Orv (orv) wrote,
Orv
orv

Fixed the parking brake on the Mercedes today. It wasn't so much broken as it was massively out of adjustment -- the pedal would go straight to the floor without affecting the rear wheels at all.

First step was to make an adjustment at each rear wheel. This car has rear disc brakes, but the parking brake is independent and works like a miniature drum brake -- when you press on the parking brake pedal, shoes move outward against the inside of the rotor hub. Like most drum brakes, adjustment is done with a star-shaped wheel inside each hub. You remove one lug bolt and turn the wheel until the star wheel aligns with the lug hole, then you turn it with a screwdriver. (It's edge-on to the hole, so you can turn it by prying on the points with the screwdriver tip.) This is about as much of a pain in the butt as it sounds; you can't really see what you're doing, and it's hard to figure out which way to turn things except by trial and error. After a considerable amount of fiddling and a few false starts, I tightened them until they locked the wheels, then backed off a bit until the wheels turned freely again. So much for that adjustment.

Testing showed the parking brake now kinda, sorta held, but still went to the floor. So I dove under the car and tightened the adjustment under there, which effectively shortens the brake cable. It took quite a few turns -- I suspect no one had ever adjusted it, and the cable stretches over time -- but eventually the brake started to take after only a few clicks, and was fully on before the pedal hit the floor.

As a side benefit, while I was under there I finally found a loose exhaust mount that had been causing an annoying rattle for...well, pretty much since I got the car.
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