Les Henson Posted September 11, 2008 Share Posted September 11, 2008 Got a really annoying problem with a 1974 swb S3. It has new shoes (fitted correctly), new springs, new wheel cylinders, new master cylinder, new brake pipes, new rear brake hose, and new snails, drums are in good condition. Bled the brakes, etc, good pedal, drive it 100yds and the pedal goes to the floor. Pump it back up and the pedal is fine, drive it 100yds and it's back to the floor again. Left overnight and in the morning the pedal is still fine, but as soon as it's driven a short distance the pedal will go to the floor again. It looks like the wheels turning makes something happen that requires the pedal to be pumped (usually 3-times), in order for the brakes to work. The snails don't unadjust themselves, but something is happening that I can't put my finger on. Anyone had this problem before, or have an idea as to what is going on? I've done loads of series brakes and never had this problem before. Les. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 11, 2008 Share Posted September 11, 2008 Is it the single or twin leading shoe fronts set-up? Servo? With the brakes OK, lift each wheel in turn and spin it a few times by hand, maybe you can trace the fault to one wheel. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted September 11, 2008 Author Share Posted September 11, 2008 It's a standard single line system - no servo, Roger. I've lifted each wheel, adjusted the snails until they bind, then back two clicks. Les. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 11, 2008 Share Posted September 11, 2008 I was thinking along the lines of trying to bring the fault on, rather then check the adjustments. Quote Link to comment Share on other sites More sharing options...
ThreeSheds Posted September 11, 2008 Share Posted September 11, 2008 Caveat - I haven't actually looked inside a series drum for ooh, twenty years, but I would guess that, taking into account your experience and the checks you have performed so far that it would have to be a dodgy component somewhere? The only 'mechanism' I can think of that could possibly cause the stated symptoms would be that one of the trailing shoes is not locating correctly and is contacting the drum and moving around and pushing it's piston in. But I can't quite imagine how this could happen... That's it I'm afraid - thought I'd post it just in case it helps... Roger Quote Link to comment Share on other sites More sharing options...
SteveRK Posted September 11, 2008 Share Posted September 11, 2008 Following that thought about the shoes trying reversing (100 yards i know is not easy) to see if the fault occurs. Quote Link to comment Share on other sites More sharing options...
Jon White Posted September 11, 2008 Share Posted September 11, 2008 Les, Sounds to me like you've got a dodgy master cylinder. Firstly have you checked the free play of the pedal? I've heard of problems before with cheapo pattern parts with things like misaligned holes that dont allow the plungers to return correctly and hence the fluid doesnt get through as it should do. Jon Quote Link to comment Share on other sites More sharing options...
Gazzar Posted September 11, 2008 Share Posted September 11, 2008 I presume bearings and all are fine and there is no other way for the drum to vary relative to the shoes? I'd try to eliminate possible causes. Clamp the flexi hoses one at a time, Starting with the rear one. Test drive in a safe place. Sorry: teaching grandfather to suck eggs. No effect then swap out master cylinder for known good. If it helps when I brought my S3 109 to be tested I told the tester I wasn't happy with the brakes. He asked had I changed the cylinders and when I confirmed this he said it sometimes happens that the pedal is soft at first?! I'm still not convinced but they do work. G. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted September 11, 2008 Author Share Posted September 11, 2008 Well I changed the master cylinder last as I couldn't see what else it would be. This made no difference unfortunately. The marks on the new shoes from the drum contact seems normal to me - high at the front and low at the back (pushing in and pulling in). I agree with a mechanical component problem, but can't understand what is happening and why. Bearings are fine, drums are fine, every-bluddy thing looks fine, but it ain't. teaching grandfather. Watch it - sonny Les. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 11, 2008 Share Posted September 11, 2008 Jack it off the ground on 4 axle stands, engage 4WD and "drive" it forwards to see if the fault comes on. If it does try 2WD, if the fault still occurs look at the rear brakes, if not suspect the front. Having found the axle, lock each wheel on the axle (one at time) using the adjusters, this should narrow it down to a wheel. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted September 11, 2008 Share Posted September 11, 2008 The snails don't unadjust themselves, but something is happening that I can't put my finger on. Anyone had this problem before, or have an idea as to what is going on? I'm not sure how you have verified "The snails don't unadjust themselves". The significant thing with this installation is that, with only the backplates and the front hoses being original, this installation has never ever worked before. Almost anything could be wrong, nothing can be taken for granted. I've seen a problem where the pins on some new shoes were too long and caught on the boss of the snail, (where the snail is held in the backplate). Thus on releasing the snail the shoe only half released, stopping when the pin hit the boss. ISTR this prevented the drums being fitted, so I don't see that causing this problem. But what if the pin was just too short, and being knocked off the snail as the drum moved the shoe slightly? Pumping the pedal 'might' just drop the pin back onto the snail, thus restoring the adjustment. Weak, but the best I can think of, having no practical experience of Series 3 brakes. Checking against a parts book, I seem to see that the pre-1980 88" has Leading and Trailing shoes in both front and rear brakes, and that there is only one adjuster, located near the wheel cylinder rather than the dead pivot. This location would allow the piston to move the adjuster end of the shoe far enough so the pin can re-engage with the snail. The problem might not be a short pin, but a snail cam that is for some reason too close to the backplate. (The 109" has the adjusters at the dead (static) end of the shoe, if the pin slipped off the snail it could not recover, as all the shoe movement due to the piston would be at the unadjusted end of the shoe). Good Luck. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted September 11, 2008 Author Share Posted September 11, 2008 I'm not sure how you have verified "The snails don't unadjust themselves". Well, because I never had to readjust them. Almost anything could be wrong, nothing can be taken for granted. Yes, I know that. I've seen a problem where the pins on some new shoes were too long and caught on the boss of the snail, The pins are fine - they locate on the snails correctly and don't catch on anything. With the drum off and the snail turned - the shoe moves in and out as it should. As I have said - the shoes are fitted correctly, the snails are new and also fitted correctly. It seems to me that the fault can only possibly lie with the trailing shoe somehow. Seems ridiculous, but manual adjustment is never needed after the pedal sinks. Perhaps it is the front hoses - they are the only old part of the system left. I'll replace them and see if that fixes it. I'll also try the 4-wheels up test too. Les. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted September 12, 2008 Share Posted September 12, 2008 Sorry if you thought I was stating the bleeding obvious, and was insulted by that. I was mainly thinking aloud, so to speak. Quote Link to comment Share on other sites More sharing options...
ThreeSheds Posted September 12, 2008 Share Posted September 12, 2008 Perhaps you could arrange to drive for 100yards, coast to a halt without using the brakes and then remove the drums and have a look? Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 12, 2008 Share Posted September 12, 2008 . Seems ridiculous, but manual adjustment is never needed after the pedal sinks. Perhaps it is the front hoses - they are the only old part of the system left. I'll replace them and see if that fixes it. I'll also try the 4-wheels up test too.Les. Did the pedal sink before you overhauled them? If not the hoses should be OK. If the hoses are bulging that much it should be visible to a watcher. Quote Link to comment Share on other sites More sharing options...
Gazzar Posted September 13, 2008 Share Posted September 13, 2008 Any results? G Quote Link to comment Share on other sites More sharing options...
Les Henson Posted September 14, 2008 Author Share Posted September 14, 2008 Got them sorted at last. I raised it on 4-axle stands as Roger suggested, checked the front hoses, which were fine. I checked adjustment on the snails and on the master cylinder push rod, 'drove' it, and the pedal sank straight to the floor. I bled the system and checked the adjusters several times and eventually the brakes seemed to sort themselves out. The pedal is good after a short drive, so MOT retest on Monday and it's back on the road for the first time in 8-years I still don't know what was wrong with them - perhaps they just needed to bed in or something. The wheels sometimes spin freely and then sometimes catch. Might be just cheapo after market shoes though. Les. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 14, 2008 Share Posted September 14, 2008 I'm always suspicious of faults that just go away. Certainly sounds like the trailing shoes were pushing the pistons back. Have you got those key-hole shaped retainers in place on the pivots of the trailing shoes? Quote Link to comment Share on other sites More sharing options...
Les Henson Posted September 14, 2008 Author Share Posted September 14, 2008 The retainers are there Roger - new ones with new bolts too. Les. Quote Link to comment Share on other sites More sharing options...
dave88sw Posted September 15, 2008 Share Posted September 15, 2008 i don't like the way you say it "might be cheapo aftermarket shoes" id it were me, with something as fundamental as brakes, you would make sure they were decent quality even if that meant you spent a fortune, but hey, it's your life Quote Link to comment Share on other sites More sharing options...
Les Henson Posted September 15, 2008 Author Share Posted September 15, 2008 Well no, it's not my life - it's the customers, and he supplied (and also fitted some) of the parts. Les. Quote Link to comment Share on other sites More sharing options...
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