Bleeding brakes

[red_slr]

I have changed brake fluid many, many times over the years. Mostly on Caterhams.

To that extent I have a sealey one man ez bleed kit that works great.

I have a piece of plant that I need to change the brake fluid on but having problems.

There is only one caliper. That's connected to the master cyl which is connected to the remote brake fluid reservoir.

If I pressure up the system there is no leaks and holds 20psi nicely. Then if I crack the bleed screw it lets out a tiny few drips of brake fluid but that's it. I have tried a few times and cant get it to pass anything through.

The brakes work but very soft pedal. Anyone aware of any special system that might be in place or where I might be going wrong?

I have even tried the 2 man "up down" method and that yields even less... I wonder if the master cyl is dead or perhaps some kind of blockage?

Cheers!

[GreenV8S]

I assume this is a straight forward system with no ABS or anything like that - otherwise all bets are off.

The master cylinder will only be connected to the reservoir when it is right back against the stops. If the master cylinder pushrod is adjusted too tight that might not happen. I've known master cylinders which have got gummed up or worn to the extent that doesn't happen even when the pushrod is completely slack.

If you can push the piston back in the caliper and see fluid pushed back into the reservoir, you know the path is open so you should be able to bleed it by pressurising the reservoir.

[red_slr]

No ABS or anything like that its an FLT.

Just a simple master cyl, 2 lines in and out and that's it. Single caliper.

[Richard-D]

I would be suspecting the bleed nipple. Is there enough thread showing to be able to get a replacement before removal?

[red_slr]

I have removed the bleed nipple to check its not blocked etc all ok there.

[colin_p]

Have you tried getting a bit of stick and wedging the pedal down whilst you pressure bleed?

I'd be more inclined on something that simple (what is it by the way?) to do it the old fashioned manual way.

[GreenV8S]

colin_p said:

Have you tried getting a bit of stick and wedging the pedal down whilst you pressure bleed?

How's that going to work?

[colin_p]

GreenV8S said:

colin_p said:

Have you tried getting a bit of stick and wedging the pedal down whilst you pressure bleed?

How's that going to work?

There is a possibility that the port into the master cylinder from the reservoir may be closed in the resting position.

[GreenV8S]

colin_p said:

There is a possibility that the port into the master cylinder from the reservoir may be closed in the resting position.

Have you ever known a master cylinder where the port to the reservoir was closed in the resting position and open when moved away from the resting position? That's the opposite of the normal behaviour. How would such a design ever work?

[red_slr]

Its a JCB. Very simple set up on the brakes. Yes I did try having the brake pedal down but this made no difference. I think we will have to replace the master cylinder as the next step and blow out the lines. Its old, but not that old. About 12 years.

[red_slr]

New master cylinder installed, all sorted.

Still couldn't get the ez bleed to work but disconnected the line going into the calliper and managed to use it to blow all the old fluid out and then had a good pedal so used the up down method from there and 10 mins later all sorted.

[colin_p]

Glad you sorted it and reported back.