One way valve

[driftin jo]

You need an 8 mm triple square (aka "serrated") bit to remove and replace the oil pressure check valve.



Any chance you are running a "built" engine with ARP main bearing studs? I don't understand this but apparently it is possible to crush the oil check valve in the block when running these studs:

http://forums.quattroworld.com/s4s6/msgs/144645.phtml

You mean triple square ( spline )

[driftin jo]

Just changed the oil but has been doing this a few months on and off

It does sound like the check valve is sticking shut, never seen this happen before and a bit odd as the oil pressure should force it open. They normally stick open and this it typified by the oil pressure taking a second or 2 longer to rise on start up as the oil has to fill the feed path to the head.

[driftin jo]

Fortunately for you there is not a lot that goes wrong in a hurry with a temporary lack of oil to the head, apart from making a tapperty crescendo.
I'm not saying it's good, just not very bad like having no oil pressure to the bottom end would be.

[UrS4boy]

You mean triple square ( spline )

I said triple square. They are are sometimes also called "serrated" in NAmerica.

Apparently also "spline" in some areas.

Triple square is the most correct term.

(Not to be confused with double hex BTW).

[Rikki Kitto]

Cheers for the input, I hate starting her up at the mo because I know I have to go through the routine of blipping the throttle which shouldn't need doing. Hopefully the valve is the problem not something much more complicated

[UrS4boy]

Oil pump and temp sender info

... Hopefully the valve is the problem, not something much more complicated

The check valve is common to many Audis and VWs so it should be easy to find.

*IF* it is something else, it would maybe be the oil pump. Here is some oil pump info that would help in that event.

http://forums.quattroworld.com/s4s6/msgs/93029.phtml

[mcandmar]

What oil filter have you got on there? If its the wrong one or faulty it could be draining itself causing your problem.

Other possibility is the pressure relief valve in the oil pump stuck open.

[Ross]

Interesting thread, I've been keeping a keen eye on all the oil pressure topics that have been coming up of late!

I have very similar symptomns, and have done since... well, I can't remember, some time post-rebuild. I see 1-1.2bar on warm idle, seen it at 1bar or a smidge below after some real thrashing, not concerned because by 1,000rpm it's at 2bar already.

However I have noticed tappeting for 2-3s after a cold start of late too...

Mark - how could the oil filter cause this? Interested because I'll just wait for an oil change if that is a viable cause... assuming it doesn't get any worse (hasn't done so far). If no change then I'll finally be making use of my spline set!

[DJones]

Interesting thread, I've been keeping a keen eye on all the oil pressure topics that have been coming up of late!

I have very similar symptomns, and have done since... well, I can't remember, some time post-rebuild. I see 1-1.2bar on warm idle, seen it at 1bar or a smidge below after some real thrashing, not concerned because by 1,000rpm it's at 2bar already.

However I have noticed tappeting for 2-3s after a cold start of late too...

Mark - how could the oil filter cause this? Interested because I'll just wait for an oil change if that is a viable cause... assuming it doesn't get any worse (hasn't done so far). If no change then I'll finally be making use of my spline set!

Ross

Standard VAG filters have a none return valve in them stopping the oil from running back from the higher parts of the engine. Alternatives sometimes dont have this feature.

Darren.

[mcandmar]

Yes basically, or if the rubber diaphragm under the holes around the outer edge is damaged they will drain back. I also recently had a faulty Knecht filter on my fathers 993, didnt show up any oil pressure issues because they are dry sumped and the filter is at the bottom of the tank on the outlet. We only noticed it as the car made all kinds of gurgling noises when running. Problem was the filter element had detached and was rattling around inside the can. On a conventional wet sump engine it would caused all sorts of problems from draining everything back into the sump and random oil pressures, never mind the fact it wasnt filtering any more. I just dont trust them any more.

And if you ever see an orange Fram filter take it off and throw it as far as you can, they are complete crap and can cause all sorts of problems. Though i do believe they are standard fitment on Ferrari's.

Personally i would only use Mann filters on an Audi, a 719/30.

[Rikki Kitto]

What oil filter have you got on there? If its the wrong one or faulty it could be draining itself causing your problem.

Other possibility is the pressure relief valve in the oil pump stuck open.

Proper Audi filter from dealer

[Rikki Kitto]

The check valve is common to many Audis and VWs so it should be easy to find.

*IF* it is something else, it would maybe be the oil pump. Here is some oil pump info that would help in that event.

http://forums.quattroworld.com/s4s6/msgs/93029.phtml

Many thanks hopefully not this as I priced the pump at £400 then fitting on top of that would be scary

[Rikki Kitto]

Got the valve today just waiting to fit it now, will let you know what happens

[Rikki Kitto]

Why ? The check valve is there to stop oil draining back from the head so you get oil
pressure there quick, if it sticks open you will just take longer to get oil to the head on start up, you WILL still have oil pressure, just won't build up as quick as it should.

Think I might be getting the wrong end of this thread, does this valve affect the flow of oil to the head or is it just to adjust flow to the sensor? Still not fitted by the way

[driftin jo]

The one way valve simply stops oil draining back from the head so that the oil pump
does not have to fill the the oil ways up to the head when it starts pumping.
This is so that you get oil to the head straight away and the system pressure as a whole will build quicker.

As I said earlier it does sound like your valve is sticking shut, thus stopping oil getting to the head and also the pressure sender so you don't get any gauge pressure. They normally stick open thus causing a slight delay in getting oil back to the head and building oil pressure.

I've not seen one of these stick shut before (apart from the ones damaged/ crushed by ARP head studs) but it is not beyond the realms of possibility and seems to be what is happening with yours.

If it is not the case then it must be an oil pump problem and you would have had no oil pressure at all even in the bottom end and this would have killed your main and big end bearings by now for sure.
The most likely scenario is that to your valve is all sludge up and when the oil is cold will not re open to allow the oil to the head until a bit of heat frees it up.