i have recently bought a 07 clk350 with 70000 miles on it, it runs smooth and i have taken a pre purchase inspection before i bought it and the mechanic said the car has no issues found.
But what Im worrying about is the brake which i have to step so deep to let the car stop totally ,it is not sensitive as i think that when i touch the brake the car will stop. is it a common issue on clk or is the problem on my car ? ( brake pads are replaced half year ago)

 

Hard to tell without driving it whether it feels normal or not. A lot of things can make the pedal feel soft, including some brands of pads. You wouldn't think they would make that big a difference, but they can. But fluid is supposed to be changed every two years anyway, so flushing won't hurt in case you have some air in the lines.

 

The long:

This is a common problem with 2 main causes - Calipers over returning or changing the front pads without doing the rears. A third reason would be air in the system.

The pistons in a brake caliper depend on the distortion of the D shaped seal to return them to the brakes off or resting position. When changing pads on these cars great care should be taken not to push the pistons back too far in the caliper to get the old pads out. You should just push them back sufficiently to release the old pads. If you don't do this, stiction of seals on the caliper bore can cause the piston to move forward but not bring the seal with it down the bore surface & cause the piston to over return when you release the brakes. You then need more fluid to bring the pads back in contact with the disc (rotor) which gives you a low or mushy pedal.

There are two ways to fix this - one laborious & the other risks popping the pistons out of the calipers so be carefull.

If replacing all pads does not fix the problem - then you need to remove all pads. Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores. Then push back gently until you can just slip the new pad in & you should should have cured the over return.

The alternative is to strip & dry all fluid out of the braking system. Reassemble the calipers with pads, shims, pins & all. Blow the pads against the discs with compressed air & then bleed the braking system.

And the short:

I've mentioned it on the forum many times. When changing pads you need to be careful not to push the pistons back any further than is necessary to insert new pads or this can lead to caliper over return & give you a low pedal (search caliper over return). You should also crack open bleed screws before pushing pads/pistons back or you can damage the ABS block.

- First step - jump really hard on the brakes first stab. Try to move pads hard against discs & make seals on pistons slide down their bores.
If this does not work:
- Pressure bleed brakes from longest to shortest line & then stomp on them. (Apply hard)
If this does not work:
- Remove pads & install a set of old pad back plates & gently put your foot on the brakes to slide the pistons & their D shape seals down the caliper bores without popping them out of the caliper. Then push back just enough to fit new pads.

If none of this works then dry strip braking system. Rebuild calipers dry. Fully assemble & blow pads against the discs with compressed air while blanking the ABS unit & then pressure bleed.

Good luck!

Excuse the cut & paste. I'm lazy.

 

And a few other things for thought...

If you are used to driving a BMW, their brakes tend to be far more "grabby" than MBZ. In fact, even some Asian makes can have grabby brakes. I actually prefer MBZ's way of doing things )brakes, suspension, steering, etc.) where the first 25% of actuation is easy, and then things get more firm from there. For me, ut makes for a a much more comfortable driving situation.

Another possibility are crappy brake pads. I put Akebono pads on my CLK and they were terrible - noise at low speeds and a soft pedal, and even a lack off stopping at "full" pedal. I replaced them with Porterfields and have been happy, though OEMs seem to be best.

 

I have always found the brakes on the clk to feel somewhat soft compared to most other cars I drive. However, I have never felt as though they were unsafe. I do think they characteristically have a different feel than most other cars. I suppose I am agreeing with Rudeney in this regard.

 

Yes ~ I think we need to differentiate between progressive brakes & a low pedal. I'm responding to a low pedal. (e.g. brakes take at 50% of pedal travel etc.)

Funnily enough with stock pads & very low mileage I find my close-out CLK's brakes just a touch over sensitive. It does not take as much pedal pressure to activate the ABS as previous Benz cars I've owned.

 

The OEM brakes that came on my CLK550 are the most firm and sensitive brakes I have ever experienced on an MBZ (save for the super-cars like the SL65 or SLR, etc.) MBZ brakes tend to feel very soft for the first 50%, then get firm.

 

OK ~ interesting so I'm not imagining things.