Volvo 780 wiggeling front brake calipers

[BertoneP]

Hi,

Both my front break calipers move slightly and make a knocking sound if I wiggle then back and fro. They seem to be a little "loose". Is this normal?

When I break a suttle noise "clonck" is heard when I press the pedal. But only the first time...if I release the pedal and then press the break again, it does not make the noise...only first press/break.

What can I do to remove this?
Tried tightening the two caliper bolts, but does not help.

Thanks for your help.

[Laird Scooby]

From your description, it sounds like the caliper guide pins are worn.

Also you don't say how soon after starting it you press the brake pedal and it gives a clonk from the front caliper? If it has ABS (seem to recall it does) then the ABS goes through a self-test procedure that cycles the ABS modulator and pump - if you happen to press the brake while this is happening, it makes the calipers clonk as there is a sudden surge in pressure but only very briefly so you don't actually feel it as braking action - you might feel a slight jolt on the pedal as well.

If this is within the first 30 seconds or so of starting, it's normal, any other time and further investigation is needed.

Every 7xx i've had has done this, every Rover 827 i've had has done this - they share the same Bosch ABS-2E system

[BertoneP]

Hi Dave,

The clonk noise is when the car is on the open road, I.e. not when just starting. So I believe it is not related to any initial ABS test sequence.

Not sure what you mean with guide pins....the caliper has no other bolts than the two that fastens it to the wheel. Inside the caliper the brake pads do not have any fastening clip either.

This is how it looks like

https://www.volvopartswebstore.com/s..._driveLine=417

Thanks for helping.

[Laird Scooby]

Originally Posted by BertoneP

Hi Dave,

The clonk noise is when the car is on the open road, I.e. not when just starting. So I believe it is not related to any initial ABS test sequence.

Not sure what you mean with guide pins....the caliper has no other bolts than the two that fastens it to the wheel. Inside the caliper the brake pads do not have any fastening clip either.

This is how it looks like

https://www.volvopartswebstore.com/s..._driveLine=417

Thanks for helping.

The guide pins are item #9 in this pretty picture :



They wear, they get dirty, they stick - all of which in different ways can cause various noises and clonks from the calipers and/or pads.

Most people remove them, give them a through clean with a wire brush, lube using either copper grease, silicone grease or red rubber grease and refit. This often cures a lot of the problems.

While you have the caliper in bits, give the carrier a good wire brushing where the metal backing of the pads contacts it, likewise the metal backing on the pads themselves and if there are any burrs on the edges of the metal backing, take these off with a file. Smear a very light coat of copper grease on the metal edges of the pads where they contact the carrier and on the metal backing where the caliper pistons and/or the caliper "fingers" contact the pads.

If this lot doesn't cure it, you'll have to renew the guide pins.

[BertoneP]

Ok, thanks. Will try to lube these pieces.

It seems the guide pin nr9 can not be purchased since it has no reference number.

Thanks again!!

[Laird Scooby]

Originally Posted by BertoneP

Ok, thanks. Will try to lube these pieces.

It seems the guide pin nr9 can not be purchased since it has no reference number.

Thanks again!!

They're NLA from Volvo but not ebay :

https://www.ebay.co.uk/itm/Volvo-740...6/331834681881

Fairly sure those are the right ones but double check against what you've got - measurements are on the pics.