Any tricks to bleeding the master cylinder?

wshtb

Member
Long story short: a snow chain broke, tore out a rubber brake hose, now I have a bone dry master cylinder.

Finally installed the replacement brake hose. I tried to bleed the brake system, but something seemed off.

I used this Motive bleeder tool, which screws on top of the master cylinder, and pumped it to 15psi. Initially I got a lot of airs out of the bleeder valve on the affected caliper. But after the out flow turns solid, it basically stopped, despite the 15psi pressure on the master cylinder. I tried the brake pedal, it felt solid.

I was running out of daylight so I had to stop; that's when the odd thing happened: as soon as I cracked open the Motive bleeder, all the fluid shoot out of the master cylinder. Now I have a almost empty master cylinder again. So there must be a lot of air somewhere in the system...

I plan to try bleeding the system again, doing all 4 corners next time. But, is there any trick to this? Are there any bleeder valve on the master cylinder?

I'm kinda hoping to get this to the point where it is safe(ish) to drive, so I can get it to a dealer if necessary. Thanks!
 

Cheyenne

UK 2004 T1N 313CDi
Right, from previous posts you have a 2013 NCV3 so you do have ABS/ESP whatever.

Are you activating the valve block when you try to bleed the brakes? If not then I would suspect you have air in the valve block.

Keith.
 

smiller

2008 View J (2007 NCV3 3500)
If the system was bone dry then you probably need a service tool to activate the ABS system and fill the valve block, as above. In the absence of a scan tool you can sometimes get this done by filling the system and then locking the brakes a few times (obviously a lot easier on dirt) which will cycle the ABS. Then re-bleed and repeat until things are normal. This is pretty cumbersome of course so the proper method is best, but the backyard method can sometimes work in a pinch.
 

Thump_rrr

Active member
I’ve owned the Motive tool for about 15 years now and I’ve never had It shoot brake fluid out of the master cylinder.
I’m assuming the valve block is full of air as the others have mentioned.
Since you have the Motive bleeder, fill the reservoir and pump up the Motive bleeder to just a few PSI then crack each fitting on the master till you get fluid..
 

showkey

Well-known member
Agree what was already said.....

There several methods on brake bleeding.........some better than others when a problem occurs like the OP.

Trying a slow gravity bleed or vacuum bleed ( at the caliper) or fluid pressure push from the caliper back to the reservoir at each caliper might provide a fix.


Did not mention the mileage or age (2013 ?) on the van........the pressure build ( from the tool) in the reservoir can be caused by debris blocking one or more of the ports on the master. Stroking a dry or low master can cause problems like torn or damaged cup or debris blockage.
Reverse bleeding might clear the debris or blockage.......but once the cups are damaged the master is done.
 
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