Brake Fade issue

[rapserv]

2001 Disco TD5.... just finished renewing the fluid in the disco and also took the opportunity to install a new seal kit in the master cylinder as well.
Put everything back together and used a Gunson Eezibleed system to completelt bleed all air from the lines. When finished, jumped into vehicle and put my foot on the pedal and found it to be pretty firm with no real give... better than its ever been, Started the engine with booster assist and pedal goes all the way to floor? Any ideas

[DiscoDB]

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

[rapserv]

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.

[Outback 1]

have a read here
http://www.aulro.com/afvb/discovery-2/174097-sinking-brake-pedal.html

[Roverlord off road spares]

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

[rapserv]

have a read here
http://www.aulro.com/afvb/discovery-2/174097-sinking-brake-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.:mad:
Dave . (Wangaratta)

[rapserv]

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.:mad: 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. :confused:

[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

[rapserv]

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.:o

[Jazzman]

Reading that the brakes work, are not spongy but the peddle will continue to the floor and you know this is not right.

Assuming the master cylinder is working correctly. And there is no fluid leaking everywhere (you seem like a pretty smart bloke who would have noticed this)

Is it possible there is a valve that enables the pressure to be released when the ABS is doing its job? If so, maybe this valve is faulty and allowing the brake fluid to bypass instead of applying max pressure the the rotor caliper.

This would explain no fluid loss, a working master cylinder pushing fluid, brakes that still work (probably would have to pump the peddle for long periods of braking), but the break peddle traveling too far.

[Xtreme]

I had the same problem with my Td5 Defender a few years ago.
Replaced master cylinder with new one - pedal still slowly went to the floor.
Problem was eventually traced to the front calipers by clamping off all wheel calipers and then releasing one at a time while checking pedal. The front calipers were overhauled but alas, pedal still slowly went to the floor.
Further testing with brake hose clamps still indicated problem with front calipers.

Problem was eventually resolved by bleeding with both front calipers removed (but still connected to brake lines) and held in such a way that the bleed nipple was as high as possible.

Your problem may or may not be the same but testing with the brake hose clamps was most valuable in isolating exactly where the problem was and is recommended before simply replacing bits and pieces.

[rapserv]

Reading that the brakes work, are not spongy but the peddle will continue to the floor and you know this is not right.

Assuming the master cylinder is working correctly. And there is no fluid leaking everywhere (you seem like a pretty smart bloke who would have noticed this)

Is it possible there is a valve that enables the pressure to be released when the ABS is doing its job? If so, maybe this valve is faulty and allowing the brake fluid to bypass instead of applying max pressure the the rotor caliper.

This would explain no fluid loss, a working master cylinder pushing fluid, brakes that still work (probably would have to pump the peddle for long periods of braking), but the break peddle traveling too far.

hi jazzman & thanks for your reply,
In fact I have been wondering the same. Is there a relief valve within the abs unit that operates to prevent too much pressure being applied. A safety feature in fact. If there is, it does not seem to be documented

[rapserv]

I had the same problem with my Td5 Defender a few years ago.
Replaced master cylinder with new one - pedal still slowly went to the floor.
Problem was eventually traced to the front calipers by clamping off all wheel calipers and then releasing one at a time while checking pedal. The front calipers were overhauled but alas, pedal still slowly went to the floor.
Further testing with brake hose clamps still indicated problem with front calipers.

Problem was eventually resolved by bleeding with both front calipers removed (but still connected to brake lines) and held in such a way that the bleed nipple was as high as possible.

Your problem may or may not be the same but testing with the brake hose clamps was most valuable in isolating exactly where the problem was and is recommended before simply replacing bits and pieces.

hi roger,
sounds like a plan!!
this lines up with what I was told today by the local brake repair business. He said that if a vehicle came in with this type of pedal problem, the first thing they would do is to use a pair of vice grips to carefully clamp the hose near each caliper in turn to see if the problem can be rectified which would indicate a problem at that particular caliper. I think I might give this a go :o Will be tied up for the next day or two, but will post back here the results either way :)

[Epic_Dragon]

mine has been doing very similar after replacing the front pads last week. system bled twice and new fluid put all way through as old fluid was yuck. but they work, but pedal goes to the floor just about and cant seem to lock them up. they just seem ''soft'' if that makes any sense? my car is down at triumph rover at the moment getting the welshplug and oil leak fixed (just too ahrd to do myself with my disabilities now :() and talking to them about the brake issue, they said some brands of brake pads are too hard a compound for the landrovers?

[Jazzman]

hi jazzman & thanks for your reply,
In fact I have been wondering the same. Is there a relief valve within the abs unit that operates to prevent too much pressure being applied. A safety feature in fact. If there is, it does not seem to be documented

To be honest I don't know. It was the only thing i could think of.

[rapserv]

hello all,
I have not as yet carried out the procedure as noted by Roger above.
I started out intending to do this but once I had put the disco up on the ramps (home made & heavy duty) that raise the front (or rear) off the ground 500mm I thought this would be pretty much the same as releasing the calipers and raising them as far as possible. I initially was going to 'clamp' the brake hoses to try and isolate a fault but once I got under the car and found a clamping position, I really didn't feel comfortable 'crushing' the flexible hose in this manner even though it was probably quite ok to do so. I felt that I really didn't need the possibility of another brake problem to deal with as well 😨 I performed another bleed with the disco raised like this and noticed quite a lot of air still in the lines. Went through another 3 litres of fluid (in addition to the first 5 litres) and all looked ok. Lowered the vehicle, found engine off brakes to be rock hard, then started up to use power boost only to find that they still went slowly to the floor whilst under firmish pressure. 😠 Have just done a run down to Melbourne with the caravan and the brakes performed well, however, I think when I return I will undertake Roger's procedure fully and see where this takes me. I will update this thread when this has been done. It would be good, for me and probably other members, to be able to have a definitive answer to this issue. 😕

Footnote: The reason for the trip from Wangaratta to Melbourne was to take our pet 8 year old galah 'Max' to a specialist 'bird only' vetinary clinic to get the best care for treating a broken leg from last weekend. Unfortunately, whilst undergoing an operation to 'pin' his broken leg (which was successful) he did not recover from the anesthetic and passed away.
We will dearly miss our little man, who very happily travelled around Australia with us, knew all the galah gangs in the towns we travelled through and was a real character an absolute
joy to be around. RIP little man 😢

[Epic_Dragon]

i am so sorry for the loss of your little feathered family member. i had a galah (also named max incidently) whom had fallen out of the tree so i raised him. i had to give him away when going through relationship issues as there was no way i could have taken him with me :( hardest thing i ever did, as ive never parted with an animal only when they go to rainbow bridge. i can still see his face watching me as they drove away. i regret the decision. i wish i had figured out a way to bring him with me. he went to a good home. but i miss him. they are such characters.

talking about brakes, i have no idea what is going on with mine. no leaks, told ok by mechanic. then the other day they completely failed twice, had to pump pedal and then they worked. they are not working to full capacity. you cannot lock the wheels up if oyu wanted to.

[rapserv]

i am so sorry for the loss of your little feathered family member. i had a galah (also named max incidently) whom had fallen out of the tree so i raised him. i had to give him away when going through relationship issues as there was no way i could have taken him with me :( hardest thing i ever did, as ive never parted with an animal only when they go to rainbow bridge. i can still see his face watching me as they drove away. i regret the decision. i wish i had figured out a way to bring him with me. he went to a good home. but i miss him. they are such characters.

talking about brakes, i have no idea what is going on with mine. no leaks, told ok by mechanic. then the other day they completely failed twice, had to pump pedal and then they worked. they are not working to full capacity. you cannot lock the wheels up if oyu wanted to.

thanks for your thoughts regarding 'max' 😢. I have been teary-eyed over the last couple of days reminiscing over our experiences with him. He was just a member of our family and we really are both devastated and our travels throughout Oz now will never be the same. Only another pet owner, who is close to their pet, could possibly understand what it is like to loose such a friend, and I really feel for you having to part with your 'max'.

Back to brakes.... I think you may still have air in your lines as I could not force the brakes to lock (or activate abs) either, until my second last bleed. The brakes now pulse when stamped on hard (on a dirt road) and seem to work quite effectively... the only issue is the uneasy feeling of the pedal actually being able to go all the way to the floor 😯
Sounds like you too should be trying roger's method. Would be interested to know how you fair as well.

[DiscoDB]

Hmmmm......tried the same test and sure enough with firm pressure and engine running I can also slowly push the brake pedal to the floor. Stomp the brakes when driving and no issue pulling up quick. I doubt I could get the pedal to the floor when driving as you would be stopped well before you got past half-way.

So is this a fault or a feature?

[ScotsD2]

You may have air in ABS modulator

Always bleed with ignition off

Try this If you want to make sure the modulator is bled,
Put the transfer box into low and select HDC,
(A couple of notes HDC will not function above 31mph or if brake or clutch pedals are pressed.)
Accelerate up to 25mph then take your foot fully off the throttle HDC will slow you down to 5mph.

Run through this a few times then rebleed.

[rapserv]

You may have air in ABS modulator

Always bleed with ignition off

Try this If you want to make sure the modulator is bled,
Put the transfer box into low and select HDC,
(A couple of notes HDC will not function above 31mph or if brake or clutch pedals are pressed.)
Accelerate up to 25mph then take your foot fully off the throttle HDC will slow you down to 5mph.

Run through this a few times then rebleed.

thanks for your reply,
I have done the abs modulator procedure and re-bleed several times now but still the same result. 😨