Door Check / Broken Spot Weld Fix - PeachParts Mercedes-Benz Forum

bodyart27 · #1 03-31-2007, 09:58 PM

I had my driver's side door check start to fail. It didn't lock solid, but it was making horrible noise / pops, with dicey resistance and the worse part - the door jam was flexing where the door check connects the door to the car's door frame (see pics - it will make sense).

So here is the problem with the inner door frame. The door check (strap?) connects via a pin and reciever. That pin / receiver piece is a plate that spot welded in place (from the inside?). As the door check wears out (I think what happens is that the grease inside the door check deteriorates) the plate starts getting stressed. Cracks start to appear on the paint, and then the spot welds start to fail. I had one fail (top left corner). In the first pic, you can barely see where the other spot welds are (two per side of the pin receiver).

Since I was going to do the door check, I wanted to repair the pin / receiver / plate as well. I had a slight hole where the spot weld had broken (sorry - din't get a pic before I drilled the hole). I went to the hardware store and brought home a variety of bolts.

I decided to go with a 5mm .80 x 12 bolt. I wanted it to be beefy enough, yet I didn't know how wide the plate was inside the door. I couldn't go crazy big with the bolt as I risked drilling into the edge of the plate rather than drilling into the plate safely inside the edge.

You can't put a nut behind the plate - no way to get to it, even if you remove the hood release handle and try to go up through the kick panel. So, I needed to put threads on the plate to draw it tight against the door jam with the bolt.

Per my tap and die set - I drilled a #19 drill (.166 decimal equivilant) so I could tap it with a 5mm x.80 tap. Some folks have used a sheet metal screw. I wanted the repair to be a little more elegant.

I just put it on and it seemed to work nicely. The bolt pulled the plate up gainst the door jam sheet metal. The door jam is not flexing and the new door check is like butter

.

In the pics you can see that the plate behind the door jam sheet metal (pic #3).

Ara T. · #2 04-01-2007, 04:14 AM

You could also just remove the door check... not really needed I suppose. Noticed how much nicer the door opens and closes without the check when I installed my new one.

Palangi · #3 04-01-2007, 08:44 PM

Weld broke on my 240D drivers door. I removed the ball and spring from the door check. It works well. Door opens smoothly, and the wind can't grab it and open it past the limit. Only drawback is that it doesn't hold its position.

benzforlife · #4 04-01-2007, 10:31 PM

you dont want to remove the door check, it will cause the rear doors to swing out far enough to make contact with the front doors.

bodyart27 · #5 04-02-2007, 09:12 AM

A few had posted about the door locking open - so I knew I was on borrowed time. You should have seen me the last couple of weeks slithering in and out of a barely open door.

It's only been a couple of days, but it seems to be doing well. The door jam sheet metal barely flexes now (normal amount?) and the door has been silent int operation

SD Blue · #6 04-02-2007, 12:09 PM

My drivers door has this same problem. How do you gain access to the back side to install a reinforcement plate? Does removal of the kick panel where the hood release handle is, allow for access?

bodyart27 · #7 04-02-2007, 03:31 PM

The "plate" I'm refering to in the first post is the plate inside the door jam that is spot welded in the four corners - the receiver for the strap pin is connected to this plate - the rings of the pin receiver pokes through the door jam body work.

I took the hood latch release handle off the driver's left foor kick panel and started to pop the kick panel off, but there was no access to the back side of the door jam to put a nut on the bolt. That is the reason I used a tap to put threads on the plate inside the door jam. The bolt the can grab the plate via the new threads and pull it tight up against the back of the door jam - so no need for a nut.

bgkast · #8 04-02-2007, 03:47 PM

Maybe you should drill the ends of those cracks too.

bodyart27 · #9 04-02-2007, 05:49 PM

I'm hoping that it's just the paint that's cracked. If you look real close in the first picture you will see that crack crosses both of the spot welds (imagine where the spot welds should be - you can kinda see them) on the right side.

With the fix and the new check strap in place, the flexing is minimal (normal?). I'll let it be and see if another weld fails rather than drilling more holes.

SD Blue · #10 04-02-2007, 07:24 PM

So you are saying the door-check breaks loose from the plate behind it and essentially only the sheet-metal is holding it?

bodyart27 · #11 04-03-2007, 09:17 AM

the spot welds seem to hold the plate that is inside the door jam up against the sheet metal.

the rings of the pin receiver are attached to this plate and poke through the holes in the door jam. to answer your question, the reciever rings for the pin don't separate from the plate, the plate inside the door jam looks to be separating from the door jam as the spot welds break

if all the welds are holding and the door check is in good condition (not binding), it doesn't seem to flex much at all

from what I could tell, when the grease in the door breaks down and the door check starts to bind, it torques / flexes the door jam end more than it should

the constant opening and closing the door with that much resistance takes a toll on the spot welds and then they start to fail. when it gets this bad the door starts to make some awful groaning and popping when opening and closing

hope that answers the question. I'm sure if we had a pic of the inside of the door jam it would make more sense

mikeecollins · #12 09-10-2009, 07:05 PM

Thanks for all your help this is the best repair I have seen, very smart

Whiskeydan · #13 09-10-2009, 08:39 PM

Shell, How's it holding up?

This is a much less invasive repair than welding.

I need to do this on the wagon.

brainlair · #14 09-10-2009, 08:46 PM

Oh man, I'm glad this thread got bumped... I have the exact same problem on my 1984 300SD, but on mine it's even worse- both of the spot welds to the left of the door check hinge have failed on the driver's side.

I think i'm going to do this, but I need to be careful... since I've already lost two spot welds, there's the risk that I push the back plate into the frame while drilling the holes. It would be ideal if there was a way to get into the frame to brace the plate from behind, but i suppose holding it by the hinge should do.

Are we sure there's no way to get in there? There's got to be some way, I'd be surprised if there was a sealed void behind it.

Whiskeydan · #15 09-10-2009, 09:21 PM

You can pull the plate up snug by inserting a long pin (large nail, screwdriver...) where the check pin goes and wedging behind it and the jam.