FredR

Hi,

Do any of you wise chaps happen to know why I might have received a "brake booster failure" alarm last night? I was accelerating- presumably under some boost- when the alarm appeared. I backed off- the brakes felt just as powerful as ever and when I stopped and restarted the engine the brake pedal dipped as the engine fired.

I understand these cars have some kind of "vacuum support" sub system that automatically kicks in when under boost- presumably to ensure you have instant braking rather than some notional short delay whilst vacuum is established.

i dare something [vac line/ vac pump?] may have taken a dump- then again [hopefully?] maybe a false alarm.

Thoughts/suggestions on likely cause/solutions/costs much appreciated

Much as I know my 928 inside out I know little about this amazing vehicle as yet.

Thanks in advance

Fred R

bigbuzuki

Take a look at post #6

http://www.renntech.org/forums/topic...ting/?p=224473

FredR

Thanks for the link- sounds as though that is the likely source of the problem- managed to catch my pal who is the main dealers chief mechanic- a common problem at this age it seems.

Apparently to replace that pipe altogether with a new pipe[s?] you have to remove a few more bits and pieces but nothing too drastic.
Seems Porche have not learned too much about how to spec pipes for high temp regions!

Not too comforting knowing you have a problem in the braking system. I was also advised that if you leave the old pipe in there it may eventually cause further damage to the vac pump.

If I was going to do a repair along those lines I would consider a strip of duct tape- seems a bit more resiliant.

The joys of Porsche ownership! Had to use my 928 to go to work this morning!

Regards

Fred

FredR

The vac line was cracked and had come away from the spigot it sits on just in front of the firewall.bulkhead whatever. I am sure it could have been temporarily fixed up but once plastcis start cracking like that I suspect it is only a question of time before something else goes. Unfortunately there are two complete assemblies and [surprise surprise] you cannot purchase the component parts.

As I took the thing in this morning the car also experienced what felt like a low down misfire- the main dealers advised this is symptomatic of this failure- sounded a bit suspect to me- anyone got any comments on this?

Regards

Fred

bigbuzuki

Regarding the misfire, get them to check out your coils for cracks whilst it's in for surgery. If any are cracked, change all of them.

FredR

Gdday Sport,

The coils were replaced not too long ago by the PO [a very decent Aussie chap now back down under]. No guarantees of course but she seems to be running fine once more.

The main items I kind of figure fall into the guaranteed replacement category were the coils, the Cardan shaft and the cooling pipes- two out of the three done. Doubtless there will be a raft of smaller other such items.

My first 928 snapped its drive shaft 3 months after I purchased that- ouch!

The joys of Porsche ownership. When you buy any s/h Porsche I advise folks to price the car as though you are going to spend $2.5k in the first year of ownership- assuing it is in top notch condition and previously owned by a real enthusiast, add that to the purchase price and if you do not need it consider yourself fortunate. Looked at in that perspective a factory extended warranty package does not look too bad- if you can get one- not sure what they run at these days- something in the region of $1500 for a year? Do the maths and roll the dice type of thing.

Regards

Fred

ignited

In addition to the bulkhead leak another was found by way of a smoke test done by a local garage. It seals the entire vacuum system and pumps vapor into an open port. Leaks can't hide from this test! The other leak, much smaller, was the check valve underneath the engine's torque arm which is in front of the brake booster. The bulkhead leak was massive and was plugged to discover the other much smaller leak in the check valve.

abushark

Hello
Shame on Porsche, expensive super cars built with cheap material.
Average every two months I am having new break down new defect new problem with my Cayenne
It is silly, hardly have peace of mind, every two months new story,
Yesterday "Brake booster failure" warning light comes on,
It is a common defect, it is a vacuum leak,
Crack in Vacuum hose, I fixed it with epoxy glue and tape, and then drive the car for 10 minuets the warning massage disappear
The cracked vacuum hose location on the passenger side right behind the coolant reservoir tank
Do not worry it is easy job to fix yourself.
See attached picture

[IMG]file:///A:/Car%20Service%20Manuals/Porsche/Re%20pair%20Pictures/IMG_5252.JPG[/IMG]

abushark

here are some pictures

jumper5836

Thanks good info. I have had that warning come on but it was due to the secondary air system blowing the fuse in the engine compartment fuse box. This happened after I pressure washed the engine bay. Didn't think I was putting to much pressure on it but something got wet and it kept blowing the fuse until a month later. I figured it finally dried out and the short was fixed.

porsche3.2

When its cold in the mornings, I get the brake booster alarm when I touch the brake pedal, after a while it goes away.
Any ideas please?, I've read this, but I can't see the brake booster pipes in my car in that area.

No error messages and have garage has plugged in diags, no faults displayed

https://rennlist.com/forums/cayenne-...ing-light.html

Thanks
2009 GTS 4.8

Dilberto

I was able to unplug the vacuum pump connector and run error-free for a year. Brakes actually felt BETTER, while not over-boosted.

v10rick

Need to be specific about the year and model.

GenI turbo only engines used both manifold vacuum and a vacuum pump for the brake and evap. emissions system.

GenII uses only the engine driven pump for all systems requiring vacuum.

porsche3.2

Hi 2009 GTS 4.8 957

nodoors

You just pulled the power harness from the electric pump and there were no errors?!