The Stovebolt Site Forums The Shop Area Engine Shop Stuck GMC 248

I have had Liquid wrench sitting in my cylinders for 2 months on my 248. today I changed the oil and hooked a battery to it and its still stuck. I am starting to regret buying this truck. Is there any way to hook a breaker bar to the crank without taking the radiator out?

Pull the cover off under the flywheel. You can rock it with a big screw driver in the teeth and against the bottom of the bell housing. Take baby steps. Just little ones back and forth.

Steve is right on.
You may want to try a mixture of half AFT and half diesel fuel.
Patience is the key....even after two months.

I will try that. There was no cover over the bottom of the flywheel, I hope that doesn't mean someone else also tried to unstick it.

All the advice given is spot on in my opinion, just remember it didn't get stuck overnight and it will take some patience to get it loosened up. One good point is rocking it back and forth rather than going the same direction, it could very well have a valve or two stuck also. If in doubt loosen the rockers and try rotating. I have seen many a bent pushrod from a stuck valve.

Any idea of how long the motor has been locked up? You mentioned that you have had it soaking for a couple months, did you have the spark plugs out when you tried to turn it over? When you drained the oil what did it look like? Had all the Liquid Wrench you put in the cylinders traveled to the oil pan? I would remove the fan belt, you never know if the generator or water pump could be locked up adding to your problem. It was also mentioned about stuck valves, probably a good idea to take the valve cover off and see if you can move each valve. I would also use a pry bar on the flywheel to try and move the engine back and forth. The process to free a stuck motor takes time and lots of patience. Do a little more detective work and you will have a better idea if the motor can be freed up without taking it apart. Good Luck, Don

Don't give up on it! I'm too new, and too novice to give any feedback other than what I read on here for un-sticking one; BUTafter going from battery, to cables, to starter, to pulling plugs and squirting a bit of liq wrench in cylinders (then krill later) , to barely prying on flywheel, to tensioning belt and urging fan/balancer back and forth 1/8", my 55 235 finally turned over with the plugs out. A week later (thursday) I put plugs back in & it started!

I know I'm not helping with advice, but I read every post I could on the topic, and the "trick/tip" that trumped all was patience. 15 minutes a day easily nudging it for a month & it finally woke back up.

I'll post pics & video when I can- keep charging!

Brad

Pull the valve cover and loosen or remove the rocker arm shaft. Remove the pushrods. This will solve the potential problem of stuck valves adding to the resistance of the engine to turning. Pull the spark plugs and add several ounces of a 50:50 mixture of acetone and ATF, or Kroil if you have any. After a few days, use the chisel-shaped end of a shepherd's crook wrecking bar between the flywheel teeth and the bellhousing, being careful not to break or damage any teeth. If the flywheel moves at all, alternate between moving it a few teeth in both directions. Patience!

Worst-case scenario, remove the cylinder head and use a chunk of hardwood such as oak or maple that will be a close fit in the cylinders, and smack the top of the pistons with a BFH to break them loose.
Jerry

I knew that some one would break out the BFH. I just knew it. Best advise? Take your time. If you get a little and take your time it will come loose. And yes when all else fails..that BFH is your new friend.

When i was trying to unstick my motor, i was going thru the samething. My motor had thick like tar oil from setting all those years which was unknown how long. I had the rocker rusted and had to do like jerry said tap the pistons out. The only thing i could not get out was my lifters which the machine shop had to remove. I think mine was a worse case senerio. Now everything is go to go. Patience is the key.