any one familiar with the mity vac brake bleeder/flush system Bleeding Brakes using the Mityvac MV6835 - YouTube i use this at work so i know how to use it and just performed a complete brake flush on the 91 toyota 4x4 thismornig before i attemptem my 07 cobalt 2.4l. with 47,000 miles. when i crack open the bleeder valve starting with pass rear (farthest from master cylinder) i get barley any fluid out more bubbles than anything, left it on for 20 minutes and cant get but a few ounces out tryed the same with drivers rear and same thing. i havent touched the front yet. any reason why my calipers would not be letting brake fluid out of the bleeders after there cracked open. i completley flush my extended cab toyota in 20 minutes time. thanks for any help guys. possibly the pin hole on my bleeder valve is rusted shut. i live in redding ca so not like its moist humid weather to build corrosion

 

ABS Unit blocking the fluid?

Maybe you need to gently pump your brakes so that new fluid from the resavour can be pumped into the lines.

ABS Unit blocking the fluid?

Maybe you need to gently pump your brakes so that new fluid from the resavour can be pumped into the lines.

 

do u have the cap for the master cylinder resovoir open?

 

ya the cap is open as during the brake flush process you add a 40oz container full of brake fluid that clamps to the top of the master res. to ensure you dont drain the resivor low and get air in the system. the bottle in no way makes a seal so thats not my problem. i guess it could be something to do with the abs but i did my gf 06 corolla today just fine (all 4 corners in 20 min.) as every car i do at work (toyota dealership) also has abs brakes and never ran into this problem. my cobalt bleeds just fine by holding the brake down and loosing bleeder valve.

 

do it old school. to me thats the better way.

 

im gonna have to do it the old school way for the rear i found out thismorning the rear dics brakes take 80-125psi of sucking power to get the abs valve to open in order to get the fluid to flow freely out the bleeder valve or hooking up a scan tool and communicating with the abs and having the computer open the abs valves one at at time sound like a huge pita. i will just do the slow process of pumping and hold the pedal. the fronts can be bled normally the chevy tech said its only the rears that require a scantool or special bleeder machine other than the one i am using. Thanks guys

 

Sounds like no matter how powerful your vacume is it's impossible. Seeing as how sea level air pressure is only 14.7 PSI, then the most powerful vacume device in the world would only be able to apply 14.7PSI of suction.

 

I used that little mity vac when I changed my fluid a few weeks ago. I borrowed it from a buddy. Its slow, but it works. The bubbles I got were because I couldn't get a super tight seal around the bleeder valve but I just kept pumping every 10 seconds or so and eventually I'd fill up a whole container before I saw the new fluid coming out. I also didn't have a thing to screw on to the reservoir like you so I would have to check it and fill it back up every so often. It worked for me. I will say though that I noticed the brembos were easier to vaccum fluid out than the rears.

 

Anytime you bleed an ABS system you have to discharge the pressure from the accumulators. You do this by pumping the brake pedal 25-40 times ignition off. I always do 40 to be sure. That's most likely why its not working for you.