Diagnosis please

[KERRSURF]

Right, my new caliper is fitted and combined with fitting both rear halfshafts I lost a lot of brake fluid.

I bled the brakes in this order, no leaks in the system were detected.
I adjusted handbrake prior to bleeding and it works fine.
New pads fitted in fronts.

Rear LSV bleed nipple, took a long time to get all the air out, then n/s rear brake cylinder followed by o/s brake cylinder.

Then n/s front caliper (the new one) and then the o/s caliper.

The brakes pedal with engine off was rock hard and not sinking.

Turn engine on and brake pedal got easier to push due to servo assistance but continued to sink towards floor.

Bled whole system again, same result but this time pedal never reached the floor with engine running but still a lot of pedal travel, pumping the pedal gave less travel but the brake light on dash illuminated and the brake feel went very hard but less effective braking, another lighter press of pedal and the light went off but pedal sank.

I have brakes but just not good ones and the pedal will sink if you keep pressure on it.
No leaks and fluid level is not dropping.

Has the master cylinder had it?

If so, can Rich or any of the breakers help me out?

[KERRSURF]

I also took vac pipe of to check and vac to servo is working, all ok.

[KERRSURF]

anyone?

[BUSHWHACKER]

Master cylinder seals are worn allowing fluid past.
Motor factors should stock them as they're probably the same as Hilux pick-ups.

[NiftyNev]

Bleed the master cylinder at the brake line connections and then the brakes again and see if that helps. If not then I also think master cylinder should be replaced.

Nev

[Shalershasker]

Have only just started reading up on braking systems ect so bear with me here but could someone explain why if the pressure produced from the master cylinder was fine before (not loosing fluid), why would the seals suddenly let go after simply having the fluid drained, refilled and bled?
Also learned something new in this thread as I thought the order was n/s rear, lsv then o/s rear, think I've got a lot more reading up to do yet before I tackle this lol.

[tintin]

Alan, if you find the old thread, you'll find i had exactly the same prob after i did my brakes!
Everybody was convinced the cylinder was kaput so i got a new one from Milners. Made no difference so i sent it back for exchange (Milners were great about it) Fitted the second new one, still no difference!

As you found, i had brakes but not good and if you leave your foot on the pedal it slowly sinks,
In the end i took it to a local 4x4 place who Pressure Bled the brakes!
That seems to have worked as they got much better!

Hope this helps
And BTW i think Shalershaker is right on the order of bleeding, rear passenger side first as it's the furthes from the cylinder!

Good luck sorting it mate

Alan

[Shalershasker]

Alan, if you find the old thread, you'll find i had exactly the same prob after i did my brakes!
Everybody was convinced the cylinder was kaput so i got a new one from Milners. Made no difference so i sent it back for exchange (Milners were great about it) Fitted the second new one, still no difference!

As you found, i had brakes but not good and if you leave your foot on the pedal it slowly sinks,
In the end i took it to a local 4x4 place who Pressure Bled the brakes!
That seems to have worked as they got much better!

Hope this helps
And BTW i think Shalershaker is right on the order of bleeding, rear passenger side first as it's the furthes from the cylinder!

Good luck sorting it mate

Alan

So that is the right way round to do it then, am learning that this can be a real minefield of a topic for a novice so to speak lol.

[Albannach]

I don't think it's the master cylinder either, it's just air in the system. Perhaps it does need Vacuum or Pressure bled?

Also, just to add my tuppence worth in the bleeding sequence. Starting furthest away in the system, it's N/S/R - O/S/R - LSV - N/S/F - O/S/F. In the system (and physically) the O/S/R is further away from the MC than the LSV.

EDIT: Before anyone starts on me! I would bleed the LSV first, the above was to point out that the 'Furthest Away' thing isn't necessarily a rule.

[Albannach]

Also, from experience, vehicles with LSVs tend to be a pig to bleed anyway (2 pipes means there's another route for the air to follow).

What method were you using Alan? Best one is; Pump the pedal until there is pressure, hold the pedal down then open the bleed screw until the pedal goes to the floor, close the bleed screw, pump up a pressure again and repeat until there is no air.

Those wee pipe things that folk use to contain the fluid can cause more hassle than they are worth too. The best way to move the air is to get the pressure drop as large and fast as possible, those tubes don't allow that to happen.

[Shalershasker]

I don't think it's the master cylinder either, it's just air in the system. Perhaps it does need Vacuum or Pressure bled?

Also, just to add my tuppence worth in the bleeding sequence. Starting furthest away in the system, it's N/S/R - O/S/R - LSV - N/S/F - O/S/F. In the system (and physically) the O/S/R is further away from the MC than the LSV.

EDIT: Before anyone starts on me! I would bleed the LSV first, the above was to point out that the 'Furthest Away' thing isn't necessarily a rule.

Ah gotcha, so that's the order cleared up (dulely noted, thanks).
I take it by this then, the MC would not just give up with a drain and refill, there would be some warning yes?
What is this pressure bleed that Kerrsurf needs to do then?

[Albannach]

Ah gotcha, so that's the order cleared up (dulely noted, thanks).
I take it by this then, the MC would not just give up with a drain and refill, there would be some warning yes?
What is this pressure bleed that Kerrsurf needs to do then?

Alan's brakes were fine before he messed with them, so just draining the system won't break anything. The symptoms he has do appear to be like those he would see if the MC was gubbed though.

Pressure bleeding the system is as it says, a pressurised bottle of fluid is connected to the master cylinder where the cap would be. Once the system is pressurised, the bleed nipples are opened in sequence until all the air is evacuated. Vacuum bleeders suck from the bleed nipples. They are both using the same theory to bleed the system (air will always move to the point of lowest pressure), it's just the method of creating the pressure drop that's changed.

[NiftyNev]

If the master cylinder got air into it then it will be very difficult to force this air through the brake lines. Pressure bleeding may do it. Bleed the master cylinder first.

Nev

[Shalershasker]

Alan's brakes were fine before he messed with them, so just draining the system won't break anything. The symptoms he has do appear to be like those he would see if the MC was gubbed though.

Pressure bleeding the system is as it says, a pressurised bottle of fluid is connected to the master cylinder where the cap would be. Once the system is pressurised, the bleed nipples are opened in sequence until all the air is evacuated. Vacuum bleeders suck from the bleed nipples. They are both using the same theory to bleed the system (air will always move to the point of lowest pressure), it's just the method of creating the pressure drop that's changed.

Cheers for that, understand much better now , my truck is in today for a new drivers side brake pipe, that's what's prompted me to start learning about this as I can't do this sort of thing at the mo but am certainly learning.

[KERRSURF]

Thanks for all the info guys.
Yeh Andy, I was using the rubber pipe and pump method.
I'll try and bleed the MC and then use the method you describe, perhaps you could pop round at the weekend and see?