Carbon built up under the valve cover of our 2006 TDI New Beetle

We had to replace the valve cover to replace the PCV valve in our 2006 VW New Beetle. The area between the top of the motor and the valve cover was packed with carbon. The mechanic cleaned it off the top, but was not sure what to use to dissolve any of the carbon that remained in the motor. since it is a TDI what can we safely use to clean that carbon?

Never seen that happen before unless someone was running some of that nasty WVO as fuel. In that case, not much you can do besides take the money not being spent on diesel and save it up to replace the engine every so often.

The m0tor is running fine, and we have never put cheap diesel in it. We pulled the valve cover because that was the only to replace the plugged PCV valve and that is when the carbon buildup was discovered. Could we use something like Seafoam or a similar product?

I would sure like to see a picture of this, since the innards of the TDI typically stay whistle clean. Shiny metal parts. They do not even get that brownish bronze coating on the inside of the aluminum cylinder head or anything.

Since I am not really sure how/what/why this stuff is in there, I would have a reservation as to say what course of action should be taken.

May want to drop the oil pan off and see what that end of the engine looks like too.

BG and others make some good products for degunking engines, but generally only needed on gasoline engines, not diesels.

So your saying that a huge build of of carbon from the exhaust was built up INSIDE the valve cover, like over the valves? YOU MUST post a picture of that, this would be the first time i have veer heard of such a thing! The only thing i can think of, If this is where it is built up, is that you have a bad exhaust valve seal and guide and its just pumping exhaust up into the valve area and past the CCV. When oil vapor or in this case strait up motor oil meats diesel exhaust, it turns into a messy pile of hell. Seeing as newer fuel has solved a lot of this issue, its more burnt oil than it is sulfur. in any case. post a picture before you do ANYTHING please. if it is like i think, your head is coming off, magnafluxed for cracks, new guide and a valve with a new seal, and thats if your lucky.

the only way to clean it, is to take supper high care nothing falled down into the pan, i would pull the oil pan like Oil hammer said, it could be from piston ring blow by and its like that all over the internal down low. a usual amount of blow by is normal but to see anything up in the head is un head of, even in a old damaged engine, trust me, i have seen a few diesels with no rings left on them and lots of blow by so much it was blowing all the oil out the tail pipe.

you probably have not damaged anything yet, as its been running but you never know, until you get to the bottom of this, dont even try and start it. that much build up could ruin lots of moving parts as it could clog up the oil pick up or the filter, i have no idea, all i know is that this is unheard of, not normal in any regards and a sign of major engine damage to either a valve or a piston.

2006 tdi new beetle

Perhaps the buildup is coming from the EGR valve. We are going to check this out.
Thank you

how could it go backwards from the EGR? the only way the EGR could get into the valve cover would be to backtrack up the boost pipes and past the turbo, impossible. Maybe im not understanding where this issue is, its inside the valve cover in the head above the valves right?

What oil have you been using? How many miles on it? Howzit been running?

My best guess is that the oil was rarely changed. The tell for that is that the CCV (PCV) valve was clogged. Just guessing, but I would imagine the engine leaked/used a fair amount of oil.

MY Grand Daughters 2007 Hyundai must have never had the oil changed in it. With 85K miles on it, it used about 2 quarts of oil a week. It developed a burnt exhaust valve, which isn't directly related to the oil consumption, so I removed the head to fix the valve.

When I removed the VC there was massive amounts of carbon looking deposits inside the V/C and the surfaces of the head under the V/C. In addition, the PCV valve and PCV port in the VC were completely clogged solid with the same carbon looking deposits.

I would clean out what you can get to and just keep doing normal oil changes. Do not try to do additional cleaning with any kind of solvent etc because all you might accomplish is breaking loose a chunk of the deposits somewhere which could clog an oil gallery and cause something to be starved for oil.

It would be better to just do normal oil changes or even a little sooner and let the detergent action of the oil hopefully slowly clean the deposits over time that you couldn't get to and clean.

I took the engine pretty far apart, and it seemed like for the most part, anyplace that had continuous oil pressure flowing did not get deposits. I found that inside the pan, deposits were not extreme and what was there seemed more like a sticky varnish than chunks of carbon.

good point Ol'Rattler, i would start there and follow up with a compression test just for good measure. if you add anything at all, add some seafoam to the oil 1/3 bottle, drive for 50 miles after warmed up then do a oil and filter change. You can always send out a oil sample to Blackstone, its an oil analysis company, to see if the exhaust is contaminating it more than normal. its like $15 to do it.

IMHO Seafoam or anything like that would be a bad idea because it could cause crud to break loose and clog oil passages.

A little history. Back in the day some folks would use non detergent oil and get massive amounts of baked on crud inside their engines. The common wisdom was that it was a good idea to mechanically clean what you could get to and to switch to a detergent oil with regular oil changes and definitely not use solvents like ATF, solvent, Seafoam ETC. Over time, the detergent in oil will tend to clean without the risk of dislodging chunks of crud.

Pulling the pan to clean inside of that area including the oil pickup screen and oil pump pressure and relief valve would be a good idea, as well.

On the Kimche Kruzer, the oil control rings were completely clogged up with crud. Except for the cylinder with the burnt valve, compression was still 195 PSI on the other 3 cylinders(Gasser). Probably slightly high because of normal carbon build on the pistons.