GuyllFyre

Yea, I've got light lifter tap but with low oil pressure warning at idle, it's kinda expected. Then again, I think all my VWs have had lifter tap, so I've never thought twice about it in the Audi.

How does one know if the valve is actually bad? Since Bentley shows "Oil check valves, replacing." Is there an "Oil check valves, testing?"

If I can even get the valves, they're $55 each new and I'm running low on cash at the moment.

grillage

The test is just noise in the valve train.

Lago Blue

<u><b>Introduction:</b></u>

I'm going to argue that your key issue is lack of oil supply.

<b><u>Background:</u></b>

Although a little hard to find, the functional description (from 12v.org) for the cylinder head oil pressure relief valves, and the steadying chamber oil check valves; can be read here:

http://www.12v.org/engine/index.php?section=hw&sm=oil

<b><u>Why not:</u></b>

a.) <u>Cylinder Head Oil Pressure Relief Valves.</u>

1.) Perhaps the heads are a small customer in terms of the total oil supply the engine requires? I say this both because of the construction details listed in the above link, that these items are located a long way from peak pressure and your biggest leak, and the fact that despite the leaks many of us have, engine failure due to a lack of oil, save for inattention on our part; is rather rare!

Even if these valves where both stuck partially open and relieving too much pressure, and all the time, I don't think that would cause your low pressure indication due to the description of the head gasket's "calibrated holes" purpose; at the above link. (See also 1st drwg.) &

2.) Although your lifter-tap may indicate low oil pressure at the heads, that you also have a light hooked to a sensor so close to your oil pump, to me indicates oil pressure is low; everywhere.

From 12v.org: (see location of item "F" in 2nd dwrg.) "Oil pressure switch: sender for oil pressure warning light (0.9 bar / 13 psi): gray connector"

b.) <u>Steadying-Chamber Oil Check Valves (OCVs).</u>

It may be possible to functionally bench test them, but that's not what I did. I think your own visual inspection will suffice.

The OCVs or anti drain-back valves are so simple (a ball-bearing and a coil spring trapped in the valve body) and accessible once uncovered, it is quick and easy to clean, inspect and re-install.

Here's what I did and why:

After unscrewing them, I cleaned them with Brake-Kleen, compressing the spring by pushing the ball a few times, the ball felt sufficiently resistant, the valve opened and closed without sticking and the ball-bearing and all surfaces looked perfect. They "held water" so to speak, so I put them back in and re-torqued them.

Here's how I think they work:

As they are located in the small diameter oil pressure passage going up to the heads, the ***** are pushed open by normal oil pressure, and as their position during engine operation is supported by oil pressure, the ball is raised against the spring; and gravity. After engine shut-down, the ball-bearing <i>falls</i> down onto the valve seat. All the spring has to do is <i>help</i> it fall and keep it there. If its' clean, I think it will seal; perfectly.

When you have everything out ans in your hand, if the spring has any ability to push the ball-bearing sufficient to close the passage, and if the ball seals it, I think it is functioning as designed. After oil pressure falls, or before it builds, which are the only times the OCVs provide benefit, all they have to do is stay closed; gravity will do most of that work.

By visually inspecting and forcing the valve to cycle, I think you can judge your valves ability to fall closed and stay that way. They need to seal sufficient to hold back the weight of that small column of oil above in the heads. Rust, debris or some mechanical defect in either manufacture or installation are the only reasons I can think of why they might not work.

<b><u>Conclusion:</u></b>

First let me offer that I don't think oil, having escaped from the valley pan, can be brought into the intake tract and the EGR system. You may have EGR issues due to oil, but that oil is from your CCV system.

I don't think that either of these oil valves are having an impact on your issues because they don't leak externally, and I don't believe that their malfunction would cause the low pressure indication you have. That and you have an as yet undiagnosed oil leak <i>near</i> your alternator leads me to think you have a oil supply problem; not relief or retention.

Please tell me what your oil usage has been like both historically and more recently. I suspect you currently go through a lot.

GuyllFyre

Thanks for that response.
The car has used quite a bit of oil, at it's worst a quart a week and I typically only go about 100 miles a week. I figure that most of it is leaking from the top of the engine, so it has to have some sort of pressure to move it up there so it can leak out.

I guess once I have the intake off and can locate the oil leak that's coming from somewhere up there, I might be able to see where else it's leaking or solve that problem and move on to the next diagnostic. I'll be temporarily plugging in a gauge since I now have the proper sending unit, so it'll give me a bit more information as well.

Something that hasn't yet become clear, is the oil pump in the lower sump where it's accessible if it needs replacement?

Lago Blue

On both versions, it's fastened to <b>both</b> the front of the block; and to the upper pan. In fact apparently, if your lucky, it may be just that those bolts into the block are loose, perhaps causing both your loss of pressure; and your leak.

I figure most of your leak is downstairs. Remember that oil pressure is reduced upstairs, and the valley pan is part of the crank-case vent system, not oil pressure supply. A good deal may pool in the valley over time, but only because it's trapped there, there's no oil pressure loss there.

I think that the pressure gauge will confirm you have low oil pressure throughout the system.

GuyllFyre

There doesn't seem to be any oil leaking in the area where the oil pump would be mounted, it's all coming from above and leaking down.

I don't want to have to do the oil pump, that looks like one of the stupidest places to mount it.

Wish I could afford a better car, this one is pushing the limits of my patience and money.

hubturn

Please tell me that green stuff at the water pump and oil cooler isn't (gasp) Prestone?

Lago Blue

It might be, not my car or photo.

grillage

Lago,
You make a lot of sense. The sensor seems to be way too far away from those valves for them to be the culprit.

I would say that a trip to the valley pan to re-seal it seems a very good idea. While he's there a cleaning and checking of the valves would make a lot of sense. I have the ones I took out of my car this spring. I'll check their movement and opening/closing over the weekend.

My 93 90q used to leave drops all over my driveway but has stopped since I re-sealed the valley pan (the second time). Now I just burn a quart a month thanks to bad rings on one cylinder.

GuyllFyre

So today's task has been getting the OEM aux gauges ready to install.

Now that I've got the gauges hooked up for testing, the oil pressure pegs the needle over 5 bar as soon as the car is started!

I rechecked my wiring, all is connected properly. I re-checked the plugs on the sensor, both are connected to the correct connections. The sensor is brand new from GAP, so it should be pretty straight forward.

Do I really have too much pressure rather than too little?

Am I doing something wrong?