I am pulling my hair out over these brakes!! I replaced the master cylinder with a new unit. I bench-bled it and hooked it up, and have been trying to bleed off the lines for days now. The pedal still goes to the floor. I am reading other threads about this and can't make sense of a good procedure. Also I am getting input from friends, and none of it seems to be the same. Some say bleed from the furthest point, like pass rear, then driver rear, then pass front, then driver front. The manual says to bleed them the opposite way, shortest leg to longest leg. Then there's this metering block/valve or whatever it is mounted on the frame rail below the MC. Supposedly I can't bleed the system properly without opening that thing up.

Another buddy of mine told me the air is in the lines up by the MC, and I need to bleed it at the fittings that connect to the MC by cracking them the same way I would at the wheel cylinders, THEN go to the wheel cylinders. He didn't say anything about this junction block on the frame rail though.

I am alomst embarassed that I can't do this, and am humbly asking for some help.

Can someone link me to a good "how to" on this or please just tell me how to do this right? Thanks.

Make sure all fittings are tight and not leaking.

Start with pass. rear, go to driver rear, then pass front, driver front. Longest leg first, that way if there is any air left it will be in the short lines only.

I don't know if you're using speed bleeders or a vaccuum pump, or having a helper open and close the valve but obviously there are a few things that could go wrong there.

If using a helper, make sure you have good communication. When the pedal is up the valve should be closed, then have the helper(or you, vice versa whoever is at the pedal) slightly put pressure on the pedal, open the valve. Once the pedal is at the bottom, close the valve and return the pedal to the top. Repeat procedure.

If using speed bleeders, you only need to get them a little bit unscrewed for them to work. Opening them too far may let air into the system.

I've never used a vaccuum pump to bleed brakes, so I'm of no help there.

Cracking fittings open in locations other than the bleeder will cause you more problems and let more air into the system. Do not do that.

I just put a master cylinder on my daughters tracker, I used a vaccuum pump, it worked really well

The speed bleeders...

When I bought the MC, I picked up 2 two-packs of them, in different sizes, because I wasn't sure which I needed. Then, I wound up with one of each on the front brakes, and came up short for the rear brakes. I don't have a pump, by the way. You said nothing about this metering/junction block. Am I to assume that nothing needs to be done with it?


Thanks...

Hi Jake-daddy, I'm no mechanic but I've bled my share of brakes. As Mike said, farthest to the closest. Pass rear, driver rear, pass front, driver front. Do not open any other fittings, prop valve etc. I always keep the MC cover on locked in place but you must check it in between a few of the pump and release's. If you let either of the resivoir's go dry, you have to fill it and start from scratch. My method, have someone pump up the brakes( communication comes in now ) he has to hold the brake pedal you open the valve ( I have a tube and a bottle to catch the fluid, laess of a mess ) when you you don't get anymore fluid or air, close the valve. I repeat the procedure 2 or 3 times on that wheel and then repeat to all wheels. (The brake pedal will go down when the bleeder valve is opened, do not let your helper release the pedal until you have closed the valve. Be certain you check the MC, do not let it run dry, the brakes should get better and better each time after this procedure. You may have to do it 3 times on each wheel, and then do the procedure all over again 2 or 3 more times. I'd say if you don't get brake pressure on the completion of 4 wheels going on to wheel # 5 you may have a leak. Jerry

I use a Corona bottle epoxied to a piece of plywood so it stands up by itself, and run a rubber brakeline from the bleeder fitting to the bottom of the bottle. Put the little bleeder wrench on the fitting flats first. As you bleed, it fills up and prevents you from sucking air back into the cylinder or calipers. Do not open the fitting any further than possible, air gets back in around the threads.

Have you checked some off the wall things, like the bleeder screws at the wheels being mounted at the highest point of the caliper or cylinder? Some can be mounted wrong. Is the master cylinder/brake pedal pushrod the right length and correctly adjusted?

I have used the Mityvac hand vacuum pump process also, but always prefer the "wife helps" method, (mostly because she hates it) as a final process. Sometimes it takes a lot of fluid to clear all the air.

I have never had any trouble with the proportioning valve or abs stuff on my brand F vehicles. They all bleed with the above. I will be doing this to my Chevelle soon.

It's done, I've got all kinds of brakes now. :D

Just started at pass rear and went after it again, with a different helper this time. It took a good while to do, and the quart mason jar was half full when we finished. I didn't mess with the junction block at all.

Thanks for the tips fellas.:beers:

I'm having the same problem after my front disc conversion. New lines in front and from front to rear. No pressure what-so-ever. I'm trying to gravity bleed at the moment. When you say this took "a good while" to do, about how long do you estimate? Just don't want to give up before I should. Thanks.

I'm having the same problem after my front disc conversion. New lines in front and from front to rear. No pressure what-so-ever. I'm trying to gravity bleed at the moment. When you say this took "a good while" to do, about how long do you estimate? Just don't want to give up before I should. Thanks.

Simon,

I'll bet we worked on each wheel cylinder for 15 minutes. Each corner probably warranted 3 refills to the MC. There was a huge difference after the rears were done. Even if you have the speed bleeders, you really still need another person to watch what is coming out, air or fluid. Then, when it looked like just fluid was bleeding out, we'd go two or three more pumps just to make sure, and wind up pushing out a little more air.

Two things to check if you're having bleeding problems is master cylinder piston to brake pushrod clearance and the proportioning valve position. If you don't have enough MC piston to brake pushrod clearance, the MC piston will be held in causing the relief valves to be covered, and any air in the MC or lines near the MC won't find it's way out like it's designed to.
When bleeding brakes, any air in the MC or lines near the MC will work its way out of the MC if you work the pedal gently.
You also have to make sure that the proportioning valve is centered or is "clipped" if it is one that needs to be.
Also, when bleeding brakes, make sure your assistant lifts his foot all the way up when he's pumping. If not, the relief valves in the MC don't get uncovered and they won't bleed properly. Also, make sure your assistant doesn't pump the brakes too fast. If he does, the brake fluid can foam, causing very tiny bubbles to form which are very difficult to bleed completely from the system. The antidote to foaming is simply waiting a couple hours before bleeding again to let the tiny bubbles turn into big bubbles. Sometimes, you have to tap lightly on the brake components and lines with a small peen hammer to get stubborn air bubbles to dislodge and work their way out.
When I bleed brakes, I first make sure the MC and the lines near the MC are air free; then I just gravity bleed each wheel individually, then all at once for a long time. Then I bleed each wheel normally a couple of times.

The above info is for non-ABS brakes ONLY. ABS brakes require more work and sometimes special tools.

Mike

Interesting on the push rod clearance. I think the pedal travels back far enough, but I question if it's pushing in all the way. I'll check on that tomorrow hopefully. I'd love nothing more than to gravity bleed these things but I can't seem to get any movement at all out of that MC. Thanks for all the info, I've been struggling with this project for over a month.

Just a little more info .
When I did my 4 disc setup conversion the hardest part was bleeding the brakes.
The rear brakes where very stubborn. I had replaced all the lines as well.
I ended up building my own vacuum pump with the $12 harbor freight air
vacuum pump that you can buy. I hooked up to one of those plastic bleeder cans and than let the pump suck the air via the air compressor. Crude but worked fairly well. The biggest issue for me was that the proportion valve would
close the back lines and no fluid would ever go to the rear brakes,something to look out for.
So I would always start out bleeding the furthest brake line away from the M/C . Patience is key here! I got impatient and started that way but nothing happened so worked on the fronts . That will impact the PV and closes the circuit to the rear . Also the M/C has to be bench bleed to be successful.

How did you resolve the issue with the valve closing off?
Thank you all for the great input, it gives me plenty of options while working through my issues.

A test light works great ,If it turns on, the PV moved forward or backward.
If no light comes on you can keep pumping away! It will still be centered!
The test light hooks up too were the warning brake light hooks on the dash, on top of the PV. Hope this helps.FYI: A hand Vacuum pump really works good when the system has Brake fluid already in all the lines but not with all new lines and new everything!!

My '66 doesn't have a brake warning light. Didn't have it in the original block on the frame so I can't hook it up. Is there some way to hook up a warning light to the PV anyway to check it out? I have another post on the site where I mention that I took the PV off, checked the valve inside and it appears to be in the right place (not pushed back); I can blow air into the top of the PV and it comes out the back line as well as both fronts. My next trouble shooting will be to hook the PV back up to the MC without attaching the brake lines. I'll have someone gently press the brake pedal and see if any fluid is actually coming out of the MC itself.

I'm running a cpp pv valve and has the hook up for brake failure light.
So I dont know about the 66 without the center hook up? It does not have a middle
looking screw sticking out of the middle of the PV? If you are having issues with rear fluid
not coming out ,80% of time the PV is off center and blocking the rear lines.
This helps out in emergency so you still have the front circuit working .
Usually if you crack both rear bleeders at the same time with helper will re-center the PV. This usually works but if any other issues are involved such as stuck PV,M/C not bench bleed correctly or wrong brake pedal rod,all bets are off!!

Well, I've figured out what was causing all of the trouble. At the risk of sounding like a COMPLETE IDIOT, I'm willing to admit what happened. I removed the master cylinder and took a look at the push rod. I had it in the booster...backwards. Yes, it's true. So for anyone else who runs across unexplained troubles, make sure the rod has the rounded edge facing out... Now that I've pulled my head out, I'm working on tightening all the loose fittings, bench bled the MC and just need to do a NORMAL bleeding routine on all four. Thanks everyone for the help on this!

Okay, so after pulling my head out and getting the push rod installed correctly, the brakes work great! I don't notice a huge difference in the "power" aspect of the brakes but they sure as hell do stop me better than the 40+ year old drums. The only issue I have is the routing of the front-rear brake line. Doesn't exactly hug the line of the car like the original, but I think I can live with it for now. Thanks for all of your ideas during this process, it was a real learning experience.