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Author: Subject: Having trouble bleeding brakes...
John.Taylor

posted on 13/8/07 at 12:47 PM Reply With Quote
Having trouble bleeding brakes...

I'm having trouble bleeding my newly installed brakes (new Sierra Bendix mc, reconditioned Sierra callipers front & rear, and new lines).

If I leave them for a while then press the brake pedal it goes down approx half of it's original (non filled) travel before it goes hard and can be moved no more. If I pump it, it goes significantly stiffer, but not to my liking. I've been told that this is a sign of air in the rear lines, trouble is, I've now run the fluid through several times both with an eezibleeder and with my father pump the pedal up before I release the nipple, but the air isn't coming out and I now think that my fluid may be no good due to the workout and air exposure it's had.

I was wondering if the ATE super blue stuff would pass SVA as it isn't Dot approved due to the colour? At least I could see when I'd bled new fluid through with this stuff.

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shortie

posted on 13/8/07 at 12:54 PM Reply With Quote
Have you turned the rear callipers upside down and then tried bleeding them??

Rich.

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nige

posted on 13/8/07 at 01:01 PM Reply With Quote
try bleeding the m/c first





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John.Taylor

posted on 13/8/07 at 01:08 PM Reply With Quote
The calipers are the correct way around at the rear with the nipple facing upwards - I know this because they weren't last weekend when I first tried bleeding the system and I got no pressure whatsoever.

Swapping sides this weekend so the nipples face up has made a huge difference, subjectively increasing braking from 10% you could just push it with the brake pedal pushed, to 60% is whereby two people can't push it with the pedal down (held by a wooden stake against the chasis) but the pedal still goes halfway down until pumped.

How do you bleed the MC alone?

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welderman

posted on 13/8/07 at 01:17 PM Reply With Quote
if your wanting a lift, let me know, i can pop round most nights.





Thank's, Joe

I don't stalk people


http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=172301

Back on with the Fisher Fury R1

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John.Taylor

posted on 13/8/07 at 01:50 PM Reply With Quote
I'm going to give them another bleed tonight or tomorrow (subject to HWMBO) and if they're still playing up I might take you up on that offer.

I'm a bit short on helpers at the moment since my keenest friend is due to be a dad any day now (was expecting a baby on 9th August but it's overdue), and my father's just gone on holiday for two weeks.

Pumping the pedal, chocking it with a stake and running around the car is wearing a bit thin.

I'll send you a u2u if I need some assistance.

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welderman

posted on 13/8/07 at 02:00 PM Reply With Quote
okaydokay mate .





Thank's, Joe

I don't stalk people


http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=172301

Back on with the Fisher Fury R1

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2b_pablo

posted on 13/8/07 at 02:15 PM Reply With Quote
get a little one man bleeder it has a one way valve so you attach to the nipple, loosen the nipple then give a few pumps, go back and tighten the nipple.

pain in the arse but better than a bit of wood as you get a good bit of fluid through the pipes.

did you shake the bottle before pouring fluid in?

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BenB

posted on 13/8/07 at 02:38 PM Reply With Quote
I've found an Easybleed works well.... just don't use too many PSI or it can knacker the MC seals....

Taping the caliper whilst bleeding worked for me... It released a whole load of bubbles. Not sure where they were hanging out but the brakes felt much better afterwards!!!!

I think the worry about the fluid is unfounded. If you're refilling the Easibleed with the drained fluid it may have some moisture in it but not enough to cause that degree of sponginess initially. It sounds very much like air in the system. Then again, if you are re-using the fluid I'd wait until it's fully bled (ie no air) then re-bleed it with fresh fluid.... Have you got anywhere an air bubbles could hang out- like a hydraulic brake light switch???

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John.Taylor

posted on 13/8/07 at 03:10 PM Reply With Quote
I've got a switch off a tee on the footwell by the gearbox. I slackened it off to bleed it like a nipple, is this correct?

The Eezibleeder was ok for getting fluid into the system, but pumping the pedal made it better.

I'll give the calipers and MC a tap when I re-bleed them.

[Edited on 13/8/07 by John.Taylor]

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britishtrident

posted on 13/8/07 at 03:38 PM Reply With Quote
Key thing is pump the pedal S-L-O-W-LY
Yes easzibleed is a good tool but even with it the pedal has to be pumped a couple of times AND the pedal held to the floor while each nipples is closed.
------
if the above dosen't work.

Remember also the handbrake cable has an effect on the foot brake, leave the cable fully slack until the hydraulics are fully bled.
Operating the foot brake should then ratchet up the self adjusters. If that dosen't work set the rear brake adjustement by operating the adjusters manually.

Also

If any of the calipers are not presenting the pads 100% true to the discs this will cause a spongey pedal.


If you have proper OEM style "rubber" flexible hoses it is often useful when trying to track down the cause of a sponegy pedal to clamp each hose in turn and try the pedal.





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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higgsti

posted on 13/8/07 at 06:08 PM Reply With Quote
try putting a piece of metal between caliper which is same thickness as disc ,then take caliper off and suspend lower.you might not be getting all the air out because you mastercylinder is lower than caliper unlike on the car
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RazMan

posted on 13/8/07 at 07:58 PM Reply With Quote
quote:
Originally posted by britishtrident
Key thing is pump the pedal S-L-O-W-LY



I found exactly the reverse Short & fast pumps by a helper while you are attending to each caliper. It whooshes any air bubbles straight out and they don't get a chance to get lodged somewhere (like a switch)

Eezibleed was too slow for me and has left trapped air every time I have used it.





Cheers,
Raz

When thinking outside the box doesn't work any more, it's time to build a new box

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britishtrident

posted on 13/8/07 at 08:18 PM Reply With Quote
quote:
Originally posted by RazMan
quote:
Originally posted by britishtrident
Key thing is pump the pedal S-L-O-W-LY



I found exactly the reverse Short & fast pumps by a helper while you are attending to each caliper. It whooshes any air bubbles straight out and they don't get a chance to get lodged somewhere (like a switch)

Eezibleed was too slow for me and has left trapped air every time I have used it.


Problem with fast pumps is that it is not unknown for some master cylinders to draw air in past the seals on the return stroke --- this was always a big problem with ATE systems.
In fact the only way to bleed some Teeves clutch systems was to pressurise from the top down using an easzibleed or similar to keep the seals expanded durring the suction stroke.

Other thing about slow pumps is it keeps the air pockets in big slugs rather than producing microbubbles that can lodge within the system.

A good trick if a system is difficult to bleed is working one wheel at a time to take the pads out pump the caliper pistons out a little, clamp the flex hose and push the pads back venting excess fluid via the nipple.





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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NS Dev

posted on 14/8/07 at 11:52 AM Reply With Quote
Yes, do bleed the switch as you have done.

next, is the pedal "springy" or "spongy"

It could well be springy due to the pads not being bedded in.

If you are expecting a rock hard pedal, you need to drive it a bit first and bed the pads in.

My pedal had a long travel for the first 50 miles or so but its great now.





Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion retro car restoration and tuning

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