123: Firewall bushing for throttle linkage busted - PeachParts Mercedes-Benz Forum

phasmatisnox · #1 05-06-2006, 06:49 PM

Hi, the throttle linkage bushing on the firewall is broken on my 1984 300D Turbo Diesel. The joint in question is between the vertical rod(connected to the accelerator pedal, I presume) that rises parallel to the firewall and the rotating linkage that connects the rest of the throttle linkage. The whole piece will fall apart if you touch it wrong. It slips out of the bushing in the firewall occasionally. I do not drive this car at all, by the way, but I'm preparing it to be later this year. I think I got a great deal on this car ($900) because the previous owner did not spot this linkage problem, and thought the engine needed major work. I hope it doesn't. I've put 14 miles on the car since I got it.

Does anyone have any idea which parts need to be replaced, and where I can get them? Is this a common problem? There isn't a tutorial for this issue.. is there? Thanks!

#2 05-06-2006, 07:06 PM

Is this the part?

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1CQ0J3JZ41SO14VSSY&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1984&product=C7030-16051&application=000012097

TheDon · #3 05-06-2006, 07:07 PM

rember a cheap mercedes is an expensive mercedes

i had the same problem.. a friend of mine had that part laying around so he sent it to me for free. took 5 mintues to change it

83-240D · #4 05-06-2006, 07:17 PM

Quote:

Originally Posted by TheDon

rember a cheap mercedes is an expensive mercedes

i had the same problem.. a friend of mine had that part laying around so he sent it to me for free. took 5 mintues to change it

so does this mean i should ask a lot for either car i am thinking of selling?

tangofox007 · #5 05-06-2006, 07:19 PM

Yes, it's a common problem. The nylon bushings get old and brittle. The only safe thing to do is replace it. Unfortunately, you have to buy the whole assembly as depicted in post #2. You can't buy just the bushing.

phasmatisnox · #6 05-06-2006, 07:32 PM

Quote:

Originally Posted by tangofox007

Yes, it's a common problem. The nylon bushings get old and brittle. The only thing to do is replace it. Unfortunately, you have to buy the whole assembly as depicted in post #2. You can't buy just the bushing.

Darn. Is pick-a-part a bad idea, then?

tangofox007 · #7 05-06-2006, 07:38 PM

Why replace a twenty-two year old part with another 22 year-old part? Of course, you might get lucky and find one that had been replaced the day before the car was wrecked. (I'm never so lucky.)

But that part is not one to fool around with. A failed bushing could cause the accelerator linkage to jam. Then your car might be headed to the pick-a-part lot.

rs899 · #8 05-06-2006, 07:55 PM

One alternative to the only thing to do is to craft a replacement plastic bit (the piece up against the firewall) with some kitty-hair bondo. I have this on both my late 24oD and 300D and it has held up fine for two years. This assumes the flexible rubber block (the part you can see) is intact.

Rick

phasmatisnox · #9 05-06-2006, 08:12 PM

Quote:

Originally Posted by rs899

One alternative to the only thing to do is to craft a replacement plastic bit (the piece up against the firewall) with some kitty-hair bondo. I have this on both my late 24oD and 300D and it has held up fine for two years. This assumes the flexible rubber block (the part you can see) is intact.

Rick

Can you give me a little bit more info on this? I have access to lathes, mills, etc and lots of scrap- I had considered making my own, but I'm not familiar with the part at all. How did you do yours?

rs899 · #10 05-06-2006, 09:31 PM

You don't need anything more elaborate than a rough file or, better yet , one of those "cheese graters" that is made for shaping bondo. If I recall correctly, when you take that mount off the firewall, the aged "ball" part will crumble off and there will be a smaller plastic bushing that the steel shaft pivots on. Simply mix up a suitable sized gob of kitty hair (fibreglass reinforced) bondo and pack it around the bushing. When it is still in a plastic state, file it down to fit the hole in the bracket on the firewall. You may need to do this in two "coats" to get the shape right. It doesn't need to be perfect (it isn't visible) but it needs to be fairly strong.

Rick

JimmyL · #11 05-06-2006, 10:27 PM

There are places to try and go the cheap route, and there are places where it is a bad idea. A dumb idea in fact.
Just because somebody made a poor decision doesn't mean you should. Get a new one, and play it safe! And smart..........

phasmatisnox · #12 05-06-2006, 10:28 PM

Quote:

Originally Posted by rs899

You don't need anything more elaborate than a rough file or, better yet , one of those "cheese graters" that is made for shaping bondo. If I recall correctly, when you take that mount off the firewall, the aged "ball" part will crumble off and there will be a smaller plastic bushing that the steel shaft pivots on. Simply mix up a suitable sized gob of kitty hair (fibreglass reinforced) bondo and pack it around the bushing. When it is still in a plastic state, file it down to fit the hole in the bracket on the firewall. You may need to do this in two "coats" to get the shape right. It doesn't need to be perfect (it isn't visible) but it needs to be fairly strong.

Rick

Okay. I don't see any reason why it would be hard to make out of plastic on a lathe, I'll try that first, if the rubber bit is intact. However, the whole assembly has fallen off of the firewall- does that indicate that there's a bigger problem, or just that the screws rattled loose?

Just thought I'd update with my solution, an HDPE replacement made on the lathe. It's not perfect, it's generous in all dimensions, and it was annoying to make out of sheet stock, but it works.

Pushed in, normal position http://www.botmedia.vrogy.com/ned/benz/300D_01.JPG
Pulled out to show new bushing. http://www.botmedia.vrogy.com/ned/benz/300D_11.JPG

I am going to put a shaft collar on the end of it to keep it from being pulled out at all. I hope that shaft is 8mm- I just happen to have an 8mm shaft collar.
Turns out that the nylon bushing has an inner lip that is integral to keeping the shaft from being pulled out- when it rotted away, the shaft could easily rattle out.