What could cause my engine to seize?

[Darbshaw]

Hoping maybe someone smarter than me can help me figure out my issue. I'll try to break this down as best as I can, the oil pan will be coming off in the next few days as I have the time to hopefully have a better look.

Engine: Engine was pulled running out of a donor car, no issues besides slightly low compression from a blown headgasket. While the engine was out I did a full refresh outside of removing the pistons and crank. So new rod bearings, head gasket, seals etc. Engine was hand cranked and in time before installing into the car. No apparent issues. Engine has a new starter as well although this is obviously no longer the issue.

After install day 1: Cranked engine with plugs out to build some oil pressure. Seemed a bit sluggish but nothing too abnormal since I forgot to keep my battery on the charger while it sat. Put the plugs in, I got one slow crank and a quick fire, the car shutoff after. Went to crank again and only got a click from the starter. Figured it was a dead battery, let the car sit overnight while battery charged. Cleaned and rechecked all of my grounds and electrical connections

Day 2: Started with a plug out crank, same as day 1 everything seemed good. Went to put the engine under compression w/ plugs in and starter click. Nothing else to it. Stumped I decided to pull the starter thinking this may have gotten wedged in the flywheel and caused a jam, this was not the case. After I tried to hand crank the engine to find it completely seized. I have about 1-2mm of wiggle back and forth, visible from the flywheel teeth moving. No signs of piston to valve contact when looking with a borescope, everything seems normal. The cams are able to shift back and forth, so these are not obviously bound.

My first thought is that maybe something is bound up with the timing chain. Which is causing the cams and crank only able to move between the gap in the chain. Although everything looks normal from what I could see with a borescope + flashlight. Something else that came to mind, is it possible for the vanos to cause this lock somehow? Thats the only other piece I can think of that would bind the engine like this. Unless I have a large foreign object sitting in the oil pan.

[bigjae46]

Total guess here, would think it would be an issue in the cylinder head. Maybe pull the vanos off and see if the cams can turn. Then see if the crank turns. I'd probably start there before tearing the motor down again.

I have no idea if that is the best or even a good approach.

[332]

If you over trq the rod bolts, it could cause this.

[Darbshaw]

Total guess here, would think it would be an issue in the cylinder head. Maybe pull the vanos off and see if the cams can turn. Then see if the crank turns. I'd probably start there before tearing the motor down again.

I have no idea if that is the best or even a good approach.

A friend of mine reccommended to check the flywheel as well. Maybe something got caught in there or a bolt walked out. Vanos is easy enough at this point and may save me a decent headache. I'm completely lost as to what could be causing the jam, unless I have a socket extension hanging out in the oil pan. I just can't think what in the VANOS would cause the engine to sieze without there being a major colission or issue.

Not a bad idea to start eliminating variables or connected parts

[Darbshaw]

Good to know with the rod bolts, I don't think it's likely since I torqued everything to spec. I guess theres no way to know until the pan is dropped. If I have to replace the bolts, would it make sense to put fresh rod bearings? Or just send it?

[332]

Good to know with the rod bolts, I don't think it's likely since I torqued everything to spec. I guess theres no way to know until the pan is dropped. If I have to replace the bolts, would it make sense to put fresh rod bearings? Or just send it?

If you already have it opened up and have to replace the bolts, just check the bearings. Your eyes will know! Question though, did you manually turn the car over with like a pry bar before you put the pan on etc? I'm hoping you went top down, on the repairs instead of doing the rod bearings first then the HG? Nvm, I reread your OP. It's pretty easy to take the timing chain cover off, but that doesn't seem likely that the problem is there.

[Darbshaw]

If you already have it opened up and have to replace the bolts, just check the bearings. Your eyes will know! Question though, did you manually turn the car over with like a pry bar before you put the pan on etc? I'm hoping you went top down, on the repairs instead of doing the rod bearings first then the HG? Nvm, I reread your OP. It's pretty easy to take the timing chain cover off, but that doesn't seem likely that the problem is there.

I'd imagine I could see if there was binding on the timing chain through my borescope but that the only thing that makes sense to me atm. According to the TIS front timing cover is shown as a head off repair. Which I'd rather not go through and drain the coolant again. As much fluid I can save the better.

I think I'm going to attempt and peek in the trans with the scope. I'd really just love to find a smoking gun here.

[sapote]

Day 2: Started with a plug out crank, same as day 1 everything seemed good. Went to put the engine under compression w/ plugs in and starter click. Nothing else to it.

So it was hand crank ok, but after that the starter couldn't turn it, and hand cranking again only can move a few millimeters?

I would remove the chain off the cam sprockets, then carefully slowly turn the crank to see if it's locked, and if not then do the same on the cams each to see if which cam is locked.

[332]

I'd imagine I could see if there was binding on the timing chain through my borescope but that the only thing that makes sense to me atm. According to the TIS front timing cover is shown as a head off repair. Which I'd rather not go through and drain the coolant again. As much fluid I can save the better.

I think I'm going to attempt and peek in the trans with the scope. I'd really just love to find a smoking gun here.

they lied, you can get the timing cover off without removing the head. few bolts ezpz, you can see the top holes on the cover, that bolts into the head. Remove those and the rest of the bolts, comes right off.



Here is a picture with the timing cover off with the head still on.

[332]

So it was hand crank ok, but after that the starter couldn't turn it, and hand cranking again only can move a few millimeters?

I would remove the chain off the cam sprockets, then carefully slowly turn the crank to see if it's locked, and if not then do the same on the cams each to see if which cam is locked.

I would remove the chain off the front of the crank before I took it off the cams. Much easier to keep the engine in time!

[bigjae46]

they lied, you can get the timing cover off without removing the head. few bolts ezpz, you can see the top holes on the cover, that bolts into the head. Remove those and the rest of the bolts, comes right off.



Here is a picture with the timing cover off with the head still on.

The issue is the timing chain overhang is sealed against the head gasket. So if you remove the timing cover you could introduce a leak from the timing cover/block/head joint. I'd guess that is more of an issue with an old head gasket. If there ever was a situation where you could get away with not removing the head...it's this one.

You would need to remove the damper, replace the bolts and re-torque it which is a minor PIA. I still vote for removing the VANOS.

[TexaZ3]

Vanos would be my first suggestion, especially if the engine turned by hand.

[sapote]

they lied, you can get the timing cover off without removing the head. few bolts ezpz, you can see the top holes on the cover, that bolts into the head. Remove those and the rest of the bolts, comes right off.

It might not come out as easy as this sounds, because the head is pressing down on the timing cover.
They didn't lie as it is hard to seal between the head and the timing cover doing your way, and not easy to pull the timing cover as there is the dowel pin on the timing cover and it's like an interference fit between timing cover and the head.

[sapote]

Vanos would be my first suggestion, especially if the engine turned by hand.

You think bad vanos timing leading to pistons hitting valves and the lock up? It seems OP did hand turning the crank some turns, so why?

[Slideways]

OP, when you installed the VANOS unit, did you push the splined gears attached to the VANOS pistons all the way into the VANOS unit before installing the VANOS unit on to the cylinder head?

This is the only other thread I am aware of where the engine had an issue being rotated by hand - https://nam3forum.com/forums/forum/m...my-s54-rebuild