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Audi Forum: oil consumption, PCV valve, rings and compression issues - fix inside
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Old 12-15-2012, 11:15 PM
5.0rick 5.0rick is offline
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Default oil consumption, PCV valve, rings and compression issues - fix inside

Hello everyone,

I am new to the forum and new to Audis. I purchased a 2008 S4 Cabriolet some months back and to my disappointment experienced oil consumtion issues. The car was still under warranty so I took it to the dealer for the oil consumption test. The results were .73 quarts for 700 miles which made it pass by a tiny bit and got Audi off the hook for any repairs or replacement engine

The engine has 52,000 miles now so I decided to replace a few parts including spark plugs and PCV valve. I noticed that all of the cylinders had a lot of carbon build up (while replacing the plugs) and theorized on whether or not I had a faulty PCV valve which was the culprit on the oil consumption.

Since the plugs were out, I also decided to do a compression test and the results were very disappointing. The compression was really low on the 2 front cylinders on the drivers side - 123 psi (below the minimum 130 psi). BTW, the compression test was done with a hot engine.

So here is my theory, a bad PCV valve leads to the engine sucking down oil and gunking up pistons, combustion chambers, and ring lands (grooves in the piston where the rings are). This sludge basically "glues" the rings in the pistons and compression is lost due to no free movement of the rings in the piston lands.

I am a long time DIY mechanic and have always used a product called Berrymanns B12 Chemtool for carburators and for stripping fuel/oil varnish. I decided to soak the pistons and combustion chambers to see if this would restore compression (if the rings were indeed "glued" in the pistons).


Here is the procedure that I followed.

1. After all plugs are out - spray a large doze of B12 and let sit/soak for 2 hrs. I used a full can -20oz.
2. Use a manual transmission fluid pump with a small hose (one that fits through the spark plug hole) to suck out all of the B12 with the varnish and carbon bits. Some B12 will remain as you wont be able to get all of it out.
3. Place an old towel (rags) over the valve covers to catch any B12 and turn motor over a few times with the starter.
4. Repeat steps 1 through 3.
5. Install spark plugs and coils and drive the car for 30-45 minutes. I noticed a big difference in idle and throttle response.

As soon as I got back to the garage, I took out the spark plugs of the 2 sick cylinders and ran another compression test (pulled the fuel pump fuse as well). The new compression tests yielded readings of 138 psi on both cylinders. That is an increase of 15 psi but more important, a reading above the minimum of 130 psi.

Needless to say, I am extremely pleased with the results but I believe that there is still quite a bit of sludge in the motor. I have found a product called Kreen from Bano Labs and I will be adding some next week. If anyone is interested, there is an interesting thread here - http://www.bobistheoilguy.com/forums...Number=1940735

I hope this helps someone. Let me know if you have any questions.

Regards,

Rick
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