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Endless Air in Brake Line

Joined
Mar 22, 2008
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I was almost finished DS'ing my DRZ and when I was installed the hydraulic switch on the front master cylinder I pulled the lever and no resistance. I think all the fluid in the reservoir drained out when I had the banjo bolt off (the switch replaces it). I've been bleeding my brakes for over an hour and getting nothing bubbles. Do I need to bench bleed it?
 
The DRZ Master cylinder can be a bit of a pain. Purge air from the hyd live fitting, and then work on the rest. You have to keep the bars turned, bike leaned over, and master cylinder orientated the right way, so that the highest spot in the system is that little hole in the Master cylinder reservoir that feeds fluid to the master cylinder hydraulics. If there is air in the Master cylinder vice the line or calipers, and you keep that bleed hole at the highest point.. Often you can get the air to burp back into the fluid reservoir, by squeezing the lever, and letting it snap back to resting position. .. If none of this above works,, Get a plastic syringe from someplace that sells Vet supplies for ranches and back bleed the system from caliper to master cylinder.
 
What do you mean by "purge air from hyd live fitting?

Which way do you lean it? It looks like the fluid feeds from the left side of the reservoir so do you lean it to the right?
 
What do you mean by "purge air from hyd live fitting?

Which way do you lean it? It looks like the fluid feeds from the left side of the reservoir so do you lean it to the right?

Hydraulic line and banjo fitting …Sorry fat finger typing on the way to work this morning.
The banjo fitting in the line that attaches to the master cylinder can trap a bit of air, cause the master to not prime and start working (same reason you bench bleed a car master cylinder)
 
Buy a vacuum pump kit for easy one person bleeding. Less than $50 at any auto parts. After first use you'll kick yourself for not buying one sooner.
If you are a Harbor Freight risk taker they even have one for $20
http://www.harborfreight.com/cpi/ct...cpc&zmam=33951326&zmas=12&zmac=112&zmap=92474

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Vacuum systems work well :thumbs: but even they do not always move enough volume of fluid to break loose a bubble of air in a line or fitting.

Purge the big bubbles of air, use the Mity-Vac or like product and most times you can draw the rest of the air down ward against gravity to the brake caliper……
For the other times… reverse bleeding is the way to go.. Pushing a large quick burst of fluid UP the line from the caliper to the master cylinder allowing the air bubble to move UP and out though the feed hole in the reservoir, works very well
 
I'm working on it again and it looks like it was a dumb move on my part. The rubber thing that goes on with the cap was stuck in the reservoir and that's where I was pouring fluid into so no fluid was going into the system. I took it our and not I'm getting all fluid coming out at the bottom but still not getting much back pressure on the lever even when I close the bleed nipple.

I'm thinking about going to harbor freight to get a vacuum bleeder.
 
I got the vacuum pump and pretty much filled up the 120ML cup when all of a sudden a lot of bubbles came up into the reservoir and now I think I have a working front brake! I'm not sure if it's as tight at before but I can't test it until I finish installing the back tail light.
 
Keep bleeding until you get NO bubbles. Testing it at a standstill you should still be able to get constant firm pressure. That is, don't take it out on the street to test how soft/firm it is until you are getting consistent firm pressure on the first pull and not having to pump it up a couple of times to build pressure. Once you get good firm pressure on every pull the first time, and no more bubbles are coming out when you hand-bleed (I have a MityVac and still finish off any brake fluid related job by hand the last few times), THEN you can road test it carefully. Might still vibrate a few remaining bubbles after a few miles, so sometimes it helps to give it one last little hand bleed after the fact (just make SURE you don't introduce ANY air back into the system).
 
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