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Gasket

Member Since: 30 May 2020
Location: Manchester
Posts: 629

Pressure reducing valves on pre-300TDis

Hi folks.

I've actually just posted a wanted ad for one of these, but could do with some supporting info. I'm talking about an NRC8215 valve, it looks like this:

Click image to enlarge

I'll confess - this isn't for my defender, its actually for one of my Series IIAs.

I'm getting ready to reassemble a SWB SIIA from parts and one of the key upgrades I've bought is a disc brake kit. I say 'kit' its actually a couple of engineered components that let me fit a Defender brake system. I have a set of front swivel housings that will accept defender callipers and discs, plus I have a custom 8" brake servo (same size as a pre-300TDi defender) which will accept a defender master cylinder. Both of these parts have been supplied by Heystee in the Netherlands and I have a set of 200TDi rear backplates, cylinders and drums bought second hand.

This means that I can simply fit brand new 90 200TDi spec brake parts to the vehicle and end up with the same system. But this valve is NLA.

I'm keen to replicate the factory system exactly - its mostly pipes and tees, but the 200TDis had this pressure reducing valve - people generally don't fit them, bit I'm a stickler for following the factory.

So, a couple of questions - could anyone tell me where and how they mount to the chassis? I have found this picture on the NAS forum in the US, but I'd prefer a wider shot for context. I think I'm looking at a valve on the (UK) drivers side, on the outside of the chassis rail in front of the footwell below the pedals. Which is about where the SIIA steering box support bolts unfortunately.

Click image to enlarge

I'm ordering a new chassis for the SIIA and, provided the factory Defender position does not clash with anything in the SIIA then I'll fit it in the same place. I understand that angle is key with this, so I'll be asking Richards Chassis to position any fixed bracketry or mounting holes in exactly the same place relative to the chassis rails.

I see that the part comes with its own bracket, NRC8897, but I'm not sure how this chassis fastens to the chassis rail - is there a piece of welded bracketry or simply some rivets?

Finally, I can't seem to find any information on whether these valves can be serviced or rebuilt. I have rebuilt a number of PWDA valves on other restorations and I'm assuming that there are similarities.

Any help gratefully received.

27th May 2022 11:11pm

Dinnu

Member Since: 24 Dec 2019
Location: Lija
Posts: 3179

2012 Defender 90 Puma 2.2 CSW Santorini Black

NRC8897 (LRW also gives part NRC9035) does not mount to the chassis but is pop rivetted by 2 rivets to the bulkhead bracket. See Item #22 in LRW for the pop rivets.
https://www.lrworkshop.com/diagrams/land-r...ar_52927#2

Mind you, that NRC8215, although many times described as pressure reducing valve, it does not reduce pressure in normal service. What it is is a gravity sensing and flow non return valve. In the case of sudden braking, or loss of pressure to the rear brakes, a simple ball bearing shifts forward and shuts off the exit port of the valve. I could not service my unit. When I took the 3 bolts out, there is what looks to a pressed cylinder (tight fit) with a small hole in the center and a pin, but cannot get to the ball bearing inside. As long as there is no rust, I guess there is nothing that can go wrong with this valve.

As you mention, the mounting angle is of paramount importance. As gravity needs to keep the ball away from the port. Too high of an angle, and the valve probably will never work. Too low of an angle and it will operate too soon.

The valve on a 90 is located just above the right chassis rail (driver side). I am not sure if it would foul with the steering box drop arm on a SII. And on a SII the bulkhead bracket is very different from that of a 90/110 as it locates the steering box.

I will try to remember to take a few pictures next time I am next to my 90.

But in general, it is not a valve that should operate often (or ever). It had also once made my rear brake bleeding a bit of a nightmare. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black

28th May 2022 7:51am

Retroanaconda

Member Since: 04 Jan 2012
Location: Scotland
Posts: 2541

Here’s a wider picture of mine - factory 200Tdi Defender 90.

Click image to enlarge

It’s not a PDWA valve, but a pressure-reducing valve designed to prevent the rear circuit from locking up. No switches or warning lights. It is mounted specifically at a certain angle and needs to be right to work correctly. The rear brake line goes from the master cylinder into it and then out the other side and off to the rear axle.

28th May 2022 1:15pm

Gasket

Member Since: 30 May 2020
Location: Manchester
Posts: 629

that is perfect - thank you.

The valve seems to bolt to a small bracket, NRC8897 as shown here: https://www.lrworkshop.com/diagrams/land-r...rear_52927 , and then - looking at yours - it seems like the small bracket might be fastened onto a larger bracket.

Would it be at all possible to see this from another angle? I'm guessing the larger bracket us bolted all the way through the chassis rail. No worries if the car has since been reassembled.

Looking at that I wouldn't be able to duplicate the exact pouting position on my SIIA, but I can put it close and at the same angle - I'll likely just have Richards put holes in the same place and then draw up a bracket in CAD and have it cut to duplicate the same horizontal angle.

28th May 2022 1:35pm

Retroanaconda

Member Since: 04 Jan 2012
Location: Scotland
Posts: 2541

The larger bracket is the bulkhead to chassis bracket. Shown here both before and after installation of the G valve:

Click image to enlarge

28th May 2022 5:35pm

Dinnu

Member Since: 24 Dec 2019
Location: Lija
Posts: 3179

Re: Pressure reducing valves on pre-300TDis

Gasket wrote:

.....so I'll be asking Richards Chassis to position any fixed bracketry or mounting holes in exactly the same place relative to the chassis rails.

On a Series 2/3 chassis there are already 3 through holes for mounting the bulkhead brackets 592984 & 592985. On a 90/100 there are 2 through holes in approximately the same location. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black

28th May 2022 8:59pm

Linds Hanson

Member Since: 16 Jan 2021
Location: Cornwall
Posts: 432

I've got a used G valve if you need one?

30th May 2022 6:24pm

Gasket

Member Since: 30 May 2020
Location: Manchester
Posts: 629

Linds - yes I do, thank you. I had posted a wanted ad in the classifieds section.

If you could let me know what you have and what you’d need for it, I’d be very grateful. Thanks.

30th May 2022 8:57pm

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