The MB battery does not seem to be made by the company that makes Interstate batterys. Compare and OE and Interstate side by side they are very different. The OE weighs more.

If the parking brake lights stays on because the pedal will not come all the way back up here is how you fix it:
Underneath the car their is for lack of a better term what I call a "cable spliter". Just follow the drive shaft back and look up you will see it, towards the rear. One cable runs up front to the pedal, then two others are connected to it and those lead to the parking brakes. This "cable spliter" (whatever) rusts up and can get jammed. Pull it down and clean and grease it. After this is done you can adjust the cables as well. The pedal will be tight and the parking brakes will work very well.

W126 parking brakes are little drums on the inside of the rear discs. Like all drum brakes they do wear over the years and require cleaning and shoe replacment to work correctly.

At this point in the game the newest W126 is 15 years old. Any original rubber brake line is bad, replace them as you do brake jobs.

The rear wall of the trunk is right against the fuel tank, so don't screw into it. But you can remove it by taking out a couple of screws and mount anything you want on it with some rivits or bolts.

Check for rust under the rear window, these cars love to rust their.

WARNING FOR NORTHERN CARS!!!!
If your car sees salt roads inspect the rear steel brake lines above the subframe. They are out of sight and out of mind, but the salt sits up their and rusts them badly. I have had to replace a lot of brake lines on both of my W126's.

W126 shocks:
You cannot use the "bounce test" on these cars. Unless the shocks are completly blown out they will not bounce. But the ride will be gone long before that. Check the shocks for leaks, if they are leaking replace. Also 100k-150k is about all they are good for. Bilsteins are the best shocks to use.

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2006 CL500
1969 280SE
2023 Ram 1500
2026 Genesis GV70
2007 Tiara 3200