GTI Carbon Cleaning: One Dumbass DIYer's Experience
Hello! My name is DOOKIE_SHARDS, I am a dumbass DIYer, and I just finished carbon cleaning my MkV GTI. Okay, so “dumbass” is a bit misleading. I’m definitely an idiot, but I’m not a stranger to DIY car stuff. I’ve replaced all kinds of things over the years: fuel pumps, spark plugs, this GTI’s cam follower, even a transmission solenoid on my old Cavalier. I would call myself “lower intermediate.”
However carbon cleaning was definitely the most complex job I’ve ever done, and I learned a lot. I figure if any other shadetree mechanics out there are wondering if they should DIY a carbon clean, this might help.
Tl;dr it’s hard but not impossible and it’s worth it.
Background
My GTI is a 2007 6MT with 145,000 miles on it, around 70,000 of which are mine. It has the TFSI engine and is bone stock aside from upgraded coil packs. While I have been religious with regular maintenance, to my knowledge it has never received a carbon cleaning.
I had no real symptoms of carbon buildup aside from the car being a bit slower and losing 2-3mpg. But in the name of dumbassery and preventative maintenance, I decided it was necessary.
I was quoted between $600-800 for most local shops to do it. I love a project, I’m cheap, and I’m also a dumbass, so I decided to DIY. I’ve seen two methods for doing the carbon cleaning: walnut blasting and scraping/brushing. After doing a lot of research – and assuming the worst for my car – I decided to do a bit of both.
I used the Pelican Parts DIY guide. It was extremely helpful. The only caveat is that you have to pause to look at other guides for removing certain parts; I aggregated them all into one guide which you can view here. Also they indicate you need a M5 triple square, but I needed a M10.
Tools
Anyone doing this job should already have a basic set of sockets, bits, a ratchet, that sort of stuff. If you don’t, don’t do this. I had to buy:
- An air compressor
- A blasting gun
- Fine grain walnut blasting media
- A flexible bit holder
- A long bit extension
- Triple square sockets
- A magnetic pickup tool (you WILL drop a bolt at some point)
- A Shop Vac (needed one anyway)
- A cleaning adapter for the valve inlets. I got a 3d printed one from etsy.
- A fuel injector sealing tool (YMMV)
I also recommend an electric screwdriver or air ratchet, it makes this way easier.
Removing the Manifold
This shit sucks. I don’t ever want to do it again. Okay so it’s not that bad except for two particular parts:
- The throttle body. Two of the four bolts are impossible to see. You have to seat the socket by feel. To get to them, I had to create an Eldritch snake of extensions and go up from the bottom of the car. My first time, these two bolts took me almost an hour by themselves.
- The support bracket. Fuck this thing. The “Satan bolt” (as Pelican Parts calls it) is truly Lucifer, the Morning Star, Beelzebub, insurrection, spite, the force that made me be. I recommend seating the socket and flex extension first, then working outwards to get a position that attaches to your ratchet. However when I brought it into the shop (more on that later), they didn’t reinstall the bracket as they told me it wasn’t necessary. When this isn’t installed, it’s possible to remove the manifold without removing the throttle body, which is a huuuuuggeeee help.
Cleaning
Cleaning is pretty easy. I developed a routine for each cylinder:
- Initial walnut blast and vacuum
- Soak valves in gasoline for 20-30 mins
- Mop up gas and scrape
- Second walnut blast and vacuum
- Scrape again
- Vacuum out and blow dry
For the scraping, I used a combination of picks and a nylon brush and gasoline for the solvent. I could have probably used another cleaner, but I had gas on hand and I knew any leftovers would burn easily. For the blasting, my gun was great but unfortunately a bit large so it was hard to angle properly. Also my air compressor is only six gallons because $$$ so I could only run it intermittently.
I took some before and after pics. These reflect an initial pass, and I cleaned more afterwards, but even here the difference is pretty incredible.
One protip here: if you think your valves are closed when you pour solvent in and it turns out they aren’t, don’t worry. Just remove your plugs, blow out the cylinder with some air and you’re good. If this happens though you should change your oil so that shit doesn’t get mixed with it.
Roadblocks
So remember how I said I was a dumbass? I made two major fuckups during this project. Heed my words, young dumbass:
- The intake bolts are aluminum and bolt into aluminum. They are extremely soft. I snapped one (which required a trip to the shop) and stripped the threads on another (which required a thread insert.) My torque wrench apparently didn’t work properly with all the extensions required to reach the bolts. Be as careful as you can, then even more careful.
- One of my injectors stopped working. I’ve heard carbon cleaning can do this because of chunks fouling up the injectors, but part of me suspects I accidentally got some walnut shells in it. Maybe plug yours up or just remove them entirely.
- Speaking of the injectors, be prepared to reseal these squirty boys if they come out. It requires a special tool ($50 on Amazon) and some practice. Follow the instructions REALLY CAREFULLY or else you can ruin the seals and have to order another one. Not that I would know or anything, b-b-baka…….
Was It Worth It?
So this entire process took me about a week’s total worth of work, spread over a month. I had to remove the intake manifold three times to correct mistakes. It made my wife a temporary widow, exhausted me, and made my garage filthy.
But now that I’ve got it back together and driving with no misfires or codes, I can safely say yes. Throttle response is better, low-end torque is punchier, and it revs quicker both during acceleration and rev matching. The car in general feels younger and more eager. I wouldn’t call it mind-blowing, but it was significant enough for me to notice. However I’ve also been driving my wife’s automatic NA 1.4 Fiat for a month so maybe I’m just horny for power.
Did I save money? Sort of. If I hadn’t snapped the bolt I would have saved $300 in labor at the minimum, but my final tally for parts, tools, and whoopsie-doopsies was still lower than the high end of quotes I got.
But I also learned a lot in this process, which was maybe the best part. I got the opportunity to work with new tools and learn new skills, like fixing threads. I learned a lot about how my car functions, the limits of my patience (and my ability to persist in spite of them), and that I very much don’t want to be a mechanic for a living and have tremendous respect for anyone who is.
If you’re a fellow dumbass looking to do a carbon cleaning, I hope this helps! Good luck and stay sane.
EDIT: I recently had to remove my intake again to replace an injector and cleaned the valves a bit while I was in there. Rather than using a blaster, I soaked each valve overnight in Seafoam and then used a nylon drill brush. This, along with some blasts of brake cleaner, was shockingly effective. May be a good solution for those of you with no compressor or gun.