Help Needed. Can't Bleed Brakes

[jmillsUT28]

Having a heck of a time with this my 72 blazer that I bought. The guy I bought it from had it as a project since 1995. So did not drive it much at all.

Please tell me what I am doing wrong.

Problem: can not bleed front or rear brakes.

What I have done. Replaced master cylinder, front calipers and combination valve. I've bleed the mast. Pushed the needle in on the combination valve while trying to bleed the front brakes but can not get any fluid at all at the bleed valve on the caliper.

What am I doing wrong? I have not tried the rears as I have found they are missing a few spring that hook up to the brake shoes.

Can't believe I am having this much problems out of brakes!

[hemi43]

I'm going through the same crap too. I've heard these trucks can be a pain. Make sure you bench bleed the master, and tip up and down 30 degrees as you bleed it. It took quite a while to do mine. Apparently the problem is with the proportioning valve. I pressure bled mine and it seems a lot better, but will have to wait until I can road test it to be sure. If you already have everything together, then try raising the front of the truck as high as you can to try and get the master somewhat level.

[jmillsUT28]

I have not tried raising the front to level out the master. Will try that next. So you used a pressure bleeder kit to do yours? When you did the front did you push in the needle on the proportioning valve and hold it in while bleeding? Did you hear air coming from that needle when you did? I have a pressure kit but will not hold pressure when the needle is pressed in.

[hemi43]

I'm using an aftermarket proportioning valve. I didn't push the pin when bleeding.

[BMERDOC]

Try loosening the connections further down the line to see if you are getting fluid through the lines. Are any of the rubber lines new?

[jmillsUT28]

I'm using a new Classic Performance Brake Proportioning Valve PVKS-2. It has the pin on it.

[jmillsUT28]

No none of the rubber lines are new. I did just see that the rear right brake cylinder is leaking. But that should not affect the front as it is it's own system.

[BMERDOC]

Crack the lines at the rubber hose (not at the caliper) to see if you are getting fluid there. I've seen some rotten hoses that looked fine from the outside.

[hemi43]

Originally Posted by jmillsUT28

I'm using a new Classic Performance Brake Proportioning Valve PVKS-2. It has the pin on it.

FYI, I'm basically using the same valve just different manufacturer. Not quite sure what you mean about having to push the pin though. I thought this pin was to reset the internal switch and has nothing to do with the brake fluid flow.

[jmillsUT28]

Update, I tried to gravity bleed the left rear brake and after a full weekend had no fluid coming out. I actually broke off the brake line going into the wheel cylinder as I was replacing the cylinder. Even with it not connected I did not get any brake fluid that came out. From what I hear I should have. So does this mean I have a blocked brake line somewhere? Are we sure power brakes should be able to gravity bleed?

[BMERDOC]

It shouldn't matter if it is power or manual brakes. There is a union on the passenger side frame rail that connects the rear break line. I would break it loose there to see if you are getting fluid. There is a brass T in the front cross member for the front brakes. Break it loose at the line coming into that T from the MC to see if you can get fluid there.

[cleszkie]

I going by memory, but I seem to recall the pin on the stock proportioning valve needed to be held in the out position while bleeding, and there was a special tool that was called out in the assembly manual to do this. I don't know if your aftermarket valve operates in a similar manner, but a quick call to the manufacturer could verify.

[BMERDOC]

There were actually two kinds of tools that did the job. Either the clip or the screw in tool depending in which valve you have.

[cleszkie]

Originally Posted by BMERDOC

There were actually two kinds of tools that did the job. Either the clip or the screw in tool depending in which valve you have.

Good info here.

[crappie66]

Have you checked to see if both bleeders were stopped up? Sometimes its the simple things.

[jmillsUT28]

I cut both lines right before the rear wheel cylinders and have no fluid. I'm waiting on a complete new brake line kit to come in. Once I get it will update. Will also check the push rod to make sure it is long enough.

[jaros44sr]

Originally Posted by BMERDOC

There were actually two kinds of tools that did the job. Either the clip or the screw in tool depending in which valve you have.

Where were you able to buy these tools

[BMERDOC]

I don't have them. I googled "proportioning valve tool". Looking around I was able to find them through Summit Racing and eBay quickly.

[jaros44sr]

Originally Posted by BMERDOC

I don't have them. I googled "proportioning valve tool". Looking around I was able to find them through Summit Racing and eBay quickly.

thank you for your time, I don't use google enuff

[jmillsUT28]

Update: replaced the brake booster, all brake lines and rubber lines, master cylinder (same as the one I started with which is new), new proportioning valve, calipers, brake cylinders and shoes.

Outcome... still do not have breaks. I am thinking I might have a problem with the new master cylinder. When I am trying to bleed the right rear brake I get a jet of fluid that comes up from the little pin hole in the front section of the master cylinder. So if I have it topped off it over flows a little. It should not be doing this correct?

[BMERDOC]

Don't worry about that jet. It can happen when bleeding a brake system in my experience. My truck did the same thing and I've had it happen on other projects so I know exactly what you are referring to. Have you tried gravity bleeding again? Crack the lines just before the prop valve to see if you can get fluid to that point. Next see if you can get fluid to the tee on the front crossmember for the front brakes and the union for the rear brakes. If you can get fluid to those spots you can bleed the system as you normally would.

[ClassicStyle]

I've seen bleed screws that have no holes.

Goofy I know but I've had it happen. Do you any fluid down the line? If not I'd say the master,l

[kryszkuk]

Don't mean to high jack your post but also having problems with my 72 k20. New MC and complete rebuild of the back drums and new rubber brake hose in the rear. I get brake fluid out of all bleeders but truck does not like to stop. Can power brake truck and stops on a dime under 15 mph but anything faster then that it's like I have never seize on my pads and shoes. Rear shoes replaced but not the front pads, gonna replace them even though they look good but anyone have any other suggestions?
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[IronCanine]

I don't have anything constructive to add to this conversation, just commiseration. On our build, the entire system was completely new and completely stock, (even NOS prop valve) and yet the brakes were a total pain to bleed. We had some leaks to overcome to be sure, but we'd have never gotten it done gravity bleeding them...(trust me, we spent two days trying). Even power bleeding them, it took a while, multiple pulls and cycling a lot of fluid. I can't tell you why it was so laborious...but eventually the dash light went off and the pedal got firm. Best of luck.

[jaros44sr]

Originally Posted by kryszkuk

Don't mean to high jack your post but also having problems with my 72 k20. New MC and complete rebuild of the back drums and new rubber brake hose in the rear. I get brake fluid out of all bleeders but truck does not like to stop. Can power brake truck and stops on a dime under 15 mph but anything faster then that it's like I have never seize on my pads and shoes. Rear shoes replaced but not the front pads, gonna replace them even though they look good but anyone have any other suggestions?
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What size tires are you trying to stop?