 | Home > Technical > Pressure reducing valves on pre-300TDis |
 
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3413   
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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 |
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28th May 2022 6:51am |
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| Retroanaconda Member Since: 04 Jan 2012 Location: Scotland Posts: 2639 
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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. |
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28th May 2022 12:15pm |
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| 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. |
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28th May 2022 12:35pm |
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| Retroanaconda Member Since: 04 Jan 2012 Location: Scotland Posts: 2639
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The larger bracket is the bulkhead to chassis bracket. Shown here both before and after installation of the G valve:
Click image to enlarge Click image to enlarge |
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28th May 2022 4:35pm |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3413
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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 |
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28th May 2022 7:59pm |
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| Linds Hanson Member Since: 16 Jan 2021 Location: Cornwall Posts: 485 
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I've got a used G valve if you need one?
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30th May 2022 5:24pm |
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| 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. |
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30th May 2022 7:57pm |
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| Procta Member Since: 03 Dec 2016 Location: Sunderland Posts: 5161
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I know this is a pretty old post, does yours have rear discs at the back? we are suspecting the fools that rebuilt my dads landy has left this off, which is causing the rear brakes to lock up Defender TD5 90 ---/--- Peugeot 306 HDI hatch back Success is 90% Inspiration and 4 minutes Preparation # you can make it! |
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11th Oct 2024 1:57pm |
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| Retroanaconda Member Since: 04 Jan 2012 Location: Scotland Posts: 2639
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It does have rear discs yes.
I doubt the G valve could cause this, all it does is reduce pressure to the rear circuit under heavy braking. Many models don’t have one at all. Rear brakes locking up after a while is more likely to be an issue with the master cylinder pushrod adjustment. |
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12th Oct 2024 1:20pm |
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