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Recommended Posts

  • 5 months later...

Huge thanks all for this diagnostic aid. The big warning lamp 'Brake Booster Faulty' was ominous and expensive looking but with the help of this thread i fixed it easily and in a satisfying manner.

I found the cracked tube where the spigot enters at the 'JB weld' in the second photo above.

My first approach involved heavy duty metal tape, but the engine heat is intense there and the adhesive turned to mush in a few minutes.

My second approach was even easier to execute. I removed the entire tube from the silver colored booster pump to the spigot - about eight inches in length but with a few fittings - and replaced it with a cut length of vacuum hose from O'Reilly car parts. I used a hose clamp (jubilee clip) at each end, and it all felt rather robust. Total cost was $1.49 for the length of hose plus a few cents for the clamps which were part of a big assortment box i already had (very useful to have around)

The warning light extinguished itself after a minute or two, no programming required.

Thanks especially Voodoocat and Topgun.

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  • 3 months later...

I removed my torque brace to replace the bushings.  In doing this I cracked one of the lines to have the warning light come on.  I decided to replace the whole group of vacuum lines.  I bought it from ECS Tuning




To replace the group of pre-assembled vacuum tubes I did the following.


1. removed plastic cover plates

2. removed three points were the vacuum lines attach and left in position for removal later, two points are clips you can use a pliers to move and reuse.  The third is stuck on there pretty good.  I made a cut on the old part with a razor to remove.

3. removed torque brace

4. Then there is a torque brace mount.  I removed torque brace mounting nut closest to engine

5. The other nut it way inside toward the fender, so i lifted the torque brace mount as if it was a wrench.  you need about a half inch to work the old vacuum line out and new vacuum line in under that part.

6. Put all the vacuum connections on and reassembled.

Edited by greg schroeder
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  • 10 months later...

I know it's an old thread but having a problem with this too..

Mechanic says he checked the hoses aas per my advise and all is good so I bought a pump (2nd hand one) and the problem is still there..


Makes me think the hoses need rechecking? IS there anything else which would cause this fault guys?

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  • 1 year later...

You're not gonna believe this. I think I've found it !!! it was almost invisible but a quick blow job lol indicated the split might be hiding under this rubber hose.. got that welded, put another hose over it and the fault cleared.. fingers crossed !!! going to contribute to this forum for sure . sorry had few shots of jack daniels to celebrate no lights warning on dashboard after 2 years of trying lol


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  • 2 months later...

HI does anyone know where each end of this hose connects I've been plugging leaks with fuel pipe from auto zone now my pump for the brakes which one of these cables connects to is always running, could it be snapped behind the firewall under the panel which needs to have the windscreen wiper removed 1st 

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5 hours ago, Pkcayenne said:

HI does anyone know where each end of this hose connects I've been plugging leaks with fuel pipe from auto zone now my pump for the brakes which one of these cables connects to is always running, could it be snapped behind the firewall under the panel which needs to have the windscreen wiper removed 1st 

Bit hard to tell but I believe he is holding pipe 13 which connects to hose 14 in the diagram attached. 

Hose 14 then connects to the pump 19. 


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8 hours ago, Pkcayenne said:

Hi Lewis I have a pipe going through the firewall under the pump number 19 on the picture. To get to the other side I have to take off the windscreen wiper and the black panel on the passenger side.

The pipe 13 is the one that runs behind the firewall to the brake booster. The diagram is not showing its actual length I don't think. I can't find any other diagram of any other pipe so it must be 13. 

Some pictures is always good to share! :-)



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1 hour ago, Pkcayenne said:

Can someone check if there vacuum pump ticks ?

Pulsing sort of noise yes but should not run all the time which means leaking pipe, connections or the brake booster is leaking internally itself. You get psm failure light as well? 

Looking back through my service history or previous owner Porsche replaced the pipes and brake booster and master cylinder after psm light came on according to the workshop report. 

Have you tried to suck and blow the pipe 19 when you pull the hose off the vacuum pump? Check valve in the line should mean you shouldnt get anything either way with just your mouth. If you can blow or suck air then remove the whole pipe and test it off the car maybe split or maybe check valve is stuck. If no leaks then its the brake booster. 

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  • 1 month later...
  • 1 month later...

I am in the same boat now. The bad thing, i am 1000 km away from home. Why this kind of things need to happen always far from home. I inspected all tubes like explained here. Couldnt find a crack. The brakes are behaving as usual. Until now. I have to drive back 1000 km. What to do? Any idea? Thank you

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8 hours ago, ekstroemtj said:

Whats going on here:
















Whats you battery voltage like? 


Also I would be checking for broken wires of the engine loom which run from the DME to pretty much all the items of the fault code. 


Clear the codes and recheck straight away with engine running. If the codes immediately pop back up then wiring is my guess. If the codes come back after a while of driving then very strange low voltage, DME or accumulation of errors. All very strange but as we know with the cayenne even a few corroded wires in the foot well under the carpet can cause a load of warnings, lift up the carpet and see if any wires are damaged or wet, take pictures. 

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