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Motor Stuck

Mon Oct 22, 2012 8:40 am

Fix one thing, break another. Borrowed a mag while a gracious forum member fixes mine, and got engine to start - ran nice. I didn't have the kill switch connected, so I pulled the choke to shut it off. As it was shutting down, I heard light knocking. Like an idiot, I had to start it again to see if I was hearing things and it knocked a few times and stopped (engine was cold). To my horror, the engine is now locked up tight. I opened it up and pulled the rod bearings. After disconnecting, I can move #1, 2, and 4 rods, but #3 seems stuck. Of course, it's all the way up so I can't free the crank. Assuming it's a wrist pin or bent rod, how the heck do I get it out? I'm pulling the head tonight. After rod bearings were disconnected, I tried rocking the tractor in gear to see if the crank would move, but it would not. Any help is appreciated. Temptation at the moment is to drill the piston and yank with a slide hammer. Hopefully the block and crank aren't damaged. Saw a spec of antifreeze dripping from #3, so it probably hydro-locked. Add head gasket to the list....

Re: Motor Stuck

Mon Oct 22, 2012 9:22 am

Did you observe oil pressure on the gauge?

Re: Motor Stuck

Mon Oct 22, 2012 9:37 am

Hengy wrote:Did you observe oil pressure on the gauge?


No, it was running for a total of 20 seconds the first time, and 10 the second.

Re: Motor Stuck

Mon Oct 22, 2012 9:37 am

I assume that you didn't have spun rod bearings - you didn't say but that would have been an important clue to the condition. If 2 and 4 were good - 3 would probably be good too.

You're going to have to pull the head regardless to get the pistons out if you are in-frame, so you'll see what you have then.

Head gasket set is HS7560S and only about $25 delivered from Rockauto. You'll still have to drive the pistons out the top after you remove the ring groove if it's bad.

The head on my parts tractor (the '65 loboy) was a chronic gasket blower. So far the stone job, new gasket, and new grade 8 bolts with washers are holding..

Re: Motor Stuck

Mon Oct 22, 2012 9:43 am

Hydro locked. If so remove the spark plug, that will relieve any fluid in the cylinder. But that's probably not the problem. Could be loose carbon on top of the piston. Or worse, lack of lubrication.

Put solvent or light weight engine oil on top of each piston. Let set for a day. Try rocking tractor backward again.

Re: Motor Stuck

Mon Oct 22, 2012 10:12 am

Eugene wrote:Could be loose carbon on top of the piston.

Yep, Susie Q was locked up. We pulled the head at the Barnyard Bash, cleaned everything inside and in less than an hour it was back to work.

Re: Motor Stuck

Mon Oct 22, 2012 10:25 am

Barnyard wrote:
Eugene wrote:Could be loose carbon on top of the piston.

Yep, Susie Q was locked up. We pulled the head at the Barnyard Bash, cleaned everything inside and in less than an hour it was back to work.


One thing I did notice, shining a flashlight in the plug hole for #3 is the top of the piston is perhaps a little too clean. Steam cleaned perhaps... Only about 20 hours on the engine since a minor rebuild (rings and bearings). But if nothing were bent or broken and hydro-pressure is releaved, why would it still be locked up? And would it have knocked with just loose carbon?

Re: Motor Stuck

Mon Oct 22, 2012 10:40 am

Coolant introduced into the combustion chamber can immediately cause pieces of carbon to break loose from the piston tops as well as the cylinder head. If there was a sufficient amount of carbon deposits and some did in fact break loose, it may very likely be jammed between the piston and the head.

Slamming the choke shutter closed at curb or fast idle produces no change in the amount of intake manifold vacuum so killing the engine with the choke had nothing to do with drawing coolant into the combustion chamber.

Re: Motor Stuck

Mon Oct 22, 2012 11:48 am

I'm not sure the symptoms all make sense together. If you have uncapped all 4 rods and were able to move 3 of them, you should be able to move the crankshaft one direction or the other. If you can't, it implies the crank is being stopped by something other than a stuck piston.

Re: Motor Stuck

Mon Oct 22, 2012 12:29 pm

Jim makes a good point. Loosen the starter. Perhaps the starter is locked in the flywheel.

Re: Motor Stuck

Mon Oct 22, 2012 1:05 pm

Eugene wrote:Jim makes a good point. Loosen the starter. Perhaps the starter is locked in the flywheel.


I checked that and the mag before I pulled the oil pan. If it's not the piston, it's something up front.

Re: Motor Stuck

Mon Oct 22, 2012 1:51 pm

Don't attempt to bar the engine over forcefully until the head has been removed.

The amount of static pressure exerted on the main bearing journals with a piston forcefully locked into TDC position by an internal metallic failure can be phenomenal, leading one to believe the crank is locked up.

The head must be removed to service the coolant leak so wait before reading more into this problem than it actually may be.

Re: Motor Stuck

Mon Oct 22, 2012 6:32 pm

On the last locked up engine I built the first thing to freeze up from lack of oil was the idler gear up front. It was welded up tight while eveything else like rod bearings had just burn marks on them and would still move some.

Re: Motor Stuck

Mon Oct 22, 2012 6:38 pm

There's yer problem! Rod seems ok and wrist pin has no play. Debris was in the head so I'm not quite sure why it was locked up. As soon as the head was off, everything freed up. So, can I just replace the piston? Cylinder looks fine. Hydro-lock or something else?
If the picture doesn't post, there's a nice hole in the top of the piston.


Image
Last edited by mrdibs on Mon Oct 22, 2012 6:50 pm, edited 1 time in total.

Re: Motor Stuck

Mon Oct 22, 2012 6:49 pm

mrdibs wrote:If the picture doesn't post, there's a nice hole in the top of the piston.

I edited your post to show your photo.
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