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!

I vote for the acetone method.....and if the chemical is hot it works better.
As a thought....we used to de-carbon a running engine with water..!
Method was....get engine very hot....drizzle water down the carb so thee engine stayed running....rev the heck out of it....repeat as necessary.
Only problem encountered....piece of carbon might stick in the valve seat...that was the reason for reving the engine..to pound out the carbon bits.
Bob

Yup, that's an old "hill billy" trick that I've seen old time mechanics use, don't think I'd try it on a P-car engine though. :eek:

I recently cleaned basically every nut and bolt from the top end of a 964 engine in petrol. Razor blade, petrol and stiff brushes on outside of cylinders, wire wheel for the pistons.

Dito for me Tom. I talked to Tyson Schmidt about it, and he was perplexed as well. I think once Waynes book comes out, I'll have to give her a refreshing.

Why not just glass bead them? I thought that was the preferred way.

Tim

Guys,
You know, it might all hang together. Wearing valve guides allow oil into the cylinder. Long term, this causes a carbon build up. This increases the compression in the affected cylinders and this variation would affect the idle smoothness.

Next, the Nox levels. Increasing levels indicate hotter conditions, a result of higher compression.

I have 60k on my 87. Idle is a little doggy, it uses a little oil and the Nox has been increasing over the last couple of smog inspections.

Ned Monaghan

Kind of off the subject, but if your town has a wholesale restaurant supplies store/warehouse, look for the large coffee makers and consider using one as your small part soak tank.

What you'll get is a stainless steel receptacle with an internal basket. This setup lets you soak in the fluid, but use the basket on its internal stand to allow air dry/drip above the surface of the solvent. Removing the basket and the stand lets you drop the basket (without stand) into the solvent, making dunking and removal of small parts and whatnot very simple.

Finally, look for the coffee makers that have the spout just about 1" up from the bottom of the unit. This lets you drain off the "good" solvent, leaving the gunk at the bottom. A swipe with several paper towels removes the gunk: pour the solvent back in.

John

a bench grinder wire wheel for the piston crowns, a broken piston ring for the carbon in the ring grooves, and a bead blaster for the heads, after the parts washer has removed all the gooey stuff. haven't used MEK for years. bad stuff!

Doug Z., just curious, what are your plans regarding rings? I know this has been debated before, I wondered what your take was on the various opinions. New or not to (re)new, that is the question.

OK, I'm game.....

New rings work perfectly, provided that the ring grooves are within spec. If your pistons are good, new rings are the way to go. That simple.

I agree with Tony and with JW as well (always a safe bet). I'd STRONGLY suggest letting JW put the cylinders in his BFPW (large parts washer). I believe with all my heart that without running my cylinders through that washer, my new rings might not have seated properly. After washing, the cylinder wall was kind of stone-like, rather than shiny. Very matte. And my engine never made any smoke. Today it burn almost no oil at all. When I get done with an oil change, the oil level is only about a half-inch above the low mark, and I may or may not need to add oil before the next change!

I did not take the case halves to JW, and he probably would not have put them in his parts washer anyway. It is on those that I primarily used the nasty MEK.

Doug, you will save yourself a great deal of time, agony, danger and sore fingers if you just take all your parts to John. He da man!

Oh and of course you will probably take them in neat little baggies all marked properly, and he will dump all those bags into a pile and sort from there.

Won't really know until I have things apart and begin to measure.
I've been getting a lot of good advice from JW and my local wrench. Ring grooves are critical. If they are out of spec, the worn grooves may cause new rings to break. Old rings may be alright to reuse *if* the gaps are still within specs.

Presently, my engine has 75k miles on it, and consumes no abnormal amount of oil. It doesn't smoke, and is mechanically quiet. I'm thinking I won't find much wear when I take it apart.

All those near marine supply stores..... most sell a product that is specifically made to remove carbon deposits... Im not sure what chemical it is, but you fog your engine with it..... then start it after a 24 hour soak...... It will smoke for at least 15 mins after the restart...... but you wont have any mosquitos either

you can also use it it directly on piston dome if you have youw engine apart

JW's Secret Sauce
 

Doug,
It was driving me crazy that I could not remember the stuff that JW mentioned. Finally got it:

John said: "there's a product called jone's motor purr that would probably free up anything it came in contact with. it's not widely available, so call them and ask who has it in your area. 310.532.8602. great for noisy hydraulic lifters too. don't breath it."

There ya go!

"jone's motor purr"?? :confused: :D :confused:
LMAO!!

That *is* TOO funny. . . .I guess we know who needs to do the rebuild now :D

great for noisy hydraulic lifters

Yep,.......just pour the purr, punk!

Just think what would happen to anyone OTHER than JW who recommended Jones Motor Purr [in the familiar silver can] on this board. Torn and bloodied!

It's a keeper.;)

Thanks Tony for making my day with a good laugh!
I'll be searching the local stores for that "familiar silver can".