Need help with the N54 exhaust vacuum system- ISSUE RESOLVED

[Maniac]

So, nice day, up at dawn jet washing the patio, vacuuming the house etc...

Speaking of vacuum, I then moved on to the car. Reasonably straight forward to remove the required boot trim, quite a lot needs removing to get to the solenoid valve.

So got it opened up, started the car and there's the lightest of vacuum on the inbound feed (from the engine). Nowhere near enough to pull the valve on the exhaust. I put tissue as suggested on the pipe that feeds the exhaust flap valve and this only just stuck on before falling away as engine revs fell to normal.

So it seems it's the feed from the engine. So I now need help to find where that feed enters the engine bay or if there are any intermediary nodes first. If I can get to the other end I can test that vacuum and identify which pipe or engine bay component is faulty.

So niggles up to 6 years old and from there things start to get a bit tricker.

 

[Maniac]

And as requested the full oh dear what do the neighbours think result of the failed flap at start up. It's also quite a bit louder around town etc. I enciurage you listen on something with reasonable bass reproduction to get the full 'oh dear'

[youtube]OqkfRiYn6Cs[/youtube]

 

[john-e89]

Ah the vacuum's from the engine, I thought it had it's own pump. Anyway can you get it up on a ramp and trace the pipe back or how about going to a dealer and asking to look at a vacuum pipe on a schematic, they usually show them in situ as i'm sure you know.

 

[Maniac]

I'm a bit further forwards thanks to the n54 tech forum. The pipe runs from a T on the brake vacuum line. Found it, the -ve pressure from the T is high, but at the other end of this pipe in the boot it's hardly anything. So I expect it's either blocked or kinked somehow. It's wound in with the loom so there's no doing anything with it. Worst case I'd have to run a new pipe to it through the car, against the original loom.

I've run out of time now but I'll take apart the boot again next weekend and pressure test the single pipe from the engine to the boot. That should answer / confirm more.

 

[john-e89]

Yes if it's one complete pipe you'll have a hell of a job finding where the problem is, might even have rubbed a hole in somewhere from vibration over the years, what a PITA. Best of luck and let us know how you get on please, it's all very useful info.

 

[Maniac]

Issue resolved.

With the help of a vacuum gauge and vacuum gun I've resolved the exhaust flap issue. It appears the exhaust actuator had some crap in the vacuum feed. I got the same vacuum reading in the engine as I did the outlet of the solenoid in the boot. So I forced air through the system/vacuum actuator and thus appears to have resolved the fault and the exhaust actuator is now working normally.

 

[shotbybothsides]

Good to know, thanks Maniac