84SD. Frequently when I hit the go pedal or the brake I get a single click like a stone hitting metal 1 time. It drives me nuts but I haven't been able to find the cause.

The head liner, both B Pillar trim, and driver front and rear door cards are out. Sitting in my driveway engine running, car in gear push the go pedal and I hear the noise near the center of the driver door. (tap) Put in reverse, hit the pedal & "tap. This happens almost everytime.

I pulled the mirror & both of the door window squeeges so I could see down there. Nothing. I've felt everything that I can reach and nothing seems loose.

The noise goes away when I try with the door open. Apparently the inertia has to be parallel to the door.

I can find absolutely no possibilities. My next step is to pull the door glass and regulator tomorrow but I really don't want to go to the trouble. I think I want to live with the noise eve less.

I thought that perhaps there is some compartment that I am overlooking that contains a screw, rock, marble or something. I've also probed with a magnet and nothing comes out. All screws and bolts that I can reach are tight except for what I'm missing.

Any ideas?

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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.

could it be that your door itself is loose, or the latch not seating properly? maybe blow any cavities out with shop air?

worst case scenario, i think the shop tactic is to narrow in on the noise using recordings from a group of microphones.

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'77 240D, 504H, OM617.952, etc.

If sound is present regardless of window position, possibly there are internally broken pieces in door check or missing fasteners.

If sound disappears in certain window positions, possibly there are worn plastic guides or other worn, broken pieces in regulator.

Broken door checks and bent window regulators are very common issues, especially on the driver's door.
I've replaced both on my 83 300SD.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

screw holding outside door handle loose?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Check strap ??

It is independent of the window position. I'll look at the door check but it was replaced within the last couple of years. It isn't noisy or sticking but a cleaning & lube is a good idea since the card is off.

The screw that holds the door handle is easy to check. The window regulator itself is one with stouter arms than the the later cars. The window is working very well.

Pulling the regulator is sort of a job to get reinstalled and I'd rather not remove but I hear the noise every time I move from a stop or slow down.

I'll look more this afternoon and report back. Let me know if you think of anything else.

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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.

If you don't have a mechanic's stethoscope, make one using a long piece of tubing with a small funnel at the detector end
- to aid in pinpointing the area where the noise is being generated.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Remove your inner door panel and have a look. Should be obvious.

It's silly, but check the door lock pull. I had one rattling because it wasn't tight at some point.

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'85 300D - federal spec, built in late 84. 85 300D Complete AC System Rebuild

Found it. A ball bearing ~1/2" in diameter in the bottom of the door. It was in front of everything else. Eventually, I stuck some cheap Harbor Freight flashlghts in the bottom of the door, removed the outer mirror so the inner & outer window squeegees would come off. The light let it be found. A magnet got it out. It may in fact be from a door check but not from one of mine. It's been there as long as I've had the car. I think there are extra checks in the shop & the ball may be one that originally was what stops the door in various positions.

There is some rust in the lower part of the door. It is all the way through and runs the length of the door. It is in the part that forms the inner most corner that goes over the door sill. I never learned to weld but will take it to a shop while the card is out.

The plastic vapor barrier is completely destroyed on this door. How important is it to have the barrier installed? I'm thinking of finding a sheet of plastic and making another barrier. Before winter: glow plugs just quit, engine shake, mono valve, tail light gaskets, & perhaps other trunk leaks and have seat replaced &/or rebuilt. Gotta get going.

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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've wrecked a couple of those plastic barriers. I didn't think they added much protection from moisture to the door but they seem to be there to prevent the cardboard panel from absorbing the moisture which gets past the window 'sweep,' which remove water from the glass. I stored a panel for several months in my garage and found it deformed with a huge bow which made it a two man job to reinstall.

Let's be honest, moisture is going to find it's way into the doors if nothing else but heat transfer through the drain holes in the bottom of the door. The idea is that none of that moisture softens and deforms the cardboard backer that holds the panel together. MB may have also intended that none of the cardboard flake off and plug the drains too.

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84 300SD
85 380SE
83 528e
95 318ic

Sounds like the ball came from the door check strap. You may want to remove and inspect it.

The vapor barrier protects the cardboard and keeps moisture from leaking into the passenger compartment. What I use is a 3mil black garbage bag (contractor bag from HD). Slit two sides to make one big sheet and cut to size. Use contact cement to hold it to the door.