 | Home > Maintenance & Modifications > Brake Pressure Valve - Don’t have one, why? |
 
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| Grenadier Member Since: 23 Jul 2014 Location: The foot of Mont Blanc... Posts: 5839   
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Evening all.
As per the subject, I’m in the process of replacing and/or upgrading braking parts on the DC. As a reminder I have a non-ABS MY2011 2.4 DCPU with vented discs. It seems during my investigation that I have no Brake Pressure Valve. I’ve read up on what they’re for (prevent front wheels locking up), so I’m wondering: A. Should I have one? B. If not, why not? C. If not, should I upgrade to one? (I’m doing new pipes, braided hoses, LOF Powerspec, and possibly new calipers with SS pistons). Would this be a worthwhile addition? Just wondering?  Monsieur Le Grenadier
I've not been everywhere, but it's on my list..... 2011 Puma 110DC - Corris Grey |
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18th Jan 2022 5:05pm |
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| Grenadier Member Since: 23 Jul 2014 Location: The foot of Mont Blanc... Posts: 5839
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Mmm? No idea. I’ve been liaising with Matchap from the forum who is also doing his pipes. He also has a 2.4, albeit a 90, and has the valve. Maybe 90s have them because they’re lighter and a 110’s mass will prevent lock up? Massive hypothesising there….
 Monsieur Le Grenadier
I've not been everywhere, but it's on my list..... 2011 Puma 110DC - Corris Grey |
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18th Jan 2022 5:46pm |
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| dailysleaze Member Since: 23 May 2013 Location: United Kingdom Posts: 237 
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It's for the rear locking up on 90s and pickups that are lighter at the back
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18th Jan 2022 5:56pm |
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| geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410
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Hi Grenadier.
I have also done the exact same research and found that initially these were fitted the the early 90s and 110s to reduce the pressure going to the rear drum brakes to prevent their cylinder popping seals. When the Defender added disc brakes to the rear axle the valve was retained to reduce the risk of the rear wheels locking up. The valve was supposedly left off vehicles around 2002-2003 when the P38 axle was introduced and the proportioning of braking pressure was dealt with inside the master cylinder. With respects to that when depressing the brake the MC engages the rear brakes before the front brakes to prevent front end lock up's. So, Miffy being a 2003 shouldn't have a remote brake pressure valve, but she does  Also a vented, non-ABS Defender 110.
In the long run what this means is that if your MOT guy (or French equivalent) says that your rear brakes are under braking and as long as your callipers, pads and discs are in good nick, then your MC is probably by-passing fluid across the internal seals. As well as the pipes you already know are sitting in my shed ready to go on Miffy, there is also a new MC and servo. Both of these are originals in the vehicle (222k miles) and looking their age. |
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18th Jan 2022 7:45pm |
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| Leamreject Member Since: 19 Dec 2020 Location: Middle Earth - Leamington Spa Posts: 970  
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Yes they prevent rear lock up and normally fitted to vans so active at different levels if load or not.
Simply you don’t want rear lock up if your empty so the laden valve reduces rear brake performance Ride like you stole it!! If I’m not on a bike it’s because only a 4x4 will do… 2011 2.4 Puma 90 HT |
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18th Jan 2022 8:18pm |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3430  
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The early 90s had what was called a G Valve, part number NRC 8215.
I have just opened one, just to check and clean... cannot fully disassemble, as internally seems like it has been press fitted. But I could feel that internally there is just a ball or plunger, not spring loaded. It looks like that in the event of high flow rate, or perhaps high G force, possibly even high gradient, the valve would shut off the pressure to the rear brakes. The installation angle is important for those G valves. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
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18th Jan 2022 8:24pm |
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| geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410
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That is a good point there are two versions of an in-line valve in the braking system. The brake pressure valve (aka brake proportioning valve) and the "G-valve". The first is not effected by cargo weight, angle or change in momentum, the latter is. I believe the former superseded the latter but at what VIN I do not know. Could be the point at which disc brakes were standard on the rear. The former is also mounted perpendicular to the longitudinal axis of the vehicle and the latter I believe is mounted in-line with the longitudinal axis of the vehicle and direction of momentum.
From my research I believe this is true, does anyone else know any different!? |
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18th Jan 2022 9:02pm |
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| landy andy Member Since: 15 Feb 2009 Location: Ware, Herts Posts: 5732 
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I thought the later was auto adjusted by the pressure that was provided by the pedal, hence being plumbed into the front brake line, to adjust pressure to the rear.
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18th Jan 2022 9:05pm |
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