95 Suburban 4X4... last couple of weeks, we've had a couple problems (3 or 4 times) starting the truck warm... it would appear to catch and then die. Second try would start with no problems. ( Up until this, no problems at all with starting, oil pressure good, temperature fine, etc. - good fuel economy.

This morning, tried to start after it was warm. The truck gave a small "backfire" sound, started to smoke badly. Within a few blocks the temperature started going up & no heat from vents. Shut off engine immediately and could not find any leaks. Waited for engine to cool down and restarted. Temperature went up again very quickly. Got it home without overheating it (couple km) and called a tow truck to take it to diesel repair shop.(No coolant in the oil and coolant reservoir was over full)

The diesel shop says engine is completely seized (cannot turn in either direction). I'm totally baffled as to what could have possibly happened in such a short time to an apparently healthy truck? Repair shop says can't be rebuilt... does this sound right???

Sounds like head gaskets with coolant over full, backfire sound could have been piston hydraulic in chamber full of H20, not good.

Yep, happened to me once. The # 7 cylinder filled with water or "hydrolocked" and I thought the motor was siezed. I pulled th motor, pulled the heads and the motor was fine. U just need to check to make sure that the bearings are OK and that the rod is not bent. Pull the glow plugs one at a time and see which one spits out coolant. Is the level low? If ther is a blown head gasket, that will cause the motor to run hot as the fluid is purged out of the motor and hot exhaust gas is put into the motor.

Thanks for the idea but I dont think that the problem is coolent in the cylinder because I could still start and drive the truck home. The motor seized after it went into the shop.
G.C.L. diesel here in Edmonton can't turn the motor clockwise or counter clockwise seems to be piston seized.
Any idea why the local rebuilders are not willing to rebuild the 6.5?

Chicago
When your motor hydrolocked was it possible to turn the crank? Maybe my idea that the hydrolocked piston should allow a counter rotation is out to lunch?
Any idea why the motor didn't just suddenly stop if it is hydrolock? Seems to me that it should.

You did say that engine started smoking badly. You could have a cracked piston that seized the rings and scuffed the bore. I would remove heads for a better look. The only thing that would keep from letting you rebuild the engine would be a broken crank that cracked the main webs on the block. In any event if the engine is going to be rebuilt, check the main webs carefully for cracks.:(

I just sugest pullin the heads. Even pull the filter and cut it open CAREFULLY. Check for fragments and metal. But my motor locked up at 65 MPH!!!! Just stoped, actually made a little squel and that was all she wrote, hydrolocked. Don't let me get your hopes up, I am just sending some passed experience along. Pull the heads, the only way to know without pullin the motor. Good luck man, I have a blown motor right now though, cracked a piston, droped the rod and DESTROYED the block. I know EXACTLY how u feel. Let me know how things turn out.

Tzing,local rebuilders wont touch a 6.5 because they are garbage. Too many heads/blocks/cranks cracking/snapping. You need to buy a brand new crate engine,and even that isnt a sure thing.If you have mechanical abilitys consider a swap to a Cummins B,and the truck will be fixed permenently.There are brand new take out ISBEs ,and Cummins 600's on http://www.fordcummins.com/. Other than that your rolling the dice by putting another 6.5 in there.There are factory cummins adapters to bolt your trans to the cummins engine,and the engines new/complete are priced around 6500 for an 03-04 205hp and 7200ish for a brand new 05 "600" complete w computer/harness. If there's anyone handling low miles duramaxes/or new take outs. I would consider a dmax too,at this time they arent readily available like the Cummins engines are,maybe down the road there will be.

Further research suggests that the cracking problem may have been resolved in newer versions of this engine by increasing the nickel content. Anyone know how you can tell for sure that you are getting the newer block?

im not knocking cummins in any way, but they have their problems too, just not as many as the 6.5. there are plenty of cummins drivers having lift-pump problems and i have heard of some broken cranks, too. and then there is the dreaded "53" block as well.

I think all of those problems are related to the early VP44 pump and 24v setup. The old 12 valves with P pumps were about as bullet proof as you can find.

Further research suggests that the cracking problem may have been resolved in newer versions of this engine by increasing the nickel content. Anyone know how you can tell for sure that you are getting the newer block?
Reference the cast number/date. Anything from '00-present, iirc is the "newer" cast.