Question, did you find one like mine while you were looking around?
So I think we both agree it is more likely to be the trailer brakes than the towing truck brakes.I did and already new of it but as I stated I read from his post that this simply happens when he hooks the trailer up not from prolonged brake usage which i found very bemusing.
Yes but brake fade doesn't cause the pedal to travel further , only air in the system can cause the pedal to travel further as air compresses where fluid doesn't.
He could test this quickly (and illegally) by unplugging the plug and driving it a bit, including braking obviously.That's why i said "odd" cos some backfeed through the brake pedal switch's circuit in a peculiar way can affect the management to open the IV's in the moduator and lower the pressure... even if it's not likely IMO it should be ruled out cos the symptom is odd too
i've seen so many oddities on LRs that nothing can surprise mee
mee too but worth to be ruled out anywayI'd give this about a 1000 to one chance of being the reason,
Could it simply be air still in the abs system? If the pedal goes to the floor when the abs kicks in, it certainly sounds like air.Apologies for the late reply. Ended up bleeding one more time and putting it back to work for a day to see if they were any better. They were not.
There's no specific trailer it pulls, there's about 3 different ones, and another 2 trucks which brake them fine. Was mentioned to me that whilst braking when someone pulled out Infront the pedal was low but working, but when the abs kicked in the pedal hit the floor and had to be pumped back up. Doesn't seem to be temp related. Happens as soon as the weight is put on. But as mentioned I doubt brake fade etc would cause the pedal to drop but rather just be inefficient.
There's only 2 parts left I could think of changing, one being the ABS pump (leaking internal seals) not sure on that one. And the other being the britpart cylinder (possibly letting fluid bypass the seal with the extra pressure)
I have all these spare parts so it's not a big deal to try them..
I suppose being brand new brakes it could be a slightly higher pedal without the trailer too, but seems pretty average to me.
As far as im aware the slabs ECU uses the ABS module to monitor the pressure sent to each brake/axle and adjusts it accordingly, I assume it measures how much pressure is needed to brake each axle and compares it to the speed reduction to determine weight load, although just a guess for a very complicated system.For these symptoms on a general towing commercial vehicle normally it would imply a problem with either the load sensing valve or the rear brakes.
In normal operation less brake force is applied to prevent the rear wheels locking up when more weight is imposed the valve opens up and allows more forceful braking which would mean the fault is either pressure escaping at the load sensing valve or some leak on the rear system only becomes more apparent to be noticed at the pedal under this higher pressure braking.
As far as I'm aware though the D2 doesn't have a load sensing valve although I would have thought it ought to have some system fitted given the significant axle load variation between a single driver and all seven seats being filled so don't know if it does it by using the ABS system to modulate brake force between the front and rear axles by something like measuring the pressure in the rear airbags to assess load then altering brake force to the rear axle but I would be very surprised if it was as sophisticated as that but the reason vehicles on air suspension can't use traditional brake load sensing valves is they are activated by steel springs sinking to indicate load whereas on an air sprung vehicle it remains level the whole time.
I would have thought though if you drove on some loose gravel and locked up a few times and the ABS worked and the pedal went hard and didn't sink that ought to mean everything is OK and that side of things though.
It does not measure any pressure as there is no pressure sensor in the system, the algorythm is based on a deceleration value induced by the wheel speed sensor's inputs on which is calculated the VSS(vehicle speed signal) so if the vehicle doesnt decelerate enough according to the calibration of the system the ECU will manage the modulator's pump and inlet/outlet valves as to increase/decrease pressure untill the deceleration threshold is acceptable for it's stored(mapped) values.... it's a very complicated system... took me about 2 years of hard study to understand it and that's why i'm "obsessed" about tyre dimensions too... belive me or not, i'm sure that there are smarter guys than me out there, so called "specialists"... the difference is that i provide well documented informations for free not for profit, i can give you a small part of what's involved, i've studied at least 10 doc more and corroborated the info but the attached doc is quite relevant and if somebody is determined enough to read it at least twice like i did will understandAs far as im aware the slabs ECU uses the ABS module to monitor the pressure sent to each brake/axle and adjusts it accordingly, I assume it measures how much pressure is needed to brake each axle and compares it to the speed reduction to determine weight load, although just a guess for a very complicated system.