Thread: Bleeding the Brakes

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My master cylinder is rusting, so I am planning to take it off, sand it off and clean it up. When I replace it, do I need to bleed the system from all 4 drums, or just one? I have not yet done this before -- but I understand the brakes have small bleeding valves that can be unscrewed.

there's a little valve right next to the brake line inlet on the drum. You're supposed to stick a clear plastic tube on it so that when you bleed them you can see if air bubbles are coming out with the oil, that way you know when your done.
You'll have to have somebody step on the brake while you open the bleed valve, then close it again before they release their foot off the brake. Every time you open and close the valve some air and oil will come out. Then repeat.
It will probably take a while to get that little bit of air out because it will be starting at the beginning of the lines.

In addition to the basics t gave you, you may want to read over these articles to give you a more detailed explanation since the concepts are new to you.

http://www.stoptech.com/whitepapers/...rakesright.htm

http://www.misterfixit.com/brakbld1.htm

The second one on bench bleeding the master cylinder will be useful since I assume in "detailing" the m/c you'll drain it of it's fluid.

I would also flush and refill the entire brake system with new fluid. Just keep bleeding till clean fluid comes out

If you have removed,,or gonna remove your Master cylinder,,,you are going to open your lines to atmosphere,,letting air into the system,,so yes,,you will have to bleed all four wheel's thoroughly.
If you have a single circuit brake system ( most pre 1964 ) you have to do a complete four wheel bleed.
If your's is a Dual Circuit system and you have only opened the rear,,,or just the front,,,,you can just bleed the circuit you have opened.
Better still,,,get someone who know's what they are doing to help you bleed the brakes. ( Don't start until you can stop )

If that master is rough it wouldn't hurt to check out the wheel cylinders. They're simple to work on and rebuild and cheap to replace. 4 Drums work good, but you gotta keep'em in shape or they will pull you around or leak.

I just ran the brake lines on my truck. The master cylinder had a 1/4" line for the rear, which I ran back, then put into junction that split it into 2 3/16 lines. I then took those lines to each tire, which I will have to connect with flexible line to finish it.
I know most people run the main line right above the center of the housing, then run one piece of flexible line down to the housing, then split it and run solid line right up to the drum cylinders.
For some reason this way didn't even cross my mind when I was doing it.
Is there anything wrong with the way I did it?
The only flexible line I am seeing in jeg's says it has 03AN fittings, does 03AN thread into 3/16 solid line????

why not just leave the master cyl on the car and paint it. Ives rdhotfrd

Originally posted by tcodi
I just ran the brake lines on my truck. The master cylinder had a 1/4" line for the rear, which I ran back, then put into junction that split it into 2 3/16 lines. I then took those lines to each tire, which I will have to connect with flexible line to finish it.
I know most people run the main line right above the center of the housing, then run one piece of flexible line down to the housing, then split it and run solid line right up to the drum cylinders.
For some reason this way didn't even cross my mind when I was doing it.
Is there anything wrong with the way I did it?
The only flexible line I am seeing in jeg's says it has 03AN fittings, does 03AN thread into 3/16 solid line????

The problem is that the brake lines (and the fuel lines for that matter) are getting pretty rotten. I have heard that re-fitting brake lines is a nightmare.

Take the master cylinder off, clean it all up, bench bleed it, put all new lines on, flare them and all the other usual stuff, put em on and then put the master cylinder back on bleed the air outta the lines. Better to just go ahead and do everything. The wheel cylinders aren't expensive either, around 20-26 bucks. They don't make many rebuild kits for those anymore. That way you don't have to worry about the rust, moisture and problems later.

I agree...while at it, do it up right. I just paid $17 for both rear wheel cylinders on a 76 F-100 truck. Id also inspect the front calipers (assuming you have front disc brakes). Also, when bleeding brakes, always start at the furthest wheel from the MC (ie. RR, LR, RF, then LF).

Remeber, a chain is only as strong as it's weakest link, and brakes are nothing to second guess.

Greg

Originally posted by Dan
If that master is rough it wouldn't hurt to check out the wheel cylinders. They're simple to work on and rebuild and cheap to replace. 4 Drums work good, but you gotta keep'em in shape or they will pull you around or leak.

I did it the way you mentioned and used two stainless steel flex lines for a clean look over the rear end . nothing wrong and leaves the reare end free of tubing . Ed ke6bnl

Just my thoughts on older car brakes.

First take a look at the age of the car, IMO it it's older than 25 years and still has the original steel and rubber lines, they should be replaced, no matter how they look on the outside. Non Dot 5 brake fluid will absorb moisture that will collect in low spots in the system (wheel cylinders and brake lines). In the case of the brake lines, they will rust from the inside out, and yes I have seen what's look like a perfectly good line bust due to this. Replacing the lines is one of those jobs that is a major pain, but it really is not that difficult or expensive. I spent yesterday running new lines on a 63 Galaxie yes it was dirty and a little frustrating but it's one of those jobs that will last the rest of the cars life. As far as the rubber lines, I suspect that if you look closely you will find they are likely deteriorating and this would be a good time to replace them.

As far as the wheel cylinders chances are if they are very old water has settled in them and will likely need replaced. For the cost of new wheel cylinders, I generally do no rebuild them. My experience is that the rust pits caused by water settling in the cylinders are generally too deep to hone out. If you can't get the pits out and make the inside perfect REPLACE IT. The same applies to the master cylinder.

As far as bleeding, the first step is to bench bleed the master cylinder to remove all the air. Most master cylinders come with instructions for doing this and the appropriate fitting and hoses. After it is bench bled and installed the next step is to bleed it at the fittings. Snug the fitting(s) and have someone press the peddle, loosen the fitting, then tighten and release the peddle. Repeat until no air come out with the fluid. The next step is to start bleeding at the wheel cylinder farthest away from the MC and bleed until all the air is removed. Rove to the next furthest away and repeat until all the wheels are done.

Now a few tips.

1. If only the master cylinder is replaced, chances are you will only need to bench bleed the MC and bleed the line where it is attached to the MC. If you have a good peddle, your done.

2. Never let the MC go dry or you will have to start all over. As you keep adding fluid,and bleeding, always put the cover back on the MC and during the bleeding process it will squirt out of the cylinder and make a mess.

3. While bleeding the MC on the car requires 2 people (or a pressure bleeder), one person can bleed the wheel cylinders/calipers by building a simple bleeder tool. Take a piece of vacuum line that's long enough to reach the floor and fits tightly over the bleeder. Plug one end and using a razor blade, cut a 1" slit near the plug. Place the other end over the bleeder and open it slightly and the other end in a jar or can to prevent making a mess. Slowly pump the peddle until you don't hear air, close the bleeder, remove the hose and move on to the next wheel. Streets suggestion about gravity bleeding prior to actually bleeding the system will help save a lot of time doing the bleeding process.

4. Especially on car that sit for long periods of time MC and wheel cylinder life can be greatly extended by annually flushing the brake system. This basically involves completely bleeding the system until all the old fluid is removed. This will remove any moisture that has accumulated over the prior year.

Mike P basically told you exactly how to do it. Not much to it, pretty darn easy if you ask me, if I can do it, ANYONE can do it. haha