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piston distruction

this happend to my bone stock 6.5 td before i replaced the engine.
#2 cyl seperated at the wrist pin broke the rod which broke the crank case and then went down hill from there both heads cracked 3 broken pistons and rods crank in 3 pieces, 2 holes in block plus several in the oil pan. all happened at idle. man the wife was really pissed having 2 gallons of diesel oil spilled on the driveway....
wes
 
midniteplowboyy said:
Didn't you turn the fuel up also, that advances the timing even more.
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no i never got around to it

slim tell me more about why this happend.
my idle has been erratic for some time when truck is cold it would idle at around 8-900 and when warm at 1000-1100 rpm. i did notice when i took it all apart that the idel adj screw had fallen out and was in the vally.:eek: how dose the cold start advance work on a DB2? the PO said something about it not working and had a switch wired to 12v to the stepper motor and he said to turn it on before start up which after doing some reading that is the only way to make a high idle on a db2 that i have found.

should i have my pump rebuilt just to be on the safe side?
 
chevyCowboy said:
no i never got around to it

slim tell me more about why this happend.
my idle has been erratic for some time when truck is cold it would idle at around 8-900 and when warm at 1000-1100 rpm. i did notice when i took it all apart that the idel adj screw had fallen out and was in the vally.:eek: how dose the cold start advance work on a DB2? the PO said something about it not working and had a switch wired to 12v to the stepper motor and he said to turn it on before start up which after doing some reading that is the only way to make a high idle on a db2 that i have found.

should i have my pump rebuilt just to be on the safe side?
Click to expand...

The cold start works by running a 12 volt solenoid in the DB-2 cap. The solenoid is engaged through a temp switch located on the cylinder head.
When the solenoid is energized it closes off the fuel return line of the IP it effectively raises the IP case pressure from about 5 to 7 psi to around 12. Timing is advanced and fuel is slightly more. This is effective when cold but produces a problem when the engine is warm.

The little black fitting on the top of the IP cap is a pressure regulator, Glass ball with a glass seat and a spring. If that gets plugged it is like running with the cold advance on all of the time, bad for the motor. The little grey arm on the side of the case with the little cam is the timing "advance arm " it is really the timing retard arm because it moves the advace piston causing the cam to move in the direction of rotation rather than against it as we would expect. If your timing advance piston froze in the bore you could have advanced or retarded timing all of the time, motor would be sluggish on either the top or bottom end depending on where it froze.

I think you get the idea, have the pump looked at. I think this may have caused your engine failure.

The fuel metering shaft could also cause more fuel then you want and this would give you the erratic idle and accel pedal feel. Check the pump !
 
By the way a single injector failure may have caused you melted piston, Pulling pistons apart or breaking at the ring land is a heat related problem on these motors.

On the sleeve repair for the cylinder, I have been running a 6.2 hybrid with three cylinders sleeved for awhile now. Sleeving is a good repair, if the block is sound sleeve that cylinder. I run mine hard and tow with it and have never had a problem. Think fix not replace, same with the heads if they are cracked. Mine are lock stitched and brass sleeved (did it myself) . Not a leak in 30,000 miles of hard running. ):h
 
Slim Shady said:
That folks is fuel induced failure.
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I didn't know the exact cause of failure but knew it wasn't oil related, it will seize a rod or main bearing before a piston/or pin lets go.

chevyCowboy said:
should i have my pump rebuilt just to be on the safe side?
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Hell yeah, and fix the patch wiring job.


Slim Shady said:
The little grey arm on the side of the case with the little cam is the timing "advance arm " it is really the timing retard arm because it moves the advace piston causing the cam to move in the direction of rotation rather than against it as we would expect. If your timing advance piston froze in the bore you could have advanced or retarded timing all of the time, motor would be sluggish on either the top or bottom end depending on where it froze.
!
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Yep, my old pump had this hard spot on the gas pedal, I had to push thru it, had no idea what it was until I had to replace the IP for a massive fuel leak. Turned out it was that and the valve fell out after the arm broke off. It had a nasty flat spot/hesitation just off idle, :mad2:
 
that and the gouges higher up the cylinder. i was kind of thinking it might still be useable beacouse it is so low it the cyl and bellow where the rings seal. i was under the impression that sleves did not go down that far. that they only went to just below where the rings are when the piston is a the bottom of its stroke. so they can machine a land for the sleeve to set on
 
chevyCowboy said:
just found these on ebay claims that they are only .010 reduced comp hight what would that lower the compression to? iv been told that .010 thicker head gaskets will lower comp to like 19:1 would these do the same thing

http://cgi.ebay.com/ebaymotors/GMC-...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
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Josh the compression is reduced approximately 1 point per each .010. Not quite but close.

I would make sure what size the pistons are and do a bore measurement of your engine. If you are stock and the taper is not bad you can use stock size pistons. If you need a .010 or .larger oversize piston that needs to be determined before you buy pistons. Don't get ahead of yourself, talk with the machinist first. The sleeved cylinder can be made almost any size even smaller than stock if you wanted to do that, Don't ask and I won't have to tell :D has to do with stroking and keeping the same cubic inch displacement, an experiment and a lesson a long time ago when I had money to experiment. :rolleyes5:
 
ok ill hold off on buying untill i get with the machinest
so .010 thicker head gaskets would make it approximatly 20:1

i was looking over the crank this am and found this gouge im guessing im going to have to have it turned
 

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I believe the Mahle 6.5 marine/18:1 pistons essentially have the piston pin 0.030" higher in the piston body.

Does anybody know if the latest/current Mahle pistons in the stock comp ratio have the black skirt coating? The marine pistons do & I would have expected the stock comp Mahle's to have it as well.

Maybe those ebay pistons are new/old Mahle stock from before they incorporated the skirt coating?

Also, maybe Slim knows if the stock crank is nitrided for surface hardness? My engine's crank was fine so I didn't check further about nitrided/tufftrided.

If the stock crank is nitrided, you typically loose some of the long-term wear durability when a nitrided crank is turned - the hardened surface doesn't go very deep.
 
Missy Goodwrench says that they are turnable. That is why undersize bearings are available.
 
Certainly nitrided cranks can be turned & the corresponding bearings sizes used to get the proper oil clearances.

I haven't even confirmed if the stock cranks were nitrided. If they were, the turning cut will remove the hardened area. Will still work, you just loose some wear durability.
 
well i got it all cleaned up today and did some looking around on the main webs and surenuff i found 3 cracks one is reall noticable the other two not so big. also heres a better picture of the broken spot in the one hole. talked to the mechinest today and he thinks he can do something to fix it so that positive but i dont know bout these cracks!:eek: isnt the idea behind the block girdle to prevent these cracks from forming.
 

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