Thread: 300Tdi - no brake pedal pressure

The gizmo looks like a cruise control actuator.

Brake problems may be due to an internally collapsed flexible rubber brake hose at the diff end.

Hi. Is your M/cyl off the car now? One simple test if it is is to clamp it in a vice and put some fluid in it. press a finger over each of the outlet ports and push the piston in with a rod or screwdriver or something. If the fluid pushes your finger off the port it is working. Repeat on the other circuit. In fact, back in the olden days when I was doing this stuff we used to do this to "activate" the m/cyl. Of course, if you meet no resistance when doing nthis it's the m/cyl that is faulty, but that is unlikely. A new cylinder is unlikely to be completely without some seal.

I would try pressure bleeding next. If all seals are OK, then only air can be your problem. Unless you left out the rod from the booster....

Originally Posted by bee utey

Brake problems may be due to an internally collapsed flexible rubber brake hose at the diff end.

Producing "zero pressure, no resistance at all."?

Originally Posted by bee utey

The gizmo looks like a cruise control actuator.

Brake problems may be due to an internally collapsed flexible rubber brake hose at the diff end.

Arrr, yes that will be what it is, cruise control. I have been removing bits of this since i bought the project vehicle.

Thanks for advice bee utey. I shall replace that hose too.

Originally Posted by johntins

Producing "zero pressure, no resistance at all."?

Of course. Brake hose is blocked during bleeding due to initial fast fluid movement dislodging the lining:

but bleeding the rear brakes very very little fluid came through but there was peddle pressure.

then rubber moves to allow air in rear circuit to percolate forward resulting in:

But then when I went to test the vehicle there was zero pressure, no resistance at all.

Only a theory, of course. Based on experience with old hoses on various old vehicles that I've had the privilege of fixing up. But yeah, I could be wrong.

Originally Posted by johntins

Producing "zero pressure, no resistance at all."?

Hi johtins. The cylinder is on the vehicle now and i am reluctant to remove it unless as a last resort. I will replace the rubber hose at the rear as bee utey suggested and get it pressure bleed and see it that sorts it.

Originally Posted by bee utey

Of course.



Only a theory, of course. Based on experience with old hoses on various old vehicles that I've had the privilege of fixing up. But yeah, I could be wrong.

It was merely a question, and an appropriate one given the car has a dual braking circuit.

Before I replaced the master cylinder I at least had some pressure and the second pump there was plenty. Even when bleeding (before replacing the cylinder) I would get pressure and good flow at each wheel.