Serious annoying brake issue (Cayenne 18Z on A3 3.2)

[MathiasS]

I have been struggling with my Cayenne 18Z brakes for 2.5 months now.

Cayenne 18Z
MBT 2 piece 350 x 34mm rotors
Stahlflex lines
OEM Fluid

They are rebuilt and painted completely by Porsche in Holland, Initially I fitted EBC Greenstuff pads but from the moment I fitted the kt I noticed that after some hard abrubt stops it seems my whole car is falling apart up front and I hear a clacking clunking sound...

Searched for ages but then my mate who's a mechanic took a drive and when I brake very hard and then go over a slightly bump road it starts to rattle and clunk (not a bit but very hard) but when you "slightly" let your foot rest on the brakes Ssssshh perfectly quiet !

We discovered the pads are not being pressed firmly by the pistons after hard braking , when I undo the pin on the caliper in the middle my pads just fall out

If I let the car stand for a awhile after the symptoms occur the noise goes away and it seems the pads are being pressed again also if I drive the car from home to work very gentle and don't brake hard I don't hear the pads rattle or clunk but after 1 hard stop it's completely messed up and everything sounds loose

I then tried new Ferrodo pads, another flush in the system and also new rattle springs on top ( OEM Porsche) also fitted those sticky pads on the pistons that supposedly stick on the pads and make em quiet but all with no affect


And the weird thing is they brake like hell ! I Even when the kit is making the extreme clunk clunk clak clak noises over bumps and roads it still bites like hell but it's making me crazy !!!

There are no leaks , everything is bone dry inside the caliper, no damage , new fluids, pads etcc


Is this due to the stock master brake cylinder or is there something wrong with my calipers ?

Quick pic to show off how good they look on the car

Would be great to have this fixed cause we have checked EVERYTHING on the calipers/discs/pads etc and I'm really desperate and if I can't find it I'll need to take the brakes of the car and search another setup.

 

[Chillout]

Abs coding maybe noticed that while exploring vcds

 

[MathiasS]

What do you mean ?

Did I need to do something with Vagcom after I installed em ?

 

[Chillout]

I think it's not fact just a thought that different callipers are coded differently I could be typing S@&t here but I noticed that in abs coding it lists a few brake option from memory that is but I am sure someone knows on here.

 

[MathiasS]

Ok let's see what the brake guru's have to say about this. from all I'm reading there seem to be alot of knowledgable guys over here !

 

[wuta3]

Not bothered about your brake issues mate, forgot everything you said when I saw the pic. They look epic I want. Now.

... However, does make the back set look like they are off a BMX

 

[Sevv]

out of curiosity unrelated to your problem but did you need to modify / use the 18Z calliper brackets or did you just use the one already on the car to the hub?

stunning picture by the way your gonna make me buy a set esp when they are cheap

 

[MathiasS]

Thanks for the positive comments guys

Yes indeed, I was planning on sourcing Boxster 4 pot for the rear and making a custom bracket and handbrake but first I wanna solve this problem cause it's making me crazy

 

[c_w]

Forget hooking your car up to a computer to diagnose a rattly pad

The pads sound like they are a little short for the caliper. I would search other forums using this caliper and see what pads they are using. If the pads aren't tall enough the disc just gently lifts the pad as it moves and then they hit the top and drop and the process continues causing the annoying rattling. I have some race pads in my other car that have no rattle clips so they are like this (with the windows down it sounds like something is going to fall off, but lightly touch the brakes and it goes silent!). But I doubt a Cayenne would have rattley brakes from the factory so there must be either a pad or anti rattle shim that will solve your problem.

A light brake application, as you found, stops the noise completely as it stops them moving. You probably get a thunk when you reverse and stop too?

 

[MathiasS]

Hmm I have EBC greenstuffs here that were on there + we also tried OEM Porsche pads for the Cayennes that my buddie uses regularly at his shop and they are all the same

Its only after a really hard stop + there's also the factor that the pads just slip out when you undo the center pin , I have been told thats not normal either

 

[Chillout]

Hmm I have EBC greenstuffs here that were on there + we also tried OEM Porsche pads for the Cayennes that my buddie uses regularly at his shop and they are all the same

Its only after a really hard stop + there's also the factor that the pads just slip out when you undo the center pin , I have been told thats not normal either

Do you have excessive travel in your brake pedal before they bite and are your discs the correct thickness for the calliper.

 

[MathiasS]

No pedal is prety instant. After bleeding them with the machine pedal feel was very good

What I do notice is something weird but when I'm standing still with the engine in P or in N the brakes feel mushy, but thats maybe normal ?

My discs are 33.4mm and 32.8mm , one of them had a slight warp and needed to be skimmed a bit. But before the skimming the problem was there too when they were both around 33.6-33.8

 

[Chillout]

What is the minimum thickness as per spec though cant explain the mushy feeling while stationery as the vacume applied should be fairly consistent .

 

[MathiasS]

They come new as 350x34mm and say min is 32mm

But I do see JHM uses 350x32mm rotors with their cayenne kit so this "shouldn't" be the issue I guess

 

[phil76]

I think i read you have but did you get the porsche anti-rattle shim pads or did you fit them with which ever pad your using ? i know euro car parts sell them and you normally fit them to most porsches,if not it can only be some kind of anti rattle clip missing or something,is your set up the one where there are two pins that run through the pads and caliper per-side ?

 

[MathiasS]

I have those shims on every piston + also fitted a new set of OEM anti rattle springs

I have one big pin in the middle

 

[MathiasS]

Anyone ?

It seems nobody has a solution to this problem. It's getting to the point I don't wanna drive my car anymore ...

 

[daz.h]

could it be a fluid movement from the stock master cylinder ? them are very big calipers and will need a serious amout of fluid against the pistons to work correctly.

 

[NHN]

I also thinking MC upgrade needed as N8 had to do this for his big brakes, I wonder if the pistons are receding to much allowing for the pads to rattle as such, how many shims have you placed on the pads, test purpose only, see if adding more shims helps the issue of rattling, its not the fix but it helps to analyse the issues & work backward, but MC is probably related.

 

[MathiasS]

Where can I get an uprated MC or can I use an OEM part and are these just bolt on or do they require any modification on the 8p?

 

[Chillout]

I find this one a bit odd because if the mc is too small it moves less fluid to extend the pistons but on the other hand it would also retract less could it be you need to adjust the brake bias so the fronts do even more kinda baffled as I have never seen a big brake kit for a conversion with a master cylinder

 

[MathiasS]

I just placed another set of Cayenne calipers. just an unpainted set of second hand calipers my buddy has for his A3

The symptoms are EXACTLY the same... So my brake calipers are not the culprit

 

[Chillout]

I just placed another set of Cayenne calipers. just an unpainted set of second hand calipers my buddy has for his A3

The symptoms are EXACTLY the same... So my brake calipers are not the culprit

I think it could be setting as in the abs module I have seen different coding for calipers

 

[MathiasS]

Can anyone verify this ?

I checked codes in the ABS section but nothing came up.

I think I'm gonna have to take the Cayenne brakes off , put back my OEM brakes and sell em if I can't find a solution ...

 

[c_w]

Looking at this from a mechanical point of view, the pads don't rest on the disc in order to stop rattling. In normal sliding claiper the inner pad will have a spring spider clip on the back which slots inside the piston and the outer pad usually has a spring that keeps pressure on the pad from the caliper on to the carrier. In calipers like yours there should be a spring tensioning clip that is held on by a pin or two across the caliper keep tension on the pads inwards (towards centre of hub).

The only thing that moves the pads towards the disc is the piston(s). How far they move or retract is down to the hydraulic system IMO.

 

[c_w]

I also thinking MC upgrade needed as N8 had to do this for his big brakes, I wonder if the pistons are receding to much allowing for the pads to rattle as such, how many shims have you placed on the pads, test purpose only, see if adding more shims helps the issue of rattling, its not the fix but it helps to analyse the issues & work backward,

That doesn't make much sense to me as the position of the pad against the disc is the same regardless of the effective thickness of the pad itself.Ie as the pad wears they don't fall out, the pistons move further out to compensate.

 

[MathiasS]

I have those springs fitted , also tried a pair of new OEM Porsche springs. Also tested a different set of calipers so it must be hydraulic system ...

Weird that nobody has a problem with the Cayenne 6 pots cause my stock brakes worked perfectly fine and from the moment I fitted the cayenne's I am experiencing this problem.

Do you think the Master cylinder is the culprit here ?

 

[c_w]

It's a wierd one. If the master cylinder was "too small" for the caliper giving long travel, it shouldn't make any difference to the piston retraction. When you say there's a gap and the pistons are loose, isn't there a lot of pedal travel before the start working?

 

[MathiasS]

No not really, nothing noticable

My buddy drives a bone stock A3 3.2 so I went back to back and my pedal feel is good

Theres not really a gap, when you loosen the shaft in the middle and the springs you can just take out the pads, they are not firm in there like with most brake setups I have seen when you change pads or take of calipers

 

[c_w]

It could be the seals are stronger at retracting the pistons? A small part in the piston retraction is the piston seals twisting. I've read this about Porsche calipers before, but this does not explain why they might not rattle in a Porsche!

 

[Chillout]

Hi I can see different front calliper options on the abs module on my 3.2 maybe one of the other options would suit your calliper s better just a stab in the dark though.

 

[MathiasS]

Anybody know the part nr for the TT-RS master brake cylinder?

 

[NHN]

Tandem Brake Master Cylinder is 8J2611021F

 

[NHN]

Any updates as to the issue?

 

[Grant-s3]

Have you managed to fix this problem ?? I have as set of Z18 callipers coming for my 8P S3 next week and wonder if I will come across this problem?