Technical Brake bleeding issue

[ducman]

Hello,
I've a 1998 1.9 Ducato Riveria camper. The long rear copper hardline failed (puncture in the pipe). I replaced it but cant bleed the brakes.
I've read a number of threads and none the wiser on issue. There's very little (none now) brake fluid even going to the hardline at the back.

The brake pedal was pushed to the floor a number of times after failure (when spongy/ no brakes at all). I can hear air escaping sound from pedal/ master cylinder when cap is on it and brakes pressed. No fluid leak anywhere and the fluid never dropped really from the bowl (i topped up anyway).

Tried to bleed by someone pressing brake. No flow at all to the back now. The bottom bleed nipples on front (left and right) has good flow - temp gave little braking after bleeding, the top on 1 side has some flow and the other nothing.

Have i wrecked the seals on the master cylinder, are my not bleeding correctly or does the master cylinder need to be bled?

Any help appreciated

 

[bugsymike]

Hello,
I've a 1998 1.9 Ducato Riveria camper. The long rear copper hardline failed (puncture in the pipe). I replaced it but cant bleed the brakes.
I've read a number of threads and none the wiser on issue. There's very little (none now) brake fluid even going to the hardline at the back.

The brake pedal was pushed to the floor a number of times after failure (when spongy/ no brakes at all). I can hear air escaping sound from pedal/ master cylinder when cap is on it and brakes pressed. No fluid leak anywhere and the fluid never dropped really from the bowl (i topped up anyway).

Tried to bleed by someone pressing brake. No flow at all to the back now. The bottom bleed nipples on front (left and right) has good flow - temp gave little braking after bleeding, the top on 1 side has some flow and the other nothing.

Have i wrecked the seals on the master cylinder, are my not bleeding correctly or does the master cylinder need to be bled?

Any help appreciated

Some have more success using pressure bleeding kit, but generally I haven't needed them.
If your brake master cylinder is very old it may not like fast pumping of the pedal to bleed.
Try filling master cylinder to the brim then slackening one at a time of the pipes coming from the master cylinder until clean air free fluid comes out and retighten, then top up fluid.
Does your vehicle have ABS braking as this sometimes holds air.
When you say the long rear brake pipe was replaced, do you mean the front to rear, or the one on the axle after any anti skid/load valve.
Sometimes if vehicle jacked up so wheels hang down the antiskid valve thinks there is no weight in rear of vehicle and restricts flow to the rear brakes.
Another thing that sometimes works is to have someone keep checking/topping up the brake fluid whilst some removes the bleeder completely and lets the fluid and air simply flow out.
Note! Do not touch the brake pedal whilst doing this, just let gravity do it's job.
The air escaping noise when pressing brake pedal is probably just the brake servo as normally it only has to travel a short distance before brake works.
Let me know how you get on, retired now but have bled brakes on thousands of vehicles since 1969.

 

[ducman]

thanks for that, will try seeing if it will flow out without pressing the pedal. Probably original master cylinder. I didnt see abs pump under the bonnet it does have sensors on the front brakes but they're not connected to anything and brake pipes from master cylinder just run down . yeah was the long copper pipe on the rear axle. it was up on stands but i tried to bled when it had wheels on and on the flat also.

 

[bugsymike]

thanks for that, will try seeing if it will flow out without pressing the pedal. Probably original master cylinder. I didnt see abs pump under the bonnet it does have sensors on the front brakes but they're not connected to anything and brake pipes from master cylinder just run down . yeah was the long copper pipe on the rear axle. it was up on stands but i tried to bled when it had wheels on and on the flat also.
View attachment 473716

When bleeding the master cylinder do the the lower pipes first, then the upper pair, just using gravity as I suggested.
Re the rear brake bleeding after the load sensor, it is often attached to a spring on the axle.
Check that the sensor lever actually moves as they can seize, then try and put it in a position that allows maximum flow for bleeding, afterwards when hopefully all good reset to original position so not too much braking effort on rear of vehicle which would cause skidding.
I had a Nissan Cabstar that unladen at MOT Station rear brakes didn't activate, so tester allowed me to adjust the sensor and we got good readings, however driving back afterwards it was skidding the rear end as empty, so I had to readjust as before.

 

[ducman]

When I slacken the pipes off the master cylinder. Only brake oil comes out the front 2. None of the other 3

 

[jackwhoo]

When I slacken the pipes off the master cylinder. Only brake oil comes out the front 2. None of the other 3

Ah .... new master cylinder time.

Check brake pedal fully returning up though.

 

[ducman]

The pedal is fully returned. I wasn't pressing it just letting to see if it flowed out per above when pipes slackenes

 

[jackwhoo]

You are most likely going to have to find and fit a new master cylinder.
If you remove and strip the one you have I expect the master cylinder piston that goes in bore last will be stuck down or partly down blocking fluid flow.

 

[jackwhoo]

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[jackwhoo]

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[bugsymike]

As a final test, you could put your finger over a none working master cylinder outlet with pipe moved back and use your finger as a "one way valve" whilst someone else gently presses the pedal down and you seal it on the return stroke a few times.
If it works for one, try on others.
But as @jackwhoo suggests "Ah .... new master cylinder time."

 

[ducman]

Thanks folks will try that