Firm brake pedal but no brake feel.

[Angle Grinder]

Wondering if anyone else recognises these symptoms.
Out driving in my Flavia coupe and every so often upon braking the pedal hard very little travel and felt very hard, but retardation felt alarmingly slight.

This scenario didn't happen everytime, but seemed to get worse if pedal was pumped.

Brake fluid is less than a year old and was thoroughly bled.

Front pads are new about 60 miles ago and do need to be better bedded in, but I don't think this would explain changing pedal feel.

[Kevinlincs]

Classic symptoms of a servo issue, either the servo itself has failed or the vacuum supply or one way valve has failed. Check the pipe from the manifold to the servo first off for splits in itself, if all appears OK then pull the pipe out of the servo which should give a sucking in of air sound if you've just had the engine running. If not then the vacuum is leaking out somewhere, or not getting there due to a failed one way valve.
Conversly if you have great vacuum and the pipe will hold to your finger with the engine running (via great vacuum) then your servo unit has failed. It's often in conjunction with rough engine running as it allows more air into the manifold than usual.

A very simple test to see if all is well with any servo brake system is to let the car idle and press and hold the brake pedal. Now switch the engine off and release then press the brake again. It should take a couple of presses to use all the available vacuum before the pedal goes hard.

If it makes no difference with yours if the engine is running or not then the vacuum assisted servo system is clearly nor working.
Hope that all makes sense and is of help.

[lancialulu]

I agree about the servo. These are “remote” and the push rod can corrode also the auxiliary air valve. It does not take much to stop these units working. If you get a repair kit it does not come with a new push rod. You need to measure the position of the old when before removing so the new one will be at the correct position. An incorrect position could result in the servo not releasing the brakes….

[Jaydub]

  A simple test in addition to what Kevin suggested. Pump the pedal with engine off until you get a firm pedal, hold the pressure, start the engine. If the servo is working the pedal will sink down slightly due to suction on the servo diaphragm.

Jaydub

[Angle Grinder]

Fortunately, a few years ago, I bought one of the modern dual circuit servos recommended by the Consortium.  Looks like it's time to fit it.

[lendickins]

Servo for sure (try the diaphragm and/or split pipe into the diaphragm end) , although I would check the master cylinder seals at the same time.