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Dual line brakes (pipes)

J

jepaton

Trekker
My 88" Series 3 has dual line servo assisted brakes, which I believe has been fitted after manufacture. I have changed the front brakes from 11" x 3" to 11" x 2.25" backplates/drums/pads. I also replaced the master cylinder with type 90577520G.

The system needs to be drained for MOT pipe replacement. I know (instruction 70.00.00) that on the 88" dual line, the front compartment is supposed to supply the rear, and the rear supply the front. This is how it is currently set up. The 109" is the opposite.

I've read that the volume of fluid sent to the front/back is different. If the dual line brakes on a 88" and a 109" are identical at the corners, then there is a conflict with that idea.

Is the pipe arrangement correct for this vehicle? (I think the rear is the 109" type... not sure).

Before I took it off-road for front cylinder/drum/pad/rubber pipe replacement, the pedal took a few pumps before it became solid. I had already bleed the system when changing the master cylinder, with little difference.

Of course, I was stupid enough to saw the hoses off before realising that I had 2.25" parts instead of 3" - in case anyone is wondering why I went from 3" to 2.25". And of course the wheel cylinder had a stuck bleed nipple too (and no replacement that fitted the backplate). Nothing quite like not being able to fit all the shiny new parts whilst my supplier loses the backplates I ordered in the post. Even still, I'm sure others have had worst moments.

When I drove to the MOT station (only place I can drive), I felt that the pedal had much improved. However, there is still room for improvement. Perhaps fitting the servo vacuum tank (see thread: https://www.lrukforums.com/forum/showthread.php?t=37958) will solve the problem, or maybe not. Seems only to affect road use though.

I would like to draw a HUGE line under this problem, and worry about lesser things like broken heater control wires and water leaks (fitted with at least two).

Jonathan Paton
 
Jonathan
You need more fluid for the front sysytem (for a similar pressure) because it has two wheel cylinders whereas the back brakes have only one (per side). This assumes that you have twin leading shoe brakes at the front.
If your brakes have failed the MOT on corroded pipes then your system was probably working OK as the MOT tester would have listed any other braking system problems on the fail sheet.
If the system was fitted wrongly there are two general posibilities, very poor brakes (pretty standard for series LRs!) or your back brakes would lock up at very light braking pressure. What you describe seems more likely to have been air in the system after you changed the master cylinder (again a common LR braking system problem).
You need to give us a bit more info to pinpoint the problem.
Lastly I would not recommend fitting the vacuum tank to your diesel, the LR (diesel) servo vacuum system is cr*p, rather than trying to find a suitable tank you'd be better off looking for a vacuum pump to give you the necessary vacuum for the servo.
Let us know how you get on.
Ian
 
Duel line brakes have the front brakes at the rear of the master cylinder and the rear brakes at the front. When you press the pedal, hydraulic (brake) fluid is pushed down the master cylinder and front pipes by the first piston. When the pressure starts to build up in the front discs or cylinders, it also pushes against the second piston in the master cylinder and starts to apply pressure to the rear brakes. This is so you get a slight front braking before the rears. If a pipe was to burst or leak on the fronts, the first piston would then contact the second and you would push the rears directly. If the rears lost pressure, the first piston would push the second to the end of the master cylinder and then apply the front brakes.

If you pipe the brakes up the other way round on the master cylinder, they still work, but you would notice a slight tendency for the rears to act first.
 
Ian,

I do indeed have twin cylinders at the front, as per 1L 03 in the parts manual (left page).

Of course I know that poor brakes are pretty standard for Land Rovers. Would be nice if the pedal didn't need pumped up as I approach roundabouts though. Most of that "character" has been lost with changing components, but not totally.

What I could never understand is why the pedal is much better when stationary. However, when you are moving the pedal would reach the floor, and need another go to start braking effort. You could wait a few seconds between presses and still get the extra braking (I think this discounts air).

What has been on my mind whilst changing everything else is whether the pipe arrangement is correct. The original master cylinder had a 0.75" bore, the 90577520 has a 1" bore. This master cylinder I know is the same as fitted to 109" dual line brakes. I am now aware that a 569671 part exists for the 88" dual line.

I would have expected that brake pedal to the floor type action should result in wheel lock-up (or at least "good" stopping) on a overrated system . The vehicle is after all an unloaded 88".

Can you suggest any vehicle types that can donate a suitable vacuum pump? There is a large breakers yard nearby, anything but Land Rovers can be found there. What how much time needs to be invested in fitted one?

Jonathan Paton
 
Templ4r,

Interestingly, the Land Rover Series 3 Repair Operation Manual states on page 70-1:

"NOTE: On dual braking systems, the hydraulic fluid is divided into two compartments. On 88" models, the front compartment supplies the rear brakes and the rear compartment the front brakes; on 109" models, however, the reverse applies and the front compartment supplies the front brakes, and the rear compartment supplies the rear brakes. ..."

I am aware that there is two pistons within the master cylinder, one for each circuit. And also that in the event of failure one presses against the other. This of course is where the safety of the dual line system comes from.

If the volume of fluid that is in each portion of the cylinder bore is different, then different volumes of fluid can be supplied to the front and back. The conclusion I am leaning towards is that the 88" dual line cylinder and 109" dual line cylinder have these volumes configured differently. And that I need to swap the lines.

Jonathan Paton
 
On my 2A 88" I had brakes from a LWB, due to my V8 engine. I Put the fronts to the rear brakes and rear to the fronts, stopped on a sixpence, then again, I put 2 remote servos from a BMW in the system.

When you fitted the brakes, did you fit them to the correct sides? You should have twin leading shoes, if they are on the wrong sides you will have twin trailing, ( It won't stop)

All the cars I service have the duals piped up this way, I don't know why the LWB is the other way round,

Have you adjusted them up correctly, pumping the pedal usually means the shoes are too far away.

Look at a Diesel Transit alternator, they have Vacuum pumps on the back, as do a lot of diesel cars.
 
Agree with Templ4r. The different diameter bore will only have an effect on the required pressure since Force = Pressure x Area you have increased the area so for the same breaking force you should have slightly less pressure. I don't believe that this would lead to the problem you are describing since brake fluid is basically incompressible if the system is full without air. Fitting the 109 master cylinder should improve the brakes not make them worse, as with the increased area in the master cylinder for a given distance moved by the piston you should get a greater distance moved by the piston in the wheel cylinder,(if it doesn't meet resistance) so as Templ4r says check the adjustment of all the shoes (6 adjusters in total). I don't know if its possible to fit the brakes so that you get trailing shoes rather than leading but when your dealing with a system that has been altered it would be worth checking.
The symptom of hard brakes at rest but poor with excess travel can also sometimes be cured by adjustment, I don't know why, but one of my friends had a SWB truck cab with very similar symptoms which dissapeared after proper adjustment. There is without doubt a logical engineering explanation but I don't know what it is! Final thought is that maybe you have a bad flexible hose(s) which is(are) expanding under high pressure, you could try fitting those expensive braided flexible brake hoses.
With regard to the vacuum pump Pugeot diesels have something you could use so I presume that anything fitted with the Pug diesel engine (Citroen, Volvo, Renault and Fords) should be useable, you need to make up a bracket arrangement to hold the pump and you need a double pulley on the crank to give you a drive to the pump, search this forum as there is a lot of information already listed. Sorry, but as a computer (semi)illiterate I don't know how to link it here. Alternatively fit a petrol engine where vacuum from the manifold isn't a problem!
Good luck keep us informed how it goes.

Ian
 
Templ4r/narc,

Finally acquired the magical MOT certificate.

The garage replaced these two pipes to the same arrangement. You were both in agreement that it should work swapped or not. Professionally re bleed, although with a garage comment about "pants" and "drum brakes". Gave me the certificate though :)

I will readjust everything once the pads start bedding in. Still got the servo to sort out. I can now at least make use of the highways and byways, and with further tweeking it might resemble the brakes I thought it would have. I suppose I should have read more about Land Rover brakes before buying one!

Jonathan Paton
 
Hi,

I am adding Defender disc brakes to my S11A, and need the same S111 servo as well as a supply for vacuum. I found two potential solutions:

1. Chris Perfect Components offers a bolt-on pump for this, looks to be complete with brackets, pulley, belt, etc. Please see:

http://www.chrisperfect.com/products/brakes-steering_vacuum_pumps_diesels.html

2. There is also a throttle body with vacuum take-off point on it. This was fitted to the later S111s. Check the breaker yards to see if you can find one.

I was originally looking at the Chris Perfect pump, but they will not ship to the States. Now I think that may be a blessing, as the trhottle body idea I found later would mean less moving parts / less things to break.

Cheers,

Steve
 
Steve,

The throttle body with the vacuum point is also supplemented by a vacuum tank in the SIII to provide an additional boost. However the system is found to be lacking in effectiveness by some, hence the reason for bolt-on vacuum pumps.

I did the modification on my SIII using an alternator / vacuum pump from a Toyota diesel engine and find the braking greatly improved now.

Simon
 
For information I checked the vacuum from the 2.25 diesel and got 2 inches of mercury maximum, (with the butterfly almost completely closed) since the 2.25 petrol vacuum (ignition) advance doesn't even start until 3.5 inches (and goes up to 25inches) it's not surprising that we are all looking for more servo power!
Has anybody got any feed back on the Chris Perfect pump? It seems expensive, but has the advantage of being a bolt on job without too much faffing about, I don't have time this winter to make brackets and such, so I was considering putting the C.P. pump on my Christmas list.

TTFN
Ian
 
Manamendra,

Thanks for the info on the tank - I did not know that was needed as well. That would make that solution less attractive to me even if it were as effective as the pump. The tank would add more stuff that could fail, so would not be much different from the pump in that regard.

Now I just need to find a way to get the Chris Perfect setup since they won't sell it to the States. Might have to ping some of the shops over there, see if they will buy and resell one to me.

I found the S111 throttle body on eBay for 95 pounds, new. I also called Rovers North who have a used one for somewhat less. But by the time I source the rest of the parts (vacuum tank, hoses, anything else required) I am guessing that the costs would be approaching the same number). Here is a link to the throttle body on Ebay:


http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=4531416664&sspagename=ADME:L:RTQ:US:1

Cheers,

Steve
https://www.lrukforums.com/forum/member.php?u=7839
 
While looking at the Chris Perfect site, I saw that they also offer an 8" servo upgrade. Does anyone have any thoughts on that? Is the standard S111 one adequate? I bought a used S111 one which will need gone through before I mount it, so the cost of the CP one may be at least partially offset by the money I would have to spend to rebuild the one I already have.

http://www.cp-components.co.uk/product_details.asp?pid=56

Cheers,

Steve
 
MilesBfree,
Don't even think about the throttle body.vacuum tank route for the defender disk set up you're fitting, you will need a decent amount of vacuum for the servo if this set up is to work well. The usual route over this side is to get the vacuum pump from a car or truck fitted with the peugeot 2.3 L diesel (many fords, citroens, renault and peugeots) and make up the necessary fittings to mount it, I'm thinking Chris Perfect since it should be a straight bolt on job saving time. Have you tried phoning them direct? maybe you could do some kind of a deal with them. Alternatively anybody planning a trip to the US in the near future?

Good Luck

Ian
 
Ian,

Thanks - I am convinced the vacuum pump is the way to go.

I emailed them, but they did not say why they do not ship to the States, just that they do not.

Cheers,

Steve
 
I found another company, TI Console, in the Netherlands that sells a vacuum pump kit. It looks a lot like the CP one, and the pump appears to the the same. I am wondering if they are reselling the CP kit (or vice versa)? I will check with them on selling to the States... Here is a linkg:

http://www.ticonsole.nl/parts/dicsbrks/servo.htm

I had heard of TI Console when I was looking at the disc brake upgrade, and they seem pretty good. I liked the Rovers North Defender disc brake conversion a lot better than the TI Console disc kit, however. I think that was because they only offered the front axle, but I may be confusing them with someone else, as it has been a while since I researched the brakes.

I also searched for Defender vacuum pumps, to see if the Chris Perfect one is just a Defender pump with the brackets, pulleys, and belts included in their kit.

Here is one on eBay, but it does not look anything like the CP one (maybe 300TDi is different from other later diesels?):

http://cgi.ebay.co.uk/LANDROVER-300...573398605QQcategoryZ31348QQrdZ1QQcmdZViewItem

Cheers,

Steve
 
Steve,

I believe this is the same pump. I know that Chris Perfect is the importer for their parabolic springs, so I guess he gets the vacuum pumps from them as well. It looks like it may be cheaper (and easier) for you to get it from Holland.
I don't think the pump on e-bay could be made to work, many vacuum pumps for modern diesels run off the camshaft and need an oil supply, even if they don't they are likely to be flat belt rather than Vee belt drive. I'm coming round to just gritting my teeth and paying for the CP unit as I was out in the station wagon over the weekend and the brakes were as bad as a .... well my powers of description fail me, lets just say bad!
Keep us posted how it goes. Still waiting for any feed back regarding the CP pump folks!

TTFN

Ian
 
Thanks Ian.

Here are some pics of the Defender disc brakes installed on mine, in case folks are interested:

restoration14.jpg


restoration15.jpg


restoration16.jpg


restoration17.jpg


restoration19.jpg


Cheers,

Steve
 
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