Paistab, et need klapid tekitavad omajagu segadust. On olemas ka kaks ühes tükis olevat ülerõhu klappi, mis on erineva pikkusega.

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Väljavõte rennlisti teemast.

Ok, I went back and looked at all of Porsche's TSB's and found TSB 19017 (Oct. 9, 1990). It clears up the confusion. The one piece OPRV's (both types) do indeed have two o-rings. However, only the o-ring on the tip can be replaced without disassembling the OPRV. The other o-ring seals the body (tube) part of the OPRV to the 24mm screw-head. The TSB says that you can disassemble the OPRV by putting the screw-head in a vice and pulling the body (tube) out by hand. Doing so, however, destroys the internal o-ring sealing those two parts. You then need to replace that internal o-ring (oiled) and press the body back into the screw-head with a "handpress or vice."

So, if you just pull out the OPRV and then reinstall it, without disassembling it, you should only replace the one o-ring on the tip (since the other o-ring is still installed inside the assembled OPRV). When it goes into the block, you will only see the one o-ring. I can supply additional info from the TSB upon request. The chart below shows the part numbers of the o-rings. The upshot is that you want to use 999 107 145 40 on the end of the 86 retrofit valve, and 999 107 144 40 on the end of the 87 and later valves. If you take the OPRV apart and need to also replace the inner o-ring, use 999 107 146 40 for the 86 retrofit valve and a second 999 107 144 40 on the 87 and later valves.






http://forums.rennlist.com/rennforums/9 ... ldo-2.html

Selles teemas ilmneb kuidas OPRV klapp võib mõjutada õlirõhku.
http://forums.rennlist.com/rennforums/9 ... -oprv.html

Selgub, et kui OPRV klapp on isegi natukene lahti, siis käivitamisel õlirõhku ei teki. Antud juhul oli klapp natukene lahti jäänud, kuna sulgemist takistas väike metallitükike.

Hea info OPRV ja vabalthingava 944-ja õlijahutuse kohta
http://www.944online.com/pdf/oilcoolertech.pdf