After brake bleed, pedal goes to floor

Question

2005 Toyota sequoia. Brake pedal was fine most of the time but occasionally it would sink to the floor while stopping and it would be hard to stop. I bled my brakes and now the pedal goes to the floor all the time with little stopping power. My auto shop teacher says I need a new master cylinder, but it was fine before bleeding the brakes. Also the brake light on the dashboard came on. Any ideas? Thank you.

Answer 1

You need to completely rebleed your system. You obviously have air in it. If you have a power bleeder which fits the master cylinder, the better.

For future reference:

DO NOT BLEED THE BRAKING SYSTEM BY REMOVING ALL THE BRAKE FLUID FIRST!!!

I apologize for yelling at you, but this is absolutely the wrong way to go about bleeding the system. The idea is to replace the old fluid as you are putting new fluid into the system. You run the old fluid out until it runs clear. As you've discovered it will cause you all kinds of issues. It may be very hard to bleed all of the air out of the system, but you need to bleed it sooner rather than later. If you don't have a power bleeder, use a friend to pump the brakes for you. Please do the following to general steps:

What you'll need:

• A brand new (never opened) bottle of brake fluid (per your vehicle specs) ... in your case, you may need two to completely redo the job
• A wrench (spanner) to open the bleeder valve (usually a 5/16" boxed end)
• A clear plastic bottle to drain the fluid into
• A piece of plastic tubing like you'd find for fish tanks
• A friend with big burly quad muscles who can hear and follow direction

What you do:

• Open your bottle of NEW brake fluid and pour about an inch worth in the bottom of the clear container
• Pop the top on the master cylinder; ensure it is full; leave the top off (you need to check it often as you go through the process)
• Start your process at the brake cylinder/caliper which is farthest away from the master cylinder

NOTE: If you need to jack the car up or take the wheel off, ensure you put the vehicle on a jack stand so you do not endanger yourself.

• At the caliper/cylinder, put the boxed end of your wrench on the bleeder valve. Use the wrench to loosen it slightly without allowing any air to seep in ... all you are looking to do is break the valve free.
• With the wrench still on the valve, affix one end of the plastic tubing over the bleeder nipple, while placing the other end into the bottle so it is submerged into the fluid.

NOTE: The reason you put the extra brake fluid into the bottom of the bottle and then submerge the end of the plastic tubing into it is, just in case you and your fiend do not communicate correctly and they lift the brake pedal too soon, the tube will draw the fluid up into itself instead of sucking air. This is very important so you don't have to start all over again.

• Have your friend pump up the brakes as best as they can. When they've pumped two or three or four times, make sure they know to hold the pedal down until you tell them to pump it up again.
• Open the bleeder valve and observe the fluid as it's going through the tube and into the bottle. You are looking for two things: first, clear fluid; two, lack of air bubbles. In your case, until you see a big gaggle of air bubbles come through the tube, you need to keep going through the process of bleeding the particular caliper/cylinder.
• Close the bleeder valve and then tell your friend to pump the brake pedal again. Keep going through this until the lack of bubbles can be seen. This is going to take several iterations to accomplish, but after the first one, it should be quite a bit less on the second wheel.

For a left hand drive vehicle (like most found in the US), the order of brakes bleeding will usually follow this order:

• Passenger (right) side rear
• Driver (left) side rear
• Passenger (right) side front
• Driver (left) side front

Right hand drive cars which you'll find in the UK should most likely follow this sequence:

• Passenger (left) side rear
• Driver (right) side rear
• Passenger (left) side front
• Driver (right) side front

This should get your car back in pretty good shape. Don't worry too much about your mistake as it happens to the bets of us. Just chalk it up to inexperience and learn from it.