Door Check Strap W123 - PeachParts Mercedes-Benz Forum

Graham · #1 07-27-2013, 08:44 PM

I have read a number of threads about repairing door check straps. My question is about the bracket that is hidden inside the front door frame.

Does anyone have a picture (and/or dimensions) of the bracket for a W123, preferable later model 82-85? My driver side is partly loose. I am thinking about using 1/4" S/S or Monel rivets but would like to drill new clean holes and leave welds intact if I can. May use machine screws if I can't find rivets in small quantities locally. It is hard to know if the holes in the W116 bracket are where the welds were or just where someone drilled them.

This is a picture of the bracket off a W116, I believe:

Graham · #2 07-28-2013, 03:21 PM

Based on the number of reads and zero answers, this must be a tough question. maybe I can learn something by poking borescope in back of door frame? Just re-installed trim, so hopefully I can find an entry point for borescope without taking that panel off again!

Graham · #3 07-29-2013, 09:14 AM

I looked inside cavity with borescope. But my borescope is a bit too large. I was able to see the back of the strap hinge. There is a weld on the inside (cabin side) of the door frame that is directly opposite the hinge forks. Inside, I could see a metal strap leading to that weld, but it was not clear where the other side went. So no further ahead.

Probably will try drilling out the spot welds, tapping and install machine screws as others have done.

ADDED: I removed the pin and I could not move the door frame hinge forks by hand. It seemed pretty solid. Welds are not broken but it seems something does flex. I removed the door check strap. As had happened once before, one of the tabs that the mounting screws threads into, had broken off. I am about to order a new OE unit at a great price ($45). Hopefully that will take the stress off the door frame.

Graham · #4 08-01-2013, 08:52 AM

Realize I am talking to myself her, but to conclude:

Greased and installed brand new Mercedes door check strap. It works well. But it takes qsome force to move out of those door holding detents. Watching the door frame strap fork, it still moves as the strap moves between detents. Passenger side does not do that. No cracks but strap hinge is not as solid as passenger side. So, maybe adding a couple of machine screws might still be an idea.

Just wish I had a pic or diagram so I know what I am drilling into.

Zacharias · #5 08-01-2013, 03:02 PM

I would guess that you are seeing metal fatigue on the driver's pillar. My high-mileage SD door pillar flexed that way, and my ex-Texas SD (that got creamed just after I got it) had a big ugly weld where someone had put in new metal to reinforce the spot (cars from hot states seem to be more prone to the check straps seizing).

So this is an actual Mercedes check strap you purchased? I ask because I had to return one aftermarket one as it was way too stiff, even after being lubed, you could barely get it to the second detent. The parts seller replaced it and the new one worked normally.

Graham · #6 08-01-2013, 04:22 PM

Quote:

Originally Posted by Zacharias

I would guess that you are seeing metal fatigue on the driver's pillar.
>
So this is an actual Mercedes check strap you purchased?

The metal hasn't fatigued yet, but could very well before long!

When I looked inside my '85s door frame, I could see a strap that runs at 90deg to the door (when closed). You can see the weld on the inside of the door frame if trim is removed. Could it be that MB added a stiffener behind the strap hinge because of experience with failures? We need someone with a parts car to have a look inside the frame on a W123 - preferable a later model.

The check strap I purchased was an original MB part - but by the look of the packaging, probably old stock. I lubed it with waterproof (marine winch) grease. It works smoothly, but that strap hinge does move.

vstech · #7 08-01-2013, 10:43 PM

I have cut apart several 123's I think I still have some frames with the strap inside, I'll check, but if not, I have another 123 to cut apart...

cook · #8 08-02-2013, 07:04 AM

Keep posting about your progress. I am very interested in what you end up doing.

I would think many of us have had issues in this area. I know I do, but just have not yet addressed it yet.

Graham · #9 08-02-2013, 10:19 AM

Quote:

Originally Posted by vstech

I have cut apart several 123's I think I still have some frames with the strap inside, I'll check, but if not, I have another 123 to cut apart...

That would be great vstech. It would be nice to know what we are drilling into when trying to address this problem. It could be that MB made changes as they went along, so year of car you cut apart will be useful.

I imagine MB have drawings or diagrams of those parts somewhere. The local bodyshop that handles MBs seems to have much more detailed sheet metal diagrams than I have been able to find on-line.

Graham · #10 08-04-2013, 08:50 PM

Hoping vstech will post re the hinge part inside the door, but meanwhile thought I would document something I noticed on the door side:

I have two old hinge strap assemblies. These two came out the same car - a 240D, I think. But they are different. One has broken ear and the other is loose in the channel/

The one on the left is the one with the broken ear, but otherwise sound. The one on the right doesn't seem to use ballbearings. It seems it is missing a spring. Could be someone removed it because it was not there when I dismantled.

I was hoping to make one good one out of the two, but so far I haven't figured a way of getting the ball bearing end into the channel!

Graham · #11 08-19-2013, 09:15 AM

Quote:

Originally Posted by vstech

I have cut apart several 123's I think I still have some frames with the strap inside, I'll check, but if not, I have another 123 to cut apart...

Quote:

Originally Posted by Graham

That would be great vstech. It would be nice to know what we are drilling into when trying to address this problem. It could be that MB made changes as they went along, so year of car you cut apart will be useful.

Any new info VStech?

kerry · #12 08-19-2013, 10:03 AM

I tried for a long time to re=assemble one of those check strap mechanism, but like you, I couldn't figure out how to get the ball bearings compressed against the spring. I wonder what jig they use to assemble them at the factory.

Stretch · #13 08-19-2013, 11:41 AM

I think these things are assembled and then the casing is bent into shape around the mechanism.

(Interesting how I missed this thread until now - you would have thought that being here virtually every day of my life would be enough...)

I'll see if I can figure out what's going on at the other end of the check...

Stretch · #14 08-19-2013, 11:53 AM

Looking through the Russian EPC I see this

Number 68 looks like a possible - the description is "lock" however...

...previous picture has a picture of a "mount" but that seems to be a hinge...

http://mb.ilcats.ru/part/class/1/ccode/F/cat/68K/type/123/subtype/130/group/63/subgr//vers//imgno/2

Graham · #15 08-19-2013, 05:41 PM

Actually, it looks like part 11 in this pic may be the part. What we were hoping to find, was some dimensions so we would know where to drill holes. I was thinking of leaving the spot welds intact and adding a S/S rivet or machine screw on each side. But may end up just drilling the welds out one at a time and rivetting. I see quite a bit of movement, so should do something before it gets worse.

PS: Did you have a good trip to Blighty?

item 5 in this pic (from MB South Atlanta)