I replaced the front discs and pads on my 2003 SL55 today.

85,000km and the next service due in 5000km. Front pads down to a few millimetres. Big road trip coming up.

The old discs were 33.96mm, the minimum thickness stamped on the discs was 34mm.

The new ones are 35.8mm thick... measured with a micrometer. Not much room for wear but the old ones had a distinct ridge on the periphery.

The discs are truly massive weighing 15kg (30lb) each.

It was great to have the advice from previous posts on various forums.

Pads were about AUD$550, discs were $500 from Silverstar spares in Sydney. Good service, next day delivery.

Disconnected the battery, jacked her up, removed the pads being careful to watch the fluid level and made sure the pistons did not extrude.

Despite the pads being down to a few millimetres the fluid level in the reservoir did not rise more than a few millimetres when the pistons were pushed back. Very mysterious.

The bolts for the calipers were 21mm. My biggest socket was 19mm then 24. or 3/4" (too small or 7/8" (too big).

Put it all back together for a run to the Auto One store for the right socket and got the red screen of death when I pushed the brake pedal. Chimes and warnings telling that the SBC had failed and to call the workshop. This continued despite pumping the pedal and reconnecting the battery. It stopped after several more pedal pushes so I assume that the system didn't like pushing the worn pads all the way back onto the discs. Probably a low pressure alarm.

Got the socket from the store and jacked her up and pulled everything to bits again.

The caliper bolts were VERY tight, lucky I had a long lever torque wrench and a steel bar to lever against the chassis.

The discs refused to budge off the hubs despite gentle bumps with a wooden mallet and not so gentle bumps with an engineer's hammer.

The photos attached show the solution.

An improvised disc puller.

Wind the clamps up tight then strike the disc on the hub face with a large hammer and "BANG": they fall off.

Reassembly was straitforward, Loctite on the caliper bolts, no red screen and everything works fine.

Time involved, less the mucking around, was probably 30 minutes per side.

Peter Cowie

 

My last post described replacing the pads and discs on my 2003 SL55.

I chose Textar pads ($AUD 500) as I had used them on various previous cars.

After the first few stops they squealed very badly. Once mildly warm they squealed every time below about 10km/h. OK for the first few stops after a 15 minute non stop drive then they would squeal again.

Ok with a hard stop but coming up to traffic lights in traffic was a nightmare.

A high pitched squeal right down to the stop. Hard to believe that the car could make such an awful noise when it was barely moving.

I searched the forums and tried the following:

Several hard stops from speed to "bed in the pads"... no change.
Wheels off to ensure that springs and clips were correctly installed... all OK.
Wheels off, pads removed and applied MB brake grease... no change.
Wheels off, pads removed, chamfered and a slot cut as seen in other pads... no change.

Last resort... Genuine pads (AUD$ 875!!!)

Fixed the problem

Lesson learned!

Photos attached.

Peter

 

Good to know. BTW, how many brake sensors are there? 3 or 4?