Humvee 6.5 seized--best way to free it up?

I purchased am M998 with a locked up 6.5--truck has been sitting 10 plus years---5000 miles on truck--the engine is gm manufactured--the glow plugs came out easy and have light surface rust on tips--injectors had surface rust on tips --I drained the oil and saw no sign of water-------I have filled the cylinders with pb blaster--what would be the best way to turn the crank--compressed air in one cylinder ?--turn by pry bar on flex plate teeth ?--been soaking 10 days- thanks

Pull the cover off of the torque converter. Make sure the starter Bendix isn't jammed and stuck in the flex plate. I have seen this happen before.

Highly likely something came unglued in the crankcase causing the seizure.

Or one or more cylinders could have surface rust; I would not spend too much time trying to turn it over before tearing it down for a hone and regasket.


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gem1410 said:

I purchased am M998 with a locked up 6.5--truck has been sitting 10 plus years---5000 miles on truck--the engine is gm manufactured--the glow plugs came out easy and have light surface rust on tips--injectors had surface rust on tips --I drained the oil and saw no sign of water-------I have filled the cylinders with pb blaster--what would be the best way to turn the crank--compressed air in one cylinder ?--turn by pry bar on flex plate teeth ?--been soaking 10 days- thanks

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Bore scope the cylinders, you can get one that will connect to your phone for $10 on ebay. Then stick it in the oil pan drain plug; have a good look before tearing it down.

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Was the vehicle parked for 10 years because the engine was locked up, or was it running when parked?

dont know--bought it as-is--seller was good guy just did not know to much--I should have checked the engine more carefully and turned it over--just got to excited with a new project

Maybe not best, but worked for me,

With plugs and injectors out, should, could, maybe easy to rock the crankshaft back and forth with a breaker bar off the front damper bolt. Oil up the cylinders and give it a try. If free or frees up, hand turn for a while till your arm falls off. Do it with the other arm. Feel for & listen for clunky motion or sounds. Check block for cracks, Blow out glow plug ports and watch out for crud blowing out injector port locations. Put it all back together (clean up the rusty stuff, check glow plugs) and run compression test or prime and run. How much to you have to loose $$ ??

I did this on an 6.2 CUCV that sat in the junk yard for years and then drove it for 9 years. Ran like a rabbit. This free info comes with a no money back guarantee. GOOD LUCK

Proceed at own risk. Save $$ for a rebuild.

CAMO

Some sort of weak acid to eat the rust. Nitric acid, vinegar, ect ect

Besides the advice on the starter above I don't see what it would hurt to put a breaker bar on the crankshaft damper bolt and see what happens. I play with old tractors a lot and if you can get it moving by hand normally you should be good to go.

I got the engine to turn today by using a crowbar on the teeth of the flex plate (flywheel)--After soaking for 10 days it moved 1 tooth at a time forward and then back--after a half hour back and forth I got the crank to move a 1/4 turn-- The Starter Bendix was extended into the teeth--pushed back easily--Have filled the cylinders with Deep Creep this time--will try again in a week--The hardest part of the job so far was getting the 400 amp alternator which weighs 165 lbs out of the way--its a tight fit--Had to use my backhoe and a come along to pull it out--In the alt picture My foot is in there to show how big this alt is

Good job.

gem1410 said:

I got the engine to turn today by using a crowbar on the teeth of the flex plate (flywheel)--After soaking for 10 days it moved 1 tooth at a time forward and then back--after a half hour back and forth I got the crank to move a 1/4 turn-- The Starter Bendix was extended into the teeth--pushed back easily--Have filled the cylinders with Deep Creep this time--will try again in a week--The hardest part of the job so far was getting the 400 amp alternator which weighs 165 lbs out of the way--its a tight fit--Had to use my backhoe and a come along to pull it out--In the alt picture My foot is in there to show how big this alt is

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Might be a fine idea to repair the finish on that alternator while you have it out. Those things cost way too much to lose one due to housing corrosion. If we were still swimming in $200 alternators like we were 2 years ago, I'd be a bit less concerned...

Was your truck a shelter carrier or ambulance? 400amps is a lot of juice. I think very few out there with that mounting kit and alt.

All the best with your engine.....

gem1410 said:

I got the engine to turn today by using a crowbar on the teeth of the flex plate (flywheel)--After soaking for 10 days it moved 1 tooth at a time forward and then back--after a half hour back and forth I got the crank to move a 1/4 turn-- The Starter Bendix was extended into the teeth--pushed back easily--Have filled the cylinders with Deep Creep this time--will try again in a week--The hardest part of the job so far was getting the 400 amp alternator which weighs 165 lbs out of the way--its a tight fit--Had to use my backhoe and a come along to pull it out--In the alt picture My foot is in there to show how big this alt is

Click to expand...

Crikey! that generator should have no problem charging your..Mobile phone!
(and) keep soaking and turning, you will soon have it running. Hopefully.