minibreakdown
6 posts
Joined: 07/07/2010 14:40:51
Location: Autevielle France
brake limiter valve/brake regulator adjustable valve
Hello all I have a 1989 998 mini flame that has just failed its French MOT for the rear brakes only have 20kg of pressure on each side. The front brakes work fine.
I have just returned from the garage where he has said it is a problem with the brake limiter valve FAM7821 and needs a new one but suggested a good idea would be to fit a brake regulator adjustable valve MS72.
I asked if the adjustable valve replaced the brake limiter or was fitted into the braking system and the both worked together. He said it would replace the brake limiter but I needed to find an adjustable that has the correct brake pipe connections as the limiter after showing him a picture of MS72 on line at the garage.
I have researched the forum and the technical manuals to see how these parts work together or not!!!
This may be a case of lost in translation between me and the mechanic.
Could anybody please let me know should I replace like for like (FAM7821) or try and fit an adjustable brake regulator? If it is fit the adjustable, what parts do I need and where does it go in the system?
Posted: Jun 26, 2014 12:39 PM
Tim
1849 posts
Joined: 18/10/2004 09:40:59
Location: Bournemouth United Kingdom (Excluding channel Islands)
If I remember correctly, that brake limiter (FAM7821) is mounted on the bulkhead and has two pipes going in from the master cylinder (because it's a dual line system) and two pipes going out - one to the front brakes and one to the rear.
The simplest thing would be to replace it like-for-like, but it's not cheap.
If you decided to fit the adjustable (MS72), then that works on the rear brakes only and is fitted on the rear subframe, where you would normally see a simple 3-way union. You would have to get rid of the brake limiter on the bulkhead, and join the two sets of pipes somehow.
Personally, I don't like limiters of any sort and on my 63 Cooper I disabled the limiter on the rear subframe by removing the insides, so it just acts like a 3-way union. I haven't had a problem with the rear brakes locking up, except on very wet or loose surfaces.
If it was my car, I would try and do the same and disable the limiter on the bulkhead. I don't know if it's possible to take it apart and put it back together again without leakage, but it's worth a try. Failing that, you can just remove it and replace it with two female-to-female connectors.
Posted: Jun 26, 2014 08:44 PM
Thanks for the comprehensive reply Tim and I now understand it a lot better.
I think that I will be replacing the brake limiter like for like and not add the adjustable onto the braking system or removing the limiter completely. Reasons for this are my son drives the car and he hasn't got the driving experience if the rear brakes locked up and I don't want some dodgy mechanic in rural France messing about with the brakes too much. Also I would like to keep the car pretty standard.
Once again thanks for the info
Posted: Jun 27, 2014 07:22 AM
OK. As per my previous post I bought a new brake limiter (FAM7821) from this fine online shop. Had it fitted at the garage and I went to pick it up this morning. To be told that the problem still exists and the rear brakes are still only getting 20kg of pressure which is exactly the same as before. I now have a spare brake limiter should the new one ever fail. I asked it it could just simply be a partly block pipe from the limiter to the rears but he doesn't think it is as he gets a good flow of brake at the rear brakes.
To pass the MOT for the rear brakes, on the rolling road test, he has suggested loading up the boot and back seat with 3 or 4 sacks of cement to see if this extra weight will increase the force on the rear wheels somehow.
If this does work, great. But in anticipation of a spectacular still only 20kg and another fail would anybody have any ideas what the problem could be? The system seems quite simple.
Tim I am seriously taking up your earlier suggestion of removing the brake limiter altogether or as the French mechanic suggested, swap over the rear and front brake outlets for the MOT then change them back after. That would make for a fun drive there and back! Would rather do things properly though.
Thanks in advance.
Posted: Jul 10, 2014 12:50 PM
I'm afraid I don't really understand what 20kg of pressure means, or whether adding extra weight to the rear of the car would make any difference to it.
One thing that you need to establish is: does the handbrake work properly? I ask this to establish if you're certain that the brake shoes themselves are OK - quite often on the rear brakes you'll find that a leaking cylinder has smeared brake fluid all over the shoes and no amount of brake pressure will make them work effectively.
On my mini, the handbrake will lock the rear wheels solid when going down my (fairly steep) driveway on a damp morning.
It's difficult if you have to rely on a garage doing all the work - especially if they don't really know what they're doing!
Posted: Jul 10, 2014 01:50 PM
Thanks again for the reply again Tim. I will try the hand brake out to see what happens.
Both rear wheel brake cylinders were replaced some 2 - 3 years ago so are hopefully OK.
I don't understand the 20 kg pressure either. I know that to test the pressure they took out the bleed nipple and screwed on a pressure gauge and then pushed the pedal, showing how much pressure in Kg's is getting to the rear brakes. One thing for me is that both sides have the same amount of pressure so I would have thought it would have been the limiter.
I'll go and try the hand brake this afternoon and see what happens.
Posted: Jul 11, 2014 12:59 PM
Interesting - I've never heard of measuring brake performance like that! Maybe something's got lost in translation, but pressure would have to be measured in kg's per square something, not just kg's. Did they tell what reading they got on the front?
Posted: Jul 11, 2014 01:35 PM
No they didn't. I don't know if they even tested the front!
Just been out in the car and on a hill near me the rear nearside locked up when the hand brake was applied. tried this several times with the same result so it looks like I'll be taking the nearside apart this weekend to see whats going on.
This is why I like forums as the amount of advice and knowledge is invaluable, especially when you live in rural France. It does make me wonder why the garage didn't think to try that. Thanks again Tim.
Posted: Jul 11, 2014 03:35 PM
Update for what it's worth.
The problem with only one wheel locking up with the hand brake was sorted by properly adjusting it.
The rear brakes. On both sides one of the pistons on each of the cylinders was binding but not leaking fluid until my son pushed the brake pedal, I stopped the shoe that was working from moving by applying pressure to it. Brake fluid then poured out from the other piston but still didn't move and remained stuck solid. 2 new cylinders about to be ordered.
When fitted and both of the brake shoes will be applying pressure to the drum instead of just the one then the 20 kg of pressure should hopefully be the right amount to get the correct braking force. Why the garage couldn't have worked it out I don't know.
I suppose now I have a spare brake limiter if anyone is around the Pyrenees Atlantique area of France and is in need of one, contact me.
Posted: Jul 12, 2014 04:10 PM
simon hellier
1 posts
Joined: 02/03/2015 21:52:43
Location: BRIXHAM United Kingdom (Excluding channel Islands)
ERA brake reducing valve replacement
Is there a replacement rear brake pressure reducing valve similar to those fitted to the ERA mini of the 90's
Posted: Sep 24, 2022 03:24 PM
SimonJ
49 posts
Joined: 31/01/2006 11:40:27
Location: South Glam United Kingdom (Excluding channel Islands)
Adjustable brake limiter valve
Hi, Some time ago i read an article on minispares (the older website) where Keith Calver said to bin the brake reducing valve that was problematic and replace it with an adjustable valve and the bigger bore wheel cylinders. I have done this (Car not on the road yet) but how to i achieve a ball park setting?
Posted: Feb 11, 2006 04:25 PM
Rob
50 posts
Joined: 01/10/2005 23:57:53
Location: Bridgwater United Kingdom (Excluding channel Islands)
adjustable brake proportioning valves for single line systems..........
looking for the proportioning valve for a single line system with 7.5s and drums on rears, the car wasnt originally disc. i have come into a problem. is there a difference between the MK1/2 and MK3 cooper s one and the MK 3 non cooper s?? i only ask because i want to make it adjustable with a threaded bolt on the spring and i cant work out whether itll make a difference........ Cheers Rob
Posted: Mar 30, 2006 07:21 PM
Andre
2 posts
Joined: 25/07/2006 15:44:04
Location: Hameenlinna Finland
Brake Pressure Limiting Valve
Good day to all,I am looking for a used early cast type brake pressure limiting valve or brake proportioning valve.If any information I would appreciate it
Posted: Jul 25, 2006 04:02 PM
Nicky
4 posts
Joined: 23/09/2004 18:23:15
Location: DESTELBERGEN Belgium
brake circuit => master cylinder + bias valve + servo
Dear Mini friends,
I'm currently rebuilding the Mini with Metro callipers and a type 4 master cylinder + bias valve + servo which were sourced from a nineties Mini. See pictures.
Before final assembly and actually bleeding the brakes, I want to make sure I've got everything connected the right way round...in other words which port of the master cylinder connects to which one on the bias valve. I've managed to sort out the front and rear port on the bias valve based on some pictures from the internet...I guess. I would appreciate it should one of the Mini friends have a quick look under their bonnet.
Here in Belgium it's not always easy getting answers to technical questions, most enthousiasts mainly care for driving around on Sundays and barbecues.
Thanks,
Nicky.
Posted: Mar 19, 2007 10:38 PM
taffy1967
1783 posts
Joined: 27/09/2006 18:58:07
Location: Rhondda-Cynon-Taff United Kingdom (Excluding channel Islands)
Have you sorted this yet Nicky?
I'll check under the bonnet of my Mini when I get a chance anyway mate.
Posted: Mar 22, 2007 05:54 PM
Right after having to lift out my windscreen washer bottle and peering under my brake servo armed with a torch, this is how my brake bias valve is connected up on my 1990 Rover Mini Cooper (Mainstream Carburettor Model): -
First of all the pipes running from the bottom of my brake bias valve are in a different order to yours?
Namely the lower left brake pipe runs to the FRONT on my car and the lower right runs along and disappears beneath the bulkhead, no doubt heading for the REAR of the car. So I think mine are in reverse to how you have labelled yours?
Going by your numbers, number 3 on my brake bias connects to number 2 on my master cylinder and then of course number 4 on my brake bias connects to number 1 on my master cylinder.
I've double checked and that's exactly how my Minis braking system is connected, but it did have some engine/gearbox work done by a gearbox specialist a few years back. But I assumed they connected everything back right when they refitted my engine?
Well it's worked okay so far anyway, so good luck Nicky and I hope your Minis running again soon!
Posted: Mar 22, 2007 07:37 PM
Hi,
Thanks a lot for your reply!
I know the bias valve is positioned differently on my bulkhead. The "shiny nose" - with the spring located in it - is pointing on my car versus the engine, whereas in a nineties mini it's mounted on the bulkhead the other way round (facing towards the body of the car). Does that add up with what you're seeing on your car?
These parts were sourced separately (loose parts in a crate), so no way of telling how they were originally connected. My Mini originally had none of this, drum brakes all around and a very simple brake circuit.
Appreciate your help!
Posted: Mar 22, 2007 10:10 PM
To be honest Nicky I couldn't tell because my brake servo was in the way and I had a job just trying to see where the pipes went.
I'll have another look, but I'd like to know whether mine is connected up right too.
So can someone else here give us a second opinion perhaps?
Posted: Mar 23, 2007 05:42 PM
I've checked it again today Nicky and your right, my brake bias valve is facing the other way around, with the "shiny nose" part facing towards the inner wing.
Anyway you know how mine is connected now, so I guess you just have to connect yours more or less in reverse?
Posted: Mar 25, 2007 06:26 PM