Spongy brakes

[dual cab hdj105]

Chasing some ideas on how to fix my spongy pedal on my non-abs 105 series.

I have been chasing this problem for a few months now, no amount of bleeding the system has helped, I’ve replaced master cylinder, all calipers and all flexible brake lines with no change.

Engine off - pedal pumps up hard
Engine on - pedal fades to the fire wall!

Absolutely stumped at the moment….yes I have bled it at the LSPV multiple different ways….
Thanks all!

 

[Mike NXP]

nice looking rig, jealous.....I'm not sure about the 105 series, does it have all the fancy electronic things attached to the master cylinder or is it mechanical

 

[hoser]

My guess is the LSPV is the likely culprit even though you've bled it several times. You can temporarily bypass it but it requires a 90 degree elbow and a plug for the LSPV return line.