Thread: Brake Fade issue

I would try again using the traditional method with a second person. Make sure you get the order correct.

Originally Posted by DiscoDB

I would try again using the traditional method with a second person. Make sure you get the order correct.

thanks for the reply.
I have tried several times now, including a powerbleed/s with the nanacom.
No air bubbles coming through now although there were quite a few in the early stages.
Still, with medium pressure on the brake pedal and engine running, pedal fairly smoothly goes all the way to the floor. Seems to me that this is most likely to be a master cylinder issue. Not looking forward to removing, inspecting, reinstalling and then another bleed.

have a read here
http://www.aulro.com/afvb/discovery-...ake-pedal.html

You put a seal kit in, maybe you put something in back to front? like cups lips?

Originally Posted by Outback 1

have a read here
http://www.aulro.com/afvb/discovery-...ake-pedal.html

thanks ken,
received the used master cylinder today (wednesday) and thanks for the quick service. Cleaned up, refitted and bled system again. Initially used the Gunston pressure bleeder before following up with a nanacom power bleed only to find I still have the same problem with the pedal going all the way to the floor, although a little slower than the original master cylinder. So it seems that the replacement used part you sent me itself is also leaking internally around the seals.
Went through the thread you mentioned above and there were a few interesting suggestions there. Tried cycling the abs actuator by driving in low range with TC and hill decent engaged up to 40km/hr then releasing throttle and allowing abs to bring me back to about 7km/hr. This supposedly will flush trapped air from the actuator into the brake lines where another bleed can be performed. Did this and brakes felt marginally better, however, pedal still goes all the way to the floor. This still indicates to me a faulty (leaking) master cylinder.
Dave . (Wangaratta)

Originally Posted by Roverlord off road spares

You put a seal kit in, maybe you put something in back to front? like cups lips?

thanks for the response mario,
I made a point of checking the placement of the parts that came out and the new ones that went in. I did also double check the new seals when I removed the master cylinder the second time. I also checked the install against the RAVE diagram. One possible problem is that there were 2 seals (1x large & 1 small) from the primary circuit (within the master cylinder) that I could not replace as I cannot find a 5 sided allen key that is required to access this area. There is also a small seal in the secondary circuit that cannot be replaced as well as the plunger assembly does not appear to be able to be disassembled. Seems to be pretty pointless for suppliers to sell a master cylinder seal kit where half the parts can't be installed.

DAVE AS I MENTIONED IN THE OTHER THREAD (I THINK) THE D2 PEDAL WILL SINK IF YOU PUSH HARD (MINE STILL DOES)BUT WITH NORMAL PRESSURE IT STOPS AND HOLDS FINE , I SENT MINE TO A DEALER TO HAVE IT BLED AS IT DID NOT FEEL RIGHT TO ME AFTER DRIVING CARS UTES ETC THEY COULD NOT GET ANY AIR OUT EITHER AND TOLD ME THE BRAKES WERE FINE HAVE YOU DRIVEN IT YET TO SEE HOW IT STOPS

Originally Posted by Outback 1

DAVE AS I MENTIONED IN THE OTHER THREAD (I THINK) THE D2 PEDAL WILL SINK IF YOU PUSH HARD (MINE STILL DOES)BUT WITH NORMAL PRESSURE IT STOPS AND HOLDS FINE , I SENT MINE TO A DEALER TO HAVE IT BLED AS IT DID NOT FEEL RIGHT TO ME AFTER DRIVING CARS UTES ETC THEY COULD NOT GET ANY AIR OUT EITHER AND TOLD ME THE BRAKES WERE FINE HAVE YOU DRIVEN IT YET TO SEE HOW IT STOPS

hi ken,
the pedal did sink very slowly before I did the seal kit, and this was the reason for doing it.
the disco stopped ok.. but not as well as it should have. With the replacement master cylinder installed, it brakes ok but still sinks all the way to the floor under medium pressure.
Whilst the vehicle brakes do work, this is not the issue. The issue is that the brakes 'should not' sink all the way to the floor. Some members on this forum seem to think this is a 'spongy' brake. It is not!!! Spongy brakes occur when air is present in the system (even a tiny amount) and whilst this is acceptable to some, it is not the same as a pedal eventually going all the way to the floor. This is going to be an issue with the master cylinder seal/s leaking and can be a dangerous thing. eg. being stopped on a steep incline / decline with the brake pedal approaching the floor and you are not in a position to be able to take your foot off to allow a fresh fluid charge into the master cylinder. I understand that a lot of members are quite content with their 'soft' spongy brakes and consider it to be quite normal but I am not... I would like to have them working correctly.... particularly as most of the time I am towing a 3 tonne caravan around Oz.