consequences of turning eng CCW? - PeachParts Mercedes-Benz Forum

Stevo · #1 01-24-2006, 11:44 PM

A friend called last night and is working on a 123 240D. He checked the timing and found it at 6 degrees using the drip and again with the bubble method so I feel he did it right. The car ran good but was hard to start. He called tonight and asked me how much slack should be in the timing chain (he checked the stretch and found -4 degrees) I said it should feel "tight" on the cam sprocket, evidently its not. I found out he had turned the engine BOTH WAYS in the course of this work. Question is "could have turning the eng ccw caused the 6 degree to show up? Seems 6 degrees is so far off it would not have ran with out allot of smoking or knocking. So what happens when the eng is turned backwards??

Tangent · #2 01-25-2006, 12:24 AM

Bump
what can happen

Lycoming-8 · #3 01-25-2006, 12:31 AM

Think that the induced slack by rotating CCW can allow the chain to jump a tooth, which would put it off time by?? amount.

Hopefully others with the actual numbers will follow.

Stevo · #4 01-25-2006, 12:46 AM

As I ponder this I assumed he just turned backwards a little, like when you over shot the mark and are tempted to just turn it back a skosh, maybe he rotated it ccw,

I shoulda ask that. Thanks for the bump

H2O2 · #5 01-25-2006, 01:06 AM

Despite dire warnings to the contrary, over the years I've turned every one of my MB diesels CCW a little to a lot, and never suffered any obvious consequences. If anything, I'd be most concerned about the plunger cam inside the injection pump--it's truly designed to only turn in one direction, and with age, it may not be able to tolerate reverse rotation without binding the plunger assembly.

#6 01-25-2006, 01:30 AM

1 tooth is about 18* at the crank.

dannym · #7 01-25-2006, 09:23 AM

Can't say about the harm it may or may not cause. I don't believe moving it just a little backwards can do harm. It will definitely throw off any readings however.

What I don't understand is how he was checking timing using the bubble or drip methods??

danny

OMEGAMAN · #8 01-25-2006, 09:36 AM

6 degrees would definatly be less than 1 tooth off so I dont think he jumped the timing chain. I think the only danger of ccw rotation would be jumping the timing chain.

Wes Bender · #9 01-25-2006, 09:42 AM

The timing chain tensioner works on the portion of the chain that has no real load. Turning the engine backwards reverses this and applies a load to the tensioner. If it is in good shape, it can probably stand the strain. If it isn't, results could be different, although I'm not sure that damage would have to occur.

(By the way, for clarification, most internal combustion engines turn CCW, looking at the power takeoff end and this is usually how rotation is described.)

Stevo · #10 01-25-2006, 11:09 AM

Quote:

Originally Posted by ForcedInduction

1 tooth is about 18* at the
crank.

Humm...18+6=24, I wonder??

OMEGAMAN · #11 01-25-2006, 12:42 PM

Quote:

Originally Posted by Wes Bender

By the way, for clarification, most internal combustion engines turn CCW, looking at the power takeoff end and this is usually how rotation is described.

Maybe in the farming world but in the automotive world rotation is viewed at the free end of the engine (where the accessory drive belts are) and the only engines i'm aware of that rotate ccw are honda's. Come to think of it even locomotive engines rotate clockwise

andmoon · #12 01-25-2006, 02:24 PM

If a socket/wrench is attached to the main pulley in front of the engine, does it rise on the passenger (exhaust/turbo) side or driver's (fuel filter) side?

CW looking at the engine from the front of the car or while seated in the car?

Stevo · #13 01-25-2006, 02:45 PM

Don't know about the rest of the world but on a 616 the eng turns cw when standing in front with my socket on the p/s pump nut. (as in tightening the nut)

So any thoughts on the 6 degrees now we have cw & ccw sorted out? I am beginning to think if he turned it the wrong way, thats simply the slack in the chain, as the tensioner would get deflated, (that doesn't sound right, but you know what I mean

)

trontek · #14 01-25-2006, 02:58 PM

Quote:

Originally Posted by Wes Bender

(By the way, for clarification, most internal combustion engines turn CCW, looking at the power takeoff end and this is usually how rotation is described.)

Surprised me when I looked this up. However - I still agree that our engines are to be turned cw (from the front) during maintenance.