head off, scrub the piston tops?

[zanzabar]

2001 VW 1.8T (Passat AUG) with 174k miles.

As you can see, lots of carbon buildup, and small dents from valve contact. What should I do here, scrub as much as I can off without letting debris get into the ring area and hope it doesn't scour the cylinder walls? The rings have already been soaking in oil and a little Seafoam. Also, should I try to grind smooth those little valve dents?

 

[heynow]

You could clean the piston tops if you're so inclined, though I would probably leave them be. I know some people that try to smooth out valve impact areas with a small die grinder, just don't take away too much material. You should be fine either way.

 

[badtlc]

Good fuel additives like Gumout, Techron, etc. would clean those up. Might take a few uses combined with an italian tuneup or two.

Someone on this board had some photographic evidence that regular use of MMO in their gas cleaned up their piston tops. That would probably work too.

 

[cptbarkey]

i wouldnt bother. are you *sure* those are not intentional valve dents?

 

[sasilverbullet]

Originally Posted By: cptbarkey
i wouldnt bother. are you *sure* those are not intentional valve dents?


I agree, those look intentional...

 

[Kestas]

I'm anal enough to remove such deposits. They provide hot spots for preignition that may occur during use. I use Scotchbrite to clean what I can't scrape off, though many people shun the use of these pads because they contain abrasives that come loose.

 

[zanzabar]

Originally Posted By: cptbarkey
i wouldnt bother. are you *sure* those are not intentional valve dents?


Yes, positive. Those are from valve contact.

 

[meep]

the carbon doesn't look to bad to me. i'd use a solvent and rags and then vacuum it all out.

but the valve contact points are problematic. sharp edges like that will hold thermal and absolutely cause detonation and pre-ignition like crazy. I assume the valves are getting replaced?? what's the rest of the story?

 

[TallPaul]

But would some bits fall down beside the piston and later scuff the cylinder walls?

How about closing it up and doing the hot engine water injection to blow out the carbon. I did that to the '92 Aerostar once and the whole area smelled like spent firecrackers for a while. Must have removed some carbon deposits.

 

[SwampSurvivor]

Why did the valves touch the piston? Slip a timing belt or something?

 

[addyguy]

I wouldn't touch it, I'd worry about bits of it scouring the walls.

What I would do, when it's all back together, is a strong water de-carb. A quart of water through a PCV line on a hot engine will vapourize that stuff right off.

 

[getnpsi]

No guarantee stuff will not sneak down between. if the oil pan was off too then I'd be more inclined to be more aggressive and/or sloppy.

Oh i just thought of something, if you had a piston ring tool for that engine you could rest it on top and have gunk that comes loose stay on top to wipe out, sort of like how they sell those cookie cutter type tools for frying eggs. Its better, but still NOT really safe.

 

[kschachn]

If you insist on removing it, put a piston at TDC. Then shove grease between the cylinder and the piston. Once you have it cleaned off, rotate the crank to bring the piston down into the cylinder, and wipe the grease off the wall.

But like others have said it's not that bad IMHO.

 

[Donald]

Originally Posted By: cptbarkey
i wouldnt bother. are you *sure* those are not intentional valve dents?


If there was impact between valves and the piston, you would have a bent valve stem or something in the valve train. Not dents on the piston top.

I would leave alone unless you are getting the pistons out. You will get [censored] down between the piston and clyinder wall.

 

[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.

 

[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.

 

[BillyTheKid]

I'd soak each cylinder and try to wipe it after a night of soaking or longer, then use a shop vac to suck up any fluid and grime left over. A good shop vac would be strong enough to pull anything from the top and around the top of the pistons.

 

[Silk]

That'll be the inlet valves hitting the pistons from a worn timing chain.

 

[Texan4Life]

You could do either. personally it would bug me and I would clean them.

I would use carb cleaner and a bronze wire brush. should clean up real nice.

 

[another Todd]

the carbon doesn't look to bad to me. i'd use a solvent and rags and then vacuum it all out.

Um, NO! Most solvent is either combustable or flammable. The vapors going through a typical vacuum motor will result in KABOOM. I've seen it happen, and no it wasn't me.