How do I change the front brake pads on a 2005 C320 Sport
 

I have a 2005 C320 Sport that needs new front brake pads. It's a very different setup than I've done before. It looks like two bolts need to be removed to get the outside pad off, then two more to take the inside pad off. I loosened the outside bolts and brake fluid came out. I tried searching the internet about it and came up with nothing, but I know this is a rare car. Is it possible I have to drain the wheel cylinders to take the pads off?

Torx bolts? 05 sport should have fixed 4 pot calipers. I think you disassembled a perfectly good caliper. It'll need to be resealed.

Replacing pads on fixed calipers is really simple. You just need to tap out the 2 pins and the pads slide out. If you're just doing pads caliper can stay in place.
https://youtu.be/QATeyA20EF0

Thats the way I read it.

Ok, I see that now. It's too simple, I'm embarrassed I didn't see it. I remember now I've had cars that changed brakes that way and was annoyed not all cars I'd had lately did that.

So I pulled the pins and changed the pads, but now the brakes do funny things. I've had this happen before but forget why, the brake pedal goes to the floor but if I pump the brakes they are ok. When I loosened the torx as soon as brake fluid came out I tightened them. I'm thinking now I have to bleed that wheel. Any opinions?

It was mentioned it was disassembled and needed to be resealed. I didn't disassemble it, I just loosened it. Does that count? And what is resealing?

Jim, air entered the hydraulic brake system so you need to bleed the air from at least the caliper that leaked brake fluid. It's best to use a pressure bleeder. For safety sake bleed the affected caliper before driving your C320 again.

Get a friend to pump the brakes pedal while you open/close the bleed screw. Have them stand on the brake pedal and carefully inspect the caliper for any leaks.

Jim, if you decide to use the 2-man technique that tjts1 mentions then be sure to place a piece of 2X4 under the brake pedal so the travel of the brake pedal is limited. Otherwise, you may damage the master cylinder resulting in additional work to restore your brake system to "normal". As I mentioned, best to use a pressure bleeder.

That's a non issue on the W203 master cylinder. It has a built in stop.

Does this car have SBC ( electronic braking )? If so, it needs to be disabled when changing parts as even opening the car door can cause the system to wake up and apply the brakes during it's test cycle. This can be a hazard if this occurs when the pads are removed or fingers are in the way.

I don't think this one had the SBC.

No SBC on any C-class in the USA.

My 2005 C240 wagon had normal sliding single piston calipers....did the 320 have upgraded multi piston? If my wagon had had the 3.2 engine I'd have probably kept it forever. the 2.6 was gutless compared to the 3.2!

All w203 wagons shipped to the US had the same 300mm sliding calipers. Only a handful of 05 C320 sedans with the sport package got the 4 piston brakes. Weirdly most C230 sedans shipped to the US included the same sport suspension and brakes with 2 or 4 piston 330mm brakes. I had to swap 4 piston brakes on my 02 C320 wagon. It's really quite easy and the braking power is phenomenal.

https://imgur.com/a/Ij4G3

I made the mistake of using 312/316mm E500 brakes because I listened to people on the forums who claimed 330mm W203 brakes don't fit inside 16" wheels. They were wrong.

And yes C240 2.6 engine is gutless compared to the C320. You can squeeze even more power out of the 3.2 by swapping injectors, airbox and throttle body from the 5.0L V8 M113. Then I got into suspension parts like C55 sway bar, springs and shocks which are direct bolt on. You can build a very fun to drive wagon out of a c320 but it takes a bit of work.

Done
 

I bled that wheel cylinder, with help from my experienced brake bleeder wife, changed the other wheel pads and the brakes are fine now. I did'nt need to add brake fluid, I guess some was added by the previous owner so when I pushed the pistons back it made up for what was bled.

But that leads me to a question: what kind of brake fluid does this car take. The brake cap says DOT 4+.

I also noticed there's a sensor only on one wheel. I reused the old one, I'll buy a new one at my future convenience.

There's a brake service notice that came up that I thought would go away when I changed the pads. It still comes on but just when I start the car, before it would come on almost every time I used the brakes. I thought there might be something wrong with the used one and took it out but the notice still comes up. Do I need to reset it or is the car smart enough to know if the sensor is good and I do need a new one?

It takes dot4 as the cap mentions. You'll have to change the wear sensor to make the message go away.

Brake pad wear sensors are either an insulated loop of wire or a single insulated wire inserted into the edge of the brake pad. As the pad wears thin, the wire becomes exposed and also rubs through. When the wire rubs through the loop breaks connection / single wire becomes grounded.

In your case, it appears that it is a single wire because it only came on when brakes were applied and it no longer does so once the pads were replaced. RE: sensor wire is now insulated from the brake rotor.

Given the light post pad change turns on at start up and not during braking, this tells me that there might be software that says. " I've seen a low pad warning at some point, I no longer see it but will still alert the driver at start up."

This start up message might clear it's self after X drive cycles if it does not see a signal from the wear sensor or it might need a scan tool to reset.