Timing chain related - Page 2 - PeachParts Mercedes-Benz Forum

gregszustak · #16 09-19-2006, 02:49 PM

Barry, Dan, Brian - Thanks all.
Still wide open to any suggestions, especially from a 240d owner.

Apparently I should start with the chain stretch.
If the chain turns out to be a problem would it make any sense putting it in and then looking at the tensioner or am I putting the cart before the horse?

As for engine behavior, 30mpg, 1 quart of oil in 2500 miles, starts on about a half a crank of the starter. (hasn't been below 45 degrees yet). Steep country hills will slow it down to 45 mph. Thruway driving, (sissy hills) it will maintain 65 limit.

Was idling a little rough when cold, possible 'misfire' which is why I opted for the valve adjustment and saw the chain.

Brian Carlton · #17 09-19-2006, 03:06 PM

Quote:

Originally Posted by gregszustak

Apparently I should start with the chain stretch.
If the chain turns out to be a problem would it make any sense putting it in and then looking at the tensioner or am I putting the cart before the horse?

If the chain is quite elongated and the valves and IP are very late, I doubt you'd get such good performance from it.

You can check the chain elongation, but, I'll bet that it's probably within acceptable limits due to the engine performance. If not, then you can either change it or consider a Woodruff key to bring the engine back to proper cam timing.

gregszustak · #18 09-19-2006, 03:23 PM

I'll start with checking chain.
May get lucky and replace only the tensioner. Funny, think that was brought up early.

As for a woodruff key, if it ain't broke......

dannym · #19 09-19-2006, 03:41 PM

Quote:

Originally Posted by Brian Carlton

What's the deal with the ratchet, or lack thereof, on the 616? Without a ratchet, what holds tension when the engine is shutdown?

There's a question that deserves an answer.

Quote:

Originally Posted by Brian Carlton

If the chain is quite elongated and the valves and IP are very late, I doubt you'd get such good performance from it.

That's exactly what I was thinking. Which led me to believe it a bad tensioner. It would be nice to know definitively since they aren't cheap but I don't see how you can do that. Maybe take it out and check it?

Danny

Brian Carlton · #20 09-19-2006, 03:54 PM

Quote:

Originally Posted by dannym

That's exactly what I was thinking. Which led me to believe it a bad tensioner. It would be nice to know definitively since they aren't cheap but I don't see how you can do that. Maybe take it out and check it?

Danny

Need someone with a 616 who knows how that tensioner functions............

#21 09-19-2006, 04:06 PM

Quote:

Originally Posted by Brian Carlton

Need someone with a 616 who knows how that tensioner functions............

I've never had one apart, but this looks like there is also some spring tension on the pin:

http://mb.braingears.com/123_DISK2/program/Engine/615/05-310.pdf

barry123400 · #22 09-19-2006, 06:49 PM

I do own a couple of 240ds. Have never had trouble in this area though. Suspect the hydralic part of the component is still functional but the pre load spring is broke perhaps. If that hydralic portion had failed with no functional spring you probably would have already lost the chain. There has to be a method of keeping the chain loaded to some extent when the oil pressure is not there. Some preload retention with a rachet might just be an aditional safety factor in case the spring is unable to handel the load. Or the racheting action stops the retraction of the rod under loads the spring cannot deal with when the oil pressure is not there. Anyways if you get a used one from a used engine it should serve you well as this part does not fail that often. As someone mentioned this part just might be pretty expensive new. Just had a look at braingears pictorial. Perhaps oil is meant to be retained by that ball bearing after the engine shuts down. If it is leaking by the oil quantity in there used to keep it extended would leak out after engine shutdown. If this is so my earlier considerations above are in error. In the end though it still amounts to the same thing. Some defective function is not keeping the preload pressure on the chain with the engine off.

Stevo · #23 09-19-2006, 10:36 PM

Quote:

Originally Posted by Brian Carlton

Need someone with a 616 who knows how that tensioner functions............

I always thought the 617 tensioner was not the same as the 616, sorry if I generated some mis-info. The 616 seems spring loaded too me, not any kind of retchet action

gregszustak · #24 09-19-2006, 10:38 PM

Dated material but interesting -

http://www.mbzponton.org/valueadded/maintenance/tensioner.htm

Brian Carlton · #25 09-19-2006, 10:41 PM

Quote:

Originally Posted by Stevo

I always thought the 617 tensioner was not the same as the 616, sorry if I generated some mis-info. The 616 seems spring loaded too me, not any kind of retchet action

I think you're exactly correct. The 616 has a spring but no ratchet. Apparently the spring will tension the chain sufficiently for the start until the oil pressure comes up.

#26 09-19-2006, 10:57 PM

The banana rail might be severly worn, and the tensioner can't make up for the wear.

The tensioner pumps up like a hydraulic lifter and keeps tension on the chain. It can bleed down a little at rest which is why you can hear the chain rattle on pre-1993 v8 models when the tesioner is worn. On the old timer models the fsm suggests using a heavy screwdriver to check for a weak tensioner when the engine is off. I think the M110 motor has a ratcheting tensioner.

Stevo · #27 09-19-2006, 11:03 PM

Quote:

Originally Posted by Brian Carlton

I think you're exactly correct. The 616 has a spring but no ratchet. Apparently the spring will tension the chain sufficiently for the start until the oil pressure comes up.

I wonder if they are interchangeable. Seems I remember someone suggesting I use a 617 tenisioner once in a 616.

dannym · #28 09-20-2006, 09:49 AM

Just read that FSM post.
It says, "Chain tensioner not giving satisfactory operation ought to be replaced complete."

It does have a spring according to that diagram but I don't think you can replace it like you can on the 617 models. If you go search for a spring for the 616 models you won't find one but you will for the 617. Probably because of that ball bearing bearing cage at the end.

Danny

barry123400 · #29 09-20-2006, 11:43 AM

The tensioner is fed by gravity from splash oil accumulating in an open chamber. The springs primary function is to allow the cylinder to be pumped up as well as extending the piston against the chain guide so oil can flow into the chamber. If it is slugged up perhaps the input check valve is not sealing. It might be worthwhile to try cleaning it out when off the car. On the otherhand when trying to pump it up if there is no return stroke the spring is broken. I do not think the spring was really designed to take any signifigant load. The ratcheting type provides a failsafe component and is a good ideal. Without the rachet feature basically any failure of the tensioner will probably result in engine failure.

This gentleman just sounds lucky or tensioner has not totally failed yet. No wonder the design was changed.