Spongy brakes...but only when running!!!

[chuggers72]

I've recently put new calipers, pads and hoses on the front end of the ol' gal.

Bled her up and flushed thro' a good 4 litres of brake fluid at all points (including rear & clutch). Also removed brake master cylinder and bench bled as system was fully drained and I had a feeling there was air in it.

All is well when parked up ie. good pressure in brake pedal, calipers working fine.......however, when I start her up the brake pedal pressure is lost and pedal travels to the floor. Pumping the pedal does not appear to do much either.......Is this a master cylinder issue or brake servo maybe?!

All help appreciated...am I missing something?

[AdrianC]

If the pedal is solid when the engine's not running, then that suggests servo to me.

[chuggers72]

Ok Adrian - I need to add something to my original post - probably should not have jumped on the forum so quickly!

When standing (engine not running) ...pedal soft initially....couple of pumps and pressure builds....hold it down and pressure is maintained......let off pedal and pump again and pedal is back to soft.

Start her up - super soft pedal as described to the floor.....pump 3-4 times and pressure builds and can be maintained....however let off pedal and pump again and back to super soft.

I'm 99% sure there is no air in the system - did not touch back brakes.

What do you think?
Cheers

[AdrianC]

Is that with the handbrake on? I'm wondering if the rear shoes are needing to be pumped out because they're way out of adjustment.

If it's with the HB on and holding, then you have air in the system.

[chuggers72]

Post above was done with handbrake on - however still behaves the same with handbrake off.

If I did not touch the rear brakes initially (apart from to bleed them) could they still need adjusting?

[AdrianC]

Post above was done with handbrake on - however still behaves the same with handbrake off.

That rules that out, then.

[chuggers72]

Bugger Any other ideas?

[scunnerd25]

You haven't put the calipers on the wrong sides have you with the bleed nipple on the bottom of the caliper rather than the top

[chuggers72]

Calipers on correctly. Actually sorted it today - adjusted the rear drums (they needed doing) and bled out the lines. Turns out there was more air in there (hat off to Adrian) and everything hunky dory. Happy days