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Coked Piston Rings?

My '88 Escort (518,500 miles) has been using more oil than usual lately. I know it has some sludge problems and think maybe the rings are coked. Anyone have any suggestions of what might be used to clean this up without engine dis assembly. The car can still be driven like this and the car isn't worth the time and effort to dis assemble everything. Would it hurt to pour an ounce or two of Marvel Mystery Oil directly into the cylinders and let it soak for a few hours? Would this likely help break it loose and clean it up or more likely to cause worse problems?


  • The Marvel oil or any light viscosity oil or trasmission fluid might help. I have done that soak down many times on all sorts of engines and never seen any damage done. The usual procedure has been to remove all the plugs, pour several ounces of oil into each cylinder, lay a shop rag loosely over the plug hole to catch the excess and turn the harmonic balancer a few revolutions. Whenever putting an engine away for the winter or longer I do that. There's a smokey startup but that's no big deal. Isn't 500,000 miles pushing the limits on that little engine.
  • There are additives in a bottle at the parts store that are sold specifically for this purpose. It'll do absolutely no harm to try some. I doubt of pouring Marval Mystery Oil in and letting it sit will do anything. It isn't a solvent.

    But I gotta tell ya, at 24 years and 518,500 miles, it may be futile. In addition to wear on the cylinder walls and rings, rings lose their tension. When they're originally installed, they have spring tension against the cylinder walls. After being heated up and pouned on million and millions of times, they lose this tension. They become a squeegee without pressure.

    I suspect the problem is not coked rings. I suspect the problem is tired old rings, beaten down with age, in worn out cylinders. But try the additive anyway. You've nothing to lose.

    Congratulations, by the way. That mileage is one heck of an achievement.
  • An oil product may soften the coke, but as soon as you start the engine, it too will coke as it has no where to go. Use a solvent product instead, like SeaFoam or kerosene.
  • I agree the cylinder walls and the rings both probably have significant wear contributing partially to the oil consumption, but since it seems to have increased noticeably over just the last few thousand miles and the engine has had some previous sludge problems I thought maybe the rings were also coked.

    Do you all think Sea Foam would be a better option? Could the Sea Foam be poured directly into the cylinders? Probably more cleansers. When it warms up, I plan to pull the oil pan off and clean it out and do an oil/filter change, so I could try any cleaner prior to removing the oil pan and doing the oil change.

    As far as the engine having the high mileage, it still runs good and I get about 40 MPG gas mileage, the only problem is the oil consumption. I checked the compression on it at around 500K miles and the compression was still 145-155 PSI across the board.
  • There are various products on the shelves. I'm reluctant to suggest a brand name, since I don't use them. They'll tell you on the bottle that they're for decoking engine insides.
  • edited February 2012
    I've used Seafoam many times to decarbonize coked up piston rings with success.

    Get the engine up to operating temperature and shut the engine off. Remove the vacuum hose from the brake booster. Adapt a hose that'll fit in the brake booster vacuum hose and into the can of Seafoam. Take a pair of pliers and pinch off the hose. Have someone start the engine and bring the idle speed up to 2,000 RPM's. Now slowly unpinch the hose so the Seafoam gets drawn into the engine. Keep the RPM's up and pinch off the hose when required to prevent the engine from stalling. Once all the Seafoam has been drawn into the engine, shut the engine off. Reinstall the brake booster vacuum hose. After a half hour has past, restart the engine and bring the RPM's back up to 2,000 RPM's. Keep the RPM's at 2,000 until the smoke out of the exhaust clears up.


  • If the rings are worn, stuck due to past overheating, or the engine has glazed and/or egged cylinder walls then no additive will help.

    The compression at approx 150 is on the way down but that's to be expected. It's amazing the compression is that high considering the total miles on the engine.
  • I don't think sucking it (sea-foam) into a running engine will do ANYTHING except blow 98% of it out the exhaust and make a lot of smoke..

    Rotate the engine to TDC, then 90 degrees more, to position all the pistons at mid-point in their bores..Remove the plugs and introduce 3 or 4 ounces of Sea-Foam or Rislone into each cylinder. Let that soak overnight. Turn the engine over by hand to clear the cylinders, then spin it with the starter, install the plugs, and fire it up..After one drive cycle, I would change the oil...
  • Keep the ideas coming. Right now I'm not driving the car much, waiting on warmer weather so I can get outside and work with it trying to give the engine a good internal cleaning, pull and clean the oil pan and do an oil/filter change. At the mileage I've got out of this engine and the condition of the rest of the car it's no great loss or disappointment if nothing helps, I'll just continue to drive it as is until the end.
  • I like Seafoam but use it at night or call the fire department first. It'll smoke like crazy and all the neighbors will think your garage is on fire.
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