questions on bleeding a virgin 4 wheel disc brake system!

[mike reeh]

I have 4 new calipers all around on my truck (thanks to derbinator) and I think im going to bleed the brake system today and get it working (new master cylinder and all the lines and calipers are dry) anyways should I fill the caliper up with brake fluid before starting? or will they fill up and bleed the air out normally..

OH and my main concern is this:

on the rear discs, the bleeder screw points DOWN... that means that if fluid enters the caliper, its going to fall right towards the bleeder screw, leaving a huge pocket of air. Now that I think about it, I guess I will have to remove the caliper and hold it in the correct position for the bleeding process.

What about the proportioning valve (stock one) ??? There is a little valve on the side with a rubber button covering it... How does that work and do I need to take any special measures for bleeding it? (1977 K20)

any advice or insight would be great. thanks! /forums/images/icons/grin.gif

 

[Pure Insanity]

The new master should have come w/ little plastic nipples and hoses to bench bleed it. Basicly what your doing is priming the master. The hose needs to be under the fluid so that when its on the return stroke it is sucking up the fluid rather than air.


</font><blockquote><font class="small">In reply to:</font><hr />
on the rear discs, the bleeder screw points DOWN... that means that if fluid enters the caliper, its going to fall right towards the bleeder screw, leaving a huge pocket of air. Now that I think about it, I guess I will have to remove the caliper and hold it in the correct position for the bleeding process.

[/ QUOTE ]


The rear calipers on flip flopped. Change left and right around and the bleeders will be pointing up. It will never bleed out that way. You CAN NOT hold them in your hand and bleed them! Dont try it. If you get lucky and dont have your hand in the way of the piston it wont break or chop off a finger when it blows the piston out. DONT TRY IT. Trust me.

The proportioning valve I have read SOME need to have that button pushed while bleeding. In over 20 yrs total of working on cars and trucks I have never seen one that did.

Once you bleed the master, try leaving the bleeders open and see if they will gravity bleed. I do this every time I open a system. If it does work it will greatly shorten the time you have someone pumping it up for you. /forums/images/icons/wink.gif Basicly you open the bleeders and drink a cold beverage and wait. In a few min youll notice that the bleeders are leaking. In theory this will bleed the system efficently but I always manually bleed them a few times after gravity bleeding just to be sure its bled good.

 

[KRAZIE87K5]

Pureinsanity has it down pat. I concur. Bench bleed the master, then get all the lines installed, mount the rear calipers with the bleeders facing UPWARDS, and gravity bleed the entire system. I ran 2 32oz bottles of DOT3 thru mine just for good luck.. My truck STOPS on a dime with the 4whl disc setup.

BTW – I used 45ACP’s brackets… and ‘80 ¾ ton front calipers, no e-brake. /forums/images/icons/frown.gif /forums/images/icons/smile.gif

-Dan

 

[m j]

when gravity bleeding a few smacks will loose the stubborn bubbles

 

[Pure Insanity]

One thing I should add that should be common sense to most but not all have done brakes before that may be reading this.

After gravity bleeding be sure to close all the bleeders before manually bleeding the system one wheel at a time. Otherwise you will just suck air back in, and you will have wasted your time.

Another thing is to work from the closest wheel to the master to the farthest. So that would be left front, then right front, then the rear, which is a pretty equal run to them, take a look and see which one is longer. Do that one last.

 

[clayoval]

Some good advice here but one more thing you can do to make the job easier. Go and buy a hand vacume pump. It will come with enough stuff to bench bleed the master. Then just attach it to the bleeder screws and pump up a vacume and open the screw keep a eye on your fluid level no need to put the cover on the master. Keep some brake cleaner handy and keep the bottle on the pump clean. You can run as much fluid thru the system as you want to get air out as you can see the bubbles pass thru the line. Once you have all the small particals out of the system you can clean the pump bottle and reuse the fluid. The vacume pump is aroud 15 bucks and is a great way to do your brakes since you do not need a second person to pump the brakes and will cut your time in half. Plus you now have a pump to check your advance for timing and any other vacume that needs checking. And dont get one bottle of fluid buy 3 big ones and flush out your system real good your brakes will last a long time with no problems.

 

[DERBINATOR]

Mike,
I just wanted to restate that if you switch your rear calipers from left to right the bleeders will point up. Making it much easier to bleed.