spongy brakes

[Dave1954]

hi i have spongy brakes, on robin hood,bled them till only oil came out,new linings all round,new rear cylinders, new master,no leaks.the only thing i can think of if the servo grommet to the master cylinder is faulty, will this give me that problem. Doing my head in now, only thing to do do for IVA,any ideas appretiated.cheers Dave

[8 Valve Ed]

Have you tried reverse bleeding from the wheel cyl to the master cyl?

If it's dual line... Which I suppose it must be, have you tried bleeding both front and rear (both circuits?) at the same time. I had an Astra which wouldn't bleed and I went out with a can of brake fluid and opened the bleed screws at for both front and back and pumped. That fixed it.

Can't see the servo being the culprit, are the brakes solid solid when the engine is off?

After pumping the brakes with the engine off, does the pedal go down as the engine starts if the pedal is held down while starting the engine? (It should.)

[Dave1954]

I bled brakes conventional way,then thought there might be air in new master, so i took pipes of master and bled then did each wheel.the pedel is fairly hard then sinks slowly under pressure.when i start engine pedal goes to floor,so servo seems ok When i pump servo air out, brakes go hard then slowly sinks down under pressure.That seems a good idea to bleed 2 circuits together. Cheers Dave

[8 Valve Ed]

Originally Posted by Dave1954

brakes go hard then slowly sinks down under pressure.That seems a good idea to bleed 2 circuits together. Cheers Dave

The pedal slowly sinking sounds familiar, I would go with bleeding two circuits at the same time.

I have also had success back bleeding with troublesome systems.

Good luck!

[Dave1954]

Cheers mate I think you hit the nail on the head ,ill try it

[lambogenie]

You probably have this sorted by now but just in case try bench bleeding the master cylinder, look it up on YouTube. Sometimes this is the only way to remove air from the master.