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I need to replace the master celinder in my 3/4 ton 53 pu. After I change in out, how do I bleed and refill the sys? These trucks didn't have a master celinder res. like newer autos. Is'nt there a tool that pumps fluid in and lets the air out? Thanks Again for all the help, Paul

Francis if you will put the master cyl on and fill it with fluid, then just push the brake pedal down slowly about an inch and let it back up with filler cap off and looking down into the fluid you will see air bubbles coming to the top of the fluid. This is the air escaping back through the fluid.when you just barley move the piston in the master it opens and closes the system to a small bleeder hole in the master cyl. If you will watch in the master cyl resovior while your moving you will see the air escaping. i have had good luck bleeding this way if the problem I repaired was just with the master cyl on the single cyl brake systems....Ronnie

Thanks, I'm going out to do that right now, will get back with the results.

Brakes. I don't want anything associated with stopping my vehicle (or yours) breaking...

I understand GMCpanel, although I'm not too sure how many others do. Don't you just hate what has happened to the Kings English? And sadly I'm not being condiscending, just expanding on your comment. I wish I could laugh it off.

I don't understand... I thought Francis needed some help with his brakes, not a lesson in spelling. How about some input on master cylinder bench bleeding! :rolleyes:


Stuart

exactly, Stuart

glad you're not being "condiscending" MoneyPit, hate to have everyone be sad with ya

Bill

Sorrrrry about the spelling guys, ya auta here me talk, like cusen Vinny, got it? Might not spell so good, but one hell of a welder! p.s. the bleeding and changing of the M.S. worked great. Thanks Again

i cant spell eather so dont wory

It's one of my pet peeves...if you really want to get me going, mix up to/too/two. :p

Proper terminology is important when dealing with technical topics.

As far as bench bleeding goes...all I can say is to do it. Great time-saver.

Bench bleeding the Master Cylinder is always a good idea.

How do you do it?

Holding the mastercylinder level, say in a vise, run hoses from the outputs back into the resevoirs. Then using a rod/stick/broom handle, depress the cylinder. This will force fluid into the spaces inside the mastercylinder 'valve/pump'. At first, bubbles will flow from the outlets (where your brake lines or lines to the proportioning valve are usually attached) into the resevoir.

Eventually, the bubbles will stop showing and all you'll see is fluid when you pump the master cylinder. once it is bench bled it is ready to go in. Be careful to keep it as level as possible until you bolt it in lest more air finds its way into the cylinder/valve.

When I bought my master cylinder it came with a kit containing plastic fittings that attach to hoses to put into the outlets of the mastercylinder. Those kits (bench bleeding kits) with the fittings and some pieces of hose are available at places like NAPA.

Best of luck!