Hi guys
Rather than tack onto old threads, I thought to start a new one here, mostly as a "PSA" of sorts. Dave and I have compared some notes as he had recently taken a hard look at his throttle linkage setup as well, and we both think that this is an area that many owners probably neglect. I myself am embarrassed to not have checked this sooner, not only was it filthy, but look what I found on the "bell crank" linkage at the fire wall:
Surely this is not right, and the rod needs to be parallel to the rest of the unit ???
Any other folks care to chime in? If this is indeed not correct, then my throttle movement has been sub - optimal all along, bugger :o
yes, that is suppose to be straight. :o
Thanks Robert, yup it was a real WTF moment for me ;D I guess if you really mash the pedal repeatedly this could happen, but still I am guessing due to other wrongness in the linkage setup this was the weakest spot and gave up?
To add to the above, note the bent arm on the this shaft. The small shaft on top should be parallel to the long shaft. The ball on the firewall was missing too, just like Daniel.
I wonder how common these issues are? They aren't easy to spot unless you look hard or take it all apart. I'm guessing the answer is "very." The car will still seem to run fine and all you might feel is play in the gas pedal, but shifting will be wrong and WOT may not actually be WOT at all. Last but not least, is the bushing on the tranny end of the shift rod still intact? It's hard to see unless you really look. If not then the throttle movement wont be correctly transferred to the transmission. This all falls into the "something isn't quite right but I can't figure out what" category. Everybody should run out to their cars right now to checK! ;D
I think maybe all of these bent issues could happen if the engine/transmission mounts completely collapse. Collapsed mounts will definitely affect the geometry of the linkages, but I'm not sure to what extent. I've gotten to where if I have to raise or lower the engine/transmission I always disconnect linkages and remove or loosen the fan shroud on the radiator to prevent damage to anything. (Years ago I broke a fan shroud on a W108 trying to raise the engine because the shroud was still connected to the radiator.....I learned the hard way). I can only speculate as to why these pieces of linkage are bent. I'll have to admit I've never seen this problem, but here it is in the flesh! I've seen a lot of bent linkages on mechanically fuel injected W108/W109 and W113 cars, but that's usually due to inexperienced shops trying to correct another underlying issue. The issues here are a mystery!
Quote from: UTn_boy on 04 December 2019, 12:42 PM
I think maybe all of these bent issues could happen if the engine/transmission mounts completely collapse. Collapsed mounts will definitely affect the geometry of the linkages, but I'm not sure to what extent. I've gotten to where if I have to raise or lower the engine/transmission I always disconnect linkages and remove or loosen the fan shroud on the radiator to prevent damage to anything. (Years ago I broke a fan shroud on a W108 trying to raise the engine because the shroud was still connected to the radiator.....I learned the hard way). I can only speculate as to why these pieces of linkage are bent. I'll have to admit I've never seen this problem, but here it is in the flesh! I've seen a lot of bent linkages on mechanically fuel injected W108/W109 and W113 cars, but that's usually due to inexperienced shops trying to correct another underlying issue. The issues here are a mystery!
yeah, mysterious indeed. I like the engine mount theory but in my case I'm quite sure that wasn't the problem. My mounts were fine when I pulled the engine.
Another possibility: tilting the engine to pull the transmission. That might also destroy that ball. I doubt it's coincidence that Daniel and I both had broken balls. ::)
I'd say that's from previous engine removal or lowering the trans as you say. It's not likely to happen by itself.
Tim
Definitely bent! The linkages are often overlooked and are the cause of stiff-throttle-frustration that many people experience when driving an old Benz. Make sure every joint & pivot is well lubricated with engine oil. I even like to use a smear of moly grease in the sockets for added insurance. Throttle balls are a serious danger to safety and can cause the throttle to jam. Make sure yours has the late design that is made from black nylon (not the old clear/yellow) and incorporates the metal insert for added protection. Ensure the whole linkage isn't binding on anything and check that full throttle can be achieved with the help of a friend and the engine (obviously) switched off.
Personally I still find the mechanical throttle way to stiff and it may benefit from a weaker return spring for added enjoyment and spirited driving...
Thanks all yup I am attempting to straighten it out on the bench. Of course most parts are NLA, especially the small white shaft bushings which is quite disappointing :'(
try the rh drive variant. another 3 foot of linkage entrails!
Guys, to add more fuel to the fire here...
Dave has discovered on his parts car that the linkage is also bent in the same fashion I found on mine.
Plus...I sourced a used linkage on ebay, 6.9 specific, and guess what, bent in exactly the same way. What the heck could be causing this :o are we in a throttle linkage twilight zone here :o
Quote from: daantjie on 13 December 2019, 11:45 AM
Guys, to add more fuel to the fire here...
Dave has discovered on his parts car that the linkage is also bent in the same fashion I found on mine.
Plus...I sourced a used linkage on ebay, 6.9 specific, and guess what, bent in exactly the same way. What the heck could be causing this :o are we in a throttle linkage twilight zone here :o
Wild guess - sticky ball joints, with dried up grease, requiring a proper "boot" to work? It could add up over the entire length.
The RHD throttle linkage (on a standard 450) is a mess, plenty of joints, but if you grease them every few months its super light.
Yup this is a mystery to me. Looking at the location of this bell crank, it would get subjected to high heat from the LHS exhaust manifold, so I guess over time the metal might get weakened as well? Pretty thick rod and I had to heat it on the bench to bend it straight again.
Hey Daniel,
Are you sure that rod is supposed to be straight?
After reading this last night I checked my cars today and ALL 3 6.9s are bent in what appears to be the exact same direction. Seems curious?
Jed
Quote from: Jed on 15 December 2019, 09:09 PM
Hey Daniel,
Are you sure that rod is supposed to be straight?
After reading this last night I checked my cars today and ALL 3 6.9s are bent in what appears to be the exact same direction. Seems curious?
Jed
Hey Jed!
Man I tell you, the more I look at this, I am pretty convinced now that this rod indeed must be bent at what appears to be a +/- 15 degree angle. No way all these specimens got subjected to the same "mystery force" here. Unless we can get a NOS one on a shelf somewhere (good luck with that!), I guess we cannot know for 100% sure, but I would pretty much bet the farm that the "bent way" is the right way...
Or, can somebody show a picture of a "straight" one still in assembled position? If that exists...(?). That will solve the mystery.
Statistically so far I would definitely say bent is the norm.
Part number is 116 300 0815 from what I can gather from the EPC. There appears to have been many versions and iterations of the linkages over the different models over the years as well KJET vs DJET, not sure if there was perhaps a model year/chassis split in this linkage for the 6.9? However I am pretty certain now that we have seen multiple examples that this "bell crank" at the firewall indeed should have an angle on the vertical rod.
OK guys, we can put this one to bed ;D I found the actual parts explosion diagram in the 6.9 service manual. You will see the bell crank in question clearly has an angled rod, case closed ;)
So if your 6.9 does not have this rod bent, then it's bench time for you 8)
Quote from: daantjie on 16 December 2019, 05:41 PM
OK guys, we can put this one to bed ;D I found the actual parts explosion diagram in the 6.9 service manual. You will see the bell crank in question clearly has an angled rod, case closed ;)
So if your 6.9 does not have this rod bent, then it's bench time for you 8)
Nice work. And that diagram is gold. Thanks for persevering.
Thanks Dave yes I was like a dog with a bone on this one ;D
To my eye this setup, which appears unique to the 6.9 gives you a "preload" of sorts on the throttle linkage. Perhaps for faster throttle response? Who knows...