brake issues
 

I have been trying to get the rear brakes working on the 67 i picked up last week. I have replaced the shoes, wheel cylinders, a brake line and the master cylinder. Im tring to bleed the brakes but i am not getting any pressure to the rear, there is fluid but no pressure and the rear brakes dont work at all. The only old part in the system is the proportioning valve, could it be the problem. Thanks for the help.

Re: brake issues
 

drum or disc on the front?

Re: brake issues
 

Did you bench bleed the master before hooking up the lines?
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Re: brake issues
 

Its drum/drum and yes i bench bled the master cylinder. Im pretty much stumped on this one.

Re: brake issues
 

After you double check by loosening the connections check the rubber brake hose on top of the rear drive axle shaft. It can collapse internally and won't allow or restricts the brake fluid from reaching the rear drums.

Only good way to check it is to remove it and look at it. You can also insure hydraulic fluid is going to the rear breaks after you remove it by placing a container to collect the fluid or by using a rubber hose that fits over the line.

Re: brake issues
 

ttt.i just blew out all the lines and every thing was fine, i didnt find any blocks, still no pressure to the back.

Re: brake issues
 

Check your free play on the pedal rod to master cylinder. If you have none then the valve cannot return past the reservoir hole and allow more fluid to enter the pressure port for the rear lines.

Re: brake issues
 

That was my problem when I did my brakes two months ago....
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Re: brake issues
 

Assuming you blew them out starting at the master cylinder then the master cylinder is defective. There is a front and rear piston internally to the master cylinder and the piston seals may be defective allowing brake fluid to be bypassed under pressure.

I had to replace couple of new defective ones a few years ago and finally went to a different auto parts store and got a different brand. Didn't have any more problems.

Re: brake issues
 

Yup I once had to replace a new remanned m/c a couple of times myself.

Re: brake issues
 

Do the front brake bleed just fine? If so, did you adjust rear brakes before bleeding?

Re: brake issues
 

Yes the front bleed out fine. Im no i didnt adjust the rear yet, im not really sure what that would have to do with any thing. There is just no pressure.

I guess im going to order another master cylinder and see what happiens.

Re: brake issues
 

What he means is that brakes have to be adjusted before bleeding so that they make contact before you run out of braking action. When I do my brakes I always adjust them so that they lightly scrape the drums as I rotate them before I bleed them.

Re: brake issues
 

reset the PV ?

Re: brake issues
 

I don't remember, does the front of the master cylinder operate the back brakes? Or does the front of the master cylinder operate the front brakes?

Here's why I ask: The pistons in the MC must move completely to the back (towards the firewall) when the pedal is not being depressed. This uncovers a port that allows fluid to flow into the cylinder.

If the piston is not completely returned it'll block the port and not allow any fluid to fill the cylinder. Of course, this assumed the bench bleed didn't go well and air is trapped in the cylinder.

If the hose that is connected to the MC is loosened, will fluid leak out if the pedal is pressed?

Re: brake issues
 

I just checked to make sure the master cylinder was returning all the way and it is.

Fluid will come out the master cylinder if the line is loose.

Re: brake issues
 

68gmsee explained it, if shoes don't make contact to drums, pressure will not build up in brake lines to rear brakes.

Re: brake issues
 

Forgot to add re. adjusting brakes before bleeding...

The only way you will get pressure in the brake system is if there's resistance by the shoes contacting the drums. Otherwise there's very little pressure.


MagmaJct: On the stock units the front is front brake and rear is rear breaks.

add again.. Just saw allchevy's post above.

Re: brake issues
 

Just wanted to update everyone on the fix. I replaced the master cylinder with a new one, not reman from napa and bled the brake again and now every thing is working great. Thanks for the help, the old truck is one step closer to going for a drive.

Re: brake issues
 

Good info for future. Subscribed

Re: brake issues
 

Fantastic.. Glad you got it going.

Re: brake issues
 

Glad to hear you got it working properly.