pootling around...

I am in danger of disapearing up my own **** on this, my garage wants to do a top and bottom strip but money is tight and I am keen to change the rod bearings and possibly the pump....,

What say you guys?

One last thing, in the strainer there was a lot of sludge, orange plastic from the dipstick and some 5mm flecks of silver coloured soft metal, quite thin... what would that be?

Thanks for the help folks

 

[aragorn]

Oil gets thinner as it heats up, which means the pressure falls. A cold engine at idle will often be producing over 5bar of oil pressure. A hot one with a good oil pump will be making 1-1.5 bar. With a poor pump you might not be getting even 0.5bar at idle once fully hot.

Stick a new pump in and go from there.

Its cheap and easy to do, and if that doesnt fix it then your in for a massive bill for a full rebuild anyway so its worth a try.