Valve Adjustment: engine won't rotate by crankbolt - PeachParts Mercedes-Benz Forum

speedy82 · #1 06-25-2012, 10:23 PM

Hello all. 1982 300D. I interchangeably used the 22 mm p/s bolt and the 27 mm. crankbolt to rotate the engine. I rotated the engine clockwise from the front grill, facing the firewall while doing the valve adjustment. Halfway thru the job, the engine completely stopped rotating. Thinking the compression was seizing the engine, I removed the glow plugs. No change. Now what? Is there any hope to get the engine to rotate if I also remove the injectors? Thank you.

Diesel911 · #2 06-25-2012, 10:38 PM

Quote:

Originally Posted by speedy82

Hello all. 1982 300D. I interchangeably used the 22 mm p/s bolt and the 27 mm. crankbolt to rotate the engine. I rotated the engine clockwise from the front grill, facing the firewall while doing the valve adjustment. Halfway thru the job, the engine completely stopped rotating. Thinking the compression was seizing the engine, I removed the glow plugs. No change. Now what? Is there any hope to get the engine to rotate if I also remove the injectors? Thank you.

Removing the Glow Plugs is enough keep compression from building up.

You have some other problem.

Look to see if the Belts are really tight whay you try to turn the Engine. that could indicate something that is Belt driven is hanging up.

Is it possible the Fan is jammed into the Radiator Shroud?

Look for a Valve that is all the way down and try loosening the ajustment to see if that frees it up.

speedy82 · #3 06-25-2012, 10:55 PM

911, thank you for the reply. The belts had recently been replaced but I did notice that while turning the p/s bolt, the belt only occasionally turned with the pulley. That is why I would crawl under to turn it at the crankbolt. There is nothing hanging up the fan/fan shroud. If one of the valves was too low, would that block the engine rotation even if I had rotated the engine fully several revolutions prior? I was half way done when this all locked up. I am really perplexed about this. Again, thank you for giving more avenues to think about.

280EZRider · #4 06-25-2012, 11:00 PM

I agree that removal of the glow plugs is sufficient for compression release, so before doing anything drastic, I would make sure all the newly adjusted valves are noted and then remove the fuel pump relay, turn on the ignition, and jump the two outer terminals of the starter terminal block and see if the engine turns.

With no compression, you should be able to manually turn the engine with just the crank bolt alone. I am wondering if something is not right with the PS pump bearing.

speedy82 · #5 06-26-2012, 12:52 AM

Fortunatly I have two weeks to research this before I get back to it. This car is 100 miles away in storage and I get a long weekend every other week. I will keep plugging away at this. Please, keep the advice and the scenarios rolling!

ROLLGUY · #6 06-26-2012, 01:05 AM

Quote:

Originally Posted by 280EZRider

I would make sure all the newly adjusted valves are noted and then remove the fuel pump relay, turn on the ignition, and jump the two outer terminals of the starter terminal block and see if the engine turns.

If the engine will not turn by hand, the above is BAD ADVICE! The starter has enough torque to destroy the engine if something inside is bound up.

engatwork · #7 06-26-2012, 07:36 AM

^x2

Don't try to crank it until you can turn it over by hand. I'm wondering if there may be an error in the valve adj.

Stretch · #8 06-26-2012, 08:28 AM

If you think there is a chance that the valves are hitting pistons then remove the rocker arms - the cam shaft can then spin and the valves will stay closed and the pistons won't be hitting the valves...

speedy82 · #9 06-26-2012, 08:39 AM

Thank you. I will take your advise and bit by bit, remove the rocker arms. I"d done valve adjustments before. This one is a bear.

635CSi · #10 06-26-2012, 08:45 AM

Just trying to eliminate all possibilities, by any chance was the engine turned counter clock wise, if so the chain may have jumped.

vstech · #11 06-26-2012, 09:23 AM

is it possible, you loosened a valve too much, and it fell in?

Graham · #12 06-26-2012, 09:32 AM

When adjusting valves on our 300D, I have never had to remove glowplugs and have been easily able to rotate engine using PS nut and a little upward pressure on the PS belt. I am no mechanic, but this is an easy enough job even for me.

If engine won't turn, something is wrong.

funola · #13 06-26-2012, 09:40 AM

Weird! Engines don't seize just sitting there like that. Check that nothing was dropped and wedged in the valve train
or pulleys.

kerry · #14 06-26-2012, 10:17 AM

It's an automatic right, so it can't be in gear?

280EZRider · #15 06-30-2012, 03:34 PM

Quote:

Originally Posted by ROLLGUY

If the engine will not turn by hand, the above is BAD ADVICE! The starter has enough torque to destroy the engine if something inside is bound up.

Of course if something happened during the valve adjustment process to cause the engine to suddenly become frozen, then my advice is not good. However, Speedy82 seems to know what he is doing, which would preclude anything "falling into the cylinder," , turning the engine the wrong direction, etc. Valve adjustment is basic stuff. I also find it hard to believe that he would not have noticed a "missing valve stem," especially during this process.