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L19MUD

Series 3 brakes, can't get a pedal on the first pump

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OK this is driving me insane. Here is the story

Series 3 swb. Purchased by a mate and had new shoes, springs and wheel cylinders plus new pipes from the distribution valve /block to each wheel including the rubber flex by the previous owner who gave up doing it up. 

 

We tried to bleed it up but no joy. Changed the master cylinder for a new one and then found both front wheel cylinders to be leaking even though they are new. Bleed the system again and getting no air from any bleed nipple. 

 

Method used to bleed was the two man tube method. I clamped the other flexy hoses other than the one i was bleeding each time and had the drum off and cable tied the shoes as far in as they would go to minimise air in the cylinders. 

 

If the front brakes are clamped I get a good pedal first go. If they are not it takes two and a half pumps of the pedal to get the pedal firm. The pedal does not creep and the brakes pull up nicely like this. 

 

I don't know what else to try. The shoes are properly adjusted so they are just off the drums. 

 

It must have had over 2 litres of fluid through it now!! 

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17 minutes ago, L19MUD said:

Did you change the leaky slave cylinders?  Assuming you have single leading shoe brakes fitted?  When you say the front brakes are clamped do you mean the hose is clamped with a hose clamp or the just the shoes as you described?

Edited by rtbarton

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Yes replaced  the cylinders, yes re the shoes. We did both. Clamped the flexibility hoses and the shoes into the cylinder

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Did you adjust the brake shoe adjuster? it is the 2 bolts at the back of the backing plate, one for each shoe. tighten up till they drag on the drum, take back about one flat. Also, are the front breaks twin leading shoes? in that case bleeding is impossible in standard form, and the setup needs changing so the bleed nipple sits on the top slave cylinder.

Daan

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I've bleed the twin leading shoe system with an easy bleed, and with a vacuum system. Not impossible, just different.

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On 20/01/2018 at 2:54 PM, L19MUD said:

OK this is driving me insane. Here is the story

Series 3 swb. Purchased by a mate and had new shoes, springs and wheel cylinders plus new pipes from the distribution valve /block to each wheel including the rubber flex by the previous owner who gave up doing it up. 

 

We tried to bleed it up but no joy. Changed the master cylinder for a new one and then found both front wheel cylinders to be leaking even though they are new. Bleed the system again and getting no air from any bleed nipple. 

 

Method used to bleed was the two man tube method. I clamped the other flexy hoses other than the one i was bleeding each time and had the drum off and cable tied the shoes as far in as they would go to minimise air in the cylinders. 

 

If the front brakes are clamped I get a good pedal first go. If they are not it takes two and a half pumps of the pedal to get the pedal firm. The pedal does not creep and the brakes pull up nicely like this. 

 

I don't know what else to try. The shoes are properly adjusted so they are just off the drums. 

 

It must have had over 2 litres of fluid through it now!! 

Clamp off the hose to the other front (the one you aren't bleeding) and rear drums. Using a friend, get them to use 3 rapid stokes of the brake pedal ( 3 strokes less than 1 sec apart), about 2/3rds of the way to the floor each time, as you open the bleed nipple. On last down stoke, close nipple, then check fluid level. Repeat another 2 or 3 times for that wheel. You need rapid stokes of the pedal to shift the fluid quickly to get the air out. Slow stokes won't work.

Repeat on other front wheel. Adjust up shoes after the cylinders have been bleed. No need to cable tie in cylinders, in fact this could make it worse, you need the fluid to move the cylinders.

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OK thanks for the thoughts. I will clamp off all three flexi hoses to see if I have a solid pedal. That's a good idea and if I do will prove that the air has to be in the wheel cylinders.

Good point about speed of pump...it was my mate doing that bit so I wonder quite how he was doing it. Definitely worth a try. I will also try with the adjusters all the way wound in but the shoes on.

 

It is a single leading shoe/single cylinder setup so should in theory be easy

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Daft point - is it on level ground?

Did you leave some free movement between the pedal and the master cylinder operating rod?

Edited by rtbarton

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No it was not on level ground. I raised the front up 1 foot in the air and put it on axle stands under the impression I was helping things.....

 

No I have not checked that, I guess it just needs a minimal amount of play?

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You stand a better chance if it's level.

There must be some play (about 1/8th inch IIRC) between the pushrod and the pedal so that the master cylinder can recuperate when the pedal is released.

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Clamping all the hoses and then releasing the clamps one at a time will tell you where the air is. If the pedal is firm before a hose is unclamped, but then pedal goes soft - shows that the air is at that wheel - or the rear (if you have single circuit brakes).

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OK, I have tried all of the above now and it has not made a single bit of difference 

 

I only have one adjuster on each wheel. I have bleed it with the adjusters holding the shoes solid against the drum and also fully slack. 

 

I have bled it on the level. 

 

With all three flexible hoses clamped I get a solid pedal so my problem exists from the flexibility hose on the front individual wheels and the back circuit. 

Unclamping one at a time gives me the same amount of pedal free movement before it goes hard. All three un clamped requires one and three quarter pumps to get a firm pedal. 

 

I am seeing no air coming though. Have bled with fast pumps and slow pumps

 

Tried to use an easy bleed but even with 20 psi it did not push any fluid through when opening a bleed nipple, not sure what I am doing wrong with this? 

All three flexible pipes are new and fitted by the last owner. I don't think all 3 could be faulty though

 

Confused and annoyed! Such a simple system so how an I having so many problems? 

 

 

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Had a thought and clamped the hoses right at the wheel end instead of towards the cylinder end

 

The difference is between a perfect pedal and 3/4 of the travel of the pedal. Time to get some new flexibility hoses, may as well get braided I suppose

 

Has anyone else had this issue? 

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Could be you've got air trapped in the flexible hose, or the hose is faulty, it shouldn't make that much difference.  Are you certain of the quality of the hoses?  Can you feel the hose expand under pressure?

If you've got one adjuster per wheel have you got the correct shoe springs?  IIRC there should be a strong spring connected to the shoe with the adjuster (leading shoe) and then to the back plate.

The trailing shoe has a weaker spring near the pivot and connects to the leading shoe.  This is called an hydrostatic setup, where the trailing shoe is always in light contact with the drum.

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Some years ago when I had trouble bleeding my S3 the local garage told me that its very hard to remove the air in the cylinders and that some gets trapped behind the piston and it won't move up and out of the bleed nipple. So you can pump the pedal as much as you want and pass fluid through but the airlock remains. The solution was that with each drum off in turn, one person lets the pistons move right out of the ends of the cylinders, at least just a crack so that fluid and the air can be pushed past (and caught) and then the pistons pushed back in, forcing the "spare" fluid back and out of the nipple. I don't know if that is understandable but what I'm trying to explain did work for me.

I think the point is that the airlock isn't directly in the fluid path that is opened up when the bleed nipple is opened.

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These problems have been coming up for decades and there are always a host of different bits of advice given!  I will add a few here...

First - you expressed doubt about the flexi hoses.  If they break down inside, they can pinch under pressure and cause problems.  Clearly it's worth checking, though they are unlikely to be the problem.

Second - I have learnt through bitter and expensive experience that sticky pistons can mean you will NEVER bleed your brakes properly.  To check, take each drum off and get a helper to (very) gently push the pedal while you watch the pistons.  Do they all move?  If one doesn't, will it move if you just hold the opposite shoe to stop the one that moves first?  A stuck piston has to be sorted anyway.  No helper? You can use a bluetooth camera but it's not ideal.

Third - this is the bit that very few people seem to get but it is The Secret.  Contrary to popular advice, it is best to loosen off the wheel adjustments on all the wheels when you bleed.  This is because, when you open the nipple after building some pressure, you get a big volume of fluid pushed through that one line (as the springs on all the brake shoes in the system push together) and that is what you need to properly push the air out.  I can assure you, from experience, that this is a very effective technique for the type of slave cylinders used on Series Land Rovers.

Finally - If the system is particularly stubborn, you can take the drums off the one wheel you are bleeding and wrap a strong tie down strap round the shoes a couple of times.  This gives that last little bit of help as the rush of fluid isn't filling that cylinder or dealing with the half full one you might have had if your drums were on.  I consider this a drastic, last gasp thing which needs special care (hydraulic pressures are high and you don't want the strap to snap or pop off!).  You really shouldn't need to do that but I did once so...

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^^ I welded some brackets to a scrap set of shoes and used bolts to compress the pistons - no chance of them coming off.

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Finally got round to this again. Changed to steel braided hose and tried again. Still not brakes for the first two pumps. I give up

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Take a picture of the shoes.  Maybe you have something installed wrong.

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It's back together now. Surely I should still get a pedal though? 

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This is just sat still in the workshop. We are at the happily pay someone to come and sort it now! Located near Ipswich 

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38 minutes ago, L19MUD said:

It's back together now. Surely I should still get a pedal though? 

Not if you put it together wrong.

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If those front cylinders leak fluid out, they'll leak air in.  I think we can all guess the source of those bad new parts if they leaked immediately...

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