brakes- help

[shadrack]

anyone whos followed will know my car failed mot on brake pipes, it them had 4x new flexi pipes, and new brake lines right round, next the brakes would not bleed, then had new master cylinder ( my brother thought this had been the problem with the padal going to the floor), next it still had no peddle, so took it to an indy who bled it on a computer as air had got in abs etc, got it back and it was enough to pass the test but the pedal is still very squishy and pushes down far further than before and also if you sit with your foot on the pedal and hold it (parked up but running) the pedal sinks (like its full of air) but with the ignition off it is hard, dont get me wrong they work bloody good but the pedal is litteraly nearly touching the floor before the brakes lock up! would it be possible the new master cylinder has been knackered by pushing the pedal to the floor before been computer bled, please help im sooo close to just saying t*ts to it and booking it into the stealers!!
i dearnt even tow anything help

[Powercat]

Don't give up, these cars are great, in fact one of the best cars I have ever owned and I have owned a lot (part-time motor trade)
my best advice would be to contact Jason,he really knows his stuff.

[shadrack]

not going to give up because i love my car (2nd x5) had bout 15 cars (im 26) the x5s are my favourite but this brakes issue is really starting to anoy me, ive been relieved of £300 so far and my brakes are 50% as good as before the mot, dealer will want to change everything!

[X5Sport]

Are the flexis OK, ie not ballooning in any way.

If the pedal is solid with the engine off then there can't be much wrong in the system. The pedal dropping is the effect of the servo vacuum coming into play. If yours is like mine there were two servos stacked to give maximum effort. No servo means very stiff pedal.

All I can list off the top of my head for what might cause this is:

Air still in the pipes, calipers, master cyl or ABS System - shouldn't be after all the efforts.
A leak in the fluid lines - you should be seeing that though.
One brake circuit not fully working - but you'd fail the MOT with that.
Too much play in the caliper piston or incorrect re-assembly - unlikely as they weren't disturbed (were they?)
Incorrect alignment of the connections from pedal to master cylinder - they must be in the same plane and centred
Flexi-pipes either 'ballooning' or pushing fluid back out meaning you have to force fluid back in there which needs more travel.
A non-return valve being open
A pipe on the wrong connection (like a crossed wire, but with brake pipes)
A problem in the ABS Modulator or replacment Master Cylinder - as in a leaking seal, but that should only affect one circuit.

What happens if you pump the brakes - while moving? Does the pedal harden up after a second press or stay spongy?
Can you get the ABS to operate on either a wet or dry road? It should be possible, although you'll have to apply full effort whether wet or dry. If your worried about stopping obviously do it where you have plenty of room, and you need to be doing more than about 20-30 mph I expect. A decent sized car park at night and empty might be a good test site, unless you have access to a nice long straight and wide road (or runway )

Obviously if testing the ABS without a rolling road (the safest way) then make certain you're safe and there's no pulling in either direction under normal braking. Two tonnes of E53 will roll nicely if you get it wrong - but then I'm probably trying to teach Granny

[shadrack]

thanks x5sport well a friend menchioned checking the flexis but i have yet to do it, they were new but non oem, if you pump the pedal with it running it hardens up, but then if you leave the pressure aplied it drops nearly to the floor, their is no fluid loss in the system at all, it will operate the abs wet or dry, all pipes are correct place, were all changed one at a time, this one interests me=Incorrect alignment of the connections from pedal to master cylinder - they must be in the same plane and centred could you enlighten me further please, also how would i check non return valve? thanks

[shadrack]

oh and the indy is adament there is no air left in the system, just by how they are there is something up, i dont know wether to try somewhere different

[X5Sport]

You need to make sure that if you drew an imaginary line from the pedal connection right through to the master cylinder that everything is in a straight line - which it probably is.

If the flexis are non-OEM and the rubber is a bit soft then you could get them expanding instead of staying the right diameter. That will cause a pressure drop at the calipers meaning the pedal moves much more to overcome the 'ballooning'.

I don't know what non-return valves there are in the system and the only way I can think that might be n issue would be if fluid was being pushed back through by another means. A solid pedal with the engine off probably eliminates that too.

I'm kinda thinking out loud - and hoping my rambling might trigger a thought from one of the others who frequent the forum.

[shadrack]

could the flexis balloning make that much difference, i will check it at the weekend if its them i will get braided brembo or oem ones, wat do you think to the master cylinder seals been pushed out, i had to drive it to the indy other week with the pedal going to the floor with the new one fitted, it was so bad i took it a 5 am so they was nothing on the road!

[shadrack]

oh if its a balooning flexi would i be able to see/feel if someone else did the pedal?

[shadrack]

well am off to bed now with all these ideas for brakes, ineed to keep this thread live as im getting so depressed with the x5 at the mo because of this, nearly chopped it in for a range rover sport the other day because of this and i love the x5 (though in my defense it was a white tdv8 one)!! i realy want to get the x5 sorted! keep it till next year and get a e70/e whatever x6s are!

[X5Sport]

Don't gt depressed. There's goung to be a straightforward solution!

Expansion of the flexis could certainly be visible if it's bad, and yes it could make a big difference as the pressure expands them rather than pushes the pads. I wold be surprised if it was all four flexis, but if the tube spec is wrong then I guess it's possible.

Mater cylinder seals are still a possibility, but when you took the old one off was there any seal damage? All I would expect in that case though is a fluid leak back past a seal and that would (or should) only affect one circuit. E53 brakes are dual circuit in an 'X' pattern - front left/back right and front right/back left - which is the standard pattern on most if not all cars now.

Are all the brakes exerting the same force? Needs a rolling road to test.

Brake fluid isn't compressible so something must be giving (ruber tubes expanding) or allowing fluid past incorrectly (seals) to cause a soft pedal.

X6's are E71s........add 90bhp and two more gears, and a very large 'grin factor'

Night Night

Send Jason a PM and see if he has any other suggestions.

[shadrack]

going to check flexis out saturday,i noted on the wy home from work the pedal is ok when driving and braking i can get my left foot between the pedal and the floor, but last weeekend when i did mothers air suspension his pedal was far firmer, the flexis were cheap motor factors so if i have any doubt im just going to bire the bullet and book it into stealers i think for oem flexis right round and maybe a master cylinder, will i get cahange from £500?

[X5Sport]

Master cylinders can be repaired - all you eed is the overhaul kit (new seals etc) from the OEM. I don't know if hat's ATE, Lockheed, Girling or another make - might be on the body - and you don't need BMW Flexis as long as you get a good make.

You're going to have to do a full rebleed if you do change them. £500 is probably a good estimate, but see if you have a good BMW indy locally who can do it all.

The one I use in Bletchley (near Milton Keynes) only charges half what BMW Dealers do. No idea where in the country you are.

There are plenty of suppliers of non-BMW badged OEM parts about who will save your money.

[shadrack]

yeh gonna have a check of flexis tmoro but can only think of getting everything redone! i noticed tnite that giving it some down hill and slaming on they work great but over a time of holding down i get brake fade, and the pedal seems slow to come back up? what would you think to the goodridge braided brake lines of eaby? tbh master cylinders are only £54 ex vat and trhey arnt bmw badged anyway even the oem one, if thats gon that would be after firring it wouldnt bleed so had to do a 30mile journey where the pedel pressed right to the stop at the bottom without the brakes been fully on (off the road of course ) and aparently this can brake the seal, thanks

[X5Sport]

Are you winning at all?