peter.blais

Hi there-

I have a '01 996TT with 77k miles on the clock. Recently, it started showing low oil pressure. Dash gauge reads under 1 bar at idle and never tops 3 bar at 4000 rpms, warm. It has 5w40 rotella T6 in it with about 500 miles on that oil.

I've done a bit of troubleshooting and no luck so far, so I'm looking for some help. Here is what has already been done:

-Checked oil level via dash gauge- 1 bar from top.
-Checked filter... Not crushed, contained no bearing material etc in the pleats. I replaced it anyways just for fun because I had the new one ready to go.
-Replaced sending unit- no change.
-Pulled out pressure relief spring, swapped it for a new spring / piston / spring guide- no change.

I need to pull out the high pressure "safety" pressure relief valve and make sure all is ok. I also need to check the oil pressure with a mechanical gauge to make sure this is not an electrical problem.

So, any suggestions? I'd also like to hear where you guys are checking oil pressure- the sender port isn't exactly easy to get to, but worst case I can build a hose and temporarily hook up there.

This came on suddenly- car had good oil pressure one day, crap the next. I'd to get it fixed because currently I am not driving it and in another few months it will be too cold to drive it again for another year

Thanks in advance!

Pete

Macster

I would think you'd want to measure oil pressure from the same location the oil pressure used to drive the dash gage is measured from.

As for suggestions it reads like you have followed the right steps.

A real long shot but are you sure the e-oil level system is functioning properly?

About the only way I know of determining this is to properly drain the oil then refill the engine with a specific amount oil and then confirm the e-oil level system readout agrees by reading/displaying the level it should.

The only other thing that comes to mind is perhaps there is some valve between the oil pump and tank that is not allowing sufficient oil to flow to the pump from the tank and the pressure is low because the pump is starved (!?) for oil?

rmc1148

Is there a screen for oil pickup I know Audis 1.8 have sludge problems even with synthetic if not changed often. I would do as you have suggested and put a pressure gauge in and get a real number.

Kevinmacd

Just a thought


Affected Vehicle: 911 Turbo (996), as of 2001(1)

Information: Due to the low position of the turbo-chargers, a non-return (check) valve is installed *between the oil tank and the engine (see Fig. 1, item 2). This prevents the oil tank from emptying into the crankcase when the engine is turned off.

In certain cases, this valve could stick in the closed position, preventing the flow of oil from the oil tank to the engine. As of May 18, 2000, a modified non-return (check) valve is being installed from *engine number M96/70 - 64 1 01282. The new part is identified by a light blue paint dot.

Caution: Possible engine damage due to the lack of *lubrication!
• Shut off engine immediately.
• Do not attempt to find the cause with the engine running.

Service Procedure:
Replacing the non-return valve.
1. Drain the oil into a clean container.
2. Loosen the oil tank mounting bolts.
3. Remove the two M6x16 hexagon socket head bolts, which secure the tank to the check valve (see Fig.1, item 4).
4. Remove the M8x30 pan-head bolt securing the check valve to the engine (see Fig. 1, item 5).
5. Carefully pull the tank back at the bottom.
6. Turn and guide the non-return valve out of the engine and oil tank (see Fig. 1, item 2).
7. Reverse the procedure to install the new valve


http://www.import-car.com/Content/Si...0000037024.jpg

peter.blais

Alright, so- we ran through the basic mechanical stuff because it was ~quick. Then we gave up and decided to check the oil pressure. To do this, I ordered a spare oil filter cap/lid, and drilled and tapped a 1/8" NPT hole in the old one. Not a bad trick if anyone else out there needs to check their pressure without tearing everything apart. - That'll be saved in my bin of "special tools".

Anyways, the car has plenty of oil pressure. 25-30psi at idle and 100+ psi at rpm. The dash gauge reading 0-1 bar at idle still, and less then 3 bar at high rpm (hot).

Soooo- now I'm going to try to figure out what pin position the oil pressure sender is at the instrument cluster, and ohm out the wiring back to the sender for a split or high resistance. I'll also check the grounds. Otherwise, it looks like I MAY need a new / used cluster. Better then an engine rebuild, but still a pain in the butt since it will mean dealing with the dealership a bunch.

Now that I look at it, the dash gauge is doing some odd stuff. At key on, before start, it often indicates ~1 bar oil pressure. Something is definitely up. At idle, the oil pressure on the gauge also fluctuates quite a bit, and on the mechanical gauge, it's very steady.

CincyScott

I do admire the tool you made to check the pressure, I'll file that one in my small brain in the event I ever need it

Macster

Consider trying this: Disconnect then reconnect the connector or connectors that carry the oil pressure signal to the DME and from the DME to the in dash gage.

The problem could just be some surface corrosion on the pin/connector of the oil pressure wiring.

NewYorkBuck

Make sure the sender is ok. Ive been through two of them already and only have 27k.

peter.blais

Yes, I think I will do exactly that. I am also going to dig around and check the grounds under the dash. This car has a bunch of aftermarket stereo / nav / etc stuff in it from some P.O. along the way. Could easily have a whole stack of random grounds under the one post making it get loose.

Symptoms are that of a high resistance on the wire or of a slight voltage offset at the cluster ground, so I'll probe around.

peter.blais

FWIW

This turned out to be a loose main engine ground causing a voltage offset that was showing up on the oil pressure gauge.

Macster

Good to hear, err read.

Which reminds me I've been advised to just loosen the fastener where the battery ground lead connects to the car then tighten this again I was told this improves the ground connection and can cure some ills, though I do not recall what they were. I've been so busy I've forgotten this advice but I really intend to do it to see if helps my oil pressure gage's bouncing needle behavior and improve the radio's performance and if it makes any difference in the voltage gage's reading.