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Hi All

This should be a simple thing but it’s gone wrong and I’m puzzled as I do not know what the problem is.

Getting an all new brake system up and running. Everything is new, never been used so I filled it with DOT4 and bled the back and front. All seemed ok’ish with the brakes stopping and wheel spun by hand. Until I discovered the 3way at the rear was leaking where it joins the flexible pipe on the pass side. So I had to remove that and renew the copper seal washer.

As I didn’t have one it did get left overnight unconnected, but put it all back together today but as I disconnected it the fluid in that main front to rear line leaked out. Well to be expected, wasted a bit of fluid but got some spare so no issue.

Just re-bleed the rears then all ok I thought.

But its not, I cannot get the rears to bleed. When depressing the brake pedal, no air bubbling through and no fluid at the bleed nipples, either side, no activation of the wheel cylinders, nothing.

No being sure of the problem re-bled the fronts and no prob, all working as expected and the brakes stop the fronts turning when the pedal is depressed.

I cannot detect any fluid or air coming out of the three way where the original leak was and there were and are not any other visible leaks so I just cannot work out what might be wrong and what to try.

I’ve bled brakes before on other cars and not had a problem and it should be a fairly straightforward process, even for me.

But this has got me stumped.

I’m sure its going to be something simple but I’m at a loss and just can’t figure it out.

Any suggestions?

Cheers   Keith

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Hi Keith

on a 6 the master cylinder has two lines one for the front and another for the rear I would bleed the master cylinder again and then work along the line to the rear

Chris 

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hi keith,

Is front and rear reservoir topped up (sorry for asking).

the amount of air can be so high notting seems to happen. 

Waldi

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Hi Guy's

I'm with Waldi that as the line will be empty i could take ages for the fluid ot come through.

But i would expect to see air bubbles to be being forced out of the line into my container half full of DOT4 when my helper presses the brake pedal but i'm getting next to nothing, the odd tiny air bubble but often nothing and we've done 20 to 30 brake pedal depresses each side, which given other cars i've done is plently.

This seems to indicate the air is not being forced out by fluid, which i cannot understand.

A block is possible but as everything is new and it all worked 3 days ago i'm thinking that is unlikely.

Its as thought the movement in the pedal is not being transferred to movement of the fluid indicating a fault in the master cylinder, but the front bakes bleed and work as expected indicating it ok.

As i said i'm stumped.

Cheers    Keith

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Keith - I'd be tempted to buy a Gunson Eezibleed and try that. It uses air pressure (from a spare wheel tyre) to push the fluid through the system. It may just be wahat is required to prime the system from new?

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19 minutes ago, Keith66 said:

Hi Guy's

I'm with Waldi that as the line will be empty i could take ages for the fluid ot come through.

But i would expect to see air bubbles to be being forced out of the line into my container half full of DOT4 when my helper presses the brake pedal but i'm getting next to nothing, the odd tiny air bubble but often nothing and we've done 20 to 30 brake pedal depresses each side, which given other cars i've done is plently.

This seems to indicate the air is not being forced out by fluid, which i cannot understand.

A block is possible but as everything is new and it all worked 3 days ago i'm thinking that is unlikely.

Its as thought the movement in the pedal is not being transferred to movement of the fluid indicating a fault in the master cylinder, but the front bakes bleed and work as expected indicating it ok.

As i said i'm stumped.

Cheers    Keith

Had this before, best way is to pressure bleed it

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If you are doing it one handed a MityVac brake bleeder is a great help. - You still have to check the fluid level in the supply tank at the pedal operated cylinder (that avoided writing M*****ster Cylinder)

https://www.tooltruck-uk.com/brands/mityvac

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Hi All

Thanks for the replies, there are a couple of things there i will recheck and it also gives me and idea to try to rig up some kind of vacum to "pull" some fluid through or try to see if someone i know has a Gunson or similar.

Cheers   Keith

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Hi All

Got hold of a previously used Gunson so have to assume it works as it should.

We after a bit of faffing around with it i got fluid at the rear drivers side bleed nipple. Had to do that side to keep out of the rain.

Yeah success, or not.

So got fluid coming through and closed the nipple off. But as the Gunson seems to push fluid throught at 15 to 20 PSI I decided to get the remaining slightly bubbly fluid out more gently the old fashioned press the pedal way.

And there I noticed the problem.

Pressing the brake pedal barely moves any fluid through the line to the rear wheel cylinder, you can tell by how much the bubbles move or don’t move.

Now I don’t know how much fluid a full brake pedal push is supposed to move but I’m pretty sure it would be more than a couple of mm worth.

And even though I now have fluid to the rear DS brake there is zero braking effect on that drum when the pedal is pressed.

So a new question is could a brake cylinder fault mean that the fronts work ok but the rears have zero pressure applied to the line via fully depressing the brake pedal?

Cheers  Keith

 

 

 

 

 

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Hi Keith, do you have a pdva valve (probably not if a UK rhd car).

It helps when you pull the handbrake lever up and keep it like that, so nothing gets lost in moving the rear wheel cylinders.

If the seal In the bottom of the MC is not closing, it will give no oil to the rear brakes, just return it to the little (front) reservoir. Keep that topped up at all times, hope you did.

Waldi

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37 minutes ago, Keith66 said:

Hi All

Got hold of a previously used Gunson so have to assume it works as it should.

We after a bit of faffing around with it i got fluid at the rear drivers side bleed nipple. Had to do that side to keep out of the rain.

Yeah success, or not.

So got fluid coming through and closed the nipple off. But as the Gunson seems to push fluid throught at 15 to 20 PSI I decided to get the remaining slightly bubbly fluid out more gently the old fashioned press the pedal way.

And there I noticed the problem.

Pressing the brake pedal barely moves any fluid through the line to the rear wheel cylinder, you can tell by how much the bubbles move or don’t move.

Now I don’t know how much fluid a full brake pedal push is supposed to move but I’m pretty sure it would be more than a couple of mm worth.

And even though I now have fluid to the rear DS brake there is zero braking effect on that drum when the pedal is pressed.

So a new question is could a brake cylinder fault mean that the fronts work ok but the rears have zero pressure applied to the line via fully depressing the brake pedal?

Cheers  Keith

 

 

 

 

 

Keith

You got it all wrong, you must pressure bleed the whole system or you will not remove trapped air. Also make sure your rear drums are adjusted correctly . 

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1 hour ago, ntc said:

Keith

You got it all wrong, you must pressure bleed the whole system or you will not remove trapped air. Also make sure your rear drums are adjusted correctly . 

Hi

I get what you mean as the pass side branch of the rears is still full of air that is compressible so braking efficiency would be reduced when braking.

But using the Gunson I do have plenty of fluid at the DS bleed valve so the single line from the front to the rear must also full to the three way. It will only be from the three way to the pass side drum its air as the DS to the bleed valve is full of fluid. I would assume that fully depressing the brake pedal when the DS bleed valve is open should drive more fluid out rather than compress air in another part of the system. The pressure generated by depressing the brake pedal should take the easiest (is lowest pressure) route which will be via the open bleed valve. But even with the bleed valve open depressing the brake pedal pushed no more fluid through.

But I’ll go with the suggestion and will bleed the pass side tomorrow. Would have done today but with a V small garage the side I’m not working on is barely 6 inches from the wall and changing sides without going outside in the rain is V difficult.

Cheers Keith

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Keith

Do not press the break pedal at any time pressure bleed the system rear passenger side first then driver side then the front last one being the driver side front use no more than ten psi and repeat then check the pedal at that point 

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Hi Neil,

can the large lid safely have 10 psi?

Not questioning/challenging it but just would like to know how much margin there is before I paint the ceiling with BF.
Are old lids (50 years old still ok for this (if not damaged off course). 10 psi is approx. 0.7 bar, which equals around 8-10 m of BF head, that should b sufficient.

Thanks,

Waldi

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Without going out to the garage to check, I think the recommended pressure for the Gunson is circa 10psi.

The lid used on the master is one that comes with the kit - it's a little while since I used mine, but I recall it comes with a selection of lids/caps to fit different masters....

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Having used an Eezibleed only yesterday, I can confirm the instructions say 20psi max but recommend 10psi for older brake systems. I used 15 which seemed OK on the '3A.  It does recommend doing a dry test under pressure to check for leaks before filling the bottle with fluid.

Edited by RobH
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Hi all

Yep i wished i had checked my system dry with a Gunson type pressure system before putting any fluid in. But bleeding manually has alwasy worked no prob in the past. But then again not from completly empty system, so we live and learn.

Used the Gunson from a tyre, which i doubt has 15psi in it so that seemed ok.

I'll give it all another go again tomorrow and see how i get on.

Cheers for the suggestions Keith

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Rod and Rob,

thanks, this is good to know.

Waldi

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Hi Keith,

You say everything is new, did you check and adjust the clearance on the servo pushrod ? If it is not set properly, the brakes can be a real pain to bleed.

Cheers.

Mark.

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