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I'm testing for air leaks between my AMM and my throttle body inlet using the approach suggested in the FAQ under Volvo Special Tool Designs.
I'm using a tire inflator with gauge to feed compressed air into the turbo inlet using the tool, while blocking the air coming out of the turbo outlet. With a minimal amount of pressure registering on the tire gauge (I believe it's much less than 5 lbs.; maybe 2-3 lbs.), I get excessive air leaking out from between the CBV cover and the turbo body. I would have expected that when the CBV cover is bolted down, it should compress the outside ring of the CBV diaphram against the turbo body well enough to prevent air from escaping, at least up to 10 psi.
I realize that if I put enough pressure in the turbo inlet, it will eventually overcome the force of the CBV diaphram spring, and push the CBV diaphram away from the turbo body. This however should only allow air to get from the turbo inlet to the turbo outlet without passing through the turbine blades; it shouldn't leak past the outer compression point between the CBV cover and the turbine body and leak to the outside. (Not at least under 10 psi, I would think).
I'm assuming that either:
a) my CBV diaphram needs replacing. Maybe years of oil have degraded the rubber to the point where it doesn't form a sufficiently thick "gasket" on the outer ring. (There is no leak through the diaphram however; it doesn't appear to have any tears. The only leak is apparently between the diaphram and the turbo body, or the diagram and the CBV cover, or both).
or
b) The CBV isn't supposed to be torqued fully against the turbo body, and someone did this at some point, bending the outside flange of the cover, so now when it's torqued down, it doesn't compress the outer ring of the diaphram sufficiently to seal.
The FAQ mentions that replacement diaphrams can be purchased from D&W Diesel; does anyone know of any other sources? (The FAQ indicate that it can't be bought separately from the dealer; only in a $300 rebuild kit).
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David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto
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