Brake pedal stiff when bleeding rear brakes

[robbyasti]

I have a 1968 Innocenti mini. It has been stood for a few years. I thought it would be a good idea to sort out the brakes.
I changed both rear wheel cylinders and attempted to bleed the brakes. When I open the bleed nipples on the fronts, there is no problem, the brake pedal goes to the floor and the fluid floods out.
When bleeding the rears, the brake pedal is hard and moves to half way and stops, there is a very small amount of fluid dripping out of the nipples. I have fully removed the nipple but it makes no difference.
Any advice would be appreciated!

[InimiaD]

If you have one fitted i would guess that the pressure limiting valve fitted on the rear subframe is partly / fully seized.
Also make sure there are no kinks in the brake pipe front to rear.

[robbyasti]

If you have one fitted i would guess that the pressure limiting valve fitted on the rear subframe is partly / fully seized.
Also make sure there are no kinks in the brake pipe front to rear.

Thanks, there is a pressure limiting valve fitted. I will check the pipes for kinks. The previous owner raised the car with a fork lift truck and could of kinked the brake pipe.

[ianh1968]

I had the same problem once on a car that had not been
"maintained" for a while....

I cured it by removing the bleed screws and poking a stiff
piece of wire up the holes - They were just blocked with
rusted up crud!

Ian

[dklawson]

There are different methods people use to bleed brakes. The method I have the best luck with requires two people and synchronized calls between them to flush the system. It involves pushing the brake pedal down VERY slowly so the spool in the pressure limiting valve does not shift and block flow to the rear wheel cylinders.

On occasion I have also resorted to cracking the fittings open one at a time from front to back and actuating the pedal to push the air out section by section. It's messy and a lot of work but it did help me bleed a couple of systems that were completely dry when we started.

What bleed method have you been using?

[robbyasti]

There are different methods people use to bleed brakes. The method I have the best luck with requires two people and synchronized calls between them to flush the system. It involves pushing the brake pedal down VERY slowly so the spool in the pressure limiting valve does not shift and block flow to the rear wheel cylinders.

On occasion I have also resorted to cracking the fittings open one at a time from front to back and actuating the pedal to push the air out section by section. It's messy and a lot of work but it did help me bleed a couple of systems that were completely dry when we started.

What bleed method have you been using?

Thanks for that Doug. I tried your method by pushing the brake pedal down very slowly and it worked. The pedal went to the floor. Does this mean that the pressure limiting valve is faulty or not?

Rob

[robbyasti]

I had the same problem once on a car that had not been
"maintained" for a while....

I cured it by removing the bleed screws and poking a stiff
piece of wire up the holes - They were just blocked with
rusted up crud!

Ian

Thanks Ian. I have done the same thing in the past and it has always worked but on this occasion the bleed nipples are new.

Rob

[dklawson]

I don't know what the proper test procedure is for a pressure limiting valve.

However, if pushing the pedal slowly lets fluid out of the bleed nipple... and pushing it rapidly does not let fluid out, I would say that is normal and what is expected.

[JC T ONE]

Might be the valve, but my personally guess = collapsed brakehoses, and yes - I have seen 2 collapse at the same time.

[ianh1968]

Thanks Ian. I have done the same thing in the past and it has always
worked but on this occasion the bleed nipples are new.
Rob

It wasn't the holes in the bleed screws that were blocked,
it was the drilling between the cylinder bore and the bleed
screw orifice.

Ian