Can someone tell me how to bleed drum brakes?

[62lwbc10]

Sorry for the noob question but the pictures in my brand new shop manual are so dark and I cant make them out, plus the manual speaks to all kinds of special "tools" to do the job. Can someone please bottom line it for me? I have a new master cylinder coming tomorrow and I want to install it and be done with it. Do bleed with the wheels still on or do you take them off? ANy special tools other than brake line wrenches? THanks alot in advance.

Mark

[Dan in Pasadena]

Doesn't matter if wheels are on or off as long as you can access the bleeders. You bleed drums the same as discs. I'd suggest you "bench bleed" the MC before installing it (do an Internet search. It'll have photos and be clearer than a lot of text here). Once installed on the car/truck you pump to move fluid through the lines, forcing air to the wheel cylinders (instead of calipers like on discs) HOLD the pedal down, open bleeder allowing air & some fluid to squirt out (catch it in a container to avoid a mess) then tighten bleeder and re-pump. Do this til ONLY brake fluid comes out. Start at wheel furthest from MC, do next closest wheel til you've done all four.

Clear as mud? Lol.
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[mr48chev]

I can't add much to the directions Dan gave.

What I can add are: Make sure that the brakes are adjusted up correctly, make sure that each bleeder screw is easy to loosen and is clean and clear of dirt or other things that plug one up. I have gotten in the habit of unscrewing each one and checking them to make sure the passage way through it is clear. Usually a small drill bit held in your fingers can be used to clear any dirt out of one. You just spin the bit in your fingers to drill any dirt out.

As Dan said it's best to bench bleed the master cylinder before installing it. I usually clamp one in the vise just tight enough so it won't move and push the piston in while holding my finger tip (s) over the ports but that does make a mess and the vise I use is outside on a work table and not near any cars or anything else that will get damaged. Sometimes they include plastic tubes and fittings so you can direct the fluid you squirt out back into the top of the master cylinder and that saves a lot of mess.

Have your helper (it takes two people) pump the pedal slowly and then hold it while you open the furthermost bleeder from the master cylinder. Make sure that they understand to hold the pedal down until you close the bleeder screw and "tell" them to pump it again. Pumping fast can get air drawn into the system and defeat the process. Repeat until you get a clear stream of fluid and check the master cylinder often and refill it so it never runs out of fluid while you are bleeding the brakes. You will soon learn how many times you can open the bleeder before you need to stop and top off the master cylinder. When you get a good stream of fluid out of the first one go to the second one and go through the process again and on to each cylinder. you may have to go the whole round more than once before you are done as that isn't all that unusual.

Also as Dan said if you put a piece of hose on the bleeder and run it into a container it saves a lot of mess on the axles of the truck and on the shop floor.

I'm sure some guy will come on and tell you how to "gravity" bleed the brakes, that is something I only heard of when I came on the internet after working on brakes for over 40 years and professionally for around 20. There was a time when I did four or five brake jobs a day at the Firestone tire store I worked at in the early 70's. I've never seen it done and never expect to as it is a pure amateur thing and isn't done in the professional world and has little chance of success.

[OrrieG]

I can hear my Grandfather Orrie hollering at me as I type "Keep pumpin' you need to get to a hundred before I can crack the screw". His belief was it took that many to get the air to the end.

Run the hose from the bleeder into a bottle with brake fluid in it. That way if your helpers foot or your wrench slips it will suck fluid back into line, not air.

[Russell Ashley]

I've been married 47 years and had old cars the whole time. I wish I had a dollar for every time I've told my wife to hold the pedal down until I say let it up.

Mr48, If the M/C is mounted on the firewall and you leave the bleeder valves open the fluid will eventually run out of them but I agree with you, I doubt it would purge all of the air and also would take a long time.

[Indian113]

I'm never able to get help when I need it so I use a tool called "Mighty Vac" works real good for a 1 man shop. You have to make sure to keep fluid in MC or your putting air right back in the system.

[Russell Ashley]

Originally Posted by Indian113

I'm never able to get help when I need it so I use a tool called "Mighty Vac" works real good for a 1 man shop. You have to make sure to keep fluid in MC or your putting air right back in the system.

I also have a Mighty-Vac and have used it from time to time, but I still prefer the old fashioned two-person way. When I do use the Mighty Vac I remove the bleeder valves and put teflon tape on the threads or it will suck air around the valve and you will continuously get bubbles in the hose.

[1project2many]

I can hear my Grandfather Orrie hollering at me as I type "Keep pumpin' you need to get to a hundred before I can crack the screw". His belief was it took that many to get the air to the end.

Wow!!! You must have gotten pretty tired of brake bleeding back then. There are some GM vehicles that are supposed to be pumped 30-40 times with the engine off before checking brake fluid level but of course, no one wants to work that hard.

I'm never able to get help when I need it so I use a tool called "Mighty Vac"

I've had troubles with vacuum brake bleeding drawing air around wheel cylinder cups in the past. I always final bleed with pressure; either pressing the pedal or using a pressure bleeder.

I wish I had a dollar for every time I've told my wife to hold the pedal down until I say let it up.

I gave up. I wedge a stick between the seat or steering wheel and the brake pedal. I've actually got an extendable hood prop rod at work that works great for bleeding. Pump the pedal several times, wedge the stick, then go open the bleeder. Yep, lots of walking. But it's a helluva lot easier than dealing with a bored / frustrated / innattentive helper.

[OrrieG]

Yes, bleeding brakes is right up there at the top of my fun list along with doing drywall work. I wasn't going to bring it up but my wife maintains her nice legs are from bleeding brakes and pushing my 6 volt VW to start it in the Winter.

[Daze57]

OrrieG

'' I wasn't going to bring it up but my wife maintains her nice legs are from bleeding brakes and pushing my 6 volt VW to start it in the Winter. ''

YOU DA MAN !!!!!!!!!!!

[JumboAMONGus]

old fashion way pump ,it and the tube seams to find its way off and then i just say screw it and let the fluid fly ,