drift a 944

I am having trouble diagnosing a locked up crank, on my 86 951. Trying to get it running again by the weekend for my 944 rally, but I'm stuck!

Here's what happened... I blew the headgasket - badly - a few months ago. I was on the highway and tried to limp the car home, but it was clearly loosing so much coolant into the cylinders that I had to stop.

I sent the head out to get properly cleaned up and rebuilt. It was done right. I reassembled the head, camtower, timing belts, intake, etc. etc. and all that upper stuff at home in my driveway.

Time to fire it up.... It cranked and cranked a few times and then suddenly stopped on it's own. Tried to crank it again and could hear the solenoid engaging but the motor would not spin.

If you've skipped reading everything down to here, this is the important part... I pulled the spark plugs and tried cranking to alleviate hydrolock or something silly like that, but got the same results, nothing.... I then tried to manually turn the crank using a long breaker bar, and the crank would still not turn!

I pulled off the timing covers and did not see any loose bolts or tools trapped in the belts or pulleys. I then pulled the timing belt off the cam gear, and could turn the cam gear back and forth a little ways with a wrench, just as it should. So therefor it's not something caught in the cam. It must be the crank! But how??

I don't suppose driving it with a blown headgasket could have hydrolocked it so badly that it bent a rod or something beyond being able to crank? The odd part is that it cranked a few times before locking up. I am just at a loss of ideas here. Any help would be greatly appreciated!!!

Techno Duck

Have you taken the starter off yet? Its possible the pinion gear seized and is stuck engaged on the ring gear.

drift a 944

lol... as a matter of fact I just tried that! came back to report... Pulled the starter and it seems to look fine, came back to the front of the crank and it's still totally jammed solid!!

I also put a borescope into the cylinders to look for any hardcore scoring or loose objects or anything.... All looks normal in there too... :/

Bri Bro

Did you drop a tool that wound up in the clutch? It is not hard to drop a tool in the TDC sight window with the intake off.

drift a 944

I don't recall loosing any tools, bolts, etc. down in that area, especially in the sight hole... but I will bust out the borescope and take a look real quick from every angle possible.... I'll be back in a sec!

drift a 944

And the results are not good. I don't see any signs of foreign objects stuck where they can possibly be stuck. Even if they were, you'd think the crank would still want to turn backwards just a bit, right?!

I'm going to pull the reference sensors out to make sure they aren't jammed on one of the pins or something.

Any other possibilities besides seized crank bearings? *crossing fingers*

Bri Bro

Nope, it tends to jam the tool between the bell housing and the flywheel and you get no movement. No movement is also a sign of a seized engine...sorry to say. You may have a piston ring digging into the cylinder wall. If it rocks back a forth a little, it could be valve to piston contact.

If you can get your scope to look around the flywheel, you might see something. Even a bolt or nut will do it.

Brian had a similar problem some time back. Looks like something fell down into the rings and locked them into place...making a nice scraper. Read the first page of posts, sounds like what you are describing.

https://rennlist.com/forums/944-turb...ml#post3368635

Don't look at post #47 if you are having a bad day!!

Grandpa#3

Does not sound good at all. Spun a rod is my guess. Time to remove the oil pan. You may not make the race this week end, Elliott.

Best of luck,
Larry

refresh951

https://rennlist.com/forums/8519731-post27.html

carlege

Good thing you have so many.

Also im not following, you get the head sent out and you didnt clear the coolant out of the cylinders and you didnt rotate the engine with the head off to check the cylinder walls?

drift a 944

Bingo!! Sad but true.

Yes, sorry, that information was left out. The coolant was vacuumed out of the cylinders and then blow dried, and all the cylinder walls looked pretty normal. There were a few very light scores but nothing that looked extraordinarily dangerous.

Also, as I mentioned above, the first several cranks felt and sounded as smooth as they normally would. And there was no strange noise when the engine stopped, it didn't come to a screeching halt or anything, haha. It just stopped!

spanky

I wld remove the plugs again check the exact position of the pistons and if each piston is clear of making any contact with the valves in its current position then remove the timing belt / balance shaft belt and very very gently move the cam back and forth to see if the problem is isolated within the head. A few mm but no more either direction should be good. If this moves freely than move down to the crank, again only a few mm of movment in either direction should do the trick. Return both cam and crank to their orignal positions after testing/ moving each. Remember move each only a mm or so. no more!!! Bent valves are no fun at all!!!

drift a 944

I've already removed the timing belt, and the cam turns nice and smooth about a half inch each way from where it stopped. The crank does not move at all... as in, less than 1/1000 of a mm.

With spark plugs, timing belt, starter, reference sensors, and clutch disengaged, the crank is still totally locked in place. It will not budge the slightest bit!

lart951

broken ring would do that, or broken rod.

drift a 944

Yep, first thing I did was drain the oil and put in some fresh stuff. I had planned on running it for a minute or two and then flushing it out to put in another round of fresh oil. But didn't even get that far..