[NeighborsComplaint]

So, I have now done 3 complete circuits of brake bleeding and still have no brakes.

I did a rear disc conversion with a kit which included eldorado style rear rotors and calipers, new disc/disc master cylinder and proportioning valve. New brake lines and hoses were installed throughout including banjo bolts and copper crush washers. I threw on new rotors, calipers and pads on the fronts also. Brake booster is a couple years old Morraine unit. The pushrod for the booster/master is in the lower hole on the brake pedal and the rear calipers have been pre-adjusted via the emergency brake cables.

I started with the MityVac on the right rear and worked around the car to a firm pedal and followed with a final manual bleed. Pedal was high and hard until I started the car and it just dropped to the floor and barely came back up.

I checked for leaks and had one slight weep on the left front. I tightened the fitting and followed the same procedure again, same result. No leaks but no pedal as soon as the car is started. Once shut off the pedal still goes straight the floor.

I removed the rear line at the proportioning valve and found the valve stuck in the rearward position. I gave it light nudge with a phillips and it popped forward. I repeated the bleeding procedure with the same result.

Anyone have any advice on what I am doing wrong here? Should I be simultaneously bleeding RR/LF followed by LR/RF (3 man operation)? I did not bench bleed the master as the shop that loaned me the MityVac said it was unnecessary using the vac.

[rexs73gto]

The proper way to bleed them is RR, then LR, then RF, then LF. You also need to bench bleed the master 1st. Are you getting fluid to each wheel when you suck the fluid out of each wheel. If the system is new with NO fluid in it at all you need to let it gravity bleed for an hour or so 1st so you have fluid coming out of each wheel before you try the bleed with your mity vac. Gravity bleed each wheel 1 at a time in the same manner as you would if you were bleeding them manually.You need to gravity bleed each wheel until fluid comes out with NO AIR.

[Sirrotica]

All the fancy brake bleeding stuff sold will never do a better job than physics and gravity.
Since I work alone almost all of the time, I've been using gravity to bleed brakes for over 45 years. As a service tech most of my life it's never failed me yet.

If you can't gravity bleed a brake system, there's another problem in the system because fluid always runs to the lowest point of the system. Physics never change.

Just a few months ago I changed all the hard lines and replaced the 2 rear wheel cylinders on my 93 K3500 dually, and did the whole bleeding procedure with just myself and gravity. No pressure bleeders, no suction pumps, had it all bled in less than half an hour. Firm pedal first time I tried it, and was done. No going over the system 2-3 times.

[NeighborsComplaint]

How can you gravity bleed the system when the bleed screws to the rear calipers are higher than the rear axle lines? Even if the lines were disconnected from the master cylinder, there is not enough "head" to force the fluid uphill from the rear axle lines to the bleed screws at the top of the calipers.

Bench bleeding the master cylinder only aids changing the master cylinder on an already filled system to eliminate the need to bleed the lines. No air (or a neglible amount) enters the lines when disconnected from the master cylinder on a filled system. I have replaced many cylinders over the years without having to bleed the brake lines by bench bleeding the master cylinder first.

The key point I am making is that my braking system bleeds normally until there is no air present at each corner. The brake pedal holds firm until the car is started at which time the pedal travels straight to the floor. Re-bleeding after this happens shows the system full of air.

[george kujanski]

As long as the master is higher than the bleeder screws, gravity bleed will work. Using a mighty vac on the bleeder screws will also suck air from around the bleeder screw threads. On a new empty system I may use a mighty vac at first to fill the lines, then let it gravity bleed, if I am without a helper. With a helper I use the pedal pump method to make sure.

Another thing I've used is a rubber ear syringe (bulb) from your friendly pharmacy. i remove the bleed screw and use the ear bulb to suck fluid down to the caliper...this avoids air leaks at the bleeder. I then let it gravity bleed.

George

[Sirrotica]

George beat me to it, excellent analogy.

As I said earlier, if the system won't gravity bleed, there is another problem letting air enter, stopping the siphon.

To get a siphon to start I sometimes just bump the brake pedal maybe an inch or so at the top of the travel so it pushes fluid into the lines with the bleeders open. Once the siphon is started let it drip and close one bleeder at a time. If you can't start a siphon air is getting into the system.

In your case a defective master cylinder would be the first thing I would suspect, they aren't all good 100% of the time, believe me. Some one installing the seals on the spool reversed or cutting a seal upon installation would act like your description by exposing the fluid to atmospheric air when the pedal is depressed, pushing air into the system as you describe.

[NeighborsComplaint]

Thanks for the replies. In the back of my mind I am thinking bad master cylinder as you have suggested. I used the MityVac for the initial bleed and when it was down to just a few bubbles at each corner I switched to manual bleeding.

I guess my next step is parts swapping master cylinder and proportioning valve just to be sure.

[HWYSTR455]

You need to bench bleed the master, or it will take forever to get the rest of the system bled. I've seen folks go through exactly what you are going through and gone back to bench bleed the master, and have it work.

When you go to bench bleed it, you will see just how long it takes to do it. Without the bench bleed, the piston just moves a column of air back and forth. With the lines looped into the reservoir, it sucks fluid back when you let off.

.

[Sirrotica]

If he has a firm pedal until the car is started, then it goes to the floor, air is being induced and bench bleeding isn't going to change that............FWIW

As I said, I never bench bleed master cylinders, and have no trouble since dual systems appeared in 1967.

In a single system no one bench bled a master cylinders.

Pressure bleeding a system with a equalizing valve upsets the balance and the valve will shift to shut off one side of the system as it is designed to do in case of a hydraulic failure. It also in an older system will move corrosion particulate making further problems by making valves stick.

Gravity bleeding won't shift the valve making a manual reset in some cases necessary, or an automatic reset when both sides of the circuit equalize pressure. Unless every part of the system is new you can be causing yourself more headaches by pressure bleeding by dislodging dirt in the system shifting valves that won't return because of corrosion.

That's my experience from doing it full time for a number of years, not as a hobby, once in a while. I'm not here to prove who is right, just trying to help someone out is all.

The OP will find out where his trouble is by a methodical search of his system.

[Sirrotica]

One other thing, by just pumping the pedal at the very top of it's travel, it covers and uncovers the ports in the master cylinder. If you watch the reservoir you will see the air bubbling up from the master cylinder and as most any gas will rise to the top of liquid effectively bleeding all the air in the highest point of the system back to the atmosphere. Most anyone does the pump and hold, when pressure bleeding and it doesn't give the air a chance to vent into the reservoir. Just slightly moving the spool at the end of the travel works fine.

If you pump the pedal say 10 times and your still getting bubbles in the reservoir, then I would suspect air is getting in from the spool side of the master cylinder because of a seal problem.

My father, (mechanic most of his life) showed me these little tricks and if I can help someone by passing them on, it's better for everyone.

[HWYSTR455]

If the car is started it goes to the floor? I missed that. But I would have to say that's a booster issue. If it were a master issue, I wouldn't think it would pump up at all.

I gravity bleed, but I still bench bleed the master. I've done many full brake systems, and that's always worked for me, so I shared. I do it by myself, and gravity is my method.

I was told due to the angle of the master when it's mounted on a booster, you can't get all the air out, because of the location of the holes in the reservoir. But that's just how it was explained to me, and again, since it's always been successful the way I do it, I never really went beyond to question it.

Sorry to interrupt, carry on...

.

[FirebirdHank]

I had a similar issue when I replaced the rear calipers on my Firebird. It is a '69 but has '81 WS6 rear brakes. I too used a vacuum bleeder and after several tries still had very spungy pedal. I called my mechanic neighbor over and he said that because of the angle of the master there was probably some air in there that couldn't get purged out.
What I did was disconnect the master from the booster which allowed it to go to almost horizontal. Then I vacuum bled them again with the master in that position, re-connected it to the booster and that solved the problem.
You didn't mention what model of Pontiac you are working on but this sure seemed to do the job on my Firebird.

[Sirrotica]

I'm not going to argue the point, however I have bled dozens of GM, fords and chryslers with horizontal and canted master cylinders and never had to remove one from the car to get it bled.

Also many of the canted GM cylinders had bleeder valves right on the master cylinder next to the line connections and I've bled master cylinders there as well as loosening the fitting at the master cylinder, and let it gravity bleed until there were no bubbles coming from the cracked fittings.

Good luck to the OP in finding his problem, hopefully all the posts send him to the problem and he gets it resolved.

[Scarebird]

Originally Posted by NeighborsComplaint

So, I have now done 3 complete circuits of brake bleeding and still have no brakes.

I did a rear disc conversion with a kit which included eldorado style rear rotors and calipers, new disc/disc master...

Did you adjust and cycle the parking brake BEFORE bleeding?

[ta-69]

Make sure your calipers are on the correct side. Bleeders on top not on the bottom of caliper.Jim

[NeighborsComplaint]

Originally Posted by Scarebird

Did you adjust and cycle the parking brake BEFORE bleeding?

Yes. Fully adjusted and fully functioning.

I took one last crack at it today. Pulled the master cylinder and did the bench bleed followed by bleeding each of the 4 corners RR-LF-LR-RF. Same result.

I am so f@cking tired of this I could scream. The bleeding instructions provided with the system are complete babble talking about leaving the bleed screws open on the blocked diagonal calipers while bleeding the other two ... WITH is a blocked caliper? They also carry on about this allowing the proportioning valve to equalize and center and the same with the combination valve. WITH is a combination valve? The system only has a MC, proportioning valve, lines and calipers.

When the system lost pressure, I pulled the fitting off the back of the proportioning valve and found the piston perfectly centered. Now I have no pedal, running or not and no visible leaks.

No mas.

I am towing it to a roadster shop to let them deal with it. I have just ordered all new lines, booster, master cylinder and proportioning valve from Inline Tube and have given instructions to the shop to start over from scratch. All my fittings are hacked from wrenching on them over and over and at this point I don't trust a single component that came with the kit. This was a system purchased from Pirate Jack ... beware the Jolly Roger, lesson learned.

As it stands, I even doubt the integrity of the rear calipers so in all likelihood, the only salvageable components from the kit will be the axle brackets and the rear rotors (which required machining the axle flanges and installation of longer wheel studs to be used). Nice kit.

[NeighborsComplaint]

Originally Posted by ta-69

Make sure your calipers are on the correct side. Bleeders on top not on the bottom of caliper.Jim

They're on top.

Everything installed as per Pirate Jack's "Treasure Map".

[Scarebird]

Before tossing in the towel try one of these:

http://www.harborfreight.com/brake-f...der-92924.html



They are cheap. Buy a gallon of fluid and go to town. Best is to get a spare pair of bleeders and drill them thru so you are not sucking air around the threads.

[BB70]

Read your story a couple times- here's my 2 cents-
Sounds like you used open end wrench instead of flare fitting wrench to tighten lines and rounded the fittings- suspect lines not fully tight and maybe sucking air. New lines need tightened and loosened a few times to seat proper- especially stainless.

The rear calipers need adjusted by working the e-brake lever untill the pads contact the rotor-they should maintain contact when the lever is in the rest position- if they retract substantially the caliper is no good. The rotor should be held on with a lug nut- then e-brake cable installed, the lever should sit at full rest when adjusted correct- very important !!

You can be fooled with a hi hard pedal with the engine not running. After running you get 2-3 assisted strokes then pedal gets hard again.

New front calipers will take a few pedal pumps to get pads against the rotor - pedal will go to the floor until contact is made.

The combo valve is a prop valve and warning switch in one. You really shouldnt be sticking a screwdriver in it, it will reset itself when everything is ok. No idea what they mean by a blocked caliper unless they mean pinching off the flex hose. Hope all this rambling points to something.
John

[NeighborsComplaint]

Originally Posted by BB70

Read your story a couple times- here's my 2 cents-
Sounds like you used open end wrench instead of flare fitting wrench to tighten lines and rounded the fittings- suspect lines not fully tight and maybe sucking air. New lines need tightened and loosened a few times to seat proper- especially stainless.

The rear calipers need adjusted by working the e-brake lever untill the pads contact the rotor-they should maintain contact when the lever is in the rest position- if they retract substantially the caliper is no good. The rotor should be held on with a lug nut- then e-brake cable installed, the lever should sit at full rest when adjusted correct- very important !!

You can be fooled with a hi hard pedal with the engine not running. After running you get 2-3 assisted strokes then pedal gets hard again.

New front calipers will take a few pedal pumps to get pads against the rotor - pedal will go to the floor until contact is made.

The combo valve is a prop valve and warning switch in one. You really shouldnt be sticking a screwdriver in it, it will reset itself when everything is ok. No idea what they mean by a blocked caliper unless they mean pinching off the flex hose. Hope all this rambling points to something.
John

Tools used:

The fittings were really crappy. On most fittings the wrenches would only fit it one position. When I could not wrench by flipping the wrench backwards, I had to resort to tapping the wrench onto the fitting with a small ball peen hammer. It was really crazy. Used a combination of US and Metric to get it done. Tightened , loosened, retightened more times than I care to talk about. Oh yeah, note how much fluid I have removed during repeatedly bleeding these f@cking brakes.

A local roadster shop advised they had a similar experience with 4 wheel disc conversions and the proportioning valve was always the issue. They suggested a manually adjustable proportioning valve and suggested pulling the piston out of the existing proportioning valve and then bleed the brakes. The advised they no longer install prop valves in their systems due to the very same issues I am having.

I went to try this and found the shop owner decided to inspect the piston by removing the end fitting and cross-threaded the end fitting when he put it back together... he told me he checked the piston and put it back together and now it was leaking like a faucet ... I couldn't clean up the internal flare thread so the proportioning valve is junk now and probably just as well as I believe it and the master are the root of the problem as I had no visible leaks anywhere. FYI, I did remove the master and bench bled it as part of the trouble shooting. After bench bleeding, I also loosened the lines at the master, held steady pedal pressure and locked the fittings down before releasing the pedal.

As nothing has worked out, I tore all the lines off (hand bent olive drab alloy lines that looked like ass anyway) and ordered a new master/prop valve and a set of lines from Inline tube.

I'll let y'all know how round 2 (really more like round 5 or 6) turns out.