Humming/rumbling brakes

[Doingitsideways]

I recently changed the brakes on my 850 TDi, Eicher discs and pads all round, Pagid HB shoes, new anti-rattle springs and pins on the rear calipers, recon calipers all round.

Done probably 1000 miles on them so nicely bedded in now.

However, for the past 100 miles or so I've been getting a loud humming/vibration when the brakes get hot which rings through the whole car when braking, which fades off once the car's stopped.

As it's coming through the whole car, logic tells me it's something from the back?

Very bizarre.

I seem to remember having something similar on my first 850 donkey's years ago but can't remember what it was.

I've had a quick look but can't see anything loose or untoward.

Everything copper greased up etc.

Any ideas anyone?

[hillmangt]

I would guess its something to do with handbrake shoes binding when brakes heat up. Had similar on a BMW 3series when dealer adjusted handbrake for MOT only to have to replace shoes a few week later as they were burnt out. They would only bind when brakes were warm.
Good luck
Andy

[Doingitsideways]

Only happens when braking though, and only seems to happen from about 15-20mph to stop, then the humming dies off a few seconds after stopping.

When it's bad the whole car vibrates and nearly shakes the fillings from my teeth!

Surely if it was something to do with HB shoes it would do it all the time once warm as the disc/drum expanded with heat. The service brakes are a completely separate system with a caliper on the disc rather than the HB shoes in the integral drum?

[Doingitsideways]

Hmm...

No-one any other ideas on this?

[Shinsplintz 101]

Warped discs. My van had a set on the rear a while back- new but wonky. They were manufactured out of true by about 2mm which cause the thrumming noise. Sent them back & got a better brand. Only way of checking is to use one of them dials you strap to the hub & turn the wheel through full revolutions - watched the garage do it.

[Doingitsideways]

Yeah, I'd thought of that Morgan.

Just don't get why the humming carries on for a couple of secs once stopped.

[Shinsplintz 101]

Harmonics?

[mr marshalltown]

Just an idea but have you checked your abs reluctor rings they might be corroded and making the abs pump work overtime as it won't be sending a true signal which may be more noticeable at lower speeds my 850 used to do a similar thing on the front and that's what it turned out to be

[craigoodwood]

how bout as the heat from the disc is expanding it thus pushing in the pads too much and its the harmonics of pad on disc...

[mr marshalltown]

Just another idea for you might be wrong but on the safe side I'd also check the caliper mounting bolts to see if they have worked a little loose now brakes are bedded in and had some heat in them and then cooled a good few times you never know
I'm sure it will be something simple nearley always is i find
Good luck

[LeeT5]

how bout as the heat from the disc is expanding it thus pushing in the pads too much and its the harmonics of pad on disc...

if that were the case then the caliper would be binding and the disc would get very hot.

[LeeT5]

Just an idea but have you checked your abs reluctor rings they might be corroded and making the abs pump work overtime as it won't be sending a true signal which may be more noticeable at lower speeds my 850 used to do a similar thing on the front and that's what it turned out to be

Sounds probable and more likely the cause.

[LeeT5]

I recently changed the brakes on my 850 TDi, Eicher discs and pads all round, Pagid HB shoes, new anti-rattle springs and pins on the rear calipers, recon calipers all round.

Done probably 1000 miles on them so nicely bedded in now.

However, for the past 100 miles or so I've been getting a loud humming/vibration when the brakes get hot which rings through the whole car when braking, which fades off once the car's stopped.

As it's coming through the whole car, logic tells me it's something from the back?

Very bizarre.

I seem to remember having something similar on my first 850 donkey's years ago but can't remember what it was.

I've had a quick look but can't see anything loose or untoward.

Everything copper greased up etc.

Any ideas anyone?

Use CeraTec brake grease.

Copper slip won't last 5 minutes and it starts to break down when it gets hot.

[hillmangt]

I am quite baffled by this, the fact that it carries on once stopped. I would suggest its possibly a pad that's coming off its backing or been contaminated but that wouldn't continue once stopped. The ABS pump may be causing some pulsing of the brakes but highly unlikely and would it continue once stopped, unlikely. It may be worth pulling the ABS fuse if that's possible on your car and see if it still does it without the ABS working.
Wheel bearings and propshaft joints can all vibrate but not at a standstill!
I would jack up each wheel in turn and check for all the usual signs of wear and check nothing is rubbing when they are spun.
Other than that I'm stuck for ideas.
Just a thought. After I changed the brakes on my Merc It developed a banging noise when braking hard. I checked everything and stripped and refitted the whole lot but could find nothing so took it to my local merc specialist who said straight away it was failing suspension bushes and it only shows up with the braking force applied as the inside of the bush fails first and cannot be seen and is only detectable with the car on a ramp and use of a large crowbar! It may be nothing to do with the brakes!
Hope you get to the bottom of it and let us know.

Best of luck
Andy