Duke48

Hi,
I'm replacing the ORPV in the oil cooler, during last 2 years I had an instance when oil pressure dropped to 1-2 bar and wasn't building at all with rpm. However, there is a second valve: 94410713900 https://www.rosepassion.com/en/parts...3YD8xt-2yEo-c8
In the topics this one is usally not mentioned nor my mechanic says this one is as important. Why is that?

Le_zOU

also, don't buy there at first glance, google the PN to find cheaper part (they're known to be expensive)
94410713900

speednme

I agree always do a search. I must add though, I've been buying from Rose Passion for the past few months. Not only have they have had the lowest price, but their shipping method is also very fast. Actually, faster than most domestic retailers.

Duke48

No worries, I don't buy from rose passion, I buy from a friend and I have very good prices, he told me that he can get me that one for circa 500$ if he remembers correctly, I already ordered the oil cooler OPRV, will see if the pressure changes. Right now I have 2 bar when hot, 4.5 at 2k rpm, but it doesn't raise above that when hot. However I got this instance of not building pressure at all 1.75 bar no matter what and the pressure is degrading over past few months, I used to have 3-3.5 bar when hot, I'm on the 3rd pressure sensor.
I would like to know the reason why this OPRV is rarely referred.

But if we are digressing @speednme which of your 911s current and former is your favorite to drive?

V2Rocket

My understanding (from years ago, so its fuzzy) is that valve is a combination oil flow restrictor and check valve in the cylinder head.
The cylinder head mechanism doesn't need that much oil flow, but the valve prevents all the oil from bleeding down after engine shutoff to keep the hydraulic lifters pumped up and quiet for the next start.

The 928 cars got DOHC heads first and have an issue of too much oil going to the cylinder heads and not draining down fast enough, to the point that liquid oil will come out the PCV ports after extended high-rpm runs.
I don't think the 928 DOHC models ever got this valve, possibly because a 928 might not be driven at those high RPMs for as long as a 944 4-cyl might be. The 944 DOHC head is a near copy of the 928 head otherwise.

tempest411

Did you verify the pressure with a mechanical gauge? For the money I think it would be worth it. If it is the valve, perhaps the piston is just hanging up on a burr that's developed, and can be removed.

harveyf

There are two reasons why. That valve, as Spencer point out, at best reduces oil flow to the head. I suspect if it was totally left out, you would not see a 2-3 bar reduction in oil pressure. Remember, the oil pressure situation is composed of multiple "controlled leaks" at the various bearings, all of which develop the back pressure that the oil system sees and that registers on the gauge. There are no "uncontrolled leaks" in the head such that flow to the head needs to be regulated with a porportioning valve.
The other reason is that it is a lot of work/expense to go after that valve.
As noted, plumb in a mechanical gauge and see what you are dealing with. I cannot really envision any mechanical factors other than the OPRV that would result in random drops in pressure. But electrical factors? You bet. Rule them out with a mechanical gauge.
BTW the last iteration of the OPRV by Porsche is a typical German overengineered device. The critical moving parts are contained in a precisely machined housing. Maybe the original spring/plunger design could "stick" but I think the last one is very robust.

https://newhillgarage.com/2013/06/25...tem-explained/