Quote:
Originally Posted by Tomnavigator
The valve cover does not have to be removed to perform a carbon cleaning on a BMW 335D. However, the intake runner is curved and it is about two inches down to the valves.
Advantages to removing the valve covers:
1) it is easier to get the intake clean since the path to the valve is more direct and easier to get to with the cleaning probes.
2) It is easier to see how clean you have gotten the area around the valves
3) Valve cover gaskets can leak once the car gets over 100k miles. Replacing them is a good idea now.
4) The first part of the intake runner is plastic and can be damaged by aggressive walnut blasting if the air pressure used is too high. Removing the first part of the intake runner eliminates this possibility.
5) It is easier to tell when the intake valves are closed when the valve covers are removed.
Disadvantage of removing the valve covers:
1) Expense of new valve cover gaskets
2) Possible contamination of head with walnut shells
3) A little more time is spent removing and installing the valve covers.
4) You have to spend more time sealing the heads to make sure no walnut shells get into the valve cover area of the heads.
The intake valve must be closed on the cylinder before the intake runner is walnut blasted to ensure no walnut shells get into the cylinder.
Many people remove the valve covers. I think I read from one of 335dici's previous posts the 335dici removes the valve covers.
I did not remove my valve covers. I made my own cleaning probes out of copper tubing and bent them to go down the curved runners. I had to bend them several times to get the angles right. After I cleaned the intake runners, I used a camera to confirm the runners were cleaned.
I made sure the intake valves were closed on the cylinder to be cleaned by blowing air down one runner with a piece of toilet paper covering the other intake runner of that cylinder. If the toilet paper blew off, the valve was open. If the toilet paper did not move, the intake valves were closed. This works because both intake valves open at the same time. If the intake valves are open, then the air goes down one intake runner into the cylinder then back out the other intake runner. Note: The intake valves are only open on one cyclinder at a time. The other cylinders are in the compression stroke, power stroke, or exhaust stroke where the intake valves are closed. I confirmed the intake valves were closed with a camera prior to starting my walnut blasting. It turned out this was not necessary.
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So this is where the shops are accumulating the bulk of the price. They are probably quoting the jobs with valve cover removal, but actually not removing the cover.
grotto this is something you should clarify with any shop doing your work.
Also make sure that the intake manifold get a good cleaning, preferably with some kind of ultrasonic bath cleaner.