For the last while my car seemed to have gone off song, but the decline was insidious and gradual so I didn't notice it straightaway. It was more of a feeling than a definite issue for me.
It was boosting as per 'normal', with no boost leaks, no misfires, or other types of 'usual' faults.
But I decided to replace the vacuum hose from the by-pass valve to the small silver metal pipe running behind the cam belt wheel at the top of the engine. It could be spun around and I have the suspicion it may not be airtight at each end of the pipe.
So I sought to replace the old hard 'brittle' rubber pipe, as part of this process of cutting off the 'use once squeeze to tighten' oem jubilee clips, I needed to undo and take out the black bypass valve.
While it was out I 'tested' the valve by sucking on the small pipe coming out of the top of the valve. It didn't appear air tight, so I tried another spare one I had in the garage. I never throw out anything.
I put everything back together and the car boosted like a fried car.
I reckon if the improvement in frying is 4, my car had dropped back to an improvement of 2, but with the new valve it is now back to a 4.
It now gives all of the boost earlier and the boost is very consistent. Previously the level of boost on the dash read out was not quite consistent avery time, and not quite as high as it should have been. It is now higher and consistent each and every time like a machine.
So in summary while the old bypass valve was 'working' and allowing the car to boost but not properly. So I would suggest you either test yours or just replace it with a new one , they are not too dear, especially considering the improvement obtained with my 'new' one.
The earlier boosting, and the higher boosting straightaway makes the car much nicer to drive. The car was like a car with a cold, and now it is back to good health.
Hope that experience helps others.
It was boosting as per 'normal', with no boost leaks, no misfires, or other types of 'usual' faults.
But I decided to replace the vacuum hose from the by-pass valve to the small silver metal pipe running behind the cam belt wheel at the top of the engine. It could be spun around and I have the suspicion it may not be airtight at each end of the pipe.
So I sought to replace the old hard 'brittle' rubber pipe, as part of this process of cutting off the 'use once squeeze to tighten' oem jubilee clips, I needed to undo and take out the black bypass valve.
While it was out I 'tested' the valve by sucking on the small pipe coming out of the top of the valve. It didn't appear air tight, so I tried another spare one I had in the garage. I never throw out anything.
I put everything back together and the car boosted like a fried car.
I reckon if the improvement in frying is 4, my car had dropped back to an improvement of 2, but with the new valve it is now back to a 4.
It now gives all of the boost earlier and the boost is very consistent. Previously the level of boost on the dash read out was not quite consistent avery time, and not quite as high as it should have been. It is now higher and consistent each and every time like a machine.
So in summary while the old bypass valve was 'working' and allowing the car to boost but not properly. So I would suggest you either test yours or just replace it with a new one , they are not too dear, especially considering the improvement obtained with my 'new' one.
The earlier boosting, and the higher boosting straightaway makes the car much nicer to drive. The car was like a car with a cold, and now it is back to good health.
Hope that experience helps others.
Ive ordered my DV it's already here and it now ends in 710 P. 
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