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Master Cylinder and 1-ton

MNorby

MNorby

3/4 ton status
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Finally got my 60 instaled last night and all went well except the brakes. They are very gooshy and go pretty much to the floor before gettng anything. I bled the brake 2X front and back but didn't help. I still have the '86 1/2 ton master cylinder on it still. Is the D60/14FF brakes too much for the 1/2 ton master cyl? Thanks. /forums/images/graemlins/truck.gif
 
If the master cylinder lost all its fluid in one or both of its resevors (I gotta learn to spell!), you will need to bench bleed the master.

Remove master, secure it so you can depress the piston with a large screwdriver or 3/8" extension. You can place it in a vice, but be careful where / how you tighten, you don't want to distort the cylinder (where the piston is). You will need a bench bleeder kit (very cheap). It is basically 2 threaded inserts where the brake lines go with hoses that are submerged in each of the respective resevors. Fill the master cylinder with brake fluid. Depress the piston ALL THE WAY until it bottoms out. Hold for a second and slowly release. Do this until there are no more bubbles coming up in the fluid when you depress. Install the master (Make sure the master stays full or you'll have to do this again) and bleed the brakes on the truck until there is no air in the lines. Be careful when bleeding, if the master goes empty during this process you will have to start again with the bench bleeding.

Pressure bleeding is the best for bleeding brakes on the truck ... but we don't all have pressure bleeders.

Let me know if this works, I've got a 60 going into my Burb soon and hadn't counted on any brake issues.

Good Luck,

Eric M.
 
I didn't run out of fluid in the resevoirs (sp) and had over half full after swapping axle then topped off then bled so I don't htink it is an issue of running out. Just curious if a 3/4 ton or 1 tons master cylinder pushes more fluid to thelarger brakes to make them work???
 
I still have the 1/2 ton MC and booster on my K5 with the D60/14BFF combo. ONLY issue I had when we did the install was same thing you are fighting - mushy brakes. Had them power bled for $60 and problem solved. The stock MC is more than adequate for one ton gear. /forums/images/graemlins/cool.gif
 
right on. When you say Power Bleed are talking about the same steps Eric gave me?
 
Mine was done at a dealer that has an actual power bleeding apparatus..........
 
is that one of those big metal ball things that use vacuum to bleed with I think. I have access to one of those really easy.
 
The best way that i have found to blead brakes by yourself it to gravity blead them. pull the top off the master cylinder and fill it with fluid the leaving it off go to th RR and open the bleader and wait till all the bubbles quit comeing out then close it. the go to the LR, RF and then LF. after all this is done fill the MC with fluid again put the top back on. after this pump the brakes 4-8 times then repeat the whole process again till they are good and solid. You might also need to adjust your rear shoes also.
 
I don't this it would be the rear being as the brakes were good when I pulled it into the garage last night to swap axles but after putting the 60 in then the brakes sucked. I think I'll try to bleed them allaround again to make sure. Thanks.
 
You forget one thing when you open the system air can go anywhere. It's not just on the front.
I would say it should be now around the middle of the truck.
I agree on gravity bleeding, and I also start with the far side which is RR.
Be patient and take your time bleed it good.
 
ok cool. I'll try gravity bleeding and reg bleeding tonight and take if from there. I wasn't sure if just openning the front would cause problems to the rear.
 
If you've got access to a pressure (power) bleeder, give that a try, it's the best way to bleed brakes.

Let us know what happens. My D60 stays on the garage floor until you work the bugs out!

Eric M.
 
Just get a new MC and start over. Bench bleed it, bleed all 4 cornors and you are set.

I have NO rear brakes and mush in the front. new 1/2 ton MC and i can lock up the rears by flexing my toes. makes for one wild rifr /forums/images/graemlins/grin.gif
 
not yet, they brakes work just not a very firm pedel. I think that maybe now that I have driven it some more I'm gonna try to bleed them again and see how it goes. It's just been too cold around he to wanna get under it and work on it /forums/images/graemlins/crazy.gif /forums/images/graemlins/tongue.gif
 
Well, started thinking abut it an might have a bad master cylinder, will chack over Thanksgiving holiday (along with installing 4.56 lincoln locked rear setup /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif) I'll let you know what I find.
 
You know what...I disagree with the traditional "farthest from master" bleeding practice on these trucks. I know it's common parctice but hear me out on this.
The last 3 weeks I have been working through my brakes on a Disc Disc conversion and have come up with some observations.
The rear is the place to start but the side you start on doesn't matter. The distance the fluid travels is almost identical and infact it's a couple more inches on the driverside. The distribution block for the rear axle is off center to the passenger side by about 3 inches.
Now why to do rear then front is this. The way the PV works if the front comes up with pressure before the rear then the PV will kick into it's safety feature that turns on the light. well when it turns on the lght for the rear it BLOCKS fluid to the rear circuit to keep the pressure up in the master. So it would be difficult to bleed the rears second.
On the front I think your far better off starting on the the driverside. The driverside brake line is on the top side of the PV. If there is air in the PV then your going to get it out the fastest by bleeding the side that has the highest fitting, the dirverside.
 
I can't argue that.
You make perfect sense.
/forums/images/graemlins/thumb.gif
 
wow, thats very intersting. I guess we get cought up in the idea of distance in a straight line but aftualy fluid flow. Thanks for the info!
 
Grimmy is right, the only system that you must start at farthest point away from the m/c is on the old 66 and older vehicles with the single reservoir m/c, the dual reservoir systems have two separate hydraulic systems and are not connected together, you can and do bleed front and rear separately
 
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