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melted piston

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derek gebhardt

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new to this so bear with me
I have a 2003 gtx supercharged no compression in the middle cylinder. Removed head to find piston melted down the side throught the first ring land and starting into the second. the hole is located in the depression for the rear valve on the center cylinder and melted a hole into the cylinder wall. i know i need a new block but have no idea what caused the problem and fear it reoccuring this is the second rebuild unfortunely i did not do the first myself so i am unsure if this is the same problem reoccuring the first one cost 7000 not sure what to do now oh yeah had to replace computer on engine after last rebuild related unrelated who knows.
thanks in advance for input on this matter
 
sounds like an injector fail lean out, 7-k you could have gottin a nother ski,
dont go to a dealer for parts make some calls that stuff is all over the place,
once back togeter see if a shop can check out injector system functions to
make sure all is running properly.
 
trapperjack1 said:
sounds like an injector fail lean out, 7-k you could have gottin a nother ski,
dont go to a dealer for parts make some calls that stuff is all over the place,
once back togeter see if a shop can check out injector system functions to
make sure all is running properly.
Click to expand...

that was one of my first thoughts when i saw the spark plug electrode melted clean off before i split the engine. is an injector fail common. i thinking of replacing them to eliminate them as the source of the lean out
 
injectors rarely fail that way. check your water pump and cooling system. the middle cylinder will overheat first due to heat build up on each side of it. what happened when it failed? all of a sudden? did it run bad for awhile? how about some pics? that will help diagnose as well.

This sounds like a good one for JFizzleJR. This is not a common failure.
 
burning holes is lean out condition
eather injector failure or impulse to injector failure
heat would warp head--blow gasket-- may even fry valves as in sealing
dont no how to check impulse on a ski but if its a car
its called (noid)--- little plug in unit that flashes to confirm impulse.
intake manifold leak in that cylinder would also cause lean out
look for crack in manifold to
 
it seems to miss a bit around 5000 rpm , if u put in the learning key and keep it at 5000 it almost quits because it runs so rough. the dealer changed the wear ring and said it works real good at top end not addressing the reason it was there, the miss at 5000. /it seems to smoke white a bit more than i think it should. When it became gutless. towed it across the lake then pulled the plugs center plug had no electrode left at all. replaced it started fine but sounded not quite right. compression test confirmed it.
 
lean out condition is more true with the 2 strokes than with the 4tec. injector problems are obvious problems and it won't run very well at all so heat typically doesn't have a chance to build up like the 2 strokes that run fantastic just before they let go from lean out.

However, overheat and leaking head gaskets that allow water intrusion will melt pistons in 4tecs. Does your piston look like this?

120.jpg
 
trapperjack1 said:
burning holes is lean out condition
eather injector failure or impulse to injector failure
heat would warp head--blow gasket-- may even fry valves as in sealing
dont no how to check impulse on a ski but if its a car
its called (noid)--- little plug in unit that flashes to confirm impulse.
intake manifold leak in that cylinder would also cause lean out
look for crack in manifold to[/

the orange o ring gasket aroud the intake port was not 100 percent but still do not suspect a leak there will definately replace it .
i just dont know 9000 into a 7000 machine and now looking at another 3500 to rebuild as i need a new block and still not sure why it is eating itself . all i remember from the first blown engine was seeing the ring grooves through thespark plug hole not even sure it was the same cylinder but now i have my suspicions if there is an underlaying problem
Click to expand...
 
you don't need a new block, that cylinder can be resleeved. A miss at any rpm is a problem. Charging $7k to rebuild a 4tec is unbelievable and any reputable dealer wouldn't do that on a machine that is worth maybe $5k. My guess is they didn't know what they were doing.

I suggest doing the rebuild yourself because any other option will cost more than the ski is worth and you've already been there. We can help here and I wouldn't worry about an underlying problem, just be thorough and careful and it will be fine.
 
ski-d00 said:
lean out condition is more true with the 2 strokes than with the 4tec. injector problems are obvious problems and it won't run very well at all so heat typically doesn't have a chance to build up like the 2 strokes that run fantastic just before they let go from lean out.

However, overheat and leaking head gaskets that allow water intrusion will melt pistons in 4tecs. Does your piston look like this?

120.jpg
Click to expand...


the pistonlooks perfect except in the bottom off the exhaust valva divit there is a hole half the size of a thumb nail through the top of piston and out the side under the rings and 1/32 of an inch into the cylinder wall. starting to wonder if there could be a small crack in the exhaust manifold allowing a drop off water to settle into the divit. Now that i have taken it apart myself the first guy would not of had to take the exhaust off the head at all justput the whole assembly on the short block . would probably b worth getting it scannned for hairline cracks. i dont know every thing looks good no obvious gasket failures
 
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exhaust manifold leaks don't usually cause piston damage, exhaust gases will push the water out.

did they replace the head gasket? or use the old one? some bad shops think they can use the old one and won't spend the $80 on a new one.
 
i know 7k purchace 3 rides 7k rebiuld half a season 1500 engine module right into wear ring replacement and now a piston failure. I never really though about re sleeving it. i just went right to re man short block ready to go for 2500. i thought the second 7k would give me a machine i would enjoy for years. I guess ill strip the block check all the tolerances on the bottom end and make sure it is all good and it should be cause it is less than two seasons old probably less than 15 hours on it
 
ski-d00 said:
exhaust manifold leaks don't usually cause piston damage, exhaust gases will push the water out.

did they replace the head gasket? or use the old one? some bad shops think they can use the old one and won't spend the $80 on a new one.[/Q

i really have no idea what they did the one i took out looks good. i was quite surprised at how tight the head bolts were though not sure what the torque specs are. it took a 1/2 inch drive L bar to get them to turn i would guess 80 ft/lbs.
Click to expand...
 
the head bolts are not done by torqe
they are done by dagrees after a light torqe spec
is reached 29.5 ft lbs then 120 digrees then 90 more digrees.
 
Last edited by a moderator:
I "ve seen the piston pictures. Kinda strange. I was thinking like ski-doo....... coolant in combustion chamber. The piston would be clean if that where the case. Give us a picture of the spark plug and cylinder head. :cheers:
 
unfortunatelty i changed the plugs last summer and cant find it now. i was so mad i just parked the seadoo till now. it looked wtite like super lean condition and the steel ground above the electrode melted right back to the threads. the head looks good no discoloration near the valves
 
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