v10rick

As I mentioned in your previous thread, purchase a vacuum gauge to confirm the vacuum is holding steady under load.

The battery dying while testing should not happen. Sounds like the battery is not charging or its defective. You should measure 14V at the jump posts just above idle.

vandal968

V10rick,
ok, will do. This one look ok?


Where do I tap into the system? I'm assuming I can connect it somewhere close to the master cylinder and snake the tube into the driver's window while driving around?

It charges fine, the battery died because the engine was off with ignition on while reading/clearing codes. Are you supposed to be pulling codes with engine running instead? I thought it was engine off but ignition on.

cheers,
c

v10rick

The Amazon gauge will work as long as it has the adapters to plug into the vacuum line.

If there are no leaks the vacuum should read the same anywhere you connect the gauge. Just pumping the brake pedal while parked should be enough to diagnose what is going on.

I have used my Durametric scan tool for over an hour with the ignition on and the engine off with no issues.

The battery should not drain while reading codes all day long.

nodoors

I went back and checked my records. I got the Audi part for $35. The only difference between the two seemed to be that the Porsche part had a polished finish and the Audi's was matte. Otherwise they were identical.

vandal968

Nodoors, was that a used or new part for $35? Got a part #?

cheers,
c

vandal968

Ordered the OTC vacuum/pressure gauge:

Also ordered the mityvac vacuum pump kit:

Gauge is here tomorrow, so going to try to get this properly diagnosed rather than just ordering the vac pump (although I'm pretty sure it's the pump). This will also let me fix some vacuum leaks on the 968 that I know exist, but that I've never gotten around to. Something about staring at a bid red warning message every time you drive that really motivates in the Cayenne. Amazing to me that Germans have always made crap vacuum and fuel lines going back to post WW2 era (I used to collect old VW's). Yet somehow, they make great A/C lines. My 968 is 24 years old and has absolutely frigid air conditioning even on 120F Phoenix days, never had service of any kind, never even been recharged.

cheers,
c

ProgRockJunkie

Kind of a pisser. It's not a big deal, but there shouldn't be a price point where I'm too lazy to avoid getting ripped off. I got lazy on that one and didn't even look for a VW or Audi part number. Did you post this up somewhere? It's great when people post up the two corresponding part numbers so it's easily searchable.

v10rick

Here is a diagram from Porsche. Its apparent that the turbo engine vacuum system differs from the NA engine.



Compared to the NA engine this should be easier to diagnose. #4 are check valves, one or more could be leaking.

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. The booster pump should NOT run while parked, assuming no leak, the engine is warm and parked near sea level.

To diagnose...

With the engine off pull the manifold vacuum line and connect the Mityvac there. Pump vacuum to the max, the reading should remain stable. If not check for a leak or defective check valve.

With engine off pull the vac line to the pump and connect the Mityvac there. Pump to the max, the reading should be stable. If not same as above.

With the engine off pull the line to the brake booster and connect the Mityvac there. Plug both the line to the engine manifold and booster pump with a golf T or ? and pump the Mityvac to the max. The reading should remain stable.

Let us know the results.

nodoors

This is the Audi part number:

8E0927317A


This pump is utilized extensively in their line from the A4, A6, A8, S5 to the Q7 (sister of the Cayenne) so you should find a ton of cheap used ones or sale. I can't remember if mine was used and the auction page is no longer available, but it is possible. It's been working like a charm.

It might help you find the VW part number. Someone really needs to develop a reliable cross reference system. It is pretty absurd that for example diverter valves for VW are $18 and for Porsche they are $60 for the exact same part!

ProgRockJunkie

Damn, that one got me, too. I felt good about not being stupid enough to buy the billet performance replacements, but still got taken buying OEM.

vandal968

Ok, so I've got my test gear. Anyone know of a formal procedure for testing the vacuum pump/ brake booster system? I'd like to attack this tomorrow.

cheers,
c

v10rick

I posted the brake system diagram and theory of operation on your other thread about this.

Look there for trouble shooting suggestions.

Two threads from a poster about the same problem often leads to confusion.

deilenberger

Rick is correct. Point me to the other thread and they shall become one..

v10rick

Don here is the title of other tread from the same poster...

Cayenne code whack-a-mole brake booster error is back

vandal968

Exactly What I needed. Thank you V10rick.

Sorry about the duplicate thread, not sure what I was thinking.

cheers,
c