Air in braking system won't bleed.

Hi all,

Tried to post in another forum with no success.

Just wondered if you can help.

I have had my Defender 300TDi for about 18Mths, since then the brakes have never been very good. when purchased I had to change both front calipers due to seized pistons.

While trying to bleed the Front calipers, there is a steady stream of air on both front calipers, Also, While braking initial application of the brake pedal goes half way to the floor with very little braking. additional pedal presses the pedal goes firmer and braking efficiency is increased.

I have changed the Non Return Valve, Checked their is vacuum from the vacuum hose from the pump which it is.

I have also had the Brake Master Cylinder off to check the seals, I had planned to replace the seals but the seal kit I had was the wrong type 88" (what does this mean?)

There doesn't seem to be any corrosion on the servo where the Master Cyl is attached.

So my query is?

Could the inability to bleed the brakes be due to seals failiure?
or
Is the fault due to the master cylinder itself?

Sorry for the long post, but I have used google exhaustively but to no avail.

So any help would be appreciated.

Carl

Ar eyou bleeding by pumping the pedal?

The eezi bleed kit (Halfrauds) can get better results

Thanks 'Station House'

I am using the EZ Bleed system, always used it. I have put about 3 Ltrs of DOT 4 through but still I get air. The tyre Pressure is around 28-32PSI.

Hope this helps.

Thanks again

master cylinder is in two bits rear most bit does front brakes front most part rear brakes ,a sign master cylinder seals are poor is splashing in reservoir when pedal pumped , its also probably that new calipers are sucking in air when pedal returns up , they should be easy to bleed in any order ,you have either got air entering at master cylinder or caliper unless pipe work fault when fitting calipers, its best to replace master if fault lies

Career 707 said:

Thanks 'Station House'

I am using the EZ Bleed system, always used it. I have put about 3 Ltrs of DOT 4 through but still I get air. The tyre Pressure is around 28-32PSI.

Hope this helps.

Thanks again

Click to expand...

Think they recommend a lower tyre pressure - nearer 10psi from memory, but would be surprised if that was introducing air into the fluid

That seems like a lot of brake fluid to get through!

Would try reducing tyre pressure just in case, and if still getting air as James says there has to be a leak - either callipers, piston seals, pipes or master cylinder

Out of interest - how was the pedal before your started the work - was it spongey, hard, did it firm up after several pumps?

Just found the eezi bleed instructions online

http://www.autoexpertproducts.com/Geezibleed.pdf

Says 20psi max for the tyre pressure

Station House wrote

Says 20psi max for the tyre pressure

Click to expand...

I can confirm that as it states the same on the bottle, however, while bleeding the rear calipers no air is present in the system.

From whats been said i'd put my money on the seals in the master cylinder. would it be worth changing the internal cylinder seals, or just change the master cylinder as a complete unit?

Thanks guys

new cylinder

Career 707 said:

From whats been said i'd put my money on the seals in the master cylinder. would it be worth changing the internal cylinder seals, or just change the master cylinder as a complete unit?

Click to expand...

probably one for james, but if me I'd swap the whole unit - chances are if one set of seals have gone, the others won't be far behind

New Master Cylinder it will be.

thanks for your help. I'll update this thread when new master has been installed as I could not find any info on this kind of problem.

Thanks to all who participated.

Carl

EDIT

Hi again, Got a new Lucas Master Cylinder on, Bled system with EZ Bleed kit, not to sure about Master Cylinder bleeding, I do not have the luxury of a second helper in bleeding the M/C, Can this process be completed using an EZ bleed kit, I have read elsewhere that bleeding the M/C can be done by pressing the brake pedal and releasing the Master Cylinder Brake Line pipes until fluid runs out, tighten lines and release pedal.

Any 1 man alternatives available for this process.

Thanks guys.

Hi again,

Got a new Lucas Master Cylinder on, Bled system with EZ Bleed kit, not to sure about Master Cylinder bleeding, I do not have the luxury of a second helper in bleeding the M/C.

Can this process be completed using an EZ bleed kit, I have read elsewhere that bleeding the M/C can be done by pressing the brake pedal and releasing the Master Cylinder Brake Line pipes until fluid runs out, tighten lines and release pedal.

Any 1 man alternatives available for this process?

Thanks guys.