Engine frozen - will not turn over by hand

[jzearfoss]

Background - 1968 280SL. Into multi-year restoration. Engine is not original. It is a replacement engine that was done back in 1983 by Silver Star Motors in Carmichael, CA. Basically a short block with rebuilt cylinder head. The engine had about 10,000 miles on it when I bought it in 1996. Drove it and enjoyed it for about ten years and then decided to do full restoration.  Complete strip down. Every nut and bolt.  Engine was put on an engine stand while all the other aspects of the car was attended to.

All I did with the engine prior to reinstalling was to clean, paint and replace fuilds. After all else was done I reinstalled the engine. As I knew I had a lot of fine tuning to do I needed to try to firing up the engine and see if I could at least get it to start and then continue working on getting it running smoothly.  It turned over and actually sputtered along for 5 -10 seconds.  Was able to get this same response multiple times. Then nothing.  Would not turn over.

I pulled the starter and it is fine. Decided to try and turn it over by hand. Got a big old breaker bar and tried to turn it over at the crankshaft and - NOTHING - would not move.  The engine should not be seized.  Did not run long enough for that to happen.

So, here is my question (finally). What might be the cause of the engine freezing up like that.  The things that run thru my head are: stuck valve, jammed timing gear,

Anyone have a clue as to what I should be looking at?

[Kevkeller]

Did you try turning it in reverse?  Did you take the valve cover off to look at the valves?
Did you take the spark plugs out?  Small possibility there’s a hydraulic lock.

[MikeSimon]

Manual or AT? Take the valve cover off and check the movements of the cam chain/cam/valves as you rock the engine back and forth

Take the spark plugs out and squirt some Marvel Mystery Oil into the cylinders https://marvelmysteryoil.com/
Let sit for a day or two and try again

[Cees Klumper]

Is it possible the transmission is in gear (I take it from your signature it's an automatic) and you are essentially trying to move the whole car?

[jzearfoss]

Thanks for the responses.

My bad on not giving enough background.  Yes, it is an automatic. Yes, I have removed the spark plugs and dosed the cylinders with Marvel Mystery oil. Yes, I have removed the valve cover and looked to see if there was anything obvious that might be binding up. Nothing that I could discern.

Since it is an automatic rocking the car back and forth would have no effect on moving the crankshaft.   I have tried turning the crankshaft (with a breaker bar) in both the clockwise and counter-clockwise direction.  No movement in either direction.

I am not familiar with anything called a hydraulic lock.  Could you elucidate on what that might be.

[Charles 230SL]

..It turned over and actually sputtered along for 5 -10 seconds.  Was able to get this same response multiple times...

jz, while it was sputtering did you have a chance to look at the oil pressure gauge?

[jzearfoss]

Charles - did not think to be checking the oil pressure gauge while doing that initial cranking of the engine. It ran really rough and only for about 4 or 5 seconds before quitting. Not really enough time for oil pressure to build.

[MikeSimon]

I am not familiar with anything called a hydraulic lock.  Could you elucidate on what that might be.

Usually hydraulic lock is defined as having one (or more) cylinders filled with fluid (gasoline) and as fluids are not compressible, the cylinder would lock. But as you have removed the spark plugs, you can rule this out.

[jzearfoss]

Say Mike - here is a question for you.

What if the engine did actually develop a hydraulic lock (as you described by excessive fuel accumulating in one or more of the cylinders)? Would the engine remain locked if all the fluid evaporated? (Intuitively my brain says no, but there have been times when physics seems to show itself counter to my intuition).

 If so - what might the solution be to get the engine unlocked?

[MarkCan]

It ran really rough and only for about 4 or 5 seconds before quitting. Not really enough time for oil pressure to build.

All the engine parts are very, very expensive! Let’s keep this in mind.
Since you cannot move the crankshaft, you have stated correctly that the engine is seized. No need to apply more force, it will only cause more damage. I’ve dealt with that issue before and it was the patience that saved the engine from complete disaster and scrap pile. I would remove all belts just in case than check the starter solenoid, make sure the drive gear is not jammed on the flywheel. Chances are slim but just make sure, than go down the list;
1. You have inspected the top end and all looks good. ✅
2. Is there tension on the chain?
3. Spark plugs removed,        Cylinders (all) inspection with the borescope (Amazon)
4. Oil condition, any glitter or foreign body present?
5. Remove the main oil pan and inspect all components.
There are lot of possibilities here so let’s be systematic. See what you can do with the list. Take your time and be thorough. Will continue when you are done. One last thing, NEVER attempt to turn the assembled engine backwards!
I hope this is somewhat helpful to you and the problems will get resolved sooner than later.
Mark

[jzearfoss]

Mark - in response to your 5 items.
1. Yes - I have removed the valve cover and do not see anything obviously amiss.
2. Yes - there is tension on the timing chain
3. Spark plugs have been removed but I do not have a borescope.  Guess it is time to add to my tool collection.
4.and 5.  Will drain and drop the oil pan today and take a hard look at the oil condition and the lower end of the crankshaft (rod and main bearings).

As an aside: the cylinder head is stamped as a 280 SE/A. In all my reference materials all I have ever seen is 280 SE/8. Is the "A" simply representative of the German spelling for the number 8 i.e. "acht"?

[MarkCan]

jzearfoss,
Is the flywheel free? Can you hear the starter solenoid trying to engage and than go back to the rest position?
Let’s not jump ahead of ourselves. Point 3 is next. Look for the camera on Amazon($20-$30) They deliver next day. There are some cameras that will allow for lens rotation. That makes the internal valve inspection a breeze. We need to eliminate possible chain jump and valve hitting the piston. Over long period of inactivity tensioner could have gone soft.

[jzearfoss]

Mark - not sure what you mean by 'is the flywheel free'.  Since it is at the rear end of the crankshaft and the crankshaft will not turn then - no the flywheel is not free.  As mentioned in one of my earlier posts I have pulled the starter and made sure that the solenoid is working and that the starting gear extends, rotates and retracts as it should.

Got an endoscope on order and should see it in a few days. I am not in a hurry and have plenty of other shop projects to keep me busy until it arrives.

The timing chain tensioner (the one that can be inspected with the valve cover removed) looks intact and I do not see anything that indicates that the timing chain may have jumped the camshaft gear.  That does not necessarily mean that it may have done so.  If I eventually have to go so far as to pull the cylinder head that possibility can be explored.   The idea that a valve is hitting a piston had occurred to me and that is what I meant when in my first post I mentioned a stuck valve.

Dropped the oil pan today and did not find metallic debris or any indication of a failed bearing or any other failed part.  The oil is clear with only a little bit of discoloration due to carbon blowby from the piston cylinders.

[MarkCan]

I have pulled the starter and made sure that the solenoid is working and that the starting gear extends, rotates and retracts as it should.

Not stuck on the flywheel, that’s exactly what I meant.

[MikeSimon]

Say Mike - here is a question for you.

What if the engine did actually develop a hydraulic lock (as you described by excessive fuel accumulating in one or more of the cylinders)? Would the engine remain locked if all the fluid evaporated? (Intuitively my brain says no, but there have been times when physics seems to show itself counter to my intuition).

 If so - what might the solution be to get the engine unlocked?

I don't think you have hydraulic lock. The engine should turn backwards if you did.

[Pawel66]

This is a bit of a brainstorming session, so maybe you do not need to be an expert to throw in an idea.

Have you tried to remove ignition distributor together with its gear and turn the engine?

Or other parts driven directly by crankshaft and gears (oil pump, FIP)?

[jzearfoss]

Pawel66 - pull the distributor - that one had not occurred to me. Nice to have a simple option to investigate. Shall do that today. If no result will then pursue FIP and oil pump (both of which require a bit more work).

Oh yeah - the hydraulic lock seems to be out of the running as a possible cause since I can not rotate counter-clockwise.

Anyone got any thoughts on the 280 SE/A question in my earlier post on Jan. 3rd.?

[BobH]

If all other suggestions fail, have a general search for frozen engine, quite a bit posted, i found this one

https://www.sl113.org/forums/index.php?topic=6587.msg41233#msg41233

Regarding your cylinder head question, look in the technical manual, use the link above left and search for engine, or cylinder head, i think that will answer your question

Good luck with your engine problem, i hope it's nothing too serious

[Charles 230SL]

When pulling the engine (or while the engine's been out of the car) did you by chance loosen or remove the tachometer bushing? The tachometer bushing holds the vertical timing gear in place. This is a longshot but if the vertical timing gear is able to move upward enough while the engine is running, it won't drive the oil pump. Lots of good information here: https://www.sl113.org/wiki/Electrical/RevCounter#TachBushing. Scroll down to Tachometer Bushing, Removal and Replacement.

[jzearfoss]

Charles -thank you for the link.

Pulling the engine was one of the first things I did when I first started this project a few years ago. So of course, disconnecting the tach cable was part of the process.  The engine was in running condition when I put it on my engine stand and there it stayed as I worked on everything else.

I never did anything else other than disconnect the tach cable from the fitting it screws onto on the block. Now, after reading through that section titled 'Tachometer Bushing, Removal and Replacement' I believe I will go thru that process and see what I find. The possibility of the vertical timing gear being able to move up far enough to cause the oil pump to stop pumping oil could definitely result in oil deprivation for the rod and main bearings on the crankshaft and possibly causing the 'frozen' condition I am now experiencing.  I am a bit skeptical of this being the case due to the fact that the period of time I was trying to start the engine was relatively short.  That being said, I cannot rule out that possibility.

I keep learning new stuff every day (or so it seems) as I follow up on the suggestions I get from my fellow SL owners.  Thanks to all of you for your taking the time to read these posts and responding.

By the way, I was able to answer my own 280 SE/A question at this site in the Technical Manual
https://www.sl113.org/wiki/DataCard/EngineNumber