Bad things happen when 6.5's 'miss' ???

[markrinker]

There have been alot of posts recently about 6.5 owners with trucks that start to 'miss', hammer, etc. Obviously, there are a myriad of possible root causes, combinations of causes, etc.

Here are recent (and expensive) observations for anyone that might benefit from my broken crankshaft experience and possibly avoid the same.

1) The dampner still LOOKS fine. However, I wish I had replaced it when I did the water pump, fan and clutch.
2) I bought, but had not yet replaced 8 new glow plugs for the truck. I would guess that 1 or 2 were not functioning ALL winter. To my credit, the truck was ALWAYS plugged in.
3) A few days before the crankshaft failure, upon start-up, I had a definate RAP on one cylinder as the truck warmed up. It was 'missing' for the first time.

Crankshaft failure soon followed.

Related? Maybe, maybe not, but believe me, I won't wait to replace inexpensive and questionable items like dampners, glow plugs, or injectors with over 100K miles of normal use after this expensive lesson - with an otherwise smooth running engine that should have lasted another 100K.

My theory? If your 6.5 misses for ANY reason, you better get to the root cause quick or it can get reeeeeeeeeeeeeeal expensive.

[92gmc]

I broke a crank a long time ago in a 6.2 w/ banks, there were absolutely no warning signs, that engine was high miles but strong and smooth.

What do you suppose your 'rap' was ? possibly a main bearing web cracked, letting the cap and crank walk from one cylinder hitting it the right way ?

Have you done an autopsy yet ? If you are so inclined, maybe plastigage the surviving mains, I wonder if excess bearing wear is letting the cranks break

thanks

[ucdavis]

In the various gleanings from TDP, I have in my PM notes:
"Harmonic balancer pulley should be replaced @ 80,000 miles to avoid failure of rubber insert which could cause crankshaft cracking."

[Polar Diesel]

My truck developed a miss while driving a few weeks ago. Discovered a broken intake valve spring. I couldn't believe it. Lucky I didn't drop it in the bore, as I had no choice but to drive 200 miles this way. Easy fix, Number one hole, $8.00 spring. Truck has 190,000 on it.

[tanker]

I also broke my crankshaft, no warning, just crusing the interstate at 70 mph. My balancer upon inspection had the rubber comming out at two places. I drove it about 50-60 miles while broken. I thought I had broken a push rod, as I lost about 10-20 psi oil pressure, but it was quiet at idle, no leaks etc. It was still quiet up to about 1700 rpms, so we tried to hobble home with it. :rolleyes: It broke just behind the 2nd. main bearing, cracked the block etc.
One other question in my mind is a blown head gasket would allow water to enter a cylinder, say overnight, then when cranked for start up, it would bend a rod or stress the crankshaft, because you can't compress water. This may also be why a crank gets fatigued, then breaks. I had a head gasket go, and also a head crack while still under warranty, could this have started the process?? :rolleyes:
Oh well, I'm fine now. Money will cure anything! :D