When bleeding brakes, do I open the master cylinder while doing it?

Question

The first time I bled my brakes, I did not check the fluid level and I ran it out. Then after checking here, I learned that I need to check the level after each valve is bled. The problem is when I open the cylinder, I hear the seal being broken and air releasing. Is this normal? If I attempt to leave cylinder lid off while bleeding, fluid goes everywhere.
Thanks for your help. It has been 15 years since I last did this...

Answer 1

i own a repair shop and you do have to keep the cover on the cylinder to bleed the brakes out,but you also have to make sure the master doesn't run dry on it,if it does you have to start all over again with it,and that's no fun at all,and if it has anti lock brakes on it you don't want to pump them to hard on it,you more or less gravity bleed those ,out it works a lot better than pump bleeding them ,brakes have changed a lot in 15 years ,you also need someone to help you with this and just keep the master from going dry on it,and you,ll be ok with it,good luck hope this helps.

Answer 2

Master Cylinder Bleeding

Answer 3

Buy the repair manual for your vehicle.

I leave the cap off the master cylinder and I have an assistant or two. One person pumps the brake pedal, the other opens and closes the bleed valve while telling the person doing the pumping when to press and when to release the brake pedal (release after closing the bleed nipple). If there is a third person, he/she would be keeping an eye on the brake fluid level in the master cylinder reservoir - and topping up as necessary. If the level of fluid in the reservoir drops too low, it may allow air into the system and you'll have to start all over again.

As for the order of bleeding the brakes, that depends on the car. Some cars have dual diagonal circuits, some are dual front/rear. Some cars have ABS and some don't. Quite often, the order is starting with the wheel with the greatest distance of brake line and working progressively to the wheel with the shortest brake line (total, from wheel cylinder to the master cylinder). I've seen ABS units with a bleed nipple (or nipples) on them too. Check the repair manual for specific details regarding order of bleeding the brakes, etc.

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Answer 4

You do not need to leave the lid off the master cylinder. Just make sure you don't run out of fluid, which is highly unlikely. Bleed the brake farthest from the master cylinder first, then the brake next farthest, etc.
Open the bleed valve, have someone press the brake, close the valve and have your helper let up on the pedal and repeat doing this until only fluid comes out.
There are machines that look like a bowling ball washer that connect to the master cylinder that pressurize the system so you don't need a helper to pump the brake pedal.
If you have a helper who presses and releases the pedal only when you tell them too, this method works fine.

Answer 5

In an instance like this, it's always good to bleed the master seperately, but in most cases you can get all of the air out by just filling the reservoir up, and bleeding them at the caliper. The cheapest way out is to have your buddy/wife, etc step on and hold the brakes, while you open the bleeder valve on the caliper, and then closing it, then, only after it's closed, they can lift their foot off the brake. Repeat this until all bubbles have come out of the system. ALWAYS bleed the shortest line first, (closest to the master) and for safety sake, it is nice to have a small bottle with some brake fluid in it, and a clear plastic hose from the bleeder into the brake fluid. However, make sure you keep your reservoir topped off during this procedure, and do not reuse the fluid you pump out. This will be full of air bubbles and will cause an issue later down the road.

Answer 6

Yes, you have to keep the cover on the master cylinder. When you pump the brakes to build pressure and to drive out the air bubbles, you need the cover on.

Check the fluid level in the master cylinder after you bleed each wheel, one at a time. If you evacuate a lot of fluid into your recovery container, you might have to top off the master cylinder more often than once per wheel.

Answer 7

The cylinder lid should be left on when bleeding the brakes. Not sure about the air noise you hear. Before you bleed, fill the reservoir to full mark,close lid, then bleed. In most cases, after bleeding, only a small amount of fluid will be used from the reservoir. Good Luck!

Answer 8

u just remove cover from reservoir. do not open master cylinder. take turkey baster and remove old fluid. replace with new. pump a given number of times. check level. add more fluid. make sure that as u bleed each brake, that the bleeding line is in a clear bottle with enough fluid already in teh bottle to keep air from reentering the tube.
have never heard of the air thing and fluid going everywhere. i dont see how it is possible to shoot fluid out of the reservoir.

it woudl be a good idea to use a flare nut wrench on your brake nipples.

Answer 9

Bleeding the brakes is a short set of steps. Leave the master cylinder open, but open the line b arely and drain a little, then close. FIll the cylinder and repeat until the air is gone.

Don';t leave it wide open, you'll drain the whole thing. The air is only in the bottom where you were working. A few short drains to fill a quart jar and you'll have removed the bubbles in the line.

Answer 10

Yes keep the lid on.
You may have to bleed the master cylinder if you ran it dry.
Top up your master the open up one bleeder screw at a time let it gravity feed.
It will start to come out after a bit.
Do each one one at a time .
The have some one pump up the brakes and hold the down.
Open the screw one at a time .
Until all air is out.
Do this for all of the bleeder screws.
Hope this helps.
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