The Stovebolt Site Forums The Shop Area General Truck Talk Front Brakes not bleeding.

As part of my rebuild, I have replaced most of the brake system. I ran all new metal lines(Some high points, not sure if that is a problem), all new rubber lines, new dual master cylinder with booster, rebuilt all 4 drums, new shoes on rear, adjusted all shoes.

Now I filled the master cylinder, running a line back up into the top, bleeding it. All air is out of both banks, and just pumps fluid now. Plugging both ports with caps, brake petal is firm and can hardly be moved, so the master cylinder must be fine. Connecting the lines, and trying to pump, it goes almost to the floor. Bleeding the rear, I get alot of air out, pedal is now about 3 inches off floor. Trying to bleed front brakes, I get a few little bubbles on first try, then nothing. No matter what I do, I get no fluid or anything from the front bleed values.

I have spend hours(20+) on this, and am frustrated to heck and back. Only thing I can think of is the metal lines are higher than the master cylinder in places causing air to get stuck? Some have also said that taking the MC off the truck and bleeding it will help, but I don't see what that would matter taking the info above into account.


Please please, any suggestions before I tow it to a pro shop and loose my entire budget for this year???...!!!

Original DRUM/DRUM brakes with upgrade Dual Master w/Booster from Classic parts.

while you were bleeding the back did you have to keep refilling the M/C? when you did the fronts did you need to add fluid? if you had to add fluid and nothing was coming out where was the fluid going?

The first thing is to make sure that the shoes are up as close as possible to the drum. The next thing is to make sure that the MC linkage is adjusted properly. If it isn't, the front port might not be getting the fluid refilled when the piston moves back. I am not familiar with these dual masters but I wonder if there is a residual valve in the front. If not, it may be sucking air in when the pressure drops and the pistons move back in the front cylinders.

The rear bank of the master cylinder had to be filled several times while bleeding. The front bank never needed more fluid as nothing was coming out at the wheel cylinders.

The shoes are adjusted close on all 4 wheels. The MC Linkage was never adjusted, but I don't believe that is the issue, as the MC bleeding works fine, and the plugged ports cause plenty of pressure.

Reading online, there is alot of articles that list lines being higher than the master cylinder is a no no, due to bubbles getting stuck. I think this is the issue. Can anyone confirm this as a bad thing or the possible cause of this problem?


Also I have read about Residual valves 10lbs are needed on these lines. Not sure if that is part of the master cylinder or not. Will have to call Classic tomorrow for that piece.


Will likely be replacing the lines again, as I don't like the job I did on them anyhow. Any one have a diagram/layout of how they routed there brake lines when they switched to dual MC??

were the wheel cylinder pistons free?

i have seen pistons stick, allowing on pedal return air to be sucked past the w/cylinder seals, also is the wheel cylinder bleeder screws clear...seen them mudded/ rusted closed not allowing and fluid to escape when opened....crack open the line
at the wheel cylinder to see if fluid comes out when pedal pressed....

The Wheel cylinders were all rebuilt, so no sticking pistons. Bleeder valves were replaced as well. Need to pull the lines by section and see if I am getting anything.

Hy TXChevy50, did you install a combination valve in your system? If you did it has probably shuttled over to shut off the system which has no pressure in it.

I'll bet that the master is not bled on the front brake 1/2 of the system and the master is not adjusted so that there is some free pedal at the top ,there needs to be free play so that the master can pull in fluid to fill the piston every time you release the pedal than it can push more fluid as long as you're bleeding the sys.right. You should be able to push air and fluid as long as the master is sucking fluid in at the top of the pedal , the brake lines being higher should not be a problem.


I would bled the master again and make sure there is free play at the top of the pedal.




Pete

Pete,

If high points are not really a concern then, I will need to pull the master cylinder out of the truck and attempt to bench bleed it. I have tried bleeding it in the truck, and it seems to have worked, atleast no air when bleeding the MC, but who knows as it could still have air in it or something cause I don't believe it sits perfectly level in the truck. Guessing that is why they say bench bleed it verse bleeding it in the truck???

Best to always bench bleed the master you should have gotten the two fittings and the hose set when you got the master if not you can get a set at the place you got the master and I leave the set in place until I'm ready to put in the fitting .Also make sure you keep filling the master as you're working on the lines and bleeding them.

Good luck,Pete

Try bleeding the lines at each fitting starting at the master cylinder.If you get fluid at the first move to the next you may have have a blockage .You will find it this way by process of elimination.If you can't get fluid at the master then i would check the push rod.

Ok, spent several more hours playing with this. I replaced all the front lines with new ones, this time routing them better. Then I pulled the master cylinder from the booster and bench bleed it. Some air bubbles came out, but not alot. Put it all back together. Then as usually the back bleed super easy. Almost with force when opened. The front I get a few bubbles but only after like 20 pumps. Its better than it was, but still not right at all. I am about at my wits end. Only thing I can think to try now, is reverse the lines. Put the back brake line on the front and the front on the back and see what happens then.

I looked at the adjusting rod, however I wasn't able to figure it out. If I disconnect the pedal from the rod, I can adjust it out, but then I can't reconnect it as it is to long.

Any ideas welcomed.

On the stroke adjustment, you want to make sure that the rod can return all the way without being stopped by the pedal linkage in the truck. If there was a problem, it would mean that the rod was too long.

No issue here. I can install it without forcing it, and as stated above, it comes all the way out no problem.

I am really at a loss. I just don't understand why this is giving me so much hell. Should be a simple process.

I guess there is no chance that they shipped you the master for the drum/disc by mistake. I just read their writeups for the descriptions of all three masters and it is the same description for all three. Obviously that doesn't fit.

I don't know what method you are using for bleeding but I use the manual equivialent of the speed bleeders. I open the bleeder and place my finger over it. The person inside slowly moves the pedal up and down until I get a consistent flow. At that point I have them stop at the floor and I shut the valve. That takes care of 99% of the bleeding process and it is extremely quick. Speed bleeders will do that for you.

Using a hose connected to bleeder, ran down to a bottle filled partially with brake fluid. 5 pumps and hold, then crack the bleeder for 2 secs or so. then repeat.

When you bench-bleed the MC, are you getting fluid flow from the port that goes toward the front? If so, there has to be a restriction somewhere downstream. I'd second the above suggestion to follow the fluid flow one connection at a time until you find whatever is causing the fluid to stop flowing. It's also possible you've got a piston seal inside the MC that's bypassing fluid and refusing to develop enough pressure to force the fluid down the lines.
Jerry

Contacted the manufacture of the master cylinder. They believe the MC is fine, and that one of the wheel cylinders might be the issue(leaking air). So tonight I will be doing what you and they suggested, removing the wheel cylinders from the lines and plugging them. Trying one line at a time etc. I will let you guys know what I find/

Dumb question, but I had roughly the same issue on my 54. Both front rubber hoses would not let fluid through. Seems the hoses we internally plugged.

check the bleeder screws.take the bleeder all the way off ,check passage.I've found some plugged with crap

Well, some good but weird news....

So tonight I went to the store and got some plugs so I can troubleshoot line by line. When I got in the shop to start working on the truck, I said... Lets give it one more try.. So I started to bleed the driver side... BUBBLES!! This was weird as last night there was nothing. Well, I also found a line leak from when I replaced the lines last night. Tighten that connection and continued to bleed whole system. The good news is, its now bleeding.


The bad news...

I have used a quart of fluid already and I am still getting air. I have checked every connection, all are tight with no leaks. All rubber hoses have been replaced. Bleeder valves all replaced. Brakes are good to a point I can't more the truck when brakes applied, but when driving it, its very very slow to stop. To me this sounds like I just need to keep at it, but.....

Is it normal to use a quart + of fluid bleeding a system???

Also, why did leaving the system overnight, suddenly make it work?? Very strange.

Most people do too much pedal pumping when they're bleeding brakes. One or two gentle pushes on the pedal should be plenty, then hold the pedal down until the fluid stops flowing, and close the bleeder. Pumping the pedal too much emulsifies the air into the fluid and it takes hours for it to form bubbles big enough to bleed out again.
Jerry

Wow!.. Didn't know that. I was doing 10+ pump per attempt. Will give that a go, next. Might be a day or two, as I am burnt out right now.. But that is good info.

The answer that you got from the supplier is a little confusing. The master cylinder should have a residual valve for front and back that maintains positive pressure on the wheel cylinders, when the pedal is realeased. This makes it impossible to draw air through a wheel cylinder. Now, if the master was meant for discs in front and drums in the back, it might not have an appropriate residual valve for the front.

Yeah, I was a little confused on that as well. He kept saying blockage or wheel cylinders. I thought it was strange that it suddenly started working again on its own. But who knows. Maybe I had a blockage in a line or the MC bench bleed helped. But for whatever reason, it didn't help the night I did those things.


Another question for you guys... Anyone here use a Mityvac(www.mityvac.com/) to bleed their brakes? I have one now, and was thinking of giving it a try as my 6 yr old son is getting tired of pumping the brakes lol

I have a Mityvac. Good tool, especially for pulling the bulk of the air out of the system. I do always follow up with a traditional manual bleed at each wheel to verify no air and pedal feel.
To add to what Jerry said, some people like to pump the pedal too fast in addition to too many times. Same result, an impossible to bleed situation.

Ok, I used the Mityvac today. Put Teflon tape on bleeder screws to make sure I was getting no leaks from around the screw. Connected the Mityvac like the maunal says. Pumped up to 18 PSI and it holds steady on screw. Open bleeder about 1/8 a turn I get a endless stream of ball bearing size bubbles. I open it up a 1/4 of a turn I get longer(like a hot dog) bearing sized bubbles endlessly. By endless I mean 1.5 hours on just the rear, with no good results. About 1/3 of a quart more wasted fluid too. All lines are tight, no leaks. Only thing I can think of is the wheel cylinders are sucking air or something... I have never had this much trouble... Opening up any more than a 1/4 and it just goes crazy like a shop vac hit the last of the water in a bucket(slurp, slurp, slurp pulses).



Could wrong size bleeder screw cause this? I took my old bleeders down to the local auto store. The outside of the screw looks the same, but the inner bore looks larger on the new bleeder, so maybe its releasing fluid faster than the lines can feel causing air???

At this point I think I am just going to order all new wheel cylinders and bleeders, unless you guys have a good idea to try??

I'm not too impressed with the mityvac- - - -too many places it can suck air other than from the brake lines. It's OK for a quick initial bleed, but that's about all. The best way to go is a pressure bleeder that forces pressurized fluid into the MC, but they're expensive, and they use a lot of fluid. Have you tried a set of "speed bleeders", the bleeder screws with a spring-loaded check ball in them? They're designed to allow you to crack the bleeder open a tiny bit, and pump the pedal slowly to push fluid and air out without pulling air back into the wheel cylinder on the upstroke of the pedal. Good luck!
Jerry

Yeah, I am not to impressed with it either. I decided to get all new wheel cylinders. My local NAPA auto store was able to source them for me cheaper than the classic guys. They are likely the cause of alot of this grief as they were in bad shape for sitting so long. They have been rebuilt atleast 3 times that I know of, and this round they weren't perfect when I put them back together, but I worked on them for a good amount of time. I will let you guys no the results in a few days.

I can't see how a Mityvac would work because it is creating a vacuum and that would surely draw air past the wheel cylinder seals. That is the reason we have a residual valve in the master cylinder, to maintain positive pressure on the sheel cylinder seals.

Hiya I think the reason they bled when left over night is you probably do have an air lock but had built up some pressure behind it, over night it crept fluid past the blockage, We used too do the same sort of thing on motorcycles that where hard too bleed, Pull the lever all the way in tape it too the handle bar and leave it over night then in the morning cut the tape and release the lever slow, what that does is if there is any air the pressure you have trapped will force it slowly too the brake cylinder where it can be bled out, or it will force fluid by it so it will be sucke back too the master cylinder. I have done the same on my Chevy with a piece of broom handle cut too length, just shove the pedal as far and as hard as it will go wedge it down with the broom handle over night then in the morning, with your foot on the pedal take out the broom handle and slowly let the pedal rise, The pressure over night will force any air sometimes past the wheel cylinder seals over a period of time. but the fluid is too thick, in a good system with good integrity. This really does work supprisingly enough.

So the drama continues...

Purchased NEW Wheel cylinders for all wheels. During install, turns out the rear wheels were indeed leaking at the wheel cylinders, front not so much. Got all 4 cylinders installed and proceeded to bleed out the brake system. After well over a hour, I am still getting bubbles and very little pedal. At this point I am just not sure if the power brake booster causes it to not have a full pedal or not??? Its enough to stop the truck now, just not very fast. Pumping up the brakes no longer helps though, so that would seem to mean most of the air has to be out of the lines?? No leaks anywhere now, I triple checked. Maybe the shoes need further adjustment. I had them adjusted at a very slight drag, when spinning the wheel. Maybe tighter?

If you haven't noticed, I am not a brake guy. Starting to think I just need to tow it to a shop and have them do the brake work.

Just spoke to my father on the phone. He thinks I didn't adjust the shoes out far enough. Feel free to school me on the proper method.. I am looking it up myself as we speak.. I simply just adjusted them to you could hear them touch previously, which could of been my problem.


Ok, yeah I am a idiot... Just looked this up on the web. Apparently it should be tight enough to only get one rotation when spinning as hard as you can. Mine currently does about 3 rotations, so that is part of the problem. Will have to get on that tomorrow.

The right way to adjust Bendix brakes is to adjust the shoes out against the drums until you get a firm drag (not locked up) and then back the adjuster starwheel off one full turn. Don't pay any attention to whether or not you can hear or feel drag- - - -the shoes self-center when the brakes are applied, and as soon as the pedal is released, they move away from the drum enough to roll freely. One turn on the adjusting wheel is 10 clicks on the coarse-tooth starwheel that does not self-adjust, or about 20 clicks on the fine-tooth self-adjuster type starwheel. Yours probably has the coarse-toothed adjusters.
Jerry

Problem.. I have Huck style Drums. I am sure the concept is the same though

OOPS! Huck brakes are a little more complicated, since eachshoe adjusts individually. The same basic concept applies, however. Each shoe needs to contact the drum firmly, then back off enough to let the wheel turn without dragging excessively. If you don't get a good contact with the drum first, the wheel cylinders have to take up the slack, and you end up with a low pedal.
Jerry

That's a very good point. Put fluid and water in a blender and it will be a couple days before they separate.

I read all the posts. I had the same experience trying it for the first time.

Are you keeping the bleeder closed while the brake pedal is pumped a couple times, then hold the pedal down (not clear to the floor) then open the bleeder letting air and/or fluid escape, and close it again before the pedal is allowed to come back up? Otherwise I think pumping it with the bleeder open is just moving air in and out of the line. That's the idea behind the speed bleeders I think.

After reading the posts from above, this weekend my son and I were doing 2 pumps, hold, open bleeder, *bubbles*, close bleeder, repeat.

I think the issue is indeed shoe alignment at this point. I will post again tonight or tomorrow night with the results of the adjustment.

So TX, what is the feel of your brake pedal? Is it low and rock hard or is it spongy and low? Or is it high and hard ect...?

I just got done installing Power drums on my 58' and brake adjustment wasnt the big issue. It seemed like bleeding was the major thing. One thing that made a HUGE difference was the pedal extention that changes the pedal ratio. Did you get something like this in your kit, and have you installed it correctly? After installing mine, my brake not longer went to the floor and I had good braking power.

Where in Texas are you by the way? I'm in East Dallas.

I am near Austin.

Thanks everyone for your help and ideas. It turns out the last problem was indeed the brake adjustments. After adjusting correctly, I now have solid braking power. With the engine off I have about 5 inches from the floor, and with it on I am about 3 to 4 inches(power). Either way it stops darn good now. :-)

As far as the adjustment rod... I simply adjusted it to install without any pull or push from the pedal. After reading the manual(50's Shop manual) last night, it says that the pedal should be almost 1 inch off the firewall if adjusted correctly. This would put pressure pulling out the piston on the master cylinder at all times?? Not sure if that is a good or bad thing, or if that is something I should do now?? Currently, when you release the pedal it hits the firewall. I don't have the rubber bumper installed, but need to get one.