Brake noises again

[europeanme]

mines exactly the same...hence me trying to find plastilube....

anyone??...

[Alistair E]

Quick revival for this thread. I've had the same problem ever since I bought the car nine years ago. It originally came with what I believe were porsche 928 4 pots. I replace the pistons at reasonable expense to no avail. I eventually picked up some boxster s calipers. Same noises from them. It seems to disappear with a new set of pads but once they've worn down a bit it re-appears. As with a few others, it appears to come mainly from the nearside.
I take it that everyone with this issue is running some kind of porsche 4 pot caliper. Do you all have braided hoses. Is there anyone out there with porsche 4 pots that doesn't have this problem.
I was wondering whether it may be related to the diameter of the pipework or a master cylinder issue. Does the porsche master cyinder have a bigger or smaller diameter.
Apologies for the rambling but it's really gettinfg on my **ts at the moment. I've even changed the wheel bearings which was a fun job.
Anybody any thoughts?

Alistair

[Colesy]

I've got this problem as well!

When hot the near side caliper sequels like hell, the noise goes away with a dab of the brakes and is reduced when turning to the right. I assumed that a piston was sticking, checked that but they all seem to move freely.

So any miracle cures would be great!

[urS6Tom]

I'm not saying this article has the answer, but it's an interesting read and there may be more relevant information elsewhere on the site

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml#

Tom

[Colesy]

When I investigated the noise my first idea of what it might be was that a piston was sticking as when I had fitted the caliper one piston was quite stiff and took a bit more effort than the others to push fully back into the caliper. So I removed the inside pad and pumped the brake pedal twice to get each piston to stick out a little. I then proceeded to push each piston back into the caliper and repeated this several times in an effort to completely free up the pistons. After doing this it stopped squealing for one 40 mile trip. But, the next day it started squealing again...



So I've got a few questions and ideas which I'm going to put out there to see what people think:

What ensures that the pistons retreat far enough when the brake pedal is released?

I would guess that the brake bomb/cylinder is designed to displace the ideal amount of brake fluid to pull the pistons back?!

If the 996 calipers require greater volume displacement could this be the problem?

Or would the length of the brake lines affect the ability of the system to move the pistons back due to more displacement being required?

It seems strange that so many people have the exactly same problem as I do, ie NSF sticking and vibrating. Could this be because that caliper is further away from the bomb? (not that I know whether it is)

Could it be caused by older/less stronger brake systems which are fine for the standard system but not for the 996's.

These are just my ramblings really after thinking about this for a while. It's probably quite obvious I don't really know what I'm talking about, but if someone could invalidate my points/ideas and maybe put a few new ones out there that would be great!

Cheers

[Alistair E]

I did hear an odd one recently where the internal walls of a flexihose had broken down and was acting a bit like a one way valve to some degree. It caused the pads on one side of the vehicle to wear out fairly quickly.
This seems unlikely in this case as there are quite a few of us with the same problem. It would seem to be some mismatch between our hydraulic system and the porsche four pot caliper. I can't believe porsche cars have the same problems with these calipers.


Alistair

[Colesy]

Just thought I would consolidate the suggestions so far:

Rubbing dust shield when hot
Caliper pins not filed short enough
Knackared/loose wheel bearing
Lack of lubrication
Corroded brake lines
Some sort of hydraulic system problem


If there was a problem with the brake hydraulic system how can different parts of this be tested?

Any other ideas

[archiboy24]

I'm shocked that no one has found a solution to this long-standing problem. Just to be sure that we're talking about the same thing; on the highway mostly, after about 20 minutes of driving at 100+ km/h my 996's start to hum/drone seemingly from the driver's side. I can feel the vibration through the pedals and steering wheel. A slight tap of the brake or wiggle of the steering wheel and the sound goes away for a moment but returns shortly after. I know the bearings are good and the pistons in the monoblocks are good. What's going on here? I can't imagine the Porsches have this problem, or do they?

[PistonBroke]

I fitted the 996 set up a few weeks ago - brand new audi discs, new anti squeal shims and new Ferodo pads. The calipers were not brand new but had had very little use. When I first used the car afterwards there was no noise or vibration at all. Not long after I took it on a 300 mile mainly motorway trip and everything was still quiet. However on the return journey it started making a kind of groaning humming sound which sounded like it was coming from the left front wheel. Touch the brakes and it would stop momentarily or turn the wheel slightly to the right and the same would happen. Sometimes it became pretty loud. I haven't used the car that much since then but it seams OK when it's cold but does makes a noise sometimes but nothing like as bad as it was.
I hadn't thought about wheel bearings until it was mentioned on here as a possible cause, the original floating calipers would of course mask any play in the bearings and as a slight movement in the steering wheel stops the noise, (without touching the brake pedal) that could make sense.
It's interesting that it's the same side for you - front left ( drivers side on a LHD car ).

[Alistair E]

Is there anyone on here running a similar setup who isn't suffering this problem? Maybe someone could setup some kind of table for us to fill in with our brake specifications. That way we could see if there is a common factor. A quick list of what could be included
Master cylinder, hose and hardline setup, model of caliper, disc dimensions.

Just another thought, does the RS2 run the same master cylinder as the ABY's and 3B's?

Alistair

[Colesy]

Found my problem!

Had the car back in the garage this weekend and think I have sorted the problem for now!

Had a good look at the discs and pads on both sides to start with. Pretty much immediately noticed that the discs had been getting hotter on the inside edge as they were slightly discoloured. So had a closer look at the inside edge and noticed that there was discloured ring around the middle of the disc.

So guessed that something must be rubbing when hot as when cold everything was fine. So had a look around the disc and the only thing that could have been rubbing was the very top of the dust shield which hadn't been bent out of the way enough. So gave both sides a tweak with a screwdriver to bend them well out of the way.

Signs so far are good, drove for 100 + miles yesterday and there were no problems at all, not even a squeak!


It's also worth adding that I replaced all the copper slip which I had used initially with Ceratec which was recommended by a forum member as a good alternative to Plastilube - bought from here: http://cgi.ebay.co.uk/ws/eBayISAPI.d...=STRK:MEWNX:IT

I also checked that all the caliper pistons were functioning as they should and according to my dad they were. ie they pushed out when the pedal was pressed and retracted slightly when released & when one piston was pushed in the others would move out.

Also checked the wheel bearings (by giving the wheel a wiggle) and both sides had very little play so seemed fine.

So hopefully this info will help someone else although I doubt all these problems are as simple as mine.

Good luck everyone getting yours sorted.

[Colesy]

It's back!

Went on quite a long trip over the weekend and after about an hours driving the offside brakes started to squeal!

So the problem has jumped from the nearside to the offside but it's definitely the same problem...

When warm they squeal like hell, it stops when you are turning at a certain angel either way and when the brakes are dabbed.

Anyone have any suggestions of what could be causing this?

[filip.krticka]

As it was written, noise is only vibration. If you are using DS2500 or similar material with high friction coefficient, let’s say it’s common. You can reduce it by adding small chamfers. How? Grind the edges of the friction area, you are increasing specific pressure. If it doesn’t producers add the antivibration shims. Producers are using various type of material to reduce noise.
Sport friction materials like DS2500 are sometimes noisy, especially after the heavy thermal load. Pads are glassy after that.
Just listen all rallye cars ... they are noisy )

[filip.krticka]

And the dust makes noise as well, but it's common sense...

[s2carlo]

I had exactly the same. Tried everything I could find on the forum. Nothing worked
I ended up having the calipers overhauled, after that (now for half a year) no noise anymore