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jessejazza2

S3 10" drums - pedal sink

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I have finally managed to get my S3 88 1971 on the road but have struggled with the brakes. I have done quite a few restorations of classic motors but this is the first landy.

I chose the single circuit and kept 10" all round (no servo). Renewed all brake tube with kunifer and chose Lockheed delphi slave cylinders as they are steel. Replaced the rear 3-way union with 'Ford' method (i.e. dispensed with the flexi hose with flat end and used a front one with both pointed ends, then have two pipes into o/s side slave cylinder, and then one going across to the n/s with the bleed nipple). The 3 way union relies on a 'butt joint' rather than a more secure full OP1 and OP2 flare joint. I just think it is better as one then has steel to steel joint and not steel into brass.

I checked the master cylinder and connections by putting a female connector on each flexi with a bleed nipple - bled the system and got a hard pedal. Step worth taking I feel to be absolutely sure of each joint before connecting the slave cylinders. Connected up the slave cylinders and put on the new shoes etc. Bled the system again obviously and hard pedal with about 3/4" movement before hard... about right I expect but maybe reduced with adjusting the snail cams.

Driving up the driveway and applying brakes results in pedal sink. Perhaps a leak in slave cylinders - drums off again but no. So what could possibly be the problem? It seems as if the shoes are bending but I can't believe that. I have read that there can be drum warping but when I rotated the drums they seemed fine. The front shoes are Allmakes and the rear Britpart. The Britpart ones did seem to bind at first but I filed the leading edge by about an inch - and that was then fine.

I have heard that filing the leading edge helps bed the shoes in. This design seems odd to me in the sense that wear is not even across the length of the shoe. The S2 had an adjuster at one end of the shoes which when taken up moves both outwards whereas with the 10" the snail cam only moves one outwards. This does not seem a good design on the S3 - whereas the S2 was better with even wear and then replaced with a fixed location for one end of the shoes and then two snail cam adjusters on the early Defender.

Would be grateful for any suggestions. I am thinking the only thing to do is to put the old shoes on which were about 1/2 worn down and see what the result is. I don't think I filed the front shoes so that is something I'll do tomorrow but I am perplexed with this 'sink'.

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Adjust the shoes hard up against the drums so they can't move.  If the pedal still sinks then fluid is seeping past the seals in the master cylinder.

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Have you got the return springs on correctly? I ask because it's easy to get them in a pickle, making the shoes sit at odd angles. This can fool you into thinking you've got the adjusters right, only to find that you get pedal sink as the shoes bite then take some time to fall into the correct alignment with the drums and travel more than they should. You can get the same effect if you get the lateral adjusters wrong on the 11" twin leading drums. 

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Pedal sink is the first action of the pedal moving the shoes out to the drums and the second application is then breaking.  The issue is that the shoes are not adjusted up.  Adjust brake adjuster on each wheel until the wheel is locked then back off just enough to allow the wheel the move.

Adjust them up and if within tolerances all should be OK - if not then either shoes are too worn, drums are too worn or a combination of both.  Make sure the adjuster post on the shoe is tight and make sure the cams are not worn and loose.

To test for air or leaks - test as advised above - lock brakes and test pedal.

Garry

 

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Thank you for your replies. I got her on stands again yesterday and took the pics with my tablet (not brilliant but that's all I have at present for a camera).

In response to your posts (I've labelled paragraphs so it easier to refer to)

a] I tested the circuit to the flexi pipes ends with female inline connector and bleed nipple. It was rock hard so no problem with new master cylinder and union connections. A bit OTT but worth doing I feel.

b] springs were new and I have had two batches. The bright red seem slightly better quality.

c] The shoes were new I bought them about 5 year ago, then had to move house and so the rebuild was put on hold for a while. I did attempt to adjust the cams but found that it wasn't necessary. The rear shoes were Britpart and the  front were Allmakes. I was hoping the cheaper shoes would be softer linings which in the past I have found better. Better? - in the sense that braking efficiency is slightly better but not in terms of mileage wear. I had Mintex on an Escort mk2 and Reliant Scimitar and found them very hard without a servo - the servo giving extra effort which helps I found. [I have found that lining quality varies even with the same brand in the past]. As you can see in pic ***331 the left hand pair were on front o/s and seem to have worn top and bottom (Allmakes and poor it would seem). The Britpart ones I did file down the leading edge but would have expected a bit more wear. I have now taken the front shoes off and replaced them with the previous ones which were only 1/3 worn (I like to put on new if I am putting a motor on the road for the first time). I should have left them on as they were bedded in which would have helped.

d] I do not seem to have any leaks and checked again yesterday. I was wondering if the slave cylinders were passing but that does not seem to be the case. I chose the Delphi Lockheed as they are steel - not sure if the 'genuine' are steel or aluminium - what makes the difference is the seal quality. I didn't bother with Britpart as I have now learnt some of their quality is questionable.

e] are the drums original? I think they are ok and not warped but just want to know.

Next stage! (away next week so can't do anything)

f] check the front wheels with the older shoes that are now on and blank off the rear flexi hose with a female inline connector and bleed nipple.

g] One rear backplate really needs replacing (very rusty and thin in a couple of places). Craddocks have new ones at £150ish (old stock whilst they still have them). Backplates seem to suffer with corrosion. But I have wondered about replacing the fronts with the Defender 11" SLS (Britpart backplates AEU2496/AEU2497) and putting the front ones on the rear. It would improve braking a bit without going down the disc conversion route albeit needing a pressure reducing valve if fitted all round at a later date (the slave cylinder would be a rear one 1" diameter instead of a 1 1/4". [anyone done this?)].

thanks

james

P.S. I know the track rod end needs to be replaced... trying to sort out brakes before I renew the steering.

 

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Edited by jessejazza2

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Are the drums definitely in spec? There's usually a "max wear" spec cast in. Well worth measuring, I've seen a few people caught out with this. 

The delphi cylinders are pretty good in my experience. It's the cheap Britpart ones you want to watch out for. 

11" fronts are definitely worth the upgrade, but worth doing a little research on which cylinder sizes you want to end up with and whether a different master cylinder is appropriate. Copying the later 88" setup - which had 11" fronts - is probably your best course of action. 

 

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With the drums back on, clamp (using a proper hose clamp), both front flexi hoses and the rear axle hose. Press brake pedal, if no air in the system, it should be rock solid and have very little movement. Release one of the front hose clamps and repeat. You should still have a firm pedal but with a bit more movement than before. If not, the trouble is in that corner. If all is well, release other front hose clamp. If the pedal suddenly sinks, that corner is where your problem is. Once you have the front ok, release clamp on rear hose. If pedal now sinks, problem is at the rear.

Another think that will cause pedal sink, is a seized wheel cylinder. As the wheel with the seized cylinder won't be doing any braking, the other wheels have to do more and you may well find much more pedal is needed. Using my method above, will highlight if you have a potentially seized/sticking cylinder.

 

Finally when bleeding the brakes, use fast/swift pedal movements to get the fluid moving more rapidly - rather than slow movements. Don't push the pedal to the floor, go about half way.

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The master cylinders are difficult to bleed as they point downwards.  Presumably you have the CV type (rather than the older CB type with the big nut on the end.)  The instructions in the s2/2a manual suggest getting the cylinder level by jacking the front of the vehicle then bleeding.

I always bleed the things using an easibleed and run masses of fluid through - as there's always a bubble that takes time to come out.

My rule is that if a light tap on the pedal gives a firm pedal - its adjustment - if it takes more than that there's air in it.

11in single cylinder brakes will be exactly the same.  (Even the cylinder is the same!)

 

 

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On 9/2/2019 at 4:41 PM, simonb said:

With the drums back on, clamp (using a proper hose clamp), both front flexi hoses and the rear axle hose. Press brake pedal, if no air in the system, it should be rock solid and have very little movement. Release one of the front hose clamps and repeat. You should still have a firm pedal but with a bit more movement than before. If not, the trouble is in that corner. If all is well, release other front hose clamp. If the pedal suddenly sinks, that corner is where your problem is. Once you have the front ok, release clamp on rear hose. If pedal now sinks, problem is at the rear.

Another think that will cause pedal sink, is a seized wheel cylinder. As the wheel with the seized cylinder won't be doing any braking, the other wheels have to do more and you may well find much more pedal is needed. Using my method above, will highlight if you have a potentially seized/sticking cylinder.

 

Finally when bleeding the brakes, use fast/swift pedal movements to get the fluid moving more rapidly - rather than slow movements. Don't push the pedal to the floor, go about half way.

Many thanks for the tips - I'll look at it tomorrow.

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On 9/2/2019 at 10:44 PM, secondjeremy said:

The master cylinders are difficult to bleed as they point downwards.  Presumably you have the CV type (rather than the older CB type with the big nut on the end.)  The instructions in the s2/2a manual suggest getting the cylinder level by jacking the front of the vehicle then bleeding.

I always bleed the things using an easibleed and run masses of fluid through - as there's always a bubble that takes time to come out.

My rule is that if a light tap on the pedal gives a firm pedal - its adjustment - if it takes more than that there's air in it.

11in single cylinder brakes will be exactly the same.  (Even the cylinder is the same!)

 

 

Are you sure? The 11" system I was thinking of was the Defender with the back plates AEU2496 and AEU2497. The slave cylinders are RTC3626D and RTC3627D. Of course different part numbers do not necessarily mean it is a different part but normally is. Fot the S3 10" the rear slave cylinders are 1" dia and the front ones are 1.25" diameter.

The backplates seem to be poor metal and one of mine has rusted through but I am hoping ok to last a while now that I have bought new slave cylinders and shoes all round. But only available backplates are the Defender ones (JHohn Craddock do have a few 10" ones left but at almost £200 each.... might as well get the 11".

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Well I found the NEW left n/s slave cylinder leaking a little slight bit as the spring paint had lifted. It does occur to me that the seals aren't a good design. What are the GENUINE ones like? Are they different... should be for £30+. But then again I have found 'you get what you pay for' is not always true.

Hopefully if it's not raining again tomorrow I can do a bit more. I suppose some of you think I am a hopeless mechanic - I've worked on vehicles for 30 years and never had trouble with brakes. My enthusiasm for land rover is not great at present. many thanks for your help so far.

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Spring paint? 

No, they're not sophisticated. Just be glad you didn't buy blue box.... Possible you've got a duff one - shouldn't leak when brand new (unless it comes in the aforementioned blue box)! 

Anyway, unless it's gushing, it won't be the cause of your pedal sink. Did you measure the drums? 

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1 hour ago, lo-fi said:

Spring paint? 

No, they're not sophisticated. Just be glad you didn't buy blue box.... Possible you've got a duff one - shouldn't leak when brand new (unless it comes in the aforementioned blue box)! 

Anyway, unless it's gushing, it won't be the cause of your pedal sink. Did you measure the drums? 

I have learnt enough of LR the hard way - I don't touch anything in a blue box. I haven't thought of a way to measure the drums - I've got a vernier but not that long. Just thinking about it now - best idea I can come up with is a pushrod (of a length I can measure) and then use the vernier upper jaws for the remaining distance and add the two together.

If drums wear that much then the shoe linings are too hard... one only has the choice of Britpart or Mintex. As I found before with other motors Mintex are fine with a servo but not so good without.

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10.06 max ins it says which would be 255.524 mm.

I used a 1/4" drive extension bar and then the vernier upper jaws to get the following measurements. Length of extension bar was 142.66 mm.

rear o/s drum 142.66 + 112.16 = 254.62

rear n/s drum 142.66 + 111.66 = 254.12

Not sure what the min is but that is inside max. The o/s could well be slightly larger as the previous owner had a front 1.25" slave cylinder instead of 1.00". That wouldn't help breaking balance and would have applied slightly more pressure on o/s. I wish I had done a test drive before starting the resto.

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Many thanks for your replies - sorry not to respond earlier but had to go away and then sort out other things. As well as doing a bit of research. Now I seem to have sorted the pedal sink but have too much travel.

It seems that I hadn't bled the system properly. In the sense that whilst I checked MC and put female connectors on the end of the rubber flexi with bleed nipples and got a rock hard pedal. [Bit 'belt and braces' but worth doing I feel]. It seems that the thread in the slave cylinders is a little iffy - as I was bleeding air was seeping back in or wasn't pushed out of the system from the flexi to slave cylinder. I found a male union was a better fit and so piped that to a 3-way with a blank and bleed nipple (as attached pic... perhaps only temp measure for now). I did buy a couple of brake hose clamps (good suggestion  thanks - not having problems with brakes on any motor before it is one bit if kit I haven't had). I then bled the rear with clamps on the front - and similarly bled front with clamp on back. Hard pedal! - thus intending to cut down the travel of the piston slave cylinders. Released the clamps - still a hard pedal BUT travel is to about 1 cm from bottom.

It would seem that suggestion of MC being incorrect is possible. The MC I fitted was one from a LR supplier dia 0.75" bore #90569126G TRW/Girling (SWB mine being a S3 88 1971 fitted with 10" drums all round) and #90569128 (for a LWB and after a bit of research it appears to be a 1.125" bore). [Most suppliers don't say what the bore is]. According to the parts manual these were for the single circuit system without servo. With the servo it seems there was only the NRC6096 BUT looking at the diagram it would seem it was a fatter cylinder and presumably 1" bore. If the CB was fitted to the SWB it was a 0.75" bore and the LWB one was 1" bore. This is where I am 'at a loss' - there is more movement in the slave cylinders with 10" drum setup than the 11" drum setup. LR had no reason to fit a MC with 1" bore to the LWB - being physically larger does not affect the brakes... the weight does and that is why it had 11". Land Rover spent ££££££ in research?

So I have tried to apply some logic and physics to the situation. Along with my kind neighbour, pair of G-clamps and a vernier.

Let's consider MCs (I have used aluminium alloy in the past - just prefer them as when new they are a sealed bag. Steel tend not to be and may have sat around in a parts store for a while). Stroke length of alloy ones I believe are 1.4" (3.556cm) whether they are integral reservoir or remote. I've bought the extension housing for integral ones and then found it can be cheaper to stay with the remote ones - prices of reservoirs seem to wildly vary. [maximum swept volume for MC I'll call msv and slave cylinder swept volume I'll call sv, csa is cross sectional area]. Using cm, cm2 and cm3 as it is easier to visualise.

MCs
0.75 (3/4") =1.905       csa=2.850     msv=10.13
0.875 (7/8")=2.2225   csa=3.8795   msv=13.795
1"          =2.54               csa=5.0671   msv=18.019
Note: certainly a big difference between 0.75" and 1" I wasn't expecting that.

Slave cylinders
10" drums
front 1 1/4"=3.175   csa 7.9173
With G-clamps applied I reckoned the front piston moved 1mm and the rear moved 2mm (new shoes fitted). Per slave cylinder that's 3mm (0.3cm)
sv=7.9173x0.3=2.3752
two drums total is 4.7504
rear 1"=2.54   csa=5.0671
sv=5.0671x0.3=1.5201
two drums total is 3.0403
Total sv 4.7504+3.0403=7.7907
msv was 10.13 so a mere 25% (approx) spare. Hence why I have a hard pedal about 1cm of the floor (if that).

S2 setup 11" TLS front with conical adjuster on rear. 
front slave cylinders are 1.125"=2.8575 say 1mm travel each if adjusted properly. Estimate but not wildly out I trust.
csa=6.413 sv=6.413x0.1=0.6413
front 4 cylinders total sv=2.5652
rear slave cylinders (assume 1" dia) say 2 pistons per cylinder each move 1mm
csa=5.0671 sv=1.0134
rear total sv=2x1.0134=2.0268
Total sv=2.5652+2.0268=4.592
If 0.75" MC was fitted it would seem that there would be hard pedal almost 1/2 way down approx.

S2 conversion setup 11" drum TLS front with 10" SLS rear (Post 1980 fitment on SWB I believe).
front sv (4xslave cylinders)=2.5652
rear sv (2xslave cylinders)=3.0403
Total sv = 2.5652+3.0403=5.6055
If 0.75 MC was fitted hard pedal would be a bit more than 1/2 way down.

Whilst mere estimates I must be in the right 'ball park'.
Let's look again at the 10" drum all round and allow for an extra 0.5mm movement.
front sv=7.9173x0.35=2.7711 both sides=5.5421
rear sv=5.0671x0.35=1.7735 both sides=3.5469
Total sv=5.5421+3.5469=9.089
Note: 9.089-7.7907=1.2983 So roughly an extra 0.5mm of movement in each piston reduces MC capacity by 13%.

I don't understand how the 0.75" MC can be adequate for the 10" drum. I noticed the #90569128G bore 1.125" was fitted later to the LWB (presumably after the CB was dropped - I gather they are the ones that give trouble with bleeding). I bought an alloy 1" which I fitted yesterday and then loads of rain!

This morning 0900ish bled the brakes and WONDERFUL hard pedal about 0.5" down which is what it should be at least on any motor. Even better no doubt with the #90569128G but that I think is a steel one and I prefer aluminium.

Thanks for your advice - as I don't know some of Landrover history I would be interested to hear if others have the 1" MC or what arrangements they have. I had no trouble bleeding, I did about 3 pedal pumps to clear the air (I listen for the spurts), and then adjusted the bleed nipple so it will just pass fluid thus giving some resistance when the pedal is pushed - always worked perfectly for the past 30 years. Only other problem I have had was yonks ago when at a union connection the pipe has been slightly bent and then the flare seal does not seat properly.

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Your 8th picture down the spring looks to be in the wrong place as it is on the adjuster and not the leading shoe? Or may just be the picture.

i spent ages chasing a brake problem only to find I had put the top spring connecting both shoes together. So had to pump the brake twice to get a hard pedal. Spring should only be on the leading shoe and into the peg on the backing plate

 

hope that helps 

Jon

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1 hour ago, Jon W said:

Your 8th picture down the spring looks to be in the wrong place as it is on the adjuster and not the leading shoe? Or may just be the picture.

It is in the right place but had to use the adjuster kit RTC3176 on the rears. the original adjuster was much more robust.

Edited by jessejazza

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