Idle adjusment bolt bracket snapped - PeachParts Mercedes-Benz Forum

daxgaz · #1 03-05-2017, 11:45 AM

I was going to adjust the idle bolt on my 1982 300D. When loosening the 14mm locking nut, the threaded bracket that holds the bolt on to the injector pump snapped! Now, obviously, the car won't run. Attached is an image of the broken bracket.

Is JB weld the only way to get that part back on and is it strong enough? Is there another clever trick I can use to adjust the idle? I'm pretty torn up about this and want to get my car back to running.

kerry · #2 03-05-2017, 12:10 PM

Adapt a dash idle adjustment knob from an earlier year 300d.

daxgaz · #3 03-05-2017, 01:46 PM

Quote:

Originally Posted by kerry

Adapt a dash idle adjustment knob from an earlier year 300d.

Thanks for the suggestion, but I have never dealt with or even seen on of those systems. Is this something can be retrofitted onto a 1982?

The hack fix I have in for now is to put another bolt on the throttle linkage a bit further up where I can get to it and had metal to clamp onto. It's working and doing essentially the same job, but there are some downsides. If i ever need to kill the engine from here, I have to pull off a throttle linkage because the bolt interferes with the stop lever. Secondly, while it's on their very secure (locked two nuts down on it), I do worry about it wiggling out of place eventually.

While this is an acceptable hack for now, I would like a more permanent fix that does not involve replacing the injector pump.

sixto · #4 03-05-2017, 03:01 PM

Can you fashion an angle to sit atop the broken flange and fasten to the threads of the throttle stop bolt?

On second thought, the angle should go below what's left of the flange so it's more rigid against the return spring.

Soxto
83 300SD
98 E320 wagon

kerry · #5 03-05-2017, 04:19 PM

I've owned a couple of 617's with the manual idle control but I never looked closely enough at it to know how easily it could be adapted. It's the same engine with very similar linkage, from a quick glance, so I would think it feasible. Perhaps someone with direct experience can comment.

kerry · #6 03-05-2017, 04:23 PM

Even though this video is about alda issues, I think the cable right above his hand is the manual idle control cable.

https://www.youtube.com/watch?v=8K4ZzW1WS1w

Diesel911 · #7 03-05-2017, 07:48 PM

There is a fix for that.

In the pic you would make a V shaped bracket out of steel that has a 9 degree angle.

The green lines show where the bracket would go and in the middle of the green circle in the pic is an actual one someone did.
Notice that it uses the opposite end of the full throttle stopl with an nut added.
I believe you also need another nut to go on the bottom of the Idle screw housing.

ROLLGUY · #8 03-05-2017, 10:29 PM

Quote:

Originally Posted by Diesel911

There is a fix for that.

In the pic you would make a V shaped bracket out of steel that has a 9 degree angle.

The green lines show where the bracket would go and in the middle of the green circle in the pic is an actual one someone did.
Notice that it uses the opposite end of the full throttle stopl with an nut added.
I believe you also need another nut to go on the bottom of the Idle screw housing.

I was going to post this exact fix. Years ago my brother broke off the tab of the adjustment screw, and I fashioned a piece of aluminum angle exactly like that. As far as I know, the car is still working till this day.

Diesel911 · #9 03-06-2017, 01:10 AM

Quote:

Originally Posted by ROLLGUY

I was going to post this exact fix. Years ago my brother broke off the tab of the adjustment screw, and I fashioned a piece of aluminum angle exactly like that. As far as I know, the car is still working till this day.

It was not my idea. I either saw it on this forum or benzworld long time ago. However, I saved the picture.

daxgaz · #10 03-06-2017, 08:47 AM

I'm so glad I posted here! The L bracket off the throttle stop bolt looks like it would do the trick. I'll do this and post my results here.

ROLLGUY · #11 03-06-2017, 10:38 AM

Quote:

Originally Posted by Diesel911

It was not my idea. I either saw it on this forum or benzworld long time ago. However, I saved the picture.

That might have been from the post I made several years ago, as it looks exactly like the one I did. I think it is the only way to fix it short of pulling the pump.

kerry · #12 03-06-2017, 11:40 AM

One advantage to the fix I suggested is that the idle speed is controllable from the driver's seat. I really liked that feature on the 123 and 116 I owned which had it. Nice in the wintertime to warm up the engine. My Fuso truck has that feature also and I like it there too. The difficulty would be finding the relevant parts from an older 123 or 116 or perhaps even a 115.

Jarod · #13 03-07-2017, 08:00 AM

The idle adjustment knob is very easily retrofitted.

The hole is in the dash, you just have to punch it out, the idle bracket bolts up where the cruise and throttle linkage bolts up to.

EDIT: the cable actually connects to the linkage in the little hole right near where your temporary fix bolt is.

I found one on a 240d in a junkyard and put it on my grey 300d. fits and works fine.

But the bracket fix looks simple enough and doesn't require finding all the parts for a idle knob.

daxgaz · #14 03-11-2017, 11:55 AM

Ok, I made the fix based on suggestions from here and it worked! I fabricated a bracket that attaches to the throttle stop bolt and replaces the cast part that held the idle adjusting bolt. I also replaced the idle adjusting bolt with a standard bolt that was in better shape and a standard thread size, so I could tap the bracket.
Thanks for all the help! I was afraid I was going to have to replace a thousand dollar part, but the fix was less than $20 in parts!!!!

Diesel911 · #15 03-11-2017, 03:31 PM

Quote:

Originally Posted by daxgaz

Ok, I made the fix based on suggestions from here and it worked! I fabricated a bracket that attaches to the throttle stop bolt and replaces the cast part that held the idle adjusting bolt. I also replaced the idle adjusting bolt with a standard bolt that was in better shape and a standard thread size, so I could tap the bracket.
Thanks for all the help! I was afraid I was going to have to replace a thousand dollar part, but the fix was less than $20 in parts!!!!

Well you still have a little problem. The original Idle Adjustment screw at least on mine has a spring loaded plunger on it.

That spring loaded plunger is there so you can use the Manual Shutoff. With that original part the Manual Shutoff is not going to work.