Engine rebuilders.....What's *your* method.........
 

......to decarbonize piston tops and combustion chambers?

And most importantly, is there a good way to do it without tearing down the engine?

Tom

Hey Tom, don't "molest" my question ;)
I *am* going to tear down the engine. The top-end anyway.
In the past, I have scraped the hard carbon off with plexiglass scrapers, old spoons, etc., but wonder if there is another (easier) way to do the job?

As long as you don't damage the ring grooves, then you can use just about any abrasive material to get the carbon off. Bench grinder with a wire wheel comes to mind. Just don't get it near the ring grooves...

-Wayne

Its ugly!
 

Doug,
My 3.2 was using a quart in 3-400 miles. The urban valve guide myth had me convinced. When I opened the top end, the pistons were so badly coked up that the oil control rings were basically frozen. Good news/bad news. Valve guides were replaced in the normal head machining refurb, but cleaning the pistons was another story. see pics below.

While there may be a smarter way, a case of carb cleaner, a box of scotchbrite and a box of toothbrushes got me from 'before' to 'after'. Something like an hour per piston. The cylinders were in beautiful shape - Nikasils had barely any measurable wear. Same for the Mahle pistons - they were gorgeous once they were cleaned up.

Low tech method - kinda nirvana for the toxic inhaler - but very effective.

Emcon..the B12/Techron/etc in the gas route helps decoke valves, but not sure how effective these are with piston/ring buildup. Might be worth a try. I suspect that once you have 150K miles of coke working against you then a top end refresh is the only way. This stuff was really tough - straight carb cleaner barely touched it.

WOW!
Thanks for that, Tony.
I hope my mill isn't that gummed up when I take her down. No abnormal oil burning issues, just a broken head stud.

Brake parts cleaner and a stiff plastic bristle brush here... about 20 minutes per piston.

Another questions... does all this burnt toast on top of the piston and in the head raise the compression ratio a tad? Also, does it cause any downside such as hidden pre-ignition, dieseling, etc..??


JA

Doug,

Berryman's B-12 Chemtool in gallon cans ...

Soak each piston overnight in an old large pickle/mayonaise jar ... completely coverd, and with the lid screwed on! Next day ... tongue depressor/popsicle stick will remove the majority of the carbon very easily. Acid brush and more B-12, maybe an old bristle brush ... should get the rest without a lot of elbow grease. Old toothbrush for the ring grooves ...

Mountain Dew
 

Doug,
Warren's B-12 suggestion is probably better than carb cleaner.

This reminds me that JW mentioned some really bizarro chemical product that he says will dissolve anything on sight. Don't have the name, but might be worth a PM to John.

Anything is that can reduce the effort required to clean these puppies is pure goodness [just don't inhale, OK?]

John,

The deposits on the top of the piston do raise compression a tad but its not the major problem.

Should one of those bits of carbon remain hot and glow just a bit when the new fresh mixture of fuel and air enters the cylinder, it could ignite before normal.

This is not good and one of the reasons why we tear down motors and clean them up as Tony did... not to mention his sticky oil control rings. Nice job cleaning them up btw!

JA

Re: Mountain Dew
 

Well, I'll ask him this weekend in person. (I hope it isn't "Judge Judy's" coffee!!)

Thanks, Warren, for the B-12 Chemtool suggestion. Just what *isn't* that stuff good for?

Rebuild Time Allocation
 

Doug,
FWIW, I tried to rough out what time I spent doing what during the rebuild. Here are the chunky bits.
Your question is right in the sweet spot:

Teardown and measurements: 15%
Cleaning parts: 50%
Schlepping: 20%
Reassembly: 15%

Schlepping covers parts finding, shipping stuff around, finding/buying/borrowing tools you never thought you would need, etc.

The nice reassembly/setup work is a small part of the game. Parts cleaning really sucks up the hours.

I have a friend who used oven cleaner. I personally would make enquiries on whats in it before trying, but it was pretty effective.

Oven cleaner contains caustic (sodium hydroxide); this is the chemical in hot tanks. It's rather hard on aluminum and other light alloys; it tends to dissolve them. I don't think I'd use it on an aluminum alloy piston. I'd rather use one of the nasty organic solvents like Berryman's B12 Chemtool per Warren's suggestion to get the carbon off. Or air blast it off with walnut shell media. Cheers, Jim

I think JW bead blasted the heads. I rubbed the piston tops against the wire wheel on my bench grinder. The pistons took about five minutes, and I am confident no damage was done, but I only did this to the tops. Actually, the humid air caused most of the carbon to raise and flake off, over a week or two of time, all by themselves. My oil rings were not plugged and I cleaned the ring grooves with a piece of broken ring (tried and true method).

I cleaned many parts during the project and although I started with the plastic brushes, they are about useless. Brass ones were quite a bit better but I ultimately found that the stainless steel toorhth brush thingies worked best and they really did not scratch the aluminum of the outer case. The case was the toughest cleaning job. Caked on, burnt on oil over almost twenty years was the toughest of all. for that, I got out the big guns: Methyl Ethyl Ketone. I know, I know. Nasty stuff. Most of you wouldn't think of being near it. But I think that's the stuff you'll hear JW say is the bizarro chemical that strips anything. I think MEK is the stuff that used to be called "carburetor cleaner" until they took it basically off the market.

See, I said you should make enquiries :o

Thanks Jim.

And MEK is probably available at auto-paint stores, if that is what you want to try (it is in New Zealand but we can buy iso-cyanate filled 2-pack paint over the counter.... so we are obviously pretty cavalier).

Cam

Trich 111 vapor vat
MEK can be found in most Home Depots or what ever they call them up north in the paint department.
Use a stiff tooth brush and of course eye lung & skin protection.
And remember it's only substance abuse if you breath in on purpose.

Also keep the sharp pointy tools away from the piston. I use the tooth brush and a teflon bone (automotive glass installing tool) it's stiff but will not harm the piston.
Chris

Ah my favorite MEK! Fantastic stuff, I use it at work to disolve adhesive. Also will dissolve carbon buildup, most paints, etc. If you really want to hit it hard mix MEK and toulene 50/50 , heavy gloves and a brass brush. Be careful though MEK really burns your skin if you're not used to it and will make you dizzy as all get out. Best bet is to do it outside in the shade with a breeze or fan blowing the fumes away. Of course my production guys mop the floor with the stuff (no really!) but they're used to it. If possible I'd soak the parts overnight if you can but you'll need a metal container with a lid. Remember to keep it of paint, rubber, plastic, etc. If you want to be a little safer but more work plain old kerosene will do the job but more scrubbing involved.

Tony, that is pretty much where I am now, 1 quart per 400 or so miles. It blows a little puff on startup and has a couple small leaks, but not anywhere near enough to explain the oil consumption. It doesn't smoke on high RPM letoff, like it should with valve guides, so my thought is gummed up oil control rings.

I know I have a top end in my future, I am just postponing the inevitable, until Wayne finishes his damn book.

Tom

Acetone and MEK are both in the ketone family, and both are very good at cleaning up freshly hardened epoxy used in fiberglass, Kevlar, and carbon fiber laminate work.

The 'old,' nasty 'dunk' type carb. cleaners used chlorinated solvents, and were not extremely volatile like the ketone family ... and they were good for cleaning heads and pistons, too! An overnight stay would enable the carbon to be brushed off with a little water and an acid brush ... but were almost as bad as isocyanates on the lungs!