P0021 Volkswagen -

Question

MY VW PASSAT W8 4 MOTION HAS A CODE P0021, WHAT SHOULD I DO TO FIX IT?

Answer 1

I believe this to be the ultimate summation concerning the W8 cam adjuster/P0021/P0011 code and will show there is more to this than just shock treatment of the solenoids but the short answer is; remove and clean the valve body under the solenoid! It is easy to do!! Really!!!

The following is a focus on cleaning the adjustor Solenoid/Valve assembly which I am convinced is the heart of the problem and what should be dealt with every time. If you want to read a more comprehensive overview of the W8 cam adjustor issue then look for my long posting under user name Billj3cub at:

http://forums.fourtitude.com/showthread.php?3943349-03-Passat-W8-Torque-Converter-and-Cam-Adjuster-Problem-in-last-10-days/page4

Note: Regarding the solenoid shock treatment, you don't need to reverse polarity. The plunger will extend out of the solenoid regardless of the polarity.

Another note: In the following description I call the parts a Valve and Valve Body because they are miniature versions of a automatic transmission valve and valve body.

When doing the solenoid shock treatment, if the solenoid clicks then it is probably good. If it does not click then pretty much guaranteed the valve is stuck depressed down in the valve body, the spring can't push the valve back up, the plunger is hanging fully extended out of the solenoid (it only moves 0.070"), and you will not hear a click because the solenoid is already fully extended. The solenoid is quite powerful, especially when applying 12 volts to it (computer only applies 5 volts), but the return spring is weak by comparison so if the valve is going to get stuck, it will get stuck in the downward position. That is what I have always found. If all 4 solenoids click but you are still getting cam adjustor codes then I would disassemble and inspect all 4 solenoids using the procedure below. The valve under the solenoid is the weak link that is most susceptible to sticking, the actual cam adjuster/sprockets are very tough and very, very tolerant of wear, debris, gunk, etc. Indeed, the chambers in the adjustable sprocket assembly will chew up and spit out anything that goes in there. I will gladly pay to have anyone with a supposedly worn out adjustable sprocket assembly send it to me so I can inspect it.
What has likely jammed the valve in the body are pieces of the super-fine mesh screen that was built into the solenoid holder and always comes apart over time. I have seen a new set of solenoids and their holder (big$$$) and the screen is a slightly thicker more robust material than original but I would never reinstall that unit, new or old, without tearing the whole screen out regardless.

The following procedure should take about two hours from start of tear down to finish of reassembly:
Take the intake manifold off.
Remove the valve cover.
IMPORTANT: Disconnect the battery so you cannot mistakenly turn the engine over then stuff rags into the cam drive openings around the chains and gears quite thoroughly so nothing can fall down there. Get even the smallest item stuck down low in the chain/gears where you can't reach it and it is game over.
Remove the two Torx screws that hold the solenoid on. Use a strong pencil magnet to catch the screws even though you previously stuffed rags in the cam drive opening. Every caution you take will be worth it.
Using two flat bladed screwdrivers carefully pry the solenoid as straight up out of its holder as you can. If it does not come out perfectly straight don't worry. When prying out, one of two things will happen:
1) If the solenoid breaks off the valve body, leaving the valve body behind in the holder, then carefully clean out the 3 cracked or chipped edges of the valve body where they were crimped/staked around the solenoid. It will be obvious what I am talking about when you are looking at these parts.
You will see the valve in the valve body with an offset oil passage hole near the center. That oil hole delivers oil to the solenoid for cooling and lubrication purposes.
Stick a straight pick tool with a tapered shaft in that hole and gently put sideways pressure on the tool while drawing the valve straight out. If it stuck, and it will be, (remember why we are in there?) then try alternately (gently!) pushing, pulling and twirling until it eventually starts moving and you can draw it out. Take your time and don't force it. It will come out faster than you initially think. You don't want to unnecessarily score or chip the valve or the bore it rides in. Pull the spring out of the bottom of the bore with a pick tool and carefully set it aside. Every one I have taken apart that was stuck had either tiny bits of screen or large chunks of screen or something in between. The valve is really simple, just wipe it clean.
Cleaning the valve body is more difficult. I suggest you remove all those rags you stuffed in the cam drive area, unplug the ignition coils from the other side of the motor if you have not already, hook up the battery, then have an assistant crank over the motor and let oil pressure flush out the debris until you are satisfied the body is clear. If you see the motor is all sludged up after removing the valve covers then this flushing procedure will verify that oil is flowing to the cam adjustors. You will see oil pulsing backwards out of the cam adjustor sprocket assembly supply passages toward the back of the motor then you will see oil flowing out of the supply passage toward the front of the motor. Clear out all of the oil in the valve body bore with paper towels, rags or compressed air (messy but it works) to verify any and all debris are gone. All this work takes less time to do than to say.
A word of advise here: I am not satisfied with purging the oil while leaving the valve body in its holder. There could still be debris trapped around the valve body and its bore that may not flush out immediately. If you look at where the base of the valve body would be you will see a cut out in the holder. Stick a large screwdriver in there and twist really hard or use a bearing puller tool that has a short stubby hook to hook the valve body and tap upwards. The 4 O-rings will be quite stuck in the bore but it WILL come out. Any scratches or chipping you cause on the bottom of the valve body are inconsequential. Now clean the removed parts and crank the motor over to flush the oil out of the valve body bore.
2) If the solenoid and valve body pull out of the holder as an assembly then you will have to pry the valve body off the solenoid then follow the procedure outlined above after 1) above. If the valve body does come out of the bore then after all the cleaning you can assemble the valve, valve body and solenoid together then apply 12 volts to the assembly and watch the valve shuttle back and forth in its body through the slots in the side of the body.

Disconnect the battery and again pack rags back around the cam drive to protect against dropsies then carefully place the spring back in the bore making sure the spring is not crooked in the bottom of the valve body! Push down on the valve to verify that it plungs down and returns smoothly then place the solenoid straight back down into position then carefully fasten the solenoid in place with the two Torx screws. The original crimping of the solenoid to the valve body is not needed here, that was only for original production assembly. Verify the solenoid "clicks" with 12 volts. Think of this work as regular maintenance (until all the screen material is gone) like cleaning the throttle body or replacing the spark plugs. The best part is you know exactly what you are doing and why you are doing it and can easily do it again if needed. No Fear, No Worry, No Sweat. The W8 lives again.