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+--- Thread: Timing Chain (/showthread.php?tid=3202)
Timing Chain - serverman777 - 12-26-2011
Yesterday I was doing 101 in a 55 and the thought came to me "Hey man, your timing chain may have over 400,000 miles on it". I really don't want it to break. I understand that om617's chains can last over 500,000 but do I really want to trust it? At at high RPM it might break sooner. Whats your ideas on this topic everybody?
RE: Timing Chain - iheartboost - 12-26-2011
idk. to much about em. but with almost 300k my timing chain has almost 0 stretch. so they are built pretty dam well. i mean if you sit at 6k all day then yea i would probably replace it lol.
but for most normal driving i dont think its an issue. (imo)
RE: Timing Chain - aaa - 12-26-2011
How do you know it hasn't been replaced already?
RE: Timing Chain - iheartboost - 12-26-2011
this is true. i have no records of the car. but from the rest of the condition i just assumed the previous owner dident do much in the way of maintenance
RE: Timing Chain - DeliveryValve - 12-27-2011
I got a few good unused chains.
http://www.superturbodiesel.com/std/showthread.php?tid=3046
With that said, my opinion is generally 300K is a bit long on a chain regardless of stretch. On the other hand I would consider running it longer if the engine has been running synthetic motor oil since day 1 and had zero stretch.
.
RE: Timing Chain - Captain America - 12-28-2011
Have you checked stretch? I did on the motor I recently got and its PERFECT!
http://www.superturbodiesel.com/std/showthread.php?tid=1479&pid=30154#pid30154
Scroll down from there
P.S. If there is no stretch, BALLS TO THE WALL!
RE: Timing Chain - iheartboost - 12-28-2011
always the best advice captain! lol
RE: Timing Chain - Captain America - 12-28-2011
Yeah buddy. I mean these things are (almost) bulletproof
RE: Timing Chain - sassparilla_kid - 12-30-2011
(12-28-2011, 01:14 PM)Captain America Yeah buddy. I mean these things are (almost) bulletproof
I've considered having an experiment to see if/what calibres/distances these cars are actually bulletproof, considering they are made out of some pretty stout steel
RE: Timing Chain - TexasSuperDecel - 01-01-2012
Most commonly on vehicles it's the timing belt/chain tensioner that fails first causing a series of events which causes the timing belt/chain to fail as well. Inside the timing chain tensioner itself on our W126 diesel models is a spring (aided by oil pressure) which keeps tension by exerting a force to the timing chain guide rail against the timing chain reducing the "slack" keeping the chain tensioned.. (Example -The chain setup on a 10 speed bike)
What usually happens is that the spring loaded timing tensioner loses its ability to maintain sufficient tension due to fatigue of the aged and worn internal timing tensioner spring (decreased spring rate) + timing chain stretch which decreases and affects the tensioners tensioning range + Wear on the timing chain guide rail where the tensioner makes contact also decreases timing tension + the groove that the timing chain can wear into the chain guide must be compensated for as well + neglected maintenence just increases the wear of already worn and wearing components. ANY bit of wear on timing related components noted plus others that I probably did not mention add up because where the wear exists the tensioner must make up for it. We all know that when a spring is compressed to 50% of it's original size when new that it is " MUCH stiffer" than it would be if it were compressed to 60% of it's original size and aged 30 years with many heat cycles, cold, wear, decreasing oil pressure and constant movement/load. The tensioner spring always has load even when the engine is not running. It's slightly compressed holding the timing chain guide rail against the timing chain to keep it's tension. Load is slightly increased when engine is running/idle, activity is increased furthermore at normal driving conditions and load is significantly increased and certainly unstable when at full throttle. When the timing tensioner develops excessive play due to the above stated causes the chain itself can skip teeth on the cam/crank gear and slip, slip, catch, timings off, engine internals collide and SNAP!! Since the tensioner fail to maintain the chains tension the chain gets play and allows for it to come off track to cause the damage since they're related timing components and the timing is no longer maintained.
The timing chain tensioner spring is a wear item. From my parts supplier the timing chain tensioner spring is a $4.72 and is a GENUINE MERCEDES-BENZ item. The timing tensioner gasket which should be replaced at the same time to avoid an oil leak is only $0.91 and is also an OEM product.
RE: Timing Chain - larsalan - 01-01-2012
That is some wicked valuable info. I have seen the spring but never knew it was a part that needed to be replaced as part of our preventative maintenance.
RE: Timing Chain - garage - 01-01-2012
Capt said it best!
Balls to the walls man!
Push her to 106 next time!
My top speed is 115ish in a w116 SD
RE: Timing Chain - SpecialDelivery - 09-12-2012
Anyone have any experience leaving an old tensioner and spring in when changing the chain? and what about the Febi vs OEM tensioners?
RE: Timing Chain - MONSTER 300D - 09-25-2012
I know this is an old thread. And dont know if anyone reallly cares or not, but just a fyi thing you can purchase offset timing gear keyways to help with the chain stretch. there is a .7mm offset avalable somewhere. Scott got one for mine when he checked the backlash on my chain & installed it. I saw no preformace difference, but was good to know that everything was properly lined back up.
RE: Timing Chain - JustPassinThru - 09-25-2012
(09-25-2012, 05:04 PM)MONSTER 300D I know this is an old thread. And dont know if anyone reallly cares or not, but just a fyi thing you can purchase offset timing gear keyways to help with the chain stretch. there is a .7mm offset avalable somewhere. Scott got one for mine when he checked the backlash on my chain & installed it. I saw no preformace difference, but was good to know that everything was properly lined back up.
According to
http://biodiesel.infopop.cc/eve/forums/a/tpc/f/159605551/m/3561056362/p/3
Posted April 20, 2011 05:41 PM by Omar...
Mercedes Benz makes 4 woodruff keys for the correction of cam timing:
* Part # 621 991 04 67, Offset 0.7 mm, For correction of about 4 degrees.
* Part # 621 991 02 67, Offset 0.9 mm, For correction of about 6.5 degrees.
* Part # 621 991 01 67, Offset 1.1 mm, For correction of about 8 degrees.
* Part # 621 991 00 67, Offset 1.3 mm, For correction of about 10 degrees.
If memory serves, MB dealers sell these woodruff keys very inexpensively. I haven't done it yet on either of my 300D's, but did install a compensating woodruff key three times on the W123 230 gasser I owned 20 years ago in Germany (in ten years I put 300,000 kilometers on it, and changed the timing chain, tensioner, rail the second of those times, along with renewing the valve guides and replacing a burnt rearmost exhaust valve).
What I always did, was just buy a complete set --they were *very* inexpensive-- and, just in case someone has already installed one of these compensating keys, you need to also buy one of the zero-offset as-from-the-factory woodruff keys, so you can first install that to see how far your chain has stretched beyond what has already been compensated for by prior installation of such a key by a previous owner (or, you yourself, if forgetful).
Compensating for a stretched timing chain, raised top autobahn cruising speed of that car from 160 kph to 185. The difference between never-out-of-the-right-lane and occasionally-into-the-fast-lane. Still had to keep an eye on the rearview mirror for cars coming up behind at 220 or more. Especially when driving near Munich.
RE: Timing Chain - Austincarnut - 09-30-2012
The most common problem for the death of a 616/617 chain is the vacuum pump bearings falling in the chain drive. The newer style vacuum pumps have a cage around the bearings and can keep then out of the drive if/when they fail. It has been common place as I've worked on these engines to recommend and replace vacuum pumps in the usual maintenance intervals rather than a timing chain. I just recently purchased a victim 616 car that some hack just replaced the pump and left the damaged chain/gears. This led to the chain wearing out the idler and breaking the chain in several places. If you have access to the EPC you can read some on the super-cession #'s and calculate which pump was the problem one, I haven't yet figured which ones are good/bad, then again, I haven't looked very hard. I need to read through the old bulletin manual, because there have been numerous changes over the years to these engines and most are documented clearly in Yerman-English. These timing chains are tough as nails, I've had hell removing this old chain and not damaging the casting.
RE: Timing Chain - dieselsmoke300d - 02-01-2015
I'm glad I found this thread. All of the sudden my 300SD's chain decided to make a freaking racket as I was driving one day. Had the shop look at it and they confirmed it's chain slap. I'm planning on replacing it soon. Does anyone know how hard it is to replace the guide rails if required? Someone told me that it takes ripping the block apart.
RE: Timing Chain - MTUPower - 02-02-2015
(12-26-2011, 10:40 AM)serverman777 Yesterday I was doing 101 in a 55 and the thought came to me "Hey man, your timing chain may have over 400,000 miles on it". I really don't want it to break. I understand that om617's chains can last over 500,000 but do I really want to trust it? At at high RPM it might break sooner. Whats your ideas on this topic everybody?101 in a 55? Can't believe no one called you out on this and someone even encouraged you to go faster. Do we really need more safety videos in high school because one or two do stuff like this?
RE: Timing Chain - fordheaded - 02-02-2015
Upper guide rails are easy, lower pins are behind crank pulley and balancer. Not to bad with the right tools.
RE: Timing Chain - dieselsmoke300d - 02-03-2015
(02-02-2015, 05:24 PM)fordheaded Upper guide rails are easy, lower pins are behind crank pulley and balancer. Not to bad with the right tools.
Good to know. Thanks.
I'm not sure if I need to mess with the rails yet. I'm pretty sure my tensioner spring broke and caused the whole Problem. Explains why the chain's messing up at only like 103k miles.