VW LT 46 Brake pedal excessive travel

[Johnetchingham]

I Have a 51 plate, VW LT46 Petrol with LPG fitted. We have just replaced the Discs and Pads and Master Cylinder to try and fix a very long pedal. The travel is just the same. With the engine off the pedal is high and feels hard. Switch on the engine adding servo assistance and the pedal goes virtually to the floor. Is the ABS system prone to trapping air ? We have used a pumped type pressure bleeder. I feel there must be some air trapped somewhere or a component in the system is being overcome by the sheer power of the servo. My friend who carried out most of the work has over 25 yrs experience with cars and light commercials. I am a Licensed Aircraft Engineer. We know of another LT with exactly the same symptoms.The pedal travel is in my opinion excessive. If it had wings I'd ground it. Any ideas ?

 

[gblades]

How are the brake hoses? They can expand under pressure. Maybe the standard ones are a bit weak.

 

[Burnerman]

Usually if the brake pedal travel is excessive, the fault is within the rear brakes rather than the front.....this is because the front pads have to be self adjusting but the rear shoes don't.
I also accept that bleeding some brake systems can also be difficult, which is why it's best to suck the fluid through using a vacuum bleeding tool.
Try this, if you want.....if you have replaced the master cylinder leave the brake connections loose and press back the caliper pistons. This has the effect of pushing hydraulic fluid back up the pipes, and may just remove any trapped air. Tighten the pipe connections afterwards, naturally!
John

 

[gregers]

and if the brakes are like the 1s fitted to the sharan/alhambra/ford galaxy the general consensus is to undo the bleed nipple or you can flip the valve/ring within the abs.