Today we’re going to be replacing the front brake discs, pads and pad wear sensors on my 1999 W202 C240 Sport.
This is a later facelift car. I don’t think that this guide will be applicable to pre-facelift cars.
To do this you’re going to need a jack, 17mm socket and breaker bar to get the wheel off (along with your locking wheel nut key if you have alloys), two axle stands, a 18mm socket and ratchet and an 18mm socket for your breaker bar, a H5 and H7 hex head socket, needle nose pliers, a flat head screwdriver and a hammer.
I also used penetrating spray, copper grease, a brake caliper rewind tool and a couple of wire brushes. I wouldn’t call these bits essential, but it made my life easier.
We’re going to start by removing the pad wear sensor. At the caliper end is a plug that you just pull out by hand, at the other is a little metal pin that clips onto the back of the brake pad that you’ll want to remove with your needle nose pliers.
As the pad material wears down it eventually exposes the little metal pin which grounds on the brake disc, turning the ‘replace brake pads’ light on your dashboard. It’s simple but very clever!
Next remove this H5 headed bolt from the brake disc. The brake disc will want to turn as you loosen the bolt. Put a screwdriver through one of the wheel bolt holes in the disc and turn it until the screwdriver hits the bottom of the dust shield behind the disc. This will lock it in place.
At this point I’d advise soaking around where the disc slots over the hub with penetrating, spray so it can soak in whilst you work on the calipers.
Next remove the caliper retention clip. Just give it a pull with your needle nose pliers and it will spring right out.
Next, insert your screwdriver between the disc and caliper and lever outwards. If you look at the back of the inside pad, you’ll see a big rubber piston that is holding the pad next to the disc. We want to retract that piston back into the caliper to make room between the pads and disc. It’ll make life so much easier when you go to remove the caliper.
You can now remove the caliper! Pop these two dust covers with your flat head screwdriver and use your H7 key to remove the two pins/bolts inside.
The bolts can be a bit grippy on the inside of the rubber boot that holds them in place. They get a little grimy over time so they don’t always want to slip in and out of that boot.
I lightly cleaned them up with a wire brush rotary tool attachment. it make it easier to slide them back in and will give them a fresh start.
The caliper should now just lift off!
Rest the caliper on a spare axle stand. don’t let it dangle from its hydraulic lines.
The brake pads should now be free to remove. The inner one on the piston is held onto the piston with three springy bits of metal. Just pull up and it will come out. The outer pad should just be sitting on its mounts and can be lifted away.
Before we insert the new brake pads we want to push that piston all the way back in. I personally use a caliper rewind tool, other people use a C-clamp with the old brake pad as a ‘face’, sone people just press down the piston with the old brake pad by hand.
It’ll need to go all the way back in so we can get the new pads over the new disc. When everything is new there’s not a lot of clearance.
Insert the new pads. I put a little copper grease on the tabs where the pad meets the caliper, just to dampen any vibration and to prevent and squeaks.
Now we can move on to getting the disc off.
To get to the disc we’ll need to remove the frame around it. It’s simply held on with these two 18mm bolts.
These can be stiff if they’ve been in there for a long time. Penetrating spray and torque will get then started.
Once they are off the frame just lifts away.
Now for the fun bit! Getting old brake discs off can be a pain in the backside. Sometimes you get lucky and they practically jump off the hub. Sometimes they need a little persuasion to come off.
Soak where the disc sits on the hub with penetrating spray. Let it soak in and then you’re going to hit the back face of the disc with a hammer.
Hit it, turn it 90 degrees, hit it again, turn it another 90 degrees and hit it again. You’re trying to shock and break the seal that’s formed between the disc and hub so don’t worry about being gentle with it.
There are stories of people hitting the back face of the disc with sledge hammers and having to heat them up with acetylene torches to get old discs off of cars. I’ve done both axles on this W202 and I think I did both axles on my W124 and found neither car needed that much force.
Once the old disc is off, pop the new one on and pop the frame and caliper back over the top. (Apologies for my dirty finger prints all over the new disc)
Don’t forget to plug your new sensor in!
The caliper retention spring thing can be a little fiddly. I found it best to get one end into the caliper, then you can manipulate the other end to get it to where you need to go. Use the first pic at the top of this post to remind you how it should sit.
Now repeat on the other side and away you go! Before you start the car, be sure to pump the brake pedal a few times to make sure that the pistons are sitting where they need to be.
Most pads have a breaking in procedure which will be on a bit of paper in the box the pads came in. If not I’d still recommend going from 20mph to stop a few times, in a place where it’s safe to do so, just to mate the surfaces.
Thanks for reading. Hopefully this has helped you! If you would like to stay up to date with all my blog posts please subscribe to the blog via email (from the box at the bottom of the page).
Follow me on the following social media platforms:
By Richard Francis