11 replies to this topic

[hazpalmer14]

Try to bleed my brakes today. New yellow tag master cylinder, new smaller bore rear wheel cylinders as the fronts are now 4 pots (were drums) new front to rear pipe etc etc. 99% new.

Topped up the master cylinder and tried to bleed the rear brakes first. And I can't seem to get any fluid through. At the end I managed to get a dribble out but this has made no difference really to the master cylinder level.

Would this suggest the Pdwa valve is shot?

[hazpalmer14]

Could have I connected or up wrong. Looking from the front of the car into the engine bay top of the master cylinder goes to the left hand side (os/drivers) of the pdwa valve. And the bottom goes to the right (ns/passenger) side of the valve.

The bottom from master cylinder does the front to rear and the top of doing the fronts. Is this right or wrong?

Edited by hazpalmer14, 08 April 2020 - 03:15 PM.

[Ethel]

I'll hazard a guess that you mean FAM7821. This one's upside down, but the ports for the front circuit are opposite one another whereas the outlet for the rear is is nearest the nut end (rear inlet is nearest the mounting hole.)

 

Bleed the rear circuit first to stop the front closing it off. Sealing the front circuit before the  FAM valve would help or use a syringe & bit of hose to pull the fluid through with vacuum. 

 

 

PDWA is "pressure differential warning actuator" an is summet else with a leccy switch.

[mad4classics]

From memory that sounds correct I think; the left bottom side looking from the front goes to the back to back connection and down to the front subframe.
When I had this problem (also yellow tag master cylinder) it turned out to be collapsed rear flexible hoses. Have since replaced everything with braided.

[hazpalmer14]

I'll hazard a guess that you mean FAM7821. This one's upside down, but the ports for the front circuit are opposite one another whereas the outlet for the rear is is nearest the nut end (rear inlet is nearest the mounting hole.)

Bleed the rear circuit first to stop the front closing it off. Sealing the front circuit before the FAM valve would help or use a syringe & bit of hose to pull the fluid through with vacuum.



PDWA is "pressure differential warning actuator" an is summet else with a leccy switch.

Yes a FAM7821. It was the NS rear I was trying to bleed first. I've heard pumping it a few downs and holding it down before undoing the bleed nipple might help and might take a few attempts to get fluid through.

How would I seal the front circuit?

Edited by hazpalmer14, 08 April 2020 - 05:40 PM.

[Ethel]

make up something to blank a pipe connection. I've a collection of old pipe unions with short bits of pipe crimped over a few times at the cut off end.

[Magneto]

I had this problem on one of my cars and used this method to get them bled.....worth a try. I didn't think this up, it was in the back pages of an old Haynes manual.

 

So, with the MC topped with fluid, open the rear brake bleeder (I use a hose into a bottle with an inch of fluid in the bottom so it can't draw air back in) push down smoothly on the pedal, hold three sec then let up slowly. Wait 15 sec, then repeat. Once you get good clean fluid and no bubbles, close the bleeder and move to the other rear brake - repeat till again clean, clear fluid with no air in it. Bleed the fronts the normal way.

 

This was the only way I could get fluid to flow out the rear bleeders on my 1980 Estate, but it worked.

[Mini Manannán]

I had no end of head scratching with my FAM7821, eventually replaced it with a brake proportion valve - all the head scratching was gone.

  This one: https://www.mcgillmo...-knob-type-677/

[MacGyver]

Happened to me too when I changed all the rear piping. If you put it under pressure, with all the air in, it will lock the rear system before you open the bleed nipple. Looks like nothing come out but actually a tiny bit of air comes out...
The only way the pdwa doesn't lock is to open the bleeders before applying présure. Actually easyer with an EasyBleed and an assistant...

Edited by MacGyver, 09 April 2020 - 06:10 AM.

[hazpalmer14]

Managed to get bleed the fronts today and get fluid out the rear on one side. I have lost the right size spanner I need for the nipple so once I got a good flow of fluid I packed up for the day. I'll revisit it when I find the spanner and do a more thorough job. Thanks for your help

[gazza82]

Managed to get bleed the fronts today and get fluid out the rear on one side. I have lost the right size spanner I need for the nipple so once I got a good flow of fluid I packed up for the day. I'll revisit it when I find the spanner and do a more thorough job. Thanks for your help

Not left it on the other bleed nipple like my Dad did once? ... found it a couple of months later ... still there but very rusty!

[hazpalmer14]

Managed to get bleed the fronts today and get fluid out the rear on one side. I have lost the right size spanner I need for the nipple so once I got a good flow of fluid I packed up for the day. I'll revisit it when I find the spanner and do a more thorough job. Thanks for your help

Not left it on the other bleed nipple like my Dad did once? ... found it a couple of months later ... still there but very rusty!

No sadly not. I think it's a 7mm. If its imperial I have 1/4 and it isn't that. Need to clean out the mini and sort out my tools. I finish working on it and don't return my tools so they are scattered in the mini some where.