Door check strap! - PeachParts Mercedes-Benz Forum

kerry · #1 03-21-2008, 02:23 PM

Careful with your door check straps. Back driver's side door had been creaking ever since I got the car. I've lubricated it periodically. Today, I park on a narrow pretty busy street and open that door to grab some tools to work on an apt. DOOR WONT SHUT. There I am parked just around a blind corner on a busy street with an open door. Couldn't drive it. Couldn't leave it. Afraid someone would make the turn and clip the door. Took me about 15 minutes to figure out there was nothing I could do to release it and then remove it. Lucky for me I happened to have a small hammer on hand so I could drive out the pin on the outboard end.
Strap is still sitting inside the door so I haven't been able to figure out exactly what jammed and whether I could have released it had I known more about how it functioned.

Chad300tdt · #2 03-21-2008, 02:34 PM

Sounds like that was exciting. I didn't think they could get jammed open. I thought they would only stop holding the door open. Is the strap bent? Did you ever lube them with the door panels off? I believe that's the best way to make sure you get all the moving parts.

Biodiesel300TD · #3 03-21-2008, 03:29 PM

Sounds like it the strap broke inside the mechanism or something is blocking it from closing. Try pulling the door panel and remove the door check, and see whats going on.

JimFreeh · #4 03-21-2008, 04:29 PM

When the check straps are not lubricated, this is the typical failure mode.

Remove door panel, remove the 3 10mm bolts and install a new one. You can also just remove it and reassemble, then close the door until you can find a new one.

Just be careful when opening the door.... nothing restrains the door and it can get damaged by opening too far.

Jim

kerry · #5 03-21-2008, 04:42 PM

Ok, got the check strap out. No need to remove the whole door trim panel, just loosen the bottom.
I've determined the failure. The 'hold open' mechanism is a tube with an internal spring and a ball bearing at each end, top and bottom. The spring pushes out the ball bearings into indentations in a track to hold the door at half open and full open. The bearings are supposed to retract as pressure is put on the door, pushing the bearings out of the indentations and into the sliding track. One of those ball bearings on mine was stuck and would not retract. There was a fair amount of rust and corrosion on the ball. I was able to disassemble it in a vice by hitting the sliding mechanism with an old screwdriver. I've now cleaned up the balls and see no reason why it would not continue to work correctly. However to reassemble the balls must be compressed into the tube against the spring to get the whole assembly into the track.
Anyone have any clue as to how to compress it? The spring is quite strong as you can imagine because you can feel it's power with the two foot lever of the door as you try to close it.
I'll try to post some pictures when I'm done but at the moment I'm stumped as to how to compress the bugger enough to get it into the track. I'm assuming that during assembly at the factory there's some kind of long graduated track attached to the end of the check strap slide that allows the balls to be slowly compressed and pulled into the track.

By the way, lubricating those ball bearings with the check strap in the door is virtually impossible because they are hidden up inside the track. If the check strap is removed, lubrication is possible with a light oil through holes at the bottom of the indentations.

JimFreeh · #6 03-21-2008, 04:51 PM

Kerry,

Once they jam, it's a fool's errand to to try to lube them.

Too little, too late, too bad. Get another.

Jim

land sea air · #7 03-21-2008, 04:54 PM

this happened to me once and I just put some heavy force on the door to get it close with a loud pop, a little wd40 later and it still works fine to this day. After that I ordered 2 extras to keep around in case it happens again. I would say don't bother repairing the check since you already have the door apart just order a new one

JimFreeh · #8 03-21-2008, 04:59 PM

Quote:

Originally Posted by land sea air

this happened to me once and I just put some heavy force on the door to get it close with a loud pop, a little wd40 later and it still works fine to this day. After that I ordered 2 extras to keep around in case it happens again. I would say don't bother repairing the check since you already have the door apart just order a new one

You're lucky.

I've had the sheetmetal in the inner door deform when forcing....

I now cut them with a sawzall so I can close the door if I'm not in the mood to pull it when it fails.

Jim

pawoSD · #9 03-21-2008, 05:23 PM

I had a rear one fail on me when I got home at 12am while it was snowing a couple years ago. Door stuck open, wouldn't shut. Had to get out my dremel and grind it off to get the door shut. Replaced it a week later.

kerry · #10 03-21-2008, 05:29 PM

Quote:

Originally Posted by JimFreeh

Kerry,
it's a fool's errand to to try to lube them.
Jim

This is probably true but they are a very simple mechanism which should work freely when clean. I've been able to compress the balls and spring inside the tube with a C-clamp but have been unable to transfer the compressed unit into the sliding track. It is very precarious when compressed with a lot of stored energy.
I don't see any possibility of preventative maintenance on the mechanism without removing the whole unit from the door.

Brian Carlton · #11 03-21-2008, 05:33 PM

Quote:

Originally Posted by kerry

This is probably true but they are a very simple mechanism which should work freely when clean. I've been able to compress the balls and spring inside the tube with a C-clamp but have been unable to transfer the compressed unit into the sliding track. It is very precarious when compressed with a lot of stored energy.
I don't see any possibility of preventative maintenance on the mechanism without removing the whole unit from the door.

I've got to tip my hat to you. For $20. you've definitely spent far more time than what would be acceptable for an individual of your stature.

No, you can't lube it unless you remove it from the door.

And, yes, they are expendable. The springs typically snap and the door is then rendered immobile.

Just toss it out before you hurt yourself............

kerry · #12 03-08-2012, 10:36 AM

It's about four years later. That replacement door check is making sounds like a geriatric patient. Is that all the life a person can expect from a door check strap nowadays? I don't even use the back driver's door that much. It probably gets used once for every 50 times the driver's front door is opened, yet it's failing.

benhogan · #13 03-08-2012, 10:50 AM

this happened to me too on the w126 and those rear door are pretty wide.

i could not close the door.

i tried to rebuild the door check and the ball and spring popped out and that was a waste of time.

once they start to creak, might as well replace them all.

gonzalo75 · #14 03-08-2012, 11:09 AM

mine are creaking badly too. That must be the worst component of the whole car

Chris W. · #15 03-08-2012, 01:42 PM

Although I've had to do the check straps on a couple doors of my fleet of 124's, in my opinion the worst component on the 124 car is the trunk buffers or whatever they are called, one on either side of the trunk opening. They are covered with what appears to be a thin layer of rubber, which deteriorates and leaves a totally scuzzy looking metal piece underneath.

They deteriorate for no apparent reason. How often does one open the trunk, maybe 1/100th of the number of times you open a door or less? How often do those buffers get exposed to sunlight? Maybe a few hours during the entire life of the car. Yet those things turn to crap.

Rgds,
Chris W.
'95 E300D, 262K