Hello all, its been a long time since I have been on this site but its good to be here again! Recently Ive been working on a '59 F-100 for a buddy of mine, and I am having such a hard time with the brake system I am almost at my wits end. I thought I would share the insanity with all of you and see what you thought...

It has the original style single reservoir master cylinder. When he first brought the truck over it was empty and looked like it had been that way for a number of years. I removed the MC, cleaned all the old gunky fluid out with clean brake fluid and parts cleaner, and bench bled it. Seemed to get all the air out just fine, I went until I saw no bubbles and my trusty wooden dowel became nearly impossible to push in.

I had a buddy come by to help me bleed the rest of the system. I cracked all the bleeders at each one of the wheel cylinders first to make sure that I wasnt going to snap any off after I called a friend over, of course closing them off again before we got to work.

I started at the right rear, got a few solid pumps of fluid, and then every pump after that had a very large amount of bubbles. We bled the right rear for about 20 pumps of the pedal, I refilled the reservoir before it emptied, and still was getting a LOT of air bubbles. No fluid was leaking from the lines. I just figured this system was a little bit harder to get the air out than most any other brake job Ive done, so we diligently kept on the bleeding process. But after about 40 more pumps, with still massive amounts of air bubbles coming from the back rear I was starting to get frustrated. I checked the fluid level in the MC and realized it was dangerously low, so I figured that we went too far, I had been introducing air back into the system, and that I should just stop while I was ahead and start on a new day.

Well today was the new day. I pulled out the MC again to bench bleed it again, in case I let the fluid level get too low. The dowel hardly moved, and no air bubbles came out so I guess it never went dry like I feared. Reinstalled the MC, started the bleeding process again at the right rear (with a different buddy, not that I was blaming my bad luck on the first guy- I guess the buck stops here right?) and it took probably 5 pumps or so and I got a solid shot of fluid, finally. Thinking bad thoughts about my first buddies capabilities, I moved onto the left rear. I had my partner do about 10 pumps of the pedal with nothing but massive air bubbles coming out of the left rear. Now there is a single line going to the rear that tees at the rear axle, so since I got a solid shot of fluid at the right rear, it should not have taken much to bleed the shorter line going to the left rear.

About this time I started to suspect that the MC actually was bad, and that somehow it was letting air into the system. I figured that since I used a wooden dowel for the bench bleed I was not getting enough of an advantage (even though a wooden dowel has been enough to bench bleed the other 13 or so other master cylinders I have bled in my short lifetime). But just to silence the voices, I left the MC in the truck this time, reinstalled the plug in the line, and had my buddy push down on the pedal very slowly while I looked in the reservoir. No bubbles, and with all his force on the pedal, it would hardly move. Again, verified that the MC was definitely bench bled, and was not introducing air to the system.

Well back to the left rear wheel cylinder. I have gone through over half a gallon of brake fluid, the MC has no trouble moving fluid through the system, but I am still getting massive amounts of air at the left rear. I know some systems like to hold onto air but this is getting absurd. How can there still be air bubbles coming out of the bleeder valve? Since I was just about to run out of brake fluid, and I was getting very frustrated by this point, I closed the valve, had my buddy push down to test the pedal thinking that maybe I was just having a bad dream and that I had magically bled the brakes even though all I could see was air bubbles. The pedal went straight to the floor, no pressure. Of course I opened the left rear bleeder while his foot was still on the floor, saw another squirt of mostly air bubbles, then closed the bleeder before I had him bring the pedal back up (heaven forbid I introduce air into the MC by having him do a test pump to test the pedal pressure)

So there you have it... How is this possible? Where the heck is air getting into the system if there arent any puddles of fluid on the shop floor? After over half a gallon of brake fluid run through the lines and still getting air bubbles I am at a total loss. Sorry to make such a long story out of my tribulations, but I wanted to make sure anyone reading this wasnt thinking 'oh great, another dummy who doesnt know how to bleed brakes' Who knows maybe you are thinking that, and if you are, please, enlighten me! Thanks all

I don't have an answer where you are getting air from, only suggestions, and I don't know all the people on here personally, but after being on this site for awhile now I can almost certainly attest that there are not too many who would think bad of you for asking a question...

With that out of the way, the first thing that comes to mind is maybe a bleeder isn't closed all the way? Maybe some crud caught in it?

When bleeding brakes I like to run a tube from the bleeder to a FRESH jar of fluid so I can see bubbles as they come but also it will draw fluid back into the system not air.

"The Master Cylinder"

Enjoying life at the beach in SOCAL

Since the mc was empty, I assume he didn't drive it over. All of the gunk that was in the master cylinder is also probably in the wheel cylinders. Those should probably be taken apart and cleaned or rebuilt or replaced.

Maybe a seal is letting air in but also keeping the fluid inside.


Lawrenceville, GA

Ok, thanks for the fast responses guys!

MasterCylinder- first off, nice name- sounds like Im talking to the guru. When I run a tube into a fresh jar of fluid do I still need to open and close the bleeder with every down and up stroke of the pedal? Or can I just open the bleeder and slowly pump the pedal up and down? I have heard of this method before but always just stuck with what I know has worked in the past. Maybe its time to break out of my comfort zone and try something new... And actually if I could get away without opening and closing the bleeder it sounds like I could do a bleed job on my own. Now that would revolutionize my bleeding procedure! No more waiting for buddies, but also no one else to blame a botched bleeding job on haha. Wait, never mind, I forgot the buck stops here...

Charlie- No, he didnt drive it over. He flat towed it over, had his son keep it in gear and used the clutch as a brake. He said the bakes had "always been bad", but I dont think he is the first owner haha. I just translated that into 'the truck has been sitting since I broke a line or the master cylinder went bad.' I agree that the gunk from the MC found its way into the wheel cylinders, but I have certainly done some flushing of the system. I would have thought that the fluid would be leaking if it was letting air in, but who knows... There definitely isnt an air source inside the system, so it is getting in from somewhere.

I will pull out all the bleeders, take a look at them and inspect the bleeder holes for any gunk that is preventing them from being closed, and if that fails I will start looking into repairing/replacing the wheel cylinders. Ive been wanting to get one of those honing bits to be able to repair wheel cylinders for a while, so maybe now the time has come. I will keep you all updated on my progress and please dont be shy if you think up any other suggestions!

Thanks again

Yes leave them slightly open and pump slowly. Don't pump them up and then open the bleeder, you'll blow fluid out of the jar if there is air in there. And yes I have bled brakes by myself with this method but it is still a good idea to have a friend do the pumping so you can watch for bubbles and keep and eye on the M/C level. And you have the friend there in case it doesn't work and you need someone to blame... HA!

Oh and no guru here. The Master Cylinder is the nemesis of Felix the Cat...

"The Master Cylinder"

Enjoying life at the beach in SOCAL

This is just my opinion but if this was my Truck I would be redoing the whole system with new Wheel Cylinders and Master.If this has been sitting for an extended period of time with no fluid in the Master there has been moisture in the system as brake fluid absorbs moisture.With a single Master Cylinder you cannot afford to have a failure in the system front or back.You need the Brake System to be in top dependable condition.Wheel cylinders and Master are not expensive to purchase new and I would also be replacing the flex hoses too.

  

I have to agree with oldcarmark, the parts you need are cheap, around $100 for all cylinders and hoses and you get an incredible amount of peace of mind, not to mention outright safety. That said, I've had good luck bleeding systems with a vacuum pump when I got bubbles forever using the conventional foot pump method.

Don

Sounds like you may have a crack in a line, however that should be obvious. There is one other thing that comes to mind . DO NOT bench bleed single circuit M/cyls ! Best way to damage the seals.

Also make sure you are not pushing the pedal all the way to the floor when installed, only half way . Put a piece of wood or brick under it if you have to. when its working correctly the fluid will just about squirt out the filler cap opening when you pressing the pedal. messy!

As Mark said you should go over the whole system if its that old that includes the lines / hard lines.. Its really not that expensive to do the whole lot and for piece of mind its best.

Get a new M/C and get some speed bleeders, its so easy if you need to get started..



"Came too close to dying to stop living now!"

Something that was only mentioned briefly - check the flex line from the body/frame to the rear end. Replace it since you got a lot of crap in the system. At least remove it and make sure it is not full of gunk. I would remove the line that goes to each rear cylinder and clean it out with brake cleaner.

Sometime these flex hoses have internal damage that you can't see. my advice is to replace it. The front ones too.

Something else you may want to do as a test. Disconnect the lines at the wheel cylinders and then apply pressure to the pedal.. If you get a good stream then the wheel cylinders are probably to blame. replace them.

If there is a brake line connection between the master and the rear, open it up and check for flow. Often there is a connection somewhere on the frame running back.

Never heard of just pushing the pedal down part way. Always replace the cap before bleeding, this stops it from squirting.

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

I agree with the others, you should really go thru the brake system before you go any farther trying to bleed the brakes. Maybe even upgrade to a duel M/C while your at it if your current M/C needs replacement. Minimal work and cost but makes for a much safer system.

"The Master Cylinder"

Enjoying life at the beach in SOCAL