brakes bleeding S1 4.2

[cooper66]

Hello,

It is definitely a newbie question, nevertheless this is my first intervention on the braking system, and I cannot bleed the front calipers short summary :
-new master vac
-new master cylinder
-restored calipers (tested)
-new brake lines (tested with compressed air and no leaks)

I implemented by the Haynes the following brake pipes :



I respected the order and started by the rear calipers, with manual bleeding (one at the brake pedal and the second bleeding at the caliper). Result is ok brake pedal is hard => issue is for the front calipers, impossible the get fluid out of the bleeding nipples and even if nipples are opened the pedal stay hard.

Any idea ? I'm stuck here ...

Thanks

[abowie]

1. Use a syringe to try to squirt fluid from the reservoir hose into the front circuit with the front caliper bleeder open.
Note that the front and rear systems are entirely separate and so make sure you are squirting the fluid in from the correct reservoir hose.
If this works, do both sides and then try your pedal again.
http://www.projectetype.com/index.php/t ... ringe.html

2. Sometimes with initial bleeding the shuttle in the tandem slave cylinder (L in your diagram) can get pushed too far forward and prevent fluid entering the front system. Try putting fluid under pressure into the caliper via the bleed nipple to see if you can move it back, then try 1 again.

3. Check that there is actually a hole in the booster for the fluid to come out. Seriously.

[Springer]

Maybe a stupid question but since the front caliper has its own master cylinder. Are you sure you got the mechanical connection from the pedal box to the cylinders correct?
Can you actual see it is pressure on the master cylinder to the front calipers?
If it is and you can open bleeders on both sides and the pedal it still hard I would have looked at the master cylinder first.

[cooper66]

Hello,

Thanks to your tutorial Andrew it works perfectly for bleeding the front. So now all the 4 calipers are bleeded the pedal is hard but when i start the engine the pedal stays hard !

I checked all the vaccum system, the pipes connections are correct according to the diagram in my first post.

Do you have any idea of the root cause ?

Thanks

[cooper66]

I'm thinking to a too long master cylinder rod, does it have sense ?

[abowie]

So now all the 4 calipers are bleeded the pedal is hard but when i start the engine the pedal stays hard !

By this I assume you mean that the pedal effort is not made easier when the car is running?

If this is the case I would still suspect a problem with the vacuum assist on the brakes.

Double check you have the hoses correct. Check that the valve on the top of the vacuum reservoir is working correctly. Check that the reaction valve in the front of the pedal master cylinder is functioning correctly.

[cooper66]

hello Andrew,

I mean that after strating the engine the brakes stay blocked and the pedal is hard.

*) hoses connections checked and correct
*) How to check the valve on the top of the vaccum reservoir ? this is a one way valve right ?
*)reaction valve in the front of the pedal master cylinder => checked and functionnal

Could it be the the shuttle in the tandem slave cylinder which may be blocked in one specific position ?

thanks

[cooper66]

issue found, it was it was the adjustement of the pedal height which did not allow the master cylinder to open enough and allow the DOT4 to come back into the reservoir !

Bleeding has been done again and it's ok now !

Thanks for the different advices

[abowie]

Good outcome.