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dump valve internals

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Well, I thought I had a more major issue than it turned out to be.

After the work identified by the factory (not all of the list) I found the dump valve wasn't functioning and the fuel tanks were pressurising. I eventually traced part of the cause to a trapped hose that leads from the charcoal canister to the inlet manifold and dump valve, so that has removed the pressurised tank issue, and occasionally the dump valve worked, but generally didn't.

I stripped the dump valve last night and found it stuck. I've cleaned it and the piston will now move when pushed (when dissembled), but the rubber ring that seals round the piston seems very loose. I appreciate it's sealing against the cylinder so has to be a bit loose, but does anybody know how large it should be compared to the piston?

Is a service kit available (I guess that would be the two rings and some lubricant)?

(I can expect some of the replies)

What lubricant is normally used. I cannot use silicone grease as a trace may go into the engine during operation, thus ruin the O2 sensor. What about rubber grease?

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Simple, I don't have a non-dump valve connector to go between the charge cooler and the intake plenum, and I don't have a suitable blanking plug.

I swapped it out to a recirculating type yesterday afternoon and that one was working fine, dumping every time I came off the throttle while on boost, the one I had on was only doing so occasionally, so i'll plumb in the recirculating one properly once I've finished working on the radiator system (I guess the car is off the road for a week or so now).


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Generally when you need to lubricate a rubber seal, you should use a bit of brake fluid. Not a large amount, just enough to wipe a thin film on it. Brake fluid will lubricate the rubber without breaking it down as the case with petroleum based products (oil, grease, etc).

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