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S3 brakes arrrgh


moose
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Morning all,

this is not my truck but a friends (as if i dont have enough to do to my own) its a 1977 series 3 88in. Its that time of year where it needs an MOT every thing is done part from i cant get a good brake peddle :angry:

If i put my foot on the brakes, the peddle will travel to the floor and there is some braking force but not enough.... on one pump i get a very good peddle and all the wheels will lock up :huh:

parts replaced are:-

new master cylinder,

new all round drum cylinders,

new shoes (and springs etc..),

new drums,

new flexible pipes (in case they were ballooning),

new copper pipes.

So the whole lot :o

is a non servo single pipe system ... so should be the simplest thing to sort <_<

I have bled 10 liters of fluid through it, so there is no air in the system or old fluid, the shoes springs are on the correct way, and each drum has been adjusted in turn.

If i camp off the fronts i get an ok (ish) peddle

I have tried every thing from my post [LINK] back in Jan (been hoping the problem would go away :ph34r: )

So any ideas on this problem would be great as its starting to do my NUT in :blink:

thanks

Paul

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I had similar probs on a S3 I used to have.

Always seemed to be trapped air despite major bleeding.

Have you still got the bleed nipples at the bottom ? Replumb with them at the top.

It involves making fiddly tight bends but is worth it.

Also as a desperate measure I removed all drums and clamped the pistons into the

cylinder to reduce the space inside then pressure bled the system (Eezybleed).

Best of luck, they are a PITA.

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I had similar probs on a S3 I used to have.

Always seemed to be trapped air despite major bleeding.

Have you still got the bleed nipples at the bottom ? Replumb with them at the top.

It involves making fiddly tight bends but is worth it.

Also as a desperate measure I removed all drums and clamped the pistons into the

cylinder to reduce the space inside then pressure bled the system (Eezybleed).

Best of luck, they are a PITA.

Actually moving the nipples to the top on twin leading shoe brakes doesn't make any difference to bleeding apart from being easier to undo.

The air gets trapped in the top of the cylinders and the ports to the pipes are on the centreline. Any air trapped in a pipe will get pushed through due to the surface tension of the fluid.

Assuming the vehicle in question is a standard SWB the bleed nipples are at the top of the cylinder so bleeding shouldn't be a problem. Clamping the pistons in towards each other will help, if you can clamp all four cylinders at the same time and you get a hard pedal then there is no air in the system and the fault is likely to be with the shoes/adjusters.

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Actually moving the nipples to the top on twin leading shoe brakes doesn't make any difference to bleeding apart from being easier to undo.

The air gets trapped in the top of the cylinders and the ports to the pipes are on the centreline. Any air trapped in a pipe will get pushed through due to the surface tension of the fluid.

Assuming the vehicle in question is a standard SWB the bleed nipples are at the top of the cylinder so bleeding shouldn't be a problem. Clamping the pistons in towards each other will help, if you can clamp all four cylinders at the same time and you get a hard pedal then there is no air in the system and the fault is likely to be with the shoes/adjusters.

Ok good idea "Clamping all the pistons" ...... set of g clamps should do it or is there a better method ?

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Use G-claps or those posy rathet things. Remember not to do them up mental tight though. They only need to prevent the pistons from pushing back out.

Could also be the adjusters. Sometimes you have to adjust, press the brake a few times and adjust again.

Les.

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Use G-claps or those posy rathet things. Remember not to do them up mental tight though. They only need to prevent the pistons from pushing back out.

Could also be the adjusters. Sometimes you have to adjust, press the brake a few times and adjust again.

Les.

thanks will give that a go

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I had this on a series 3 despite using gallons of fluid and a ezi-bleed system no joy, then used a vacum type bleed system presto brakes first time round!!!!!!!!!!!!!!!!!, but i also clamped the pistons up so maybe it was that that did it.

Regards

Keith

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Since you say that you get a good pedal after one pump, the problem is almost certainly with the adjusters. If there was a lot of air in the system, you would get a spongy pedal however many times you pumped. If you get a hard pedal after one pump, there is not likely to be much if any air in the system.

Double check all your adjusters. With some types, it is possible to put the shoes on in such a way that the adjusters don't engage on the posts on the shoes.

The problem could be at the back as well as the front. If only 1 or 2 shoes out of 8 are poorly adjusted, it can cause the symptoms you have.

Good luck!

Regards,

Diff

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Yes, I have fallen foul of this before. The rear shoes are handed. The adjustment post is higher on the front shoe, than the rear shoe (could be the other way round, need to check). If you put the shoes ass about face, then the adjusters do not sit square against the post and slip around it. A symptom of this is when pulling up to a halt, the brake pedal drops a little as the car rocks back after stopping. It took me ages to work this one out!

If you remove the rear shoes, measure the distance to the centre of the adjuster from the face of the cylinder casing. This will identify if my theory is correct.

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Morning all,

this is not my truck but a friends (as if i dont have enough to do to my own) its a 1977 series 3 88in. Its that time of year where it needs an MOT every thing is done part from i cant get a good brake peddle :angry:

If i put my foot on the brakes, the peddle will travel to the floor and there is some braking force but not enough.... on one pump i get a very good peddle and all the wheels will lock up :huh:

parts replaced are:-

new master cylinder,

new all round drum cylinders,

new shoes (and springs etc..),

new drums,

new flexible pipes (in case they were ballooning),

new copper pipes.

So the whole lot :o

is a non servo single pipe system ... so should be the simplest thing to sort <_<

I have bled 10 liters of fluid through it, so there is no air in the system or old fluid, the shoes springs are on the correct way, and each drum has been adjusted in turn.

If i camp off the fronts i get an ok (ish) peddle

I have tried every thing from my post [LINK] back in Jan (been hoping the problem would go away :ph34r: )

So any ideas on this problem would be great as its starting to do my NUT in :blink:

thanks

Paul

I'm feeling very lucky that I never had any problem bleeding my brakes (front 11" twin, rear 10" single). I agree that if you've got a hard pedal after one pump, there's probably not an air problem. Too much travel due to adjusters, wrong shoe position, brakes not centralised? Are you doing them up solid and then backing off? In fact, adjust them up solid and then check the pedal - if it's hard, definitely not air. Are there high points on the shoes - french chalk to check. Rather you than me. :blink:

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