richard_leeds

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Last week I heard something rubbing on one of my front wheels. Went to the nearby tyre/brake shop who took the wheel off, the sound continued when the discs were spun. So we concluded it was a bit of grit caught up in the brakes. The chap sprayed loads of disc cleaner all over the assembly and eventually the noise stopped. Drove home in silence.

The noise started again this evening.


It isn't a full time noise, it seems to vary with the wheel speed, as if only one part of the disc is catching on something.
Does that mean it is a defect on the disc?

Or perhaps a piece of grit in one of the disc's holes? I've checked the holes on the visible side and they are clear, although it could be something on the hidden side.

Or the disc isn't perfectly flat and a bit of grit in the brake assembly only catches on the high spot of the disc.

I guess the next option is to have someone take the assembly apart and give everything a good clean. I worry that the MB dealer will tell me to replace the discs & pads. Then they'll say both sides should be changed for balance. That's a lot of dosh for one bit of grit.

So, is there any way I can do a DIY clean up? I was thinking of sliding a cleaning cloth between the discs and pads.

The alternative is that I take it to a local mechanic I've used for over 10 years and ask him to dismantle the assembly. He's a sensible Yorkshireman so won't push me to get the discs and pads changed if they don't need it. I guess you can do that sort of thing without specialist MB kit for bleeding the hydraulics etc?

The car is still under the MB 12 month warranty.

DansSlk

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If your car's under warranty i would get the dealer to look at it, if its just muck then they will remove it.

So long as its not wear and tear the work to fix the noise once they know what it is should be under warranty

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alroumi

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sorry to hear about this mate, i would take it to the dealer if its under the warranty.

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richard_leeds

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Back from the garage. Apparently it was corrosion on my discs. So it's now quiet with new discs and pads on both sides. Wear and tear, so I pick up the bill.

I'm curious about this "corrosion". I've had to fork out for discs on three cars in three years. I though t pads were meant to be changed regularly and discs should last for ages.Where does it accumulate, how does it happen? Is there something I can do to prevent it? My car is garaged and because it is a fun car, it is only driven in the dry.


(I'll also admit to a slight suspicion that its an easy get out for a garage to lazily change the discs and pads for "corrosion")

dsb

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By corrosion, do you mean rust? I get that sometimes after washing the car and letting it sit a while. A few hard stop and it's all gone.

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DansSlk

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If this was on the contact surface then yes is should effectively be self cleaning to a point but if the car is left to sit for long enough it can build up to the point that it cannot be burn off and the disks and pads must be replaced.

It can build up very fast on these brakes for instance if i let the SLK sit outside for a few days in the wet then a strong enough bond is formed i can put the car into D and release the parking brake and the car will still be held solid (and my outside parking area is on a slope so the bond holds the whole weight of the car).

Best thing is when you park up leave the parking brake off and the garage door open for a while as the car cools down then after about an hour close the door and if you want apply the park brake, if your garage floor is level this step is not needed unless you drive a manual then it is.

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richard_leeds

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When you say build up fast on these brakes, do you mean it would happen quicker than a "reasonably priced car" due to the relative high performance setup?

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Doesn't the hand brake apply the back wheel? This was the front wheel so the pads would have been released when parked.

Although thinking about it, I do have a vague memory of a front brake sticking. Maybe that was the cause.

OK, I'll always leave the handbrake off, but that'll not help with the fronts

I had been thinking of putting a fan in the garage to help dry the car off.

Any other tips?

DansSlk

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Yes thats correct the compounds used facilitate a fast build-up.

Your right the hand brake only applies to the rear wheels but it can stick just as much as the others so if you don't need to use it then don't, it was just a tip really.

The fronts on mine stick when wet but its just tight tolerances allowing contact in the right(wrong) conditions.

Basically anything you can do to dry the car before storage will help stop this from happening.

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dsb

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Because of my aftermarket wheels (reverse lip), I use a leaf blower to dry the wheels. Actually, I use it for the whole car then finish up with a 100% cotton bath towel. Anyways, I say start using the leaf blower on the wheels and as discussed, do not engage the hand brake.

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Woolly

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Been there, done that, check out this thread from 'another' place

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richard_leeds

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Thanks Woolly. I see you got yours done under warranty. I had to pay for mine. Perhaps a grumble to MBUK about it. If nothing else it will vent my annoyance!

It's easy to paranoid about it now. My problem happened after one week, it's a weekend car. So because MB have chosen tight tolerances, I could face a £300 bill to change both pads and discs if the weather is a little wet, now how often is it wet in the UK? grrrr

DansSlk

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To be honest mate if it happens again try to burn it off first.

Get the car up to 60 (more if possible) and brake moderately hard to about 5, repeat anywhere from 5-10 times.

The tolerances are tight to maximize performance for the people who drive the cars harder, being that the SLK is billed as a sports car and some of us really push these cars to the limit.

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richard_leeds

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Cheers Dan. I did try that, but probably half hearted from your perspective, it was hairy for me though!

I was worried I would cause more damage. Next time I'll find an empty dual carriageway and be more persistent! It'll be the Burley in Wharfedale bypass, 2 miles of d/c with a roundabout at each end.

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Woolly, with ref to restaurants in your linked thread, I prefer the Drunken Duck

Portzy

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Hello Richard.

Mines a weekend/dry weather car and I suffer the same problem as you, (slight rust/odd bits of grit), although I've not yet been faced with disc replacements yet.

The particular road you refer to is perfect, I know it very well myself but you really need to get the speed on then brake big time all the way down to a stop to get some proper heat into the brakes and burn the rust off.

Regards.

Portzy.