Reply With QuoteSo I shied away from doing the job myself and booked my vehicle in at FST Automotive in Penrith. I showed Frank the VCDS fault code printout, walked him through what I had done as far as diagnosing the problem was concerned, and then told him I thought it was the vacuum actuator attached to the turbo (labeled "1 Vacuum unit" in the diagram below) that was faulty (being very clear that I was not TELLING him what the problem was as I am not a mechanic, I was just passing on the info in case it helped him).
He took a quick look at what I had, asked me a question or two, and immediately agreed that was the likely culprit. So I dropped it off with him on Wednesday and collected the vehicle yesterday afternoon. She drives beautifully again! VERY HAPPY!
Now, I am one of those inquisitive types, so I decided to take the faulty actuator apart to see if I could tell what had failed (even though I was fairly certain it was a small hole or split in the diaphragm), and also to get a better idea of how the unit works. Here's the faulty actuator they removed.
First thing I did was cut off the plastic cover off the top (after trying to see if there was any way of removing it without cutting it... there wasn't)
Not much to see there, so I bent the tabs clamping the diaphragm to the body and folded the diaphragm up (inside out) to see if I could spot the hole/split. The only damage I saw to the diaphragm was from my cutting it open - which makes sense as the hole would have had to be very small to make the high pitched whistling sound I heard.
Under the diaphragm is a spring to push the rod back up when there is no vacuum. Now it makes sense to me how the default position is to have an under-boost situation if the actuator fails as the spring would push the actuator rod up to set the vanes to their least aggressive position if the diaphragm fails. Previously I just assumed that the rubber diaphragm would have returned to it's natural shape itself when not under vacuum, in which was I wondered how safe the engine would be if the rubber diaphragm split or tore. Now I know!
To my surprise, the diaphragm is not make of a thick rubber like I expected. It is a fiber re-enforced rubberised flexible sheet material. I guess that would be more robust and reliable than a thicker rubber diaphragm, but it also makes sense that there might be a very small hole in it that caused the whistle rather than a more major tear.
Anyway, the new actuator is now fitted and with it in place you'd never know that it had been replaced. Good job by the guys as TSF imo!
Originally Posted by ian
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