No Pressure to Rear Brakes - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dccarpenter · 03-15-2011, 08:52 PM

Seeking out a bit of help from some members, we ran all new brake lines in my '75 Blazer, while trying to bleed the brakes we are getting no pressure at the rear wheels. I have the hood up and with the cover off the master cylinder when I pump the brakes the fluid shoots up so I know the master cylinder is ok. We are bleeding them with the car off by the way.

My buddy thinks he may have run them to the wrong spot on the proportioning valve, ie. the front in the back's slot. Is there any way this would cause this to happen?

Do I need to run the car for the booster to give me enough pressure to get to the rears?

Any help is greatly appreciated.

**old Rusty C10** · 03-15-2011, 09:18 PM

did you bleed the master first? I would verify that you did in fact install the lines correctly on the proportioning valve and then try gravity bleeding them

lilpoindexter · 03-15-2011, 10:46 PM

Did you press that little button on the proportioning (or whatever its called) valve on the front crossmember?

f.monroe · 03-15-2011, 11:14 PM

There are lots of little high spots in the brake lines going to the rear brakes. Yo umay want to try to bleed it at the high spots first . Bleed it at the master cyl, at the rear of the truck where it leaves the frame and goes downward to the rear axle ,at the T fitting that splits the line a tthe diff and runs to the driver and passenger side, then finally at the drum brake cylinders . It will take a bit of doing to get the air out . I have also jacked the rear up as high as possible and supported it with jack stands to bleed brakes. Air will travel up hill and you can direct it to where you want it to go . Jacking up one side at a time will also direct it to that wheel cylinder for bleeding purposes . I have found that bleeding new brake lines is a time consuming procedure with out a pressure bleeder t oforce fluid through the system . Keep at it and you will get it .
Frank

TheWhiteElephant · 03-15-2011, 11:19 PM

You can get a relatively inexpensive vacuum pressure brake bleeder at the parts stores by Mighty Vac.

dccarpenter · 03-16-2011, 09:29 PM

I got the $30 Might Vac kit from Autozone tonight, going to try it out tomorrow. Hopefully it'll do the trick. Thanks for the advice!

Hopefully it isn't the lines swapped on the valve since the two ports use different fittings, I'd have to cut the lines, swap fittings, and flare the ends to make it work if so...trying to avoid the compression union temptation.

03-15-2011, 08:52 PM	#1
dccarpenter Registered User Join Date: Jun 2009 Location: Washington, dC Posts: 176	No Pressure to Rear Brakes Seeking out a bit of help from some members, we ran all new brake lines in my '75 Blazer, while trying to bleed the brakes we are getting no pressure at the rear wheels. I have the hood up and with the cover off the master cylinder when I pump the brakes the fluid shoots up so I know the master cylinder is ok. We are bleeding them with the car off by the way. My buddy thinks he may have run them to the wrong spot on the proportioning valve, ie. the front in the back's slot. Is there any way this would cause this to happen? Do I need to run the car for the booster to give me enough pressure to get to the rears? Any help is greatly appreciated.

03-15-2011, 09:18 PM	#2
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,287	Re: No Pressure to Rear Brakes did you bleed the master first? I would verify that you did in fact install the lines correctly on the proportioning valve and then try gravity bleeding them __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

03-15-2011, 10:46 PM	#3
lilpoindexter Registered User Join Date: Sep 2010 Location: los angeles Posts: 1,132	Re: No Pressure to Rear Brakes Did you press that little button on the proportioning (or whatever its called) valve on the front crossmember?

03-15-2011, 11:14 PM	#4
f.monroe Senior Member Join Date: May 2004 Location: Caldwell,Tx. Posts: 3,648	Re: No Pressure to Rear Brakes There are lots of little high spots in the brake lines going to the rear brakes. Yo umay want to try to bleed it at the high spots first . Bleed it at the master cyl, at the rear of the truck where it leaves the frame and goes downward to the rear axle ,at the T fitting that splits the line a tthe diff and runs to the driver and passenger side, then finally at the drum brake cylinders . It will take a bit of doing to get the air out . I have also jacked the rear up as high as possible and supported it with jack stands to bleed brakes. Air will travel up hill and you can direct it to where you want it to go . Jacking up one side at a time will also direct it to that wheel cylinder for bleeding purposes . I have found that bleeding new brake lines is a time consuming procedure with out a pressure bleeder t oforce fluid through the system . Keep at it and you will get it . Frank __________________ Born and proudly residing in a Red State !

03-15-2011, 11:19 PM	#5
TheWhiteElephant God is good! Join Date: Sep 2010 Location: Texas Posts: 689	Re: No Pressure to Rear Brakes You can get a relatively inexpensive vacuum pressure brake bleeder at the parts stores by Mighty Vac. __________________ Mando *"It takes a smart man to know when he's stupid." -- Barney Rubble* My build thread: http://67-72chevytrucks.com/vboard/s...d.php?t=430367

03-16-2011, 09:29 PM	#6
dccarpenter Registered User Join Date: Jun 2009 Location: Washington, dC Posts: 176	Re: No Pressure to Rear Brakes I got the $30 Might Vac kit from Autozone tonight, going to try it out tomorrow. Hopefully it'll do the trick. Thanks for the advice! Hopefully it isn't the lines swapped on the valve since the two ports use different fittings, I'd have to cut the lines, swap fittings, and flare the ends to make it work if so...trying to avoid the compression union temptation. Last edited by dccarpenter; 03-16-2011 at 09:32 PM.



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