head off, scrub the piston tops?

[mechtech2]

Those are not intentional valve cut outs because they are clean - no carbon there. And they are not heavily carboned up, either.
This is a very bad sign to me - a stock vehicle should have plenty of clearance.
Maybe cam timing? Head been shaved?

 

[Rock_Hudstone]

Solvents won't put much of a dent in baked on deposits like that.

If you go the chemical method regular old oven cleaner works well on carbon.

Mechanical; I'd use a soft/fine wire wheel on die grinder, blow out the top ring lands with compressed air.

However, the carbon doesn't look excessive and either way will be a lot of messy work for questionable results.

 

[lord kelvin]

I actually had good luck using solvents some 20yrs ago while replacing the head-gaskets on my 84 Chevy Celebrity 2.8L-V6. Top of the pistons were all carboned up so I tried some CRC brake cleaner basically because that's all I had. Sprayed it on a rag and saturated the top of the pistons. Didn't appear to do anything, and it was late so I quit for the day. The next morning I go into the garage and the carbon was loose and flaking off. Sucked it up with the shop-vac and buttoned everything up. Never gave it much thought, but figured I should share my experience.

 

[billythekid]

Originally Posted By: lord kelvin
I actually had good luck using solvents some 20yrs ago while replacing the head-gaskets on my 84 Chevy Celebrity 2.8L-V6. Top of the pistons were all carboned up so I tried some CRC brake cleaner basically because that's all I had. Sprayed it on a rag and saturated the top of the pistons. Didn't appear to do anything, and it was late so I quit for the day. The next morning I go into the garage and the carbon was loose and flaking off. Sucked it up with the shop-vac and buttoned everything up. Never gave it much thought, but figured I should share my experience.


Nice, that is kind of what I meant. Brake cleaner is my do all in a bottle. It also didn't blow up the vac as someone else mentioned, however, I can respect that is potentially a time bomb if the solvents were puddled...but also may be pretty cool to see.

But if you're breaking the engine done to do bearings, why not pull the pistons out to do a real cleaning a part cleaner is my question to the original poster.

 

[rslifkin]

As a note, chlorinated brake cleaner is non-flammable (but don't weld near it, as you can generate phosgene). The non-chlorinated stuff, however, will burn.

 

[The_Jake]

Originally Posted By: zanzabar
Originally Posted By: Miller88
Why did the valves touch the piston? Slip a timing belt or something?


http://www.passatworld.com/forums/68-b5-...ad-rebuild.html

The head is getting rebuilt.

Thanks for the advice everyone, I'll leave it alone and allow the engine to clean itself once up and running. May try the water injection, but I'm hesitant to do that on a turbo engine.


Good luck on your project. I would have replaced the head with one that didn't have the any oil starvation pitting. But the machine shop did ok. You still have some pitting marks on the one journal that may eventually cause a failure or may run 200,000 miles. You never know. But be sure to check ALL of your valves before you put it back together. I would not clean the piston tops. You don't need any additional gunk floating around in there. I am guessing this failure was caused by using the wrong oil that did not reach the cams or way over extended oil service intervals. No doubt neglect either way.

 

[The_Jake]

Originally Posted By: Kestas
I wouldn't worry about deposits scratching metal when they're loose. Deposits are essentially hardened organic material, and not abrasive like ceramic materials (aluminum oxide, sand, etc.) They don't have the hardness to damage metal.


True. But they do have the ability to clog an oil passage which can cause real issues.

 

[zanzabar]

Originally Posted By: The_Jake

Good luck on your project. I would have replaced the head with one that didn't have the any oil starvation pitting. But the machine shop did ok. You still have some pitting marks on the one journal that may eventually cause a failure or may run 200,000 miles. You never know. But be sure to check ALL of your valves before you put it back together. I would not clean the piston tops. You don't need any additional gunk floating around in there. I am guessing this failure was caused by using the wrong oil that did not reach the cams or way over extended oil service intervals. No doubt neglect either way.


That's a pretty good summary. It was a tough call about whether to go with a new head or not, but the machine shop guy said this would work fine so I trusted him.