[335DEE]

I've just noticed a nice little visual test for the large actuator.
If you suspect you are having pressure controller issues due to lack of , or loss of power then you can start by doing this simple test

From cold ( not tested when warm )

Open the bonnet , start the car , let it idle for 1 to 2 seconds then stop it and take the key out.
Look in the engine bay and if your pressure controller is working it has withdrawn the actuator rod. Wait 30-50 seconds and the system releases the vacuum slowly releasing the actuator rod.
If this works , then you have tested your vac pipe , pressure controller and actuator diaphragm all in one go.
Unfortunately testing for the small turbo actuator isn't as simple as it's buried too deep.
If your actuator creeps over this 30-50 second period , then you have vacuum issues and need to start with replacing the vacuum hoses Of which there are plenty of threads on how to do this.

When replaced , you can run this test again to check

Video below of what I would deem a functioning system

[dxb335d]

Ok to do once in a while but not a great idea to shut down the motor from cold when the revs are high.

[335DEE]

Originally Posted by dxb335d

Ok to do once in a while but not a great idea to shut down the motor from cold when the revs are high.

sorry , maybe i wasn't clear and have adjusted the post. No need to rev the car at all .

Press the start button (no accelerator) , let it idle for a count of 1 or 2 and turn off .
Reason for this is to just get the engine to generate some vacuum. The engine is still cold , so if you want to poke about in the engine you are not going to burn yourself.

When you take the key out , the pressure controller still holds on to the vacuum for 30-50 seconds before it runs out or the system goes to sleep.

[dxb335d]

When you start your car from cold it revs higher for 30 secs or so, you don't even need to be in the car. It's best not to shut down the car during this cold start cycle. So try not do it too often.

[Mustard3]

Just tried this and glad to say the actuator rod returned after about 25 seconds.

As for the small turbo actuator rod, maybe an endoscope would work, they're under £30 on Amazon....

[confused.com]

how accurate is this test in diagnosing issues? Mine returns approx 1m 5secs after switching off the car. Do i have an issue? Will it show up as a fault code?

[335DEE]

It's not an accurate test , it's a quick test

If the actuator was creeping slowly outwards over this time period or if it didn't move at all then there would be a vacuum leak or something else wrong. This test doesnt identify a particular part of the system .. it function tests the system as a whole. If your actuator holds steady till the ecu goes to sleep and releases the vacuum then I would suggest you have no issue. That can only be said for the large turbo actuator.
The small turbo actuator is a bit harder to test because the actuator is completely hidden from view.

http://www.realoem.com/bmw/showparts...85&hg=11&fg=45