engine problem

[Rick007]

Hello Pagoda SL Members ,

This is a problem i can't get my head around and i hope you guys have some ideas .

We were driving on the freeway a couple of weeks ago , and after aprox 190 km at a 130 km driving speed my engine lost drive .
At first a small hesitation but then it died and i was lucky to get into neutral and could just roll down a exit until it stopped.
My car is a 250SL Automatic with electronic ignition ( 123 ) , and never failed me once , until now .

Standing on the side of the road i tried to start it but it would barely turn over. So my first thought was maybe the battery was low .
We were using lights , window wipers , and additional navigation and music. But this would not explain the lost of my engine at this speed.
After using jumper cables with the help of some helpfull fellow motorist , it still turned over barely.  So something was blocking the engine .

After being pickup and back in my garage i started to investigate .  I could turn over the engine by hand , although with some force and a big socket extension bar .
Drained the oil ... which looked OK and clean , no deposits of any kind.  A mechanic suggested that my ignition pump could have been stuck.
So removed my IP , which was free moving and in a good working order. Removed the valve cover and the chain and everything looks OK .
Did a compression test with the slow turning engine . Al 6 neatly at 120 PSI ( very slow turning engine with no oil )

The flex plate turns nicely and there are no strange noises when i turn it over, and the car moves freely when i put it in neutral,  but it turns over slow
Startermotor maybe , but this would not explain the sudden dying of the engine.

So before I'm  going to pull the engine apart , is there some thing I'm missing here ?

Any suggestions would be greatly appreciated !

Greetings Rick

[WRe]

Hi,
I would unscrew the spark plugs and check the cylinders with an endoscope.
A professional oil analysis would be useful for an initial analysis of possible damage of the bearings
...WRe

[Rick007]

Yes i know , have been looking inside with a endoscope but not much to see there . Some grey deposits thats all .
Engine is a 40.000 km "Mercedes Benz Tausch agregaat " so should be ok .

[Benz Dr.]

Possible failed helical drive gear. Engine will continue to run until it doesn't. 

I've had three engines in over the past year or two that had everything from broken connecting rods to broken cam bearings.

 Oil pump will not run when this gear fails and you probably won't catch it in time if driving at speed. Remove your tack cable at the cylinder head end and use a small sheet metal screw to insert into the hole in the end of shaft that spins the tack cable. If you can pull it up very much at all the bushing holding gear down is worn. This allows the two gears to come out of mesh with each other and shear the teeth off. This is a critical part of your engine and it should be at least a yearly inspection.

The gears are sold in sets only and will likely not have the extended wand on the gear that runs your tack cable.

[rwmastel]

... at a 130 km driving speed ...
We were using lights , window wipers ...

130 km/h in the rain in a Pagoda?  You are comfortable taking risks!
(That's 80mph for the mathematically challenged.)

[Rick007]

Thank you Dr Benz , I've tried that and yes I can move it slightly about 2 mm up and down.
I can hear it , but if this is the fault ?

Anyhow I'm pulling the engine for a deeper inspection.