Brake lights stay on.

[Biggles633]

I had to change my hydralic brake light switch and then I bled the whole sysem with a pressure bleeder like used by tactical repair, with dot 5.
Since doing this, as soon as I press the brake pedal the brake lights come on and stay on. Pedal returns correctly, this happens without and with air pressure.
The only way to get the lights off is to let a bit of pressure out of the airpack bleed.
Ive chacked the vent on the master cylinder, is clean and works. Taking the master cylinder cap off does not relieve the pressure.
Is there a return pipe or non return valve that could be blocked/stuck?

Im in the UK so getting a air switch kit is not an option.

 

[williamh]

It should take between 60 to 120 psi to activate the switch. Either the switch has failed or the master cylinder has an issue , it should release the line pressure back when the peddle is released

 

[glcaines]

I know you stated that the brake lights stay on after the pedal is released, but do the brakes stay on after the pedal is released. If the brakes don't stay on, I would suspect a faulty brake light switch.

 

[porkysplace]

It should take between 60 to 120 psi to activate the switch. Either the switch has failed or the master cylinder has an issue , it should release the line pressure back when the peddle is released

That's the low air warning light at those pressures ,not the switch for the brakes lights .

 

[Biggles633]

So today I popped some wheel cylinder seals. Is it possible to over pressure the brake system?

 

[G744]

There is a chance the pushrod between the M/C and pedal is set a bit too long, and not releasing a small pressure in the system.

That catches a lot of folks. It has to 'wiggle' a bit when released.

Also, having the shoes adjusted a bit too tight will cause them to swell up, get tighter, and give a lot of drag. Make sure they are set to spec clearance.

 

[Biggles633]

Thanks for all your help. ive taken the master cylinder off, had a fair bit of debris in it and stuck to the spring. Pretty sure this wpuld of been blocking the return port. I have removed two brake cylinders and they are nasty. Full system rebuild requred.