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Brake bleeding - air lock?

Posted: Mon May 29, 2023 7:42 am
Author: RussG
Hi,
I’ve fitted ZRX1100 brakes to my project so the whole set up is new, its filled with fluid, no air being pumped through but the lever still goes back to the handle bar. Thinking I must have an airlock? Does anyone have any suggestions as to how I might progress? I’ve used an Easybleed so far with the capture pot placed above the calipers.

Thanks Russ

Re: Brake bleeding - air lock?

Posted: Mon May 29, 2023 7:46 am
Author: warren3200gt
Have you got a bleed nipple by the lever to bleed the reservoir to mc?

Re: Brake bleeding - air lock?

Posted: Mon May 29, 2023 9:57 am
Author: RussG
No, I don’t

Re: Brake bleeding - air lock?

Posted: Mon May 29, 2023 9:57 am
Author: RussG
To “mc”?

Re: Brake bleeding - air lock?

Posted: Mon May 29, 2023 10:22 am
Author: warren3200gt
Master cylinder

Re: Brake bleeding - air lock?

Posted: Tue May 30, 2023 2:55 pm
Author: marmck
Pump lever until you get a firm pull , don't let it go tie wrap in this position turn bars so master cylinder is level & take top off ,place clean rag on top for safety. Leave for 4 or 5 hours ,loosely put master cylinder top back on & remove tie wrap ,then repeat process & leave overnight

Re: Brake bleeding - air lock?

Posted: Tue May 30, 2023 6:09 pm
Author: BAFF1960
Hi.
Back bleed with a syringe from the caplipers alternating between sides. This is a trick used in a/c maintenance. They have long torturous routing and it always works.

Re: Brake bleeding - air lock?

Posted: Wed May 31, 2023 3:27 pm
Author: deka
BAFF1960 wrote:Hi.
Back bleed with a syringe from the caplipers alternating between sides. This is a trick used in a/c maintenance. They have long torturous routing and it always works.


Second that, you still need to build pressure up with a few pulls on the leaver but backfilling is the best way to go and ensures yhou push the air in the direction it really wants to travel

Re: Brake bleeding - air lock?

Posted: Wed May 31, 2023 3:44 pm
Author: Philippe
Hi RussG

are you using the original brake line distributor where the stoplamp contact is screwed in?
If so, unscrew the two bolts with which it's attached to the lower yoke and turn it so that the air, perhaps trapped inside, can escape towards the master cylinder.
An other cause might be that the tiny small hole in the master cylinder is closed, it doesn't take much to constipate it; use a 0,3 mm drill to get it free. If it's constipated and you free it, you'll see a lot of air bubbles coming out of the small hole as well from out of the "bigger" hole in the master cylinder.
Good luck with it!
GrtZ
Philippe

Re: Brake bleeding - air lock?

Posted: Sat Jun 03, 2023 10:25 am
Author: RussG
Thanks guys, lots of good advice, I’ll let you know how I get on, poorly Mum sitting this weekend though…

Re: Brake bleeding - air lock?

Posted: Sat Jun 17, 2023 1:36 pm
Author: RussG
So, did it all and still no change. When I back bleed it fills the reservoir, did with the lever on and out. When I bleed normally I just get fluid, checked the hole and they’re clear. Really scratching my head now
Tried to add pics but can’t work it out. Any more ideas what could be wrong? All components are new btw

Re: Brake bleeding - air lock?

Posted: Sat Jun 17, 2023 2:59 pm
Author: floydsz1
Presumably the mastercylinder is the correct bore size for the calipers

Re: Brake bleeding - air lock?

Posted: Sat Jun 17, 2023 6:25 pm
Author: compo z1r
if u deffo have no air in system and no pressure the fluid is over riding the seals if u have rebuilt check seals are put in correct way if not get a rebuild kit and start again about it really :D

Re: Brake bleeding - air lock?

Posted: Sun Jun 18, 2023 9:04 am
Author: RussG
How do you tell if the master cylinder is the correct size? I’ve never seen them advertised by size …

Re: Brake bleeding - air lock?

Posted: Sun Jun 18, 2023 11:18 am
Author: compo z1r
RussG wrote:How do you tell if the master cylinder is the correct size? I’ve never seen them advertised by size …


never had a rex but looks like standard 5/8ths