Brake Bleeding Tips?
 

Any tips on bleeding the brakes on my 50 Silver Streak? Everything from the Master cylinder to the Wheel cylinders is new. The master is a stock unit mounted down low on the frame and it does not have a reservoir, just what the master itself will hold.
I do have a vacuum bleeder but with the small capacity of the master I don't think it will work well.

LOL, that is the reservoir, back then it was all they needed with drum brakes and single reservoir.

If I was doing it I'd raise the chassis up fairly level let the wheels hang down and see if you can get it gravity bled. To get it started open all 4 bleeders, and just bump the pedal at the very top of the travel until you get fluid dripping from the bleeders. I'd let them drip for a few minutes shut them off and see if you have a firm pedal. If you feel it's not bled do one wheel at a time and see if you get any bubbles out. Usually the air is out of the system by just letting them drip for say 2-3 minutes the first time.

You'll probably have people coming along telling you have to pump them up and hold them with 2 people, or use a pressure bleeder, etc. etc. but I twisted wrenches for over 45 years and have never used a pressure bleeder yet. Usually I was alone so the pumping the brakes up and opening the bleeders with 2 people wasn't going to happen. Gravity is a constant and physics never changes so it's been working for me for this long, I'm probably not going to change my process at this point.

That's the way I'd do it, because it's familiar to me, and works excellently. No other equipment needed, other than a bleeder wrench, and a bottle of brake fluid. Oh yeah, a little bit of patience.

Do this ^^

If you have a vacuum bleeder, go to the right rear bleeder and just bump the button on your vac bleeder 5 or 6 times for a few seconds to start the process a little faster. Keep an eye on the tiny reservoir and don't let it run dry. Gravity bleeding is still my preferred method.

Mike, it seems that anyone that does it for their profession, prefers gravity bleeding. All the fancy ways to bleed brakes and all the equipment they sell, gravity bleeding still works the best overall and most professionals use it.

Brad and Mike- I've never used gravity bleeding. Would it work on my '59 GMC with under-floor master cylinder that is barely (if at all) higher than the wheel cylindes? If not, could it work on one end at a time, jacking up the other end? Or would fluid flow back to the master from the "high" cylinders (with closed bleeders)?

Jack, once it gets over the highest point it runs downhill same as any siphon does. Just bumping the pedal at the very top of the travel will pump fluid to the highest point. Once it breaks over the top of the highest point and travels below the level of the brake fluid in the reservoir the siphon will continue. I've never seen any car or truck that when the bleeder screws are opened that fluid doesn't run out, so once the system is filled with brake fluid it's going to run out of the bleeders causing a siphon.

I mentioned letting the wheels hang, with stands holding up the frame. If you wanted to tip the chassis end to end I'm sure that physics would work just fine too, I've never tried it myself because I've only worked on a very few cars and trucks with the master cylinder under the floorboards, one mail Jeep back over 35 years ago is one that sticks in my mind. Basically you have to know how a siphon works, and bump the fluid with the short stroke at the top of the pedal travel to start it. Once the head of the fluid is below the level of fluid in the reservoir, nature takes over.

I believe most people have difficulty gravity bleeding because they don't know enough to use the short strokes at the top of the pedal travel to move fluid over the high points in the system. Once fluid is dripping out the bleeders, the tough part is over. You just wait a minute or two and the system is bled and you just stood around and watched. 99 times out of 100 you have a nice firm pedal the first time, no residual air in the system. Nothing to hook up, no special tools, no begging someone that can't follow simple instructions to assist, no matter how simple (think your wife, that doesn't like the smell of the garage anyway). It's quick, and almost always works the first time.

One other problem I've seen people make when just changing a master cylinder, or replacing a section of line, is bleed the system at that point. You don't have to go all the way to the wheel cylinders or calipers to get air out. There is only air in the part of the system that you worked on. I have replaced a section of line running to the rear, and gravity bled the system at the flex hose so I didn't have to deal with the wheel cylinder bleeders. Trying to open rusted bleeders and breaking them off is unnecessary. Again just bumping the pedal at the top of the travel will let air escape back into the reservoir. You'll see bubbles of air because air is lighter and it will seek the top of the fluid column. You do have to lightly stoke the pedal to uncover the ports by moving the spool, and let the air out of the lines. It's all physics, and no one can change them.

I got side tracked by a little bad weather that came through here on the 10th. Y'all might have seen it on the news, they called it Michael! Anyway, I have been cleaning up my property since then. I still have a large pine tree on my shop and am waiting for a tree service to come get it off. I hope to start bleeding the brakes next weekend if the tree is gone. I don't feel to good about working in the shop until it is removed.

I'm replacing the stock master cylinder and installing rebuilt booster.....

Is bench bleeding the master an option....or will the gravity bleed work...with bumping the pedal?

With the rod adjustment....is 1/8" sufficient clearance?

It works for me, I never bench bleed master cylinders, but you ask most people on PY and they'll tell you it is impossible to do. I'm not looking for a big argument, so I'll say it works for me just fine for over 50 years. Draw your own conclusions.

How long does it usually take to gravity bleed the system? The brakes on my 57 Pontiac have been an issue for almost 30 years.

2 to 3 minutes, if performed correctly. Seems that many people can't get the siphon principle sorted out, and then claim it can't be done. The master cylinder level has to be above the bleed screws same as any siphon. If the brake lines go uphill in any portion of the system the pedal can be stroked lightly at the top of stroke to push the fluid over the high spot. Gravity and physics take over from that point and the siphon will purge the brake system. When there are no more air bubbles coming from the bleed screws it's bled.

I also spun wrenches for 45+ years on fleet vehicles and Brad Yost is right on. I've also cracked the wheel cylinder bleeder screw open and with a snug fitting 2 foot length of vacuum hose, suck on it 'till you get brake fluid. Slide ithe hose off and watch the stream [or drips] from the bleeder screw 'till you stop getting air...refill the master and go to the next wheel.....repeat
I always start with the wheel furthest from the master cylinder and work my way closer to the M/C. Has always worked for me.

Thanks Rocky, The whole thing is so simple, physics never change. There are dozens of people I've tried to help get their brakes bled on this forum, only to have some insist, I'm doing it wrong, and the one and only way is vacuum bleed, pressure bleed, smart bleeders, pump and hold, you name it.

I got into a dispute with one member that needed to drag his relative into the fray, that was an engineer in a oil refinery that went on to explain how they bleed pipelines within the plant, and pressure bleeding was their standard. I wasn't impressed in the least.

The guy was so proud of his homemade pressure bleeder that everyone should have one, which exposed the fresh brake fluid to compressed air. No bladder to keep the fluid separate from moisture laden compressed air, as a professionally made unit has.

As you say after 45 years doing this stuff everyday for a living you try different things, and the simplest thing works the best. Try to convey that to help someone overcome a problem, and get questioned from someone that either has "college credentials", or is just "smarter than you are". Getting to the point where you just let people make their own mistakes, or spend more time and money than necessary, than start a crapstorm over nothing.

I have found from this forum, as well as being in the automotive repair arena for so many years, that almost anyone that has collected their paychecks from auto repairing, just goes with gravity bleeding. No setup, nothing to buy or make, no begging a second person to help you, it works on everything with wheels and it's quick, the first time you stab the pedal it's nice and firm.

Yeah, it's always worked for me.
Added bonus: Brake fluid tastes almost like cognac!

Can you guys think of a semi transparent grease that I could use on the bleeder threads to prevent any fluid from sneaking past while the bleeders are cracked & Hoses fitted tightly to the bleeder screws? I don't want to risk any drips getting between the wheel cylinders & the backing plates. That would for sure ruin my day.....

I have Dow molykote & high vacuum grease in the shop. Not sure if either have silicone in them though. Don't want to create a laboratory experiment within the threads of the bleeders. ;)

was thinking Molykote as its synthetic & I don't believe has any silicone in it.
https://www1.mscdirect.com/MSDS/MSDS...0-20190720.PDF

Thoughts?

I take it you're worried about losing paint? I think I'd tape a piece of plastic to the backing plate underneath the bleeder screw to deflect any stray drips of brake fluid.

Yes.......:(

I have way too many hours in the details to allow a drop of dot3 to find its way into somewhere I can't quickly wipe off & clean. I have been procrastinating putting the brake fluid in for this reason. Both the molykote & vacuum grease are pretty thick & transparent so I think one of those would work well to hold the build back if I just put a dab on the threads. I just wasn't sure if there could be a reaction. I suppose I could do some testing on something else first.

Over thinking things like I often too,

.
https://forums.maxperformanceinc.com...1&d=1564426668

It may not be an issue, but I'd avoid any possibility of grease somehow getting sucked into the wheel cylinder.

Thanks!

I just looked up the MSDS of both greases that I have, & both are silicone based, which I believe can't be mixed with DOT3. I wouldn't think anything could get into the cylinders., especially if I use it lightly, But I suppose there is a chance. maybe I should just use std wheel bearing grease.