#1, and most important. on my 92 300D, i have pretty serious sporadic thumping on acceleration that goes away within a few seconds. it doesn't do it every time i take off, but it seems to be getting worse.



- what i know...
the driveshaft and flex discs were replaced before i bought the car, and today upon inspection, look immaculate. however, the transmission flex disc, or the one closest to the front of the car, had about 3/16 to 1/4 inch of "play" in it when i rotate the driveshaft by hand it was as if the bolts on the trans, "coupling?" were loose allowing the shaft to have the play, but they were not. tight as hell. maybe the bolts wallowed out the holes in the flex disc? but the overall condition of the both discs looked damn near perfect, and harder rubber than a tire.



also, i noticed the trans mount was so loose i could move the transmission up and down and side to side with just my fingers. the hydraulic motor mounts i replaced a few years ago, but never the trans mount.



please advise...


#2, my wife's car the 99 E300D, upon locking and unlocking the doors the fuel door actuator clicks, loudly. locking happens almost immediately, but still clicks. unlocking, takes a while for it to "click" and unlock the fuel door. you can hear the pump under the back seat running after the last passenger door is unlocked for about 12 seconds. everytime.


- what i know, and have done....
today i pulled the carpet away from the in front of the actuator, and observed it's behavior. the sprayed silicone lube on both the bolt that locks the door, and the red plastic plunger. it helped a little, quieter now, but still clicks, and still the 12 sec wait for unlocking.



i pulled the backseat and removed the pump from its insulation and listened to it run when locking/unlocking. i didn't hear any hissing. then, i pulled the line labeled "tank" (the only one in english) stuck my might vac on the hose and slowly pumped it. i would not hold vacuum, and leaked slowly. once i got it to just over 7 psi, the actuator would click just and if it were still hooked up.



however, this is were i got confused. i left the line to the tank disconnected and put a vacuum cap over the port on the pump, and did a lock/unlock cycle. it still ran almost 12 seconds upon unlocking after the passenger doors unlocked. i would've thought if the actuator on the door was bad that would have made the pump cycle quicker and removed the 12 second run time.



please advise, and thank you.

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'92 300D 2.5
'99 E300TD

There is not supposed to be play in the drive shaft and the transmission mount is not supposed to be loose. Either tighten and/or remove to examine. The cause should be obvious.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

I am wondering as to the quality of the preciously replaced Flex Discs.

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84 300D, 82 Volvo 244Gl Diesel

trans mount just ordered from pelican.

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'92 300D 2.5
'99 E300TD

Granted it is a different model, but I had a sporadic thumping on my 83 300D. I ended up replacing the center driveshaft bearing and mount. In your case I would suggest checking out the center driveshaft bearing and replacing if necessary. I would also replace both flex discs (with new bolts) and the new transmission mount. I know you said the flex discs and such look great, but..............

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

The attached pic is from a W123. Each end of the drive shaft has a centering bushing that the arrow points to. If you shaft is wobbling around there is a good chance the centering bushing is also no good. Well the centering bushings should at least be checked.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

W124: Flex disks can look great from the outside. Once you unbolt them you wonder how it was still staying together.

W210: Replace the tank actuator, it is leaking (well make sure the hose isn’t leaking first). Note that the PSE will set a fault code (only readable with HHT or the emulator in Xentry) for pump overrun.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

thanks for all the prompt responses! i will keep you posted when the trans mount comes in, and i am able to get under it again.



as far as the fuel door actuator on the w210, can anyone tell me how that thing is removed? i cant see any fasteners and it appears to be "friction fit" in the hole in the body.

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'92 300D 2.5
'99 E300TD

so i changed the trans mount, in the rain, and although it is clear that needed to happen for some time by the way the way the car handles now, the problem, although greatly reduced, still exists.

i drove the car like i stole it right after the change, and it took a while for it to start thumping again. it is much less frequent now.

front flex disc change my next move?

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'92 300D 2.5
'99 E300TD

As I mentioned earlier, I would replace both flex discs, and definitely look at the center driveshaft mount and bearing. Probably would not hurt to look at the rear differential mount too. None of these are all that hard to change, especially since you are already in there so to speak.

Another thing you might want to look for is a binding or frozen U-joint.