Brake pedal doesn't return wel

[xychix]

My series III 109 brakes nice with a zeus front disc brake kit (original brakes at the rear) and with a new def 90 master cylinder.
However the pedal doesn't nicely return which in turn means I'm driving with my brake lights on (and the vacuum Hella UP28 I've attached with a relay to that same wiring.)

What would normally cause the pedal to really return? the 2 springs on the pedal? of also something in de big drum directly behind the pedal? 

Edited August 6, 2023 by xychix

[David Sparkes]

I suspect the 'big drum directly behind the pedal' is a brake servo. The Hella UP28 is described as "a flexible solution for providing high pneumatic-volume supplemental vacuum", so the engine could be petrol or diesel, which engine do you have fitted?

I see the Hella UP28 has a design life of 1,200 hours, which fits in with the pump only operating when the brake lights are lit.

I cannot really answer your question, I was just trying to clear some uncertainty, perhaps others more familiar with a Def 90 master cylinder can help.

Regards.

[steve b]

Is the pedal box and servo can the original 109 unit? 

Will the pedal return to the resting stop if you lift it by hand?

The brake light switch adjustment on the 109 pedal box can be a bit sensitive

Steve 

[xychix]

13 minutes ago, steve b said:

Is the pedal box and servo can the original 109 unit? 

Will the pedal return to the resting stop if you lift it by hand?

The brake light switch adjustment on the 109 pedal box can be a bit sensitive

Steve 

yes original 109.
yep lifting by hand works and then it stays there.

Assume that if the brakes aren't dragging it should be ok ish. However for the switch to turn open in the current pedal end position i'd have to fabricate a new bracket that allows for the pedal to sit ~3mm lower. The switch is already at max setting. This feels however as solving the wrong problem.... the pedal should return.

Does the Brake Servo have a task in this? 

[Bigj66]

Can a Defender master cylinder fit to a 109 servo? Are the rod lengths compatible?

 I thought you needed the Defender pedal box, servo and master to work together? Maybe not, interesting 👍

[xychix]

40 minutes ago, David Sparkes said:

I suspect the 'big drum directly behind the pedal' is a brake servo. The Hella UP28 is described as "a flexible solution for providing high pneumatic-volume supplemental vacuum", so the engine could be petrol or diesel, which engine do you have fitted?

I see the Hella UP28 has a design life of 1,200 hours, which fits in with the pump only operating when the brake lights are lit.

I cannot really answer your question, I was just trying to clear some uncertainty, perhaps others more familiar with a Def 90 master cylinder can help.

Regards.

Hi David, Thanks for the clarification. I've fitted that UP28 meself after removing the 2.25di and placing a 200di (non turbo) engine. Also the defender 90 master brake cylinder should be next to equal to the series 109 only with another bias and displacement as the def90 has discs at front and drums at rear, i quite deliberately choose that over the 110 cylinder (which I believe to have brand new in stock as well.) 

[xychix]

3 minutes ago, Bigj66 said:

Can a Defender master cylinder fit to a 109 servo? Are the rod lengths compatible?

 I thought you needed the Defender pedal box, servo and master to work together? Maybe not, interesting 👍

pretty sure that isn't the case as this setup did work correctly for a while  and got me trough french MOT with compliments on the balance in breaking. 

Edited August 6, 2023 by xychix

[steve b]

Is the pedal pivot slightly siezed or tight?

Have you tried pulling the clevis pin out of the pedal to servo rod connection to check free pedal movement?

If nothing obvious shows itself maybe an extra spring from the pedal to one of the box bolts like the series clutch return style might do it ?

Steve

[xychix]

9 hours ago, steve b said:

Is the pedal pivot slightly siezed or tight?

Have you tried pulling the clevis pin out of the pedal to servo rod connection to check free pedal movement?

If nothing obvious shows itself maybe an extra spring from the pedal to one of the box bolts like the series clutch return style might do it ?

Steve

will have another look tomorrow, i needed a small success after fighing with various stuff. So i gave the air filter a permanent place. Used the disco brackets (bending and cutting involved) and some threaded bar m6. sits rock solid now. and opening is in the right direction to meet my snorkel at the entry of the just removed heater and fan (hell that was a fight as the inserted crimp nuts came loose and it's hard to reach with hacksaw or anglegrinder)