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Brake master cylinder connections

B

Barnster

Enthusiast
Messages
28
Location
Harrogate
Hi folks!

I have a quick question during the replacement of my master cylinder on my F6 van. 3 ports and single tank on the master cylinder, previous owner cut the pipes, I guess due to seizure as they are all twisted.

Can anyone advise which pipes connect to which outlet? I'm guessing front left and front right to the two ports closest to the bulkhead (not sure if order matters) and the rear line to the outlet furthest from the bulkhead but just want a quick sanity check as can only find diagrams for 4 port master cylinders.

TIA.
 
Thanks for the reference. All connected up now and fitted and filled reservoir with brake fluid.. Next challenge.....

I'm pumping the pedal but no fluid is pushing through. I've undone the pipe unions just to double check and there is no fluid pumping.

The new master cylinder looks identical to my old one so have discounted a different length pedal pushrod. Anything obvious missing? I'm guessing the pushrod on the pedal just pushes into the master cylinder?

The pedal returns to it's "rest" position so assume there is some resistance in the master cylinder somewhere.
 
I asume you've bleed or tried to bleed the brake circuit in the right order as shown in the picture?
You'll need an extra hand to do this or you need a vacuum brake bleeder.
rem ontluchten.jpg
Otherwise there's something obstructing the brake pipes assuming you've got the right master brake cylinder
 
I've not got as far as bleeding anything yet - I have the bleed screw open on both front capliers as the system is empty at present. This issue is getting fluid into it.

It's another head scratcher. The master cylinder looks identical to the original externally - loathe to start stripping down a brand new part.

I've emptied the reservoir with a syringe and removed it from the master cylinder. The seals are all good (supplied with new cylinder) and there are some metal discs with slots in them between these and the two top ports on the cylinder. Not sure what the purpose of these is.

The pedal springs back when released even when the tension on the return spring is released but there is no suction from the ports when pressing the pedal with thumbs over them nor any pressure from the output ports.

Do these master cylinders need priming or is some pressure needed to get fluid into the body to create a syphon action at all?

The master cylinder is from DeMarco so not a cheapo one. Pedal pushrod has around 3/4 movement into cylinder when pushing pedal.

Any ideas or things to try would be welcome.
 
Fill master br.cylinder with brakefluid to the brim -Don't let it run empty- now start pumping the pedal. Do you have a poss to pressurize the master-cyl to ease the brakefluid to enter lines ? ( drill appropriate hole in old lid pop in a rubber hose-valve Make sure it's tight and holds pressure)
 
I will try this in the morning - I have done everything except pressurise the master cylinder reservoir. Every other car I've owned/built has worked just with gravity and pedal pumping. Thanks for the suggestion
 
Hi Barnster, instead of just opening the bleed screws, take them out completely and clean them with carb cleaner. Very often they're blocked.
 
Do you have free play between the brake pedal rod and the master cylinder piston?
 
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