second opinion on replacing discs

[joe prosser]

You mention juddering, my experience of a warped disc/faulty calliper piston is a pulsing through the brake pedal when braking consistent with the rate of wheel rotation. With age, corrosion on my car has left rust particles between the anti lock reluctant rings and the ABS magnetic detector heads and this causes a judder through the brakes just before I come to a halt; due to the ABS system seeing inconsistency between the wheel rotations due to the crud stuck to the detectors. Make sure these ABS components are clean and free of rust
With new discs mounted to cleaned hubs then any movement between disc and calliper has to be down to play in the wheel bearings, so check here that things are in spec. If the bearings check out it could be that the pistons are not retracting the requisite amount in the calipers after applying the brakes and drag the pads on the discs. Did you notice uneven pad wear within each calipers and between calipers when you removed the old set, they should all wear to the same degree. First check that the brake pads are free to move laterally in the calipers, remove any corrosion with a wire wheel or grit blaster and lubricate all contact points between pad and calipers with smidge of copperease. If there is still an issue then it is the calipers themselves. The caliper pins should be straight and clean (so too the bores) with only a smidge of silicone grease, too much and you get a degree of hydro lock that inhibits freedom of movement. If the caliper pistons show stiffness in movement then these will need to popped out and treated to a rub down with wire wool to remove any corrosion especially towards the outer lip. If the seals are stiff with age then new ones may provide the greater flexibility needed to retract the pistons.

 

[ash1212002]

attempted to clean the caliper, but still binding, going down the refurb route, will have to nurse the car back to my home town and hope for the best!

Will keep you guys posted

Thanks all

 

[ash1212002]

Have another update nursed the car back to my hometown which was the first time i drove the vehicle after replacing the discs and pads, the nearside disc was alot hotter in comparison to the offside

Also jacked up the wheel the resistance has some what reduced on the nearside, alot less binding but doesn't spin as much as the offside wheel

 

[Petrol Pete]

Just completed the job was a bit of a nightmare as whoever did the job used threadlock on the caliper bolts...

Replaced both front pads and discs, however once fitted one wheel moves freely with little resistance whilst jacked up, whereas the nearside moves a little until hits a hot spot and binds/drags where it comes to a point i cant cant spin the wheel a full rotation as it gets stuck. Also the nearside caliper took alot of effort to push the piston back in compared to the offside too

What would cause this? Anything I could check?

I would imagine new caliper bolts would come thread lock coated or it's specified in a rebuild. I always use thread lock on brake caliper mounting bolts. Its easy to undo with a little heat from a hot air gun or micro gas flame.

 

[Yugguy]

Worth changing the caliper slider pins too while everything is off. A set off ebay is about 25 quid.

 

[ash1212002]

Decided to order a brand new bosch caliper not much difference in comparison to a refurb

 

[chrisk2010]

Just very quickly skimmed through this. I had the same problem when i changed my discs and pads.

I had to go at the hub with a wire disc on an angle grinder (gently) to free up the disc rotation as it was sticking a little due to rust on the hub face. The tightness on the locating bolt is also important so try not to over tighten. I did change the pins, springs and locating bolts as they weren't expensive as mentioned (mine did come with a little loctight on but . Whenput the wheel back on (you probably do anyway) torque the wheel bolts up in oppsites so it presses the discs evenly back against the hub.

For maybe a week or so my dics were hotter than usual but once they bedded in everything got much better.

I took the car for an MOT at Mercedes waterhouse and i do have a slow caliper on the driver side but "within tolerence" so I'll change it at some point but I'll just keep an eye on it for now as the discs are now cool and all is right with the world.

 

[ash1212002]

Just very quickly skimmed through this. I had the same problem when i changed my discs and pads.

I had to go at the hub with a wire disc on an angle grinder (gently) to free up the disc rotation as it was sticking a little due to rust on the hub face. The tightness on the locating bolt is also important so try not to over tighten. I did change the pins, springs and locating bolts as they weren't expensive as mentioned (mine did come with a little loctight on but . Whenput the wheel back on (you probably do anyway) torque the wheel bolts up in oppsites so it presses the discs evenly back against the hub.

For maybe a week or so my dics were hotter than usual but once they bedded in everything got much better.

I took the car for an MOT at Mercedes waterhouse and i do have a slow caliper on the driver side but "within tolerence" so I'll change it at some point but I'll just keep an eye on it for now as the discs are now cool and all is right with the world.

I sanded down the hub with an electric sander was very smooth, also I attempted to clean the pistons within the caliper there was a lot of white oxidisation on one of the pistons, cleaned it as best as I could. I would say it is better as the resistance/drag has reduced when the wheel was jacked up. But I think I still need to change the caliper because I was still experiencing judder in the brake pedal when braking which makes me think the piston is not releasing fully against the disc when i release the brake pedal

 

[chrisk2010]

I sanded down the hub with an electric sander was very smooth, also I attempted to clean the pistons within the caliper there was a lot of white oxidisation on one of the pistons, cleaned it as best as I could. I would say it is better as the resistance/drag has reduced when the wheel was jacked up. But I think I still need to change the caliper because I was still experiencing judder in the brake pedal when braking which makes me think the piston is not releasing fully against the disc when i release the brake pedal

I had the same judder coming through the pedal which is why i thought it was the fronts that needed replacing but as it turned out it was the rears that were warped have you considered them ?

I didn't consider the rears because the judder wasn't coming through the seat of my pants but more steering wheel and brake pedal.

On the bright side i can strip the brakes and discs off the car in less than 10 minutes as i done it two or three times each side on the front thinking that was the cause of my problem.

 

[ash1212002]

I had the same judder coming through the pedal which is why i thought it was the fronts that needed replacing but as it turned out it was the rears that were warped have you considered them ?

I didn't consider the rears because the judder wasn't coming through the seat of my pants but more steering wheel and brake pedal.

On the bright side i can strip the brakes and discs off the car in less than 10 minutes as i done it two or three times each side on the front thinking that was the cause of my problem.

The rear pads are looking on the thin side, so will be replacing just the pads this weekend!

The new caliper will take several days to arrive, so will fit new rear pads, replace caliper and take it from there, if problem persists will then replace the rear discs

I highly suspect its the caliper as it was quite hot in comparison to to the other side

On the clk do all the four brakes apply the same amount of pressure or is it more brake pressure on the front and less on the rears?

haha that must be a world record

 

[clk320x]

The new caliper will take several days to arrive, so will fit new rear pads, replace caliper and take it from there, if problem persists will then replace the rear discs

Where are you getting this from? Mercedes?

 

[ash1212002]

Where are you getting this from? Mercedes?

Mercedes will cost me a small fortune, purchased from here, brand new with a 2 year warranty

BOSCH Brake Caliper Front Axle Left (0 986 134 076) buy cheap online

 

[ash1212002]

Replaced the caliper yesterday, decided to also replace the rear discs with new pads too

Bled just that caliper using the 2 man method, bled it 4 times is this sufficient? brakes seem to be fine...

May need to adjust the foot brake, it appears there are 2 methods, one by removing the rear seats and the other via the discs - whats the difference?

An another note I have noticed on occasions not all the time when moving gears from P to R I hear a clunk if I move from P to D quickly the noise is not apparant, an ideas what this could be?

Cheers

 

[Pathfinder]

It is not unknown for a worn suspension ball joint or rubber bush to cause a judder when braking.

 

[ash1212002]

It is not unknown for a worn suspension ball joint or rubber bush to cause a judder when braking.

In this case it wasn't the suspension, was the caliper as it was binding and not retracting back into the piston bore

 

[Pathfinder]

Removing the rear seat is only for adjustment of the handbrake cable (if required), after adjusting the handbrake shoes in the rear drums.

 

[blitz500sl]

Just completed the job was a bit of a nightmare as whoever did the job used threadlock on the caliper bolts...

Replaced both front pads and discs, however once fitted one wheel moves freely with little resistance whilst jacked up, whereas the nearside moves a little until hits a hot spot and binds/drags where it comes to a point i cant cant spin the wheel a full rotation as it gets stuck. Also the nearside caliper took alot of effort to push the piston back in compared to the offside too

What would cause this? Anything I could check?

These calipers are known for sticking. I had to rebuild mine because of this issue. This is why you were pulsing before.