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VW Diesel Carbobn Buildup

I have bad carbon buildup in my 1996 New Beetle which is a diesel.

On the advice of my car mechanic and the NAPA salesman (“can’t hurt, might help”) I bought SeaFoam Motor Treatment to dissolve the carbon but after reading the can, I don’t know where to add it to the oil or to the gas. Any suggestions?

Aslo, I know the problem is being caused by driving my VW only for very short, local trips and never getting up to speed for long distances. I’ve tried driving in low gears to blow the carbon out the exhaust but are there better ways (like this additive)?


So where is the buildup? And how do you know it’s there?

For carbon build-up in the intake runner you want to add the Seafoam to the oil. But to tell you the truth, as good as Seafoam is it isn’t going to remove the carbon build-up. This stuff is so thick that the only way to effectively remove the carbon is to remove intake and physically remove the carbon.


Sorry, I’ll have to go back to my mechanic and ask. He showed me an engine schematic and pointed out the clog point but I didn’t pay attention to the names of the parts. He said they cleaned up the clog, which was responsible for the Check Engine light coming on. But that a long, flatish component just beyond that clog point accumulates carbon. Unless I changed my driving routine my car would evidently get so thick with carbon that that component would be beyond cleaning and replacement would be expensive.

He said he has already had another customer’s VW Beetle with such an extreme carbon buildup in that component that the component had to be replaced.

Why shouldn’t I add the SeaFoam to both the oil and the gas? Any problem with that idea?

You mean diesel fuel don’t you?

Sure you can. Add a half a can of Seafoam to the oil and the other half to the diesel fuel.


You are not going to get that stuff out of there with chemicals, until you remove the intake from the car. It is kind of a pain, but doable.

Funny thing is some cars get it bad and others don't have a problem.  I cleaned mine a couple of years ago and there was only a dusting.  Other had the intake almost totally blocked.  

Get on line to the and you will find instructions, lots of TDI owners and if you want likely a local person who will help you or do the cleaning for you.

How would anything added to the oil get into the intake runner? You really meant to say “to the gas” didn’t you?

Yes, the car takes deisel fuel. Thanks everyone for the advice.

These diesel engines have a PCV valve. Crankcase gasses send oil vapors into the intake causing the carbon to build.