Well, the good news is I finally found the really small leak in my brake system that had me topping up the fluid about every 10,000 miles.
The bad news is that I found it is the PCRV that's bolted onto the fender below the fluid reservoir. The source of the leak became obvious yesterday when it became a larger leak!
Apparently, the design is such that it will slowly extrude the O ring seal inside causing fluid to escape.
Of course, I found this as I am preparing for a 2500 mile trip South for Christmas next week......
The new part is on order, but will probably not arrive in time, so the question is:
Can this be repaired?
Seems like if it has an O ring that has an issue, it can be rebuilt?
Anyone done this? Know what the O ring size is??
Cheers.

I think GeorgeB is the only person that has mentioned a similar problem, I've not heard of anyone else that has even had cause to look at it.

I had to chuckle about your answer, as RR Toadhall told someone long ago much the same thing.
Said that in all the years he worked in the shop, no one ever had any issues with one.
He was actually shocked to find several instances of reported failures.
On further research, so have you......
https://www.rangerovers.net/threads/abs-pressure-reducer-valve-help.345016/
Jos Geuze answered the question on O ring size, as he re machined and rebuilt his.
EPDM o-ring (ID is 22mm and 2 mm thick)

I have the replacement coming so not a problem for much longer.
Going to look at the old one with an eye toward refurbishment if I can get the O ring..

It's probably only a common issue on P-38s that have 500k+ miles........

Got the new valve from LK8 and it is in the dreaded Britpart box.....
Had a look at it, and I see now the flaw in the design.
O ring is already squirting out of the gap between the cap and the base casting.
This is a Chinesium pattern part, so even worse!
I will not knowingly trust my safety to CCC pattern parts......So, back it goes!
So, for 12 bucks, I have bought 30 (minimum quantity) of the correct size and formulation O rings
and will just fix the one I have.
I have a couple of photos of the new defective part, and have failed to be able to attach them....
I know there is a trick to it.....Post them somewhere and link to them??
In any event, I will report back if I succeed, also I will be offering the 29 other O rings for the cost of postage.....

Bolt wrote:

I have a couple of photos of the new defective part, and have failed to be able to attach them....
I know there is a trick to it.....Post them somewhere and link to them??

Although some have managed to link to pictures on Google drive, I've never managed to get it to work so use Imgur, see https://rangerovers.pub/topic/1021-inserting-an-image-from-imgur

I'm having a problem at the moment trying to update my avatar from this

to this

But the site keeps telling me it can only accept jpg, gif or png and it is a jpg with the same colour depth and size as the previous one?

Try "jpeg" instead of "jpg" for the file extension ??

Tried that, didn't work.....

convert to png?

I tried converting it to png, gif and changing the file extension from jpg to jpeg, uploaded all variants to imgur and tried to link to them but every time it told me it wasn't an accepted format.

URL for the old one is https://i.imgur.com/wsu0e4s.jpg and the image properties are:
150x107 pixels
72 pixels per inch
Pixel Depth/Colours 24/16 million

URL for the new one is https://i.imgur.com/uYsXAXR.jpg (so exactly the same format) and the image properties are exactly the same. If I change the file extension from jpg to jpeg, when uploaded to imgur, it reverts back to jpg.

I also sent Gordon this

so he can update the banner on the site when he gets around to it.

But all of this has nothing to do with the PCRV......

Bolt wrote:

So, for 12 bucks, I have bought 30 (minimum quantity) of the correct size and formulation O rings

Hope you don't mind me going slightly off subject... Noticed a problem with my boat hydraulic trim/tilt system allowing the outdrive/leg to drop when it was supposed to be on full tilt for getting the boat out of the water onto the trailer. I'm rebuilding the engine on it and with the engine out noticed a leak from the joint between a hydraulic pipe and the hydraulic pump. I disconnected the hydraulic line and found a damaged O-ring, this O-ring is apparently only available as part of a complete hydraulic pump refurb kit but I managed to find a replacement sold separately that is supposedly compatible. I'm wondering if the O-ring I bought separately (specifically listed on Ebay as being suitable for the line to pump joint on a Volvo SX / OMC Cobra drive) is really compatible and/or as good as an Oring that would have been supplied as part of the full pump refurb kit. Before I bought this Oring I looked at a specialist Oring manufacturer website https://www.polymax.co.uk/o-rings/ which lists the pros and cons of different types of Oring materials for different applications/fluids/etc but it doesn't seem to say anything about what material is best suited to hydraulic pipe joints for a boat application (it does mention materials for car brake line applications). I know the dimensions of the Oring and bought (from an Ebay seller not from the Polymax manufacturer) one specifically listed as suitable for the exact joint(s) they need to seal but I don't know whether the Ebay Oring is OEM spec, just a cheap random spec Chinese made Oring, etc. There are 4 Orings I'd like to change and to change 2 of them the engine needs to be out for access, the engine is out at the moment so now is the time to change them but I'm not sure whether to trust those I've bought from Ebay.

Not really off topic at all.....
That is a very real concern when buying virtually anything from anyone these days
with Chinese material substitutions being more and more common. Add lack of knowledge on
the sellers part, and here we are!
This particular part is specified as EDPM rubber as it withstands brake fluids without dissolving or going hard.
I am looking to get it from a reputable distributor, so have some small assurance it will be as stated.
I did find a simple test on a technical rubber o ring site:
"2. It can also be recognized when it is burning. When the fluorine rubber O-ring is burning, it will automatically extinguish when it leaves the fire. The EPDM rubber O-ring will not automatically extinguish, and will continue to burn".

Since I have to buy 30 pieces to get to their $5.00 minimum purchase,
I will have plenty to do destructive testing on!

I hear the pain you are having trying to decide on the OEM $$ kit or just the parts you need off of Ebay.
Since this is an engine out job, and you certainly do not want to do it twice, maybe a case of
"Pay the price or cry twice"?
In my case, the part I got is a Chinese pattern part, so already suspect, and the design flaw that seems
to have built in is still there, or even worse, so I am going to try a repair.
At least in my case, it is on the top of the fender and easy access.

So,
I attempted to remove the 2 screws on mine, and got the "correct" tamper proof Torx driver bit, which promptly
stripped the screw head. Very sloppy fit. I thought about cutting the screw heads off, but not knowing what I
would find inside, and not wanting to destroy the valve, thus leaving the vehicle unusable, I just put it back in and asked my
friend in Hawaii (who I sold 3 P-38s to when I moved) if he could look at the '95 parts car to see if it was there.
$10 dollars postage and I had it in hand 3 days later.
This one had obviously also been leaking as there was dried brake fluid caked beneath it where the
exposed O ring is. By carefully loosening each screw a bit at a time, I was able to take tension off of the
thick spring inside and easily disassemble it. It got a good cleaning with brake cleaner and a soft wire
brush to get the scaly brake fluid off.
As suspected, the O ring was knackered! Fitted a new one and re assembled. I "primed " it with brake fluid
before installing, and when installing, I attached the fitting closest to the bulkhead first, topped up the
reservoir to get the fluid level above the front pipe, and the fluid flowed by gravity through and out the front.
Waited for clear stream with no bubbles, and nipped up the front fitting. Cleaned up, and tested.
It was not necessary to bleed the system when I was done. Yea!!
50 cent fix! A new genuine one is $135 bucks, and the O ring seems to be the only failure point!
Now that I knew what was inside, I attacked my original part.
I then used the Dremel tool to cut a nice slot in the stripped screw head, and was able to renew my original part in about 5 minutes.
Got a drop in spare now, not that I will need it!
This is not an issue you hear much about, but I would bet it is more common, but goes unnoticed.
I am surprised that no one has reported catastrophic failure from the O ring blowing out!
If anyone is in need, I have 28 spare O rings. Free for the postage!