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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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