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Discussion Starter #1
Last Friday I drove down to the dealer where I bought my Duramax a year ago.


The intent was to talk to ser. mgr about secondary filter. Did so and he stated that should help and no reason to affect warranty. Said GM should be happy with the increased filtration, post or pre OEM.


Then he showed me a 2002 dmax, 67k, out in shop. First came in with crankcase full of diesel fuel. This is a small dealer and they had little experience on Duramax, so they called Chev. Tech Assistance who advised them to pull a vacuum test on return lines back toward injectors. Stated that if it wouldn't hold vac. to pull valve covers and tighten return line banjo fittings and check vac. again. If OK now, then button up, change oil and filter, and try it out.


Vac. test did show loss, and above was done, apparantly w/o a balance test, I didn't think to ask about that. Truck ran great, all appeared fine, and owner picked up truck and left.


Next day, he called and they had to tow truck back in. Crankcase again full of diesel fuel, truck had made loud clattering noise and was skipping. Investigation revealed no compression, and regional GM man now got involved. Truck had been driven 87 mi. since owner picked up!


He had the tech to pull head and engine had one bent intake valve and a cracked injector! I haven't talked to him again since Tues. so I don't know the final outcome.


My theory is that diesel fuel in oil twice in such a short time caused the valve to stick open. There is a mark in top of piston where vave and piston collided.Will report any further developments on this.
 

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hydrolocked.. and the tech line help was of know use. there are more efficient ways to check for a fuel leak..
 

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Discussion Starter #5
Patrick, I know you earn your living as a tech, and I respect that, I'm just a bit lazier than that and became a machinist. But I've owned, driven, maintained, and repaired my motor vehicles for 50 years. And that includes some pretty dang fast dirt track cars that I built totally, engine, driveline, chassis, suspension, and body. Also some fast street rods.


And I can assure you, you don't bend valves in a hydraulic lock, you bend connecting rods.


You bend valves when they and the pistons hit, usually because the valve stuck open, or got out of time, or floated fromm overrevving. And this collision leaves a mark on top of the piston, as I stated this engine had. Two episodes of diesel fuel filled crankcase within 100 miles is enough to wash all the oil and lubricity out of a lot of places.


I believe the valve seized up in the guide in an open position. Think about it!
 

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If the valve was open to hit the piston, it will not hydrolick, the fuel (or whatever fluid) would simply go out the open valve port. hydolick and bent rods go together, or they lift the heads stretching or breaking the head bolts.


Now it either stuck something open, or over reved and hit, or somehow something got out of time do to breakage,most likely the first IMO.
 
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