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940 Engine locked

H

hessam69

Well-known member
Joined
Jun 19, 2009
Location
Sydney, Australia
Beat-up neglected 940 got towed in to me, I know nothing about it's history, other than it died one day and no one could work out why.

The first thing I tried was to see if the cam belt had broken, tried turning the vibration damper by hand and see if the cam turns, crank will not turn. It is possibly seized. OR


Could the AW71 be stuck? Auto oil pump seized? I did witness another 940 some years ago that had this same problem, mechanic could not turn the crank, swapped in a junkyard AW71 and off they went.

How to tell for sure without taking it off?
 
Is there any oil in the engine? what level?
any oil leak on the engine?
If there is no oil in the engine the case for a locked up engine is stronger.
if there is oil in it it is very unlikely that the block has seized.

any oil leak on the trans? what is the ATF level?
any ATF mixed in with coolant?

Maybe remove the starter and use the hole to inspect the flexplate to see if the torque convertor bolts are still there, if you can see cracks or score marks.
Same for the plate closing off the underside of the bell housing. It's easily removeable for inspection
 
Id try a socket on the crank, I know I cant turn my engine over by hand. I think its a 15/16 deep well and 1/2 in drive rachet. Then if it wont budge, Id say engine is seized.
 
put a breaker bar and socket on the crank as suggested above, and work forward from there.

it is unlikely that a running car would seize up the pump in the automatic, anything is possible for sure, but that is fairly unlikely.. the car would have stopped driving first as the fluid level would have to be low (or the filter completely clogged in the trans) for the gears to start to build up that kind of heat. more likely that it'd rust from sitting and getting water incursion, but this was said to be running and driving.

when you put the socket on there, try easing it both ways (Without putting enough ass on it to break the bolt loose). If it's truly locked up and went from running to dead stop, it's probably partout/new engine time.

so, as others have suggested: check oil level, maybe drain the oil if the stick comes up dry, put a wrench or breaker bar on the crank bolt and try to spin it over, pop the valve cover off, and between those things (which should total to less than 20 minutes give or take tool availability) you should be able to develop a pretty clear picture of the state of engine affairs.

Also, if it rolls backwards from current position but stops before making a complete revolution, some kind of foreign object may have fallen down in the engine and gotten stuck (think bolt, nut, that sort of thing).
 
Sorry everyone, when I tried turning the engine, it was with a socket on the bolt, with an extra long breaker bar. It would not move at all either right or left. There is oil in the engine and transmission but of course the ATF is dark.

Still, can something in the AW71 oil pump break or seize enough to lock itself up to the point the crank won't turn? Some significant force would be needed to stop a driving B230
 
Take off the valve cover and see if anything broke. It may have dropped the head of a valve into a cylinder which would prevent any movement if it's a large enough chunk.
 
Thanks, I'll try that.

If all checks out there, I'll have to pull the AW71 out (leaving the torque converter on the flexplate) so I can at least get the engine started
 
Don’t do that. You can damage the converter or stator pulling a transmission that way. All you need is the flex plate in place in order to start the engine.
 
Unfortunately, without the ability to turn the engine, there is no way to remove the transmission with the torque converter still attached; there is no access to remove the torque converter retaining bolts
 
hessam69 said:
Unfortunately, without the ability to turn the engine, there is no way to remove the transmission with the torque converter still attached; there is no access to remove the torque converter retaining bolts
Click to expand...

True. I had to do the same on an 87 740 T that broke a rod and sent the intermediate shaft out through the back of the block. It was locked rock solid. Just make sure you slide the transmission straight back using a transmission jack. Don't let it hang on the converter.
 
Somebody correct me if I am wrong here. In order for a locked up tranny to prevent the engine from turning, wouldn't the torque converter have to be locked up also?
 
Harry Tuttle said:
Somebody correct me if I am wrong here. In order for a locked up tranny to prevent the engine from turning, wouldn't the torque converter have to be locked up also?
Click to expand...

The TC's shell is bolted to the flex plate.
The TC's snout turns the transmission's oil pump.
If the pump is seized/damaged, it can stop the TC (and the engine) from turning.
 
I think that is what's happened, but how? What causes an autotragic oil pump to seize?

As mentioned I did witness another 940 with this problem, crank would refuse to turn, they had the AW71 replaced and all was well. I wonder if there are any warning signs this would be about to happen.

Strange
 
  1. Wouldn't if be some funny smell/bits in the tranny fluid as hint?
  2. How to remove the transmission then? I have not taken an automatic off a car in ages. Does the troque converter just sits on the transmission shaft so it can stay attached to the engine as you pull the tranny out? If so, would you have to tilt the entire assembly down on the rear so to slide it out, or take drivetrain out and separate on the ground?
 
If this is for a customer then just say no. Too much time and going to cost too much money. If you're doing it to "know" what happened and have spare time , then just remove the engine and transmission as one. There is a good chance you'll be needing both.
 
PO reckons the transmission was working well. Had it serviced recently, but he did say there was a coolant problem with the engine. When I got the car, there was no coolant in it. He says he had the engine cranking, trying to start, it sounded funny like a lack of compression perhaps (head gasket)

So why won't it turn now? Can an engine seize up hard after sitting for 6 months with a possible blown head gasket? I want to get it running before taking the head off. How best I unseize it?
 
Maybe the engine had a blown HG from coolant passage to combustion chamber causing coolant to leak into the cylinder which could cause a hydro lock in that cylinder. Maybe remove the spark plugs and hand crank the engine to see is it moves with the coolant having a way out?
 
nel621 said:
If this is for a customer then just say no. Too much time and going to cost too much money. If you're doing it to "know" what happened and have spare time , then just remove the engine and transmission as one. There is a good chance you'll be needing both.
Click to expand...

a) ^^ this

b) Coolant in any cylinders, or in the oil ?


:-P
 
Look for a cheap USB borecam on amazon/ebay. Most come with lights built around the camera and little mirrors (which you should tie to the camera's shaft so if it falls off you can still retrieve) that are clipped in a very precarious way to said camera. Contrary to what the name implies, it is not only BDSM applications. Remove the spark plugs and then look at the cylinders, pistons, and valves.
 
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