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Rear brake question

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jjbunn

jjbunn

Jedi Knight
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Bleeding the brakes today: the fronts respond nicely to pushes of the pedal, with bubble-free fluid emerging. But the rear brakes don't want to eject any fluid from the bleed nipple. The PDWA is centered, the brake pedal is anything but firm: it has quite a bit of free travel before hardening.

My guess is a blockage somewhere in the rear circuit. What's the best way of tackling this problem?

Many thanks!
 
Assuming the master cylinder is good, I'd start at the PDWA and work toward the back until there was no fluid when a fitting was opened and the pedal pushed.

The problem is easily located this way.

You, however, will probably be covered in goo...
 
Don't know if it's true of the '6, but I've been told on the '3 to start bleeding from the wheel furthest from the MC. On the '3, this is the driver's side rear, then passenger side rear, then passenger front, then driver's front...FWIW.
 
Common practice is to always start from the furthest point and move closer to the master.

Did you "bench bleed" the master cylinder before installing it?
 
Yes, always go RR, LR, RF, LF when bleeding. On a LHD car anyways.

But, it seems our esteemed collegue has other problems.

Brosky has the most relevant question, which I assumed you did.
 
Instruction for the *8 are RF, LF, rear.
 
Don,

You do know that 8's are special, don't you???
 
The problem was very simple: the front reservoir in the master cylinder was empty!

The design of that thing baffles me. The opening to top up the front reservoir (which supplies the rear brakes) is very small. Why? I had assumed that there was some sort of connection between the two reservoirs, but there is not. Instead it appears that one is supposed to fill up the rear reservoir until it overflows into the front reservoir. Yet to do this means pouring in the fluid so that its level is awfully close to the top: it's almost brimming over.

Am I missing something?

In any case, once I topped up the front reservoir, I could bleed the rears without problem.

I am aware of the furthest-first rule, but in the case of two separate systems like on the TR6, it hardly seems like it would matter.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The problem was very simple: the front reservoir in the master cylinder was empty![/QUOTE]

Julian,

That is why I asked if you bench bled the M/Cyl first. You are not the first to have this problem, nor will you be the last.
 
Give yourself a "pat on the back" for figuring that out, Julian
 
Brosky said:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The problem was very simple: the front reservoir in the master cylinder was empty!
Click to expand...

Julian,

That is why I asked if you bench bled the M/Cyl first. You are not the first to have this problem, nor will you be the last. [/QUOTE]

Hi Paul,

Not sure how bench bleeding would have helped me, since my brain was sufficiently disengaged to not realise I had to top up the front reservoir when bleeding anyway!

Julian
 
Well, you would have noticed that nothing was coming out of that fitting and deduced the problem much earlier.
 
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