E46 M3 front wheel hot, droning noise during braking

[gav2612]

2001 E46 M3
This is driving me mental so hopefully someone can help. For the last few months, I have had a louder droning noise from the car than usual when braking(I know the cross drilled brakes generally drone a little as normal) The discs and pads were pretty worn all round so I replaced them with OE discs and red stuff pads. No marked improvement and if anything may even be a bit louder with the harder pads.

Then things started to get worse, after heavy braking there would be a slight vibration through the steering for a few miles which would then disapear. I also noticed the drivers side front wheel much hotter than the passengers side. I immediately thought the caliper must be binding, but on checking with the wheel off the ground no noticeable difference in resistance from the other side. Assumed with the heat in the hub it must then be the wheel bearing, which at 72,000 miles would be past its best anyway although there was no visible play in it. Replaced with OE bearing, still no improvement.

I hate to feel like I am throwing parts at a car for the sake of it, and hate admitting defeat, but having now dealt with all the wear and tear items, short of replacing the caliper I am struggling. Any thoughts? Any way the caliper may stick once hot but not when cold? The car has always cooled down substantially before I have jacked it up and check the resistance in the front brakes

Thanks in advance
Gavin

[chrisr29]

Build up of rust/brake dust in the caliper - usually at the top of the cylinder above the seal. Has no affect when cold but as caliper heats up and everything strarts expanding, the reduced clearance caused by the rust build up exasperates the situation causing the stated symptoms.

Either strip and clean the caliper or fit an exchange unit. If your mechanical skills are limited theh go for the exchange option.

[Y282]

chrisr29 said:

Build up of rust/brake dust in the caliper - usually at the top of the cylinder above the seal. Has no affect when cold but as caliper heats up and everything strarts expanding, the reduced clearance caused by the rust build up exasperates the situation causing the stated symptoms.

Either strip and clean the caliper or fit an exchange unit. If your mechanical skills are limited theh go for the exchange option.

Spot on.

[gav2612]

Fantastic thanks guys. Also read of the possibility of a collapsed brake hose causing a similar effect with the fluid not returning properly. thoughts on that? Would I need a rebuild kit to clean up the cylinder, or just a case of pushing the piston back in and cleaning round the seal with brake cleaner? Reasonably handy with a set of spanners, and changed the discs, pads and bearing myself, so should manage OK
Gavin

[chrisr29]

Unlikely brake hose - car not really old enough.
It's a case of removing the piston from the caliper, removing the rubber seals and cleaning away the rust from the top of the cylinder. I use a Dremmel type tool with a rotary wire brush. You then need to clean everything meticulously before reassembly and lube with a little rubber grease.

Done loads of these now on all sorts of cars. Saves a fair bit of cash over exchange calipers but is quite a bit of work to do properly.

An echange caliper will prob cost circa a hundred quid on an M3.

[gav2612]

Ok checked out a DIY on a diferent car makers forum and understand now. will need to remove the piston and clean out the brake dust/ crap round the seat. Can I get away with re using the seals if OK, or will I need a rebuild kit?
Will probably just replace the hose while I have the caliper off for piece of mind anyway
Thanks again for the advice

Edited by gav2612 on Thursday 13th October 00:28

[gav2612]

Ok checked out a DIY on a diferent car makers forum and understand now. will need to remove the piston and clean out the brake dust/ crap round the seat. Can I get away with re using the seals if OK, or will I need a rebuild kit?
Thanks again for the advice

Edited by gav2612 on Thursday 13th October 23:42

[chrisr29]

Should be ok to reuse the seals - examine them carefully for wear though. It's a fiddly operation if you've never done it before. Also check the piston for pitting, any signs then reassemble the caliper and get an exchange unit.

[Cemesis]

I think a refurb caliper is only around £80. I'd go for that option (and did on my M5 replacing both fronts).

[stuthemong]

You want to attend to this sooner rather than later or you'll have cooked your disks too.

Mine went blue. They went in the bin. That said, my calliper was a lot worse than yours, after 5 mins of driving I'd get the 'wobble', which was the calliper/brake cooking themselves.

[gav2612]

A belated thanks for all the help guys. Picked up a new caliper and changed the brake pipe while I was at it. An hours work and all seems good again! I do however still have quite a drone off the brakes under heavy braking although none of the other symptoms. Not sure if anyone else has experinced this increased noise with the redstuff pads I have fitted all round?

Gavin