Stuck up piston 1

[wr180561]

A friend of mine got the piston stuck up while he was pulling it out during major engine overhaul. He said that the engine was running ok before they started the overhaul. It seems that there was heavy carbon deposition on the liner that was not properly cleaned before they pulled the piston. The situation now that the piston is not moving neither up nor down. The engine is MaK marine engine model 16M453 rated 6000 hp. any clue on how to overcome this problem would be much appreciated. Regards WR...

 

[MikeHalloran]

If the piston is not yet projecting above the liner, he could put the head back on and pump grease into the combustion chamber to force the piston back down. A manual grease gun can develop a lot of pressure.

If it is projecting, maybe the head could push it down, with a lot of anti-seize on the bolts.

Or, a short, sturdy spacer ring between head and liner would allow greasing it out either way.

Use EP Roller Grease #2 or 'gorilla snot' or something else real thick.

Beyond that, I'd guess he has to pull the piston, rod, and liner together, and throw them away. Ouch.





Mike Halloran
Pembroke Pines, FL, USA

 

[wr180561]

MIke,

Thank you very much for your valuable tip. The piston has in fact been projected about 10 mm out of the liner and the question here, would the greasing procedure as described be capable of moving a piston of a medium speed engine with bore & stoke dimensions of 320mm, 450mm ? However, I've already informed him to fabricate the ring and give it a try. Regards WR.

 

[MikeHalloran]

The grease trick works _better_ as the object gets larger. I personally have used it on bushings as small as 1/4" o.d., on clutch pilot bushings, on 2-1/2" od blind dowels, and on punch press bushings of ~5" diameter.

The really neat part is that it leaves the parts in salvageable condition; no hammer marks, etc.







Mike Halloran
Pembroke Pines, FL, USA

 

[wr180561]

Mike,
Would it be better if a special chemical compound is sprayed around the gab between the liner & the rings to assist in dissolving the carbon and thereby moving the piston while the grease is on action? Do you have any idea what the commercial name of this compound could be?

Appreciate your tips. Regards WR.

.

 

[MikeHalloran]

I don't think so.

When you do that, you can't control where the chemical goes.

Better to use the grease to force the piston down out of the way.

Then cover the top of the piston with modeling clay or putty.

Then use a ridge reamer and/or oven cleaner and/or Permatex gasket remover to get rid of the carbon.

Then clean up the mess and remove the clay/putty.

Then pull the piston.



Mike Halloran
Pembroke Pines, FL, USA

 

[icrman]

Make sure the crank is protected well. Use a block of hard wood on the top of the piston and hit it with a hammer. After it is down in the cylinder, clean the carbon and if there is a ridge remove it. Before trying to take out the piston.

 

[rhodie]

Drop some dry ice onto and (into the underside, if possible) the piston to contract it and then ease it out.

 

[wr180561]

Thanks all for your tips, however the piston is free now and was pulled off the liner all right (they have managed to jack it down by the cylinder head). The liner as well was pulled out to investigate a water leak from the sealing surface between the liner and the cylinder block. A small hole (10mm in diameter and 0.5mm in depth) on the sealing surface of the block found to be the cause of this leak. Any recommendation to cure this hole and stop the leak would be much appreciated.

Note : Others do not recommend the use of Epoxy in this area due to the high vibration caused by pressure variation in the combustion chamber of the 4 stock cycle


Regards, WR