Sludge and the Audi / VW 1.8 L Turbo Engine

One obvious place to connect the oil gauge sender is at the location of the stock warning sender. I wanted to leave the warning light intact so I installed my gauge in place of the plug marked in red in this diagram from the Bentley manual that I modified.

I can't be sure that this is the best site, but it showed me when my pressure was low and it shows my pressure within the proper range since the sludge repairs. It is also at least as accessible as any other spot. I moved the radiator overflow tank aside to get what was at best limited access.

I went with a cheap mechanical gauge with nylon tubing, thinking that I could upgrade later if necessary. The mechanical gauges are said to be more accurate and to have quicker response than the electrical senders. I figured there was no reason to look for copper line based on the warnings I had heard about vibrations eventually cracking it. I already had 6' of 5/8" i.d. windshield washer hose around the house so I stuffed the nylon hose in that. It kinked a little when I tried to push too much at once. Pushing in no more than 3/4" at a time worked well. Once it was in the rubber hose it behaved well during the install.

To gain access for the install I removed the plastic engine cover, the weather stripping that holds the long plastic cover over the rear of the engine bay, and I pushed the coolant reservoir out of the way. Only one screw has to be removed to move the reservoir, but the plastic prongs, which go into the metal tabs on the firewall, were hard to work free (pulled up on the reservoir and towards the front of the car).

I used ratchet extensions and a swivel to get the plug out and put in the sender. Then I used a small crescent wrench to fasten the hose with its compression fitting. After dropping wrenches and having to fish them out of the belly pan it finally dawned on me that I could tie a string to the wrench.

This is viewed from above from the driver's side looking through the intake manifold. There is nothing enjoyable about manipulating parts and tools down there. You should start this part of the installation first. If you give up there's no sense in having a gauge installed in the cockpit. You can see the brass pipe fitting that screws into the oil filter housing and the brass compression fitting nut that secures the white nylon hose (which is just barely visible before being blocked by the U-shaped hose in front).

I wish I had known that the sender had a tapered pipe thread. It would have spared me from an unnecessary trip to the auto parts store thinking it had either defective or incompatible threads. It didn't take much tightening to make it leak proof and I don't think you'd want to over do it as the filter housing looks like it's made of aluminum.

There are two firewalls. On the engine side I peeled back the weather stripping and ran the hose above an oblong grommet for two metal lines. The hose is marked in the image below. It then runs to the left from there between the two firewalls.

On the inside I cut a hole through an unused round grommet shown close up in the inset of the photo. I mounted the gauge on the black plastic. I used the full 6' of hose. The gauge is partially blocked from view when I am driving so that I can't read the number at the top of the dial. I can still see the needle though. There is a chance of breaking the line when getting in and out of the car. That would cause a lot of oil to spill if the engine were running. (At over 20 psi I'm guessing it would be like a super soaker water gun). I plan to secure a larger piece of hose with electrical tape to cover the transition between the coupling nut and the rubber hose.

Another location for the gauge Also, some like to remove the center vents and install there.

Pressure Specs

Bentley CD says:

19 psi @ idle
50-65 psi @ 2000 rpm

Readings I got on the first test drive:

20 psi @ idle
45 psi @ 2000 rpm, reaching close to 70 psi during hard acceleration.

At the time I wrote:

I'm thinking the 45 is close enough. Anything to worry about? — This car had its oil pump replaced at 25k miles and has had oil light warnings since. I'm thinking that now with the proper oil, filter and interval specs the sludge problem has been reduced to one where the sludge is gradually being cleaned up and is clogging the filter. The dealer has my next oil change interval at 2000 miles.

It wasn't long before the pressure dropped again:

1300 miles since the oil change and now my pressure won't get above 30 psi (2 bar).

Finally, the oil warning light came on when the pressure was about 20 psi and below while driving. Since this car has valve tappets, which require a minimum pressure (else they begin to make a loud racket), the warning pressure threshold is higher than other cars which may not warn until the pressure drops to about 6 psi. I never reached the point where the tappets clattered.

Now comes the hard part! Getting to the oil pump suction screen.

Try this at your own risk. I'm not taking responsibility for dropped engines or worse. I dusted off an old structural engineering book for architects and made some calculations that were enough to convince me.

This does not attempt to explain all the details involved in removing the oil pan. It is only to show those special considerations for the amateur mechanic. I strongly recommend getting the Bentley Manual CD. It has the proper torque specs and tightening sequences as well instructions for lowering the subframe without messing up the alignment.

To remove the pan the subframe must be lowered (actually tipped down in the front; the back is still secure). The subframe supports the engine. Once that is lowered the only thing supporting the engine is the transmission, so the engine has to be supported while removing the pan.

Who has an engine hoist?

I didn't and I wasn't about to buy one. I decided that I would be safe with 3, 2x10s and tie-down straps with a 1000 lb. working load rating and 3000 lb. breaking point. I mistakenly purchased 2x12s which turned out to be a good thing because the length of the strap below the ratchet is fixed and rather long for this application. This thing is heavy. I used some scrap pieces on the ends and center to connect the three beams. I could barely set it in position by myself. I have since decided that with the 2x12s I could remove one of the outer boards.

The Bentley manual doesn't make clear the location of the rear engine eyelet for lifting. It is a black metal plate with the hole hidden by a plastic sleeve that supports a hose. Pull that off to attach the hoist.

Note the 2x2s used on the inner edges of the fenders. I notched the beams slightly (too much and the beams would have touched engine parts) with a circular saw to fit over these. I may have placed cardboard under the 2x2s.

Note the weather stripping peeled back and the coolant reservoir tank still connected, but placed aside. I used a scissors jack with a piece of radiator hose on top. I also added a second tie-down (not shown) for peace of mind.

The manual says that the lock carrier must be placed in the service position. I didn't do this. (I didn't really know all that implied when I started the project. I eventually learned about that to do the timing belt and stored the front end of the Audi in my living room.) There might have been more room to remove the oil pan if I had. Beyond that the only reason I can see to do so is to easily reinstall the snub mount at the front of the engine. Perhaps this is different on a car with a manual transmission, but with my automatic snub mount I was able to push on the base to compress the rubber sufficiently so that the bolts could be reinserted.

Place tension on the engine. Stop before it begins to lift.

There's a special tool to remove the two pan bolts at the end of the transmission (#T10058). The flywheel has a notch in it to gain access to the bolts. I managed to remove them with an Allen head socket placed lightly (not snapped in) on a swivel extension. It would be easy to round out the bolt this way. I noticed that most bolts break free and then turn rather easily. A bolt that feels like it's turning slowly under a lot of force is probably being stripped.

Don't mar the mating surfaces of the pan when trying to remove it. You can tap it lightly with a rubber mallet. It won't seem like anything is happening and then it will break free. 

To remove the oil pump the sprocket must be removed. You'll need a large Torx (star bit). My basic drill set didn't have one large enough. I think the size needed is a T40.

I probably needed only a new suction tube, but this job is so time consuming that it seemed pointless not to spend $100 for a new pump. I thought I was going to get a knock off, but the pump had Audi/VW and the proper part number on it. The problem was that it came with a much longer spout than the original shown below. I think it must have been intended for use in the transverse VW engine, a design that allows for a larger pan (and more oil, I've heard this may be why the VW with the same engine has fewer sludge problems). So I had to bite my lip and buy a spout from the dealer.

The yellowish bits are fragments of the oil-stained, white RTV sealant used on the pan when the dealer replaced the pump at 24,000 miles. The majority of the blockage was due to the hard carbon bits as well as some softer sludge. Since it is black it's hard to see in the photo, but most of the screen's openings had some piece jammed in and the tapered edges were packed with sludge. All my attempts to clean this part by soaking in solvents and Drain-o and by spraying solvent with an extender placed right at the back of the screen were futile.

The oil pan had hard sludge that got worse higher up on the walls of the pan. I got it spotless using a steel wire brush wheel on a rotary tool. I tried a softer brass brush initially, but it disintegrated too quickly.

Here is another analysis with information from those with some experience. Quoting from that page:

Oil Filter Media Condition

Non-turbocharged: Tan colored, small amounts of hard carbon. Filter paper should not be brittle. Dark filter media without significant hard carbon means the filter has not been changed often enough. Dark filter media with significant amounts of hard carbon indicate high oil temperatures. Suspect compression blow-by, or poor engine baffle.

Turbocharged: Tan to dark colored with more amounts of hard carbon. If filter media is brittle then filter should be changed more often or oil temperatures should be reduced.

Just to be pointlessly nerdy here's a view through my microscope of the oil filter paper from one of these filters.