Oil consumption, pcv valve, rings and compression

[RikkiTikki]

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 and I was planning on measuring the compression, I decided to do a compression test before a total cool down of the engine 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).

So here is my theory, a bad PCV valve leads to the engine sucking down oil via the intake (where the PCV valve dumps) 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. This in turn also promotes more oil consumption due to a poor ring seal. Sort of a vicious cycle.

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 help 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/ubbthreads.php?ubb=showflat&Number=1940735

Once I have ran Kreen for about 1000 miles, I will run another compression test and post all results- before and after.

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

Regards,

Rick

[RikkiTikki]

Here is a picture of the tools and the reclaimed B12, no that is not tea ;-)

http://i1223.photobucket.com/albums/dd520/50Rick/photo1_zps87983977.jpg

BTW, the clear tube helps a lot in seeing whether or not you have placed the end of the hose in the right place for the vacuuming of the used dirty B12.

Rick

[Dirtracer603]

A PCV valve is essentially a one way check valve and its main purpose is to let blow by gasses get sucked into the intake but prevent any back feed into the motor. If a piston was 100% sealed to the cylinder wall a PCV valve/system wouldnt be needed. With that said poor sealing equals low compression, more blow by and more oil consumption. Theres nothing that can be done, beside re-ringing the pistons, that would permanently fix the low compression & blowby issues.

[RikkiTikki]

A PCV valve is essentially a one way check valve and its main purpose is to let blow by gasses get sucked into the intake but prevent any back feed into the motor. If a piston was 100% sealed to the cylinder wall a PCV valve/system wouldnt be needed. With that said poor sealing equals low compression, more blow by and more oil consumption. Theres nothing that can be done, beside re-ringing the pistons, that would permanently fix the low compression & blowby issues.

You obviously did not read my post. The premise here is that a faulty PCV (positive crank ventilation) valve caused stuck rings. If the rings are indeed stuck and a solvent is used to free them, then compression is restored.

There are 2 things to consider here.
1. Can a PCV valve go bad? Yes it can. As a matter of fact, during my research I found that owners of some of the VW Passats that use the same PCV valve have reported issues with the valve.
http://www.passatworld.com/forums/91-b6-garage/317772-excessive-oil-useage.html
2. Can piston rings get stuck due to oil/fuel/carbon - sludge? Yes they can. As a matter of fact, some auto makers make special cleaning solutions to clean the piston ring lands. http://biodiesel.infopop.cc/eve/forums/a/tpc/f/159605551/m/735102933

With all that said, in my case the 2 cylinders up front on the drivers side showed an improvement in compression after soaking with B12. The compression jumped from 123 psi to 138 psi. This proves that the rings were indeed stuck and that is the reason for the decreased compression and most likely would also contribute to oil consumption on those cylinders as well.

I am currently running Kreen in the oil to provide additional crankcase cleaning. Once I put 1000 miles on it, I will run another compression test and will post the before and after results on the compression tests.

Rick

[alterdcreations]

i just removed my pcv and let it vent into the open.....seafoamed my engine but i pass it thru, i dont suck it out. works great!

[brady.]

any updates on this? feedback, criticism anybody? Curious as to what everyone has to say and want to learn [rolleyes].

[RikkiTikki]

All-

Here is a quick update. I have put approximately 800 miles on the car since I did the B-12 soak and added the Kreen to the oil. I have been monitoring the oil consumption and the results are great. The oil level has not dropped at all. Once I put 1000 miles on it, I will run another compression test and post the before and after results.

Rick

[snail_power]

Sounds promising, keep updating please. Subscribed!

[alterdcreations]

update......
ended up installing a generic autozone pcv with a elbow and reconnected it and 1200 miles later after a fresh oil change I havent lost any oil yet..
When I did the oil change, I dropped the oil pan to clean it out and makle sure all of the old oil was removed. 2 fresh gallons of Rotella t6 5-40. Oil level is stable.
I think a good catch can would solve the problem when the engine is continously abused

[Toolaa]

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.

I was hopeful that this procedure would help me out on my 1.8T with 163K. Cylinder #2 was reading 160 while all of the others were well above 180-185. I added a bit of oil to #2 and it shot right up back to 185 so it seems like it's not a valve leak that's causing the lower compression. I know it's in spec but these little details bug me a bit. I started with a warm engine (not hot) and let soak for 2hrs. Sure enough tons of black carbon bits were sucked out when pumping the cylinder dry.

I checked the cylinder pressure before running the car since I already had the plugs out. I almost crapped my pants because the pressure was now only 60psi. I thought my gauge had maybe gotten messed up so I quickly went back and checked 1,3,4 and they were all between 175 with a cold engine. I added about 1/4 oz of oil to the #2 cylinder and tested it again real quick and it had bumped up to 130 so I was still concerned that maybe I messed something up.

After re-installing the plugs and starting it up I got a plume of smoke for about 30 sec. I'm guessing from the B-12 and carbon bits that I hadn't been able to pump out. I let the car idle for about 5 min then took it for an easy 15 min drive to get things up to working temp.

When I cam back I tested compression again with the engine up to temp. The results were: 180,165,180,180. So the good news is that I didn't mess anything up but I didn't see any improvement in #2 either.

There is no doubt that the B-12 is freeing up crud in large chunks but I believe that most of it's coming from the top of the piston. If you do try this yourself I would recommend adding some oil to each cylinder before cold cranking the engine. I think the reason the pressure was so low immediately after the B-12 treatment was that the B-12 had dissolved all of the oil film on the rings and cylinder wall while cranking. It's something to be careful about if you are planning to try this yourself.


Oh one more thing about B-12. I'm not 100% sure but the solvents in B-12 seem to dissolve some types of plastic and rubber. My cheap $7 filler pump stopped working in the middle of this process. The rubber hose was a bit sticky so I'm assuming that the o-ring on the pump piston or the flap on the piston had dissolved somewhat to break the suction seal. I ended up using a air powered suction tube to get the rest of the liquid out.

RikkiTikki's original post was a good one and it seemed like it worked for his situation. I'm curious to know how his engine is working nine months later. I Hope people who are having similar issues find my information helpful.


Later,

ToolAA

[combsatl]

Sorry to drag up a post from earlier this month but I, also, am interested in the results.

Rick - anything new to add?

[hoss1]

What a great catch

[Wykdwgn]

I just bought the car and the timing stuff and valve cover gaskets were done just before my purchase. It has 137k on it and I do get a blue puff for just a few seconds on cold start up. I pulled the plugs over the weekend and the treads have a light oily appearance and black built up on the electrols just not real heavy.
I did a cold dry compression test and got consistant readings from 95-105 across all 8 cylinders. It runs strong and with that little compression wouldn't it run anemic? I was reading and the theory of bad PCV causing oil to gum up the rings and cause low compression.
Rikki Tikke talked about using B-12 Chemtool thru the spark plug holes and that it helped cure his low compression. Should I just re-do my compression test with a touuch of oil before attempting to use chemtool? I'm not new to Audi having had over a dozen although all but 2 were 5 cyclinder's I did get my first expereince with a V8 in my 02 S6. It uses oil but no puff on start up. I have pictures of the plugs I just can't figure out how to attach them.