Front brake squeal.

[AndrewT]

My car is a 2.9 987.2

A couple of months ago I had all discs/pads replaced by a local Porsche Specialist. I've probably done only 200-300 miles since then.

In the last couple of weeks the nearside front brake has been making a squealing noise (not particularly loudly) which sounds to me as though the back front pads are moving in relation to the piston as the disc rotates. This appears to only happen when the brakes are warm and the noise will go away while I hold my foot on the brake pedal.

My guess is that a light smear of copper grease between the piston and pad may solve the problem, and I can do this myself rather than have to take the car back to the specialist, however I just thought I'd mention it here in case anyone else has any suggestions as to cause and cure.

I note that in some circumstances the PSM keeps the pads lightly in contact with the discs so I'm hoping the issue I have is simply a matter of anti-squeal lubrication rather than a PSM problem.

 

[Motorhead]

Andrew,

Copper grease should help to reduce the squeal. Did your specialist also replace the anti-sqeaul shims when they replaced the pads?

As far as I know, the braking system is lightly pressurised continuously to keep the pads in light contact with the discs to minimise brake activation time.

Jeff

 

[kasspa]

Hi Andrew,

I replaced the pads, discs, shims & wear sensors on my 996 4S in May & initially had a little squeal when applying light pressure in slow moving traffic etc.... it took about 700 miles for this to disappear & I can only assume that it was at this point where the pads & discs were bedded in 'together'

The pads shouldn't move about on the shims as they have adhesive backing!!

It also improved the first time I washed the car after replacement, I guess this also got rid of a lot of dust!

hth

Regards

Paul

 

[AndrewT]

Thanks Jeff and Paul. I assumed that the anti-squeal shims were replaced but I ought to check with them.

 

[spyderman]

A recent post (possibly on another forum) suggest that you should not use copper grease because if it gets on the piston seals it can create a hot spot that will ruin the seal. There have been other suggestions that being conductive, copper grease can also adversely affect the ABS sensors. Whether either issue is true I have no idea, but given the system is suppose to work properly without grease, I have to wonder if its not best to find another solution, such as replacing the anti-squeal shims on that corner.

The idea that the pads are in continual "light contact" with the discs is wrong because they would overheat and wear extremely quickly.

Chris.

 

[AndrewT]

Chris, my comment about the pads being in light contact with the discs was based on this page about PSM [link=http://www.porsche.com/uk/models/cayman/cayman/safety/porsche-stability-management-psm/]http://www.porsche.com/uk/models/cayman/cayman/safety/porsche-stability-management-psm/[/link] where it says "Also included with PSM are engine drag torque control (EDTC), the precharging of the brake system and brake assist. If you suddenly release the accelerator pedal, PSM automatically prepares for your next action: the braking system is precharged so that the brake pads are already in light contact with the brake discs. Maximum braking power is therefore achieved much sooner." On re-reading this statement it would appear that under normal driving there will be very few occasions when the pads are in light contact with the discs.

I've spoken to the specialist who fitted my brakes and they said that my model of Cayman does not have anti-squeal shims, (I have since verified this by referring to a PET diagram), and they have suggested that I take the car to them for a quick check after which they can advise what, if any, remedial action is required.

Thanks to you all for your replies.

 

[Motorhead]

Chris,

I think you're right and that my interpretation of the brake precharging was incorrect. Andrew's comment that precharging only occurs in advance of a potential emergency braking event makes more sense.

Andrew,

Interesting to note that your 2.9L 987.2 doesn't have the anti-squeal shims because my 2009 3.4L 987.2 does. Although they're not shown pictorially on the PET, there is a reference to damping plate grey cast iron brakes (Qty 4) which are to be used in conjunction with the brake pad repair set on the Cayman S.

Jeff

 

[MrDemon]

[link=http://www.eurocarparts.com/ecp/p/car-accessories/car-maintenance-accessories/maintenance-fluids-and-greases/grease/?526770250&0&]http://www.eurocarparts.com/ecp/p/car-accessories/car-maintenance-accessories/maintenance-fluids-and-greases/grease/?526770250&0&[/link]

thread closed

 

[Motorhead]

Ta D. Not seen that stuff before - very useful.

Jeff

 

[AndrewT]

Thank you MrD for the link, and thank you Jeff for your comment about the damping plate.

I'll report back when I've visited my 'indie' in a couple of weeks.

 

[AndrewT]

I took my car back to the Porsche specialist yesterday and on the way there not a squeak was heard from the brakes, probably because it was only a short journey mostly on motorway which required minimal use of the brakes.. The specialist raised the car and span the wheels but no odd noises were heard - typical! The did confirm this time that my car does have anti-rattle shims because it is a 2.9 and not an older 2.7.

On the way home from the specialist the squeaking started so I believe that it begins when the brakes have had a reasonable amount of use which heats the pads/calipers/disks.

Initially I noticed that the squeak occurred after a light application of the brakes after I released the brake pedal. The noise went away after a few metres until I next used the brakes. The more frequently I used them the longer the noise continued but always a light pressure on the brake pedal silenced it but as soon as I released the brake the noise came back. I'm fairly certain now that the problem is a sticking piston in the caliper.

As I now think I understand the circumstances which cause the noise to occur I'll get the squeak started then return to the specialist for their opinion.

I'll report back here when I've done that so watch this space.

 

[kasspa]

Hi Andrew, how many miles have you now done since brakes were replaced?

As my previous post, it was a good 700 miles before mine were bedded in & a good wash to get rid of all the dust & whatever they may be pretreated with.....

Don't forget to always take it for a spin (not literally) after washing to dry them out to stop premature corrosion...

Hth

Paul

 

[AndrewT]

Hi Paul, I've probably done 300 miles +/- 100 since the brake pads/discs were changed, I've not yet been back to the specialist with the squeak/squeal present.

Just to be clear though, initially on a journey there is no noise at all when either braking or cruising, after several miles when I assume that the pads/discs/calipers are warm/hot the noise will start after I've braked and released the brake pedal. Forgive me if I've misunderstood you but I've assumed that the noise you are referring to is generated by the pad onto the disc during braking?

By the way the pads and discs are just standard Porsche equivalent parts, Pagid I believe.

Thanks, Andrew.

 

[Motorhead]

Andrew,

From what you're describing, rather than brake squeal it sounds as though one or a number of pads are rattling around when everything warms up. Probably best to get the brakes fully up to temperature just before visiting your specialist and hope that you can reproduce the problem when the car's on their lift; although bear in mind that it's impossible to reproduce actual driving conditions in that configuration.

If you've not had actual Porsche parts fitted, it might be worthwhile checking that the correct equivalent Pagid items were supplied and fitted. Slight dimensional differences perhaps.?

Hope you get it sorted.

Jeff

 

[kasspa]

Hi Andrew, the slight 'squeal' on mine was as I was releasing brake pressure & coming to a halt, I had no issues under braking....

I don't brake hard anyway & was wondering if that was part of the problem....

As previous post, it took a while to disappear, approx 700 miles or so but has been fine since... I think you'll find it will settle as pads & discs surfaces wear into each other...

I replaced mine with Textar pads & Sebro discs.

Keep us posted with any further info

Regards Paul

 

[AndrewWebster]

At a guess, I would say that the backing plate has come away from the back of the pads

 

[AndrewT]

I replaced the pads, discs, shims & wear sensors on my 996 4S in May & initially had a little squeal when applying light pressure in slow moving traffic etc.... it took about 700 miles for this to disappear

Paul, it's been some weeks since I've heard a squeal from my brakes so it looks as though you are right, it just needed a few hundred miles to bed-in - I'll keep listening though just in case the noise comes back when the ambient temperature rises in the spring/summer.

Andrew

 

[kasspa]

Hi Andrew,

Excellent news.... I'm sure you'll find they'll be fine now, just takes a while for both surfaces to 'mate' together..... even tyres aren't perfectly round, hence the weights for balancing....

Merry Christmas []