Ok, perhaps this is not as fixed as I thought it was. The day after I thought it was fixed, I started seeing a new behavior, I wanted to give it a week to see if a pattern would emerge and it has. This is what I see now, consistently, day after day:

1. First start of the day, no booster warning light. Within 1 mile, the brake booster failure warning appears and does not seem to clear after any amount of driving.
2. Once I park somewhere, shut down, and then later restart the car (could be as little as 5min to hours later), the error is there on start, but then clears itself in only about 300yrds of driving.
3. For the rest of the day, no matter how many trips I go on or their duration, the error will not return.
4. Next morning. See #1 above.

I thought that maybe it's temperature related and that perhaps there is a seal, or the pump itself works better once the engine compartment is warm, but I don't know. Over the weekend, I started the car for the first time of the day in the afternoon when it was 75F (according to car thermometer) rather than the 55 or so that it usually is for my first start of the day, and the pattern was exactly the same. Anyone seen anything like this? Any ideas?

cheers,
c

 

Did you try the smoke test?

Sounds like you fixed the worse leak but another is lurking somewhere.

 

Have not smoke tested yet, I thought I was done.

Just to add to the craziness... I didn't discuss the issue coming back intermittently until I had good data, because I figured it would simplify troubleshooting. I reported here after the car did THE EXACT SAME THING every day for a solid week. So what happens yesterday? Within hours of posting here, the behavior changed. The light came on in the afternoon (which it has not done all week since I sleeved that cracked line) and now has not gone out after several trips. So either that vacuum line repair has failed, or some other line has failed, OR and this is just a WAG, maybe it's a dirty electrical connection on the pump in addition to the original leak?

I've had multiple light bulb warnings on this vehicle since I got it. One was an actual bad bulb (driver's cornering light), all other light messages have been good bulbs with dirty contacts. In ALL cases, the car has reported a bulb failure when cold (first drive of day on a chilly day) never when hot. This has happened about a dozen times in 2 months. When I've tried to identify the bad bulb using blinkers or emergency flashers they usually all worked. Eventually, the drivers front turn didn't light once (a few weeks ago) and I cleaned the bulb, bulb socket and headlight assy connector with contact cleaner and it's been good ever since. Same thing recently happened with front passenger side turn and the bulb finally failed to light last thurs (was triggering error but still working so I couldn't find it). Same deal, I cleaned all with contact cleaner, and now all is well. A surprising amount of crud came off the contacts onto a q-tip considering that everything looked clean. So, all of those warnings (except cornering light) were false positives due to dirty connections and they ALWAYS triggered the warning when cold, never hot. It has me wondering if maybe the booster pump also has a dirty connector, so I cleaned both halves of the connector this morning with contact cleaner (Booster warning light has been on continuously since yesterday afternoon and it's been cold here). I wonder if all these electrical gremlins that these cars are known for has something to do with Porsche changing connectors? Maybe they changed the plating material or something? My 24yo 968 which spent the first several years of its life in NJ outdoors with rain, snow and salted roads never has any electrical connector issues. My 11 year newer Cayenne, which has lived exclusively in warm, dry, snow-free Los Angeles and Phoenix seems to have lots of connector issues.

I'll report back.

cheers,
c

 

GEN1 Cayennes were known for electrical issues but not the type you are experiencing with the lamps .

Any chance this was a flood car? PO pressure washed the engine bay?

The good thing...CE light remains on so you should know for certain when the gremlin is fixed.

 

I think power-washing is likely. I've got leaky valve covers that weren't leaky when I bought it just two months ago. The front turn signal bulbs are the only electrical gremlins I've seen, I had some codes early-on but they all went away and haven't returned after the 4yo battery was replaced. I'll order a smoker today, at this point I think that it's either a small additional vac leak as you said, or a bad/intermittent air pump. The pump is only 2 or 3 years old (based on the sticker), and it pulls good vacuum when I tested it, but if that leak has existed a long time (maybe since the 2 or 3 years ago that they replaced the pump) perhaps it's had a hard life.

I've never seen a CE light. Only the "Brake Booster Failure" and the occasional "check turn signal bulb"which was definitely just crud on the terminals.

cheers,
c

 

Referring to a previous post in this thread...

The turbo engine brake booster vacuum is supplied by both the engine manifold vacuum and pump. The pump is a booster when the manifold vacuum falls below a fixed threshold.

Engine vacuum should be near maximum at idle when parked so the pump should not be running at this time. The booster failure light should be extinguished as well.

BUT this lamp may be one that requires extended drive time to extinguish.

What happens if you clear the error with the scan tool? Does the lamp remain off while parked at idle?

 

It has never come on while idling, although it if came on during the previous trip, it would be there immediately after start and clear itself only after driving (post sleeving). With the original vacuum leak (before sleeving) If I cleared it with the scan tool, it would be off when the car first started and for several minutes of idling, but would reappear within 4mi of drving (0-50mph). After sleeving (when the behavior changed) it would turn on during the first drive of the day in less than 1mi then clear itself within 300yrds on the second drive of the day and remain off for the entire rest of the day regardless of the number of trips or their duration.

It has always turned on or turned off while driving. The state of the light has never changed while idling.

cheers,
c

 

Since we don't know the factory spec for pump activation this makes it a challenge to isolate.

Is there not enough engine vacuum?
Is the pump too weak to maintain the desired vacuum level?
Is there a leak causing a loss of vacuum?
Is the sensor that detects the vacuum defective?
Is it a combination of any of the above?

I would drive around with a vacuum a gauge attached. Compare the readings when the booster warning lamp is on and off.

 

I just went for my second drive since cleaning the vac pump terminals and the light has still not gone out, so something changed for the worse yesterday (it has been on continuously since yesterday afternoon). It's a bit too hot in the engine compartment right now for poking around, in 10 or 15 mins I'll see if I can spot what's changed. Maybe the tube that I sleeved has cracked beyond the patch, or maybe the fuse blew for the vac pump, or maybe the pump died. It was definitely happier for a week.....

cheers,
c

 

Ok, I just checked a few things. Vac pump fuse is good (#16 30a thankfully under hood). I pulled the pump again and checked my sleeve repair and it's good. I also checked all the hard lines that branch from it on that side and they're good too. I discovered that if they had just mounted the vac pump backwards in the same bracket, in the same place, that they could have eliminated 2ft of hard lines, about 8 bends, and the one necessary tee would be on-top and visible instead of being buried under that weird side engine mount. The more I look at this vehicle, the more things I see that appear to have been designed purely to increase billable hours for the service department (sorry, I'm an engineer).

Anyway, the one thing that looks suspect is my repair to the tee directly in the back on the firewall behind the intake manifold. Those connections are not as tight as they could be. Does anyone know if a leak there will give the "Brake Booster" error, or is that a separate system? It has tubes that disappear under the cosmetic valve covers, as does the booster system, but I don't know if they connect to each other or not. I made repairs to both at the same time last week when my problem partially went away, so I don't know.

Does a decent vacuum system diagram exist for this vehicle?

cheers,
c

 

I just bought a smoke machine, and I also bought a silicone replacement hose from CosmoRacing. I'll resume the fight against vacuum leaks when these items arrive.

This is the smoker I ordered:
https://www.ebay.com/itm/172575041384

I offered $140 and the seller accepted. I like that this type has a built in air-pump. When I'm working on my car, my air hose is usually connected to my lift (for the safety release) so a built-in pump means I don't have to connect and disconnect air lines (garage is very tight).

cheers,
c

 

OK, I've got my smoker and it's time to fight the final battle with this stupid vacuum leak. Where do you guys hook up the smoke? The vacuum pump would be the easy place, but all the check valves point the wrong way. The brake booster itself is obviously the best choice, but it's got a hard plastic 90 that plugs into one of those hard plastic lines (the one that transits behind the false firewall). So, if I disconnect there, which would be difficult due to the placement of the brake fluid reservoir, I think I've got a good chance of breaking one (or both) of those fitting turning my fake booster warning into a real problem (brakes work great). There's also a uncapped t-fitting under the 4.5l name plate, but the check valve in that is biased in the wrong direction. Where's the best place to insert the smoke?

cheers,
c

 

Still haven't found any leaks.

Here's a question: Is there any way to tell if the car is throwing the code because it's detecting inadequate vacuum from the pressure sensor, vs detecting that the vacuum pump is drawing too much or too little current?

cheers,
c

 

Have you tested all of the check valves? If any of them are passing backwards, you could be getting some intake manifold pressure when on boost causing a high pressure on the vacuum side.

 

Good point. I'll check them.

cheers,
c