Piston Slap: Oil Burning and Carbon Cleaning?

Sajeev Mehta
by Sajeev Mehta

Arley writes:


I have a 2003 Jetta TDI with 178k miles. Runs 100%. My mechanic recommends a carbon cleaning. What are the positives and negatives? To be more succinct, what can go wrong?

You can tune a piano but you can’t tuna fish. (Good to know! – SM)

Sajeev answers:

Conventional wisdom (for both diesel and gas engines) is carbon buildup occurs more often when the owner subjects the engine to excessive idling and a severe lack of full throttle acceleration. Today’s direct injected, EGR equipped diesels (and direct injected gas engines lacking a piggyback port-EFI setup a la Toyota V6s) are sensitive to carbon buildup due to idle time, EGR design and cooling system inadequacies, and perhaps even fuel (i.e. varying quality of bio diesel). Don’t take my word, this company’s blog did a good job assessing the problem.


So carbon cleaning is commonplace and a good idea. And be it a seafoam-alike treatment or physical removal/cleaning of critical parts, there’s no downside if performed with even a modicum of care.

Question is, do YOU have a problem?

Considering your mileage (less idling and more highway driving?) and engine performance: probably not. Watch this video (go to 1:39) and DIY if you are even the least bit handy. From the video, make a trip to the parts store for vacuum lines too!

Or just do nothing aside from performing an Italian Tune-Up. That’d work for sure, and it’s totally fun.

[Image: Shutterstock user sasha2109]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

Sajeev Mehta
Sajeev Mehta

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  • 415s30 415s30 on Jun 17, 2015

    One of the first things I did when I bought my W123 was cap off the EGR. Diesels are exempt.

  • TammyRice39 TammyRice39 on Mar 13, 2019

    Engine Carbon is headache for me, but you clear my thought regarding Carbon. thanks for the information. bets of luck for future.

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