Open bleeder screw.
Helper pushes the brake pedal up and down several times.
Close bleeder screw.
Is this incorrect? Does this let air back into the lines?
Should I close the bleeder screw (each time) BEFORE helper raises the brake pedal ?
Should brakes be rock hard after a bleeding?
Almost like the hardness when pressing the brake pedal with the car not running?
Yes, that’s incorrect. Here’s the proper procedure:
You tell the helper the following two commands: “ON” means press firmly, but not too hard (don’t stomp it) on the pedal. “OFF” means stop pressing on the pedal.
You tell the helper “ON”
You crack the bleeder screw, watch fluid come out for a couple of seconds, then retighten the screw.
You tell the helper “OFF”
Repeat until dirty fluid is replaced by clear and no bubbles appear.
Every time you release the pedal, you’re drawing air back into the cylinder.
The process I prefer includes hanging a clear plastic bottle half full of brake fluid near the bleeder and running a clear plastic tube from the bleeder into the fluid in the bottle. With this method, every time you push the pedal it pushes fluid and air out the bleeder and into the fluid in the bottle. The air burps out as bubbles in the bottle, and drawback from releasing the pedal pulls only fresh fluid back into the caliper. Once the caliper no longer burps, close the bleeder, remove the tube, and you’ll have a caliper full of fluid with not air in it.
Be sure to top the master cylinder off before starting, and be sure you don’t allow it to run dry while you’re performing the procedure.
I started using the “no helper” procedure for bleeding brakes decades ago. I agree 100% with the same mountainbike here because it works and it works very well.
If you are patient, and I mean very patient, you can gravity bleed most cars. Dip the bleed hose in a half filled container like tsm recommends, crack the bleeder a 1/2 to a full turn. The fluid will slowly come out and displace the air in the bleeder tube. Let is run a while, 30 minutes or so, while keeping an eye on the reservoir. Close the bleed screw and repeat for the other 3. This works well for completely changing the fluid, too.
As long as we’re discussing alternate bleeding methods from OP, by far the easiest and fastest would be Speed Bleeders. They cost around 7 bucks. You permanently replace the bleeder screw with the Speed Bleeder.
To use, you just crack them open like a regular bleeder screw and then pump the brakes. They have a spring-loaded ball valve that opens when you press on the brake and closes when you stop. No air gets past the ball valve.
You can bleed the whole car in much less time than it took you to put it on jackstands and get the wheels off.
I like the gravity bleed myself for the initial bleed but I don’t think it needs a full half hour. A few minutes will completely flush out the system unless yo are just barely cracking the bleed valve, and barely cracking the bleed valve will keep air trapped in high spots, you need good flow for it to work.
You can get clear vinyl hose from the fish tank area at your local WalMart. You can use any plastic bottle you have laying around. Put some type of hanger in the bottle so that you can hang the bottle above the bleed valve, then cut the hose to length, just long enough to go from the bleeder to the bottle bottom. Air only will travel upwards so you want everything higher.
Most brakes are cross connected, that is RR to LF and LR to RF. You can do both brakes on the same circuit at the same time, or do both rears first, then both fronts. You can do all 4 at the same time but you better have someone standing over the master cylinder keeping it full as it will drain fast.
Check to make sure before you start that the ABS plug is disconnected and look for a bleed valve in the line near the rear axle if RWD or 4WD. Sometimes where the brake line goes over the axle, there is a bleed valve because air can get trapped in this location and its near impossible to get it out.
Do the pressure bleed with an assistant as described above, the valve must be closed when the brake pedal is raised and it must be raised slowly. Hard and fast down, easy and slow up.
I don’t use on and off, but up and down. The wife seems to understand that better. Yeah you have to close the bleeder screw again before the pedal goes up or you draw air in again.
Also there is a proper sequece as to which wheel is done 1st, 2nd, 3rd, 4th. I believe it is LF, RR, RF, LR.
On a cross connected system, it doesn’t matter which side you do first as long as the rears are done first. The exact order mattered in the old single cylinder master cylinders (and dual master cylinders that are not cross connected) and you started with the one furthest from the MC as measured by the brake lines, not the crow flies, and worked to the closest.
I don’t think the gravity bleed method is foolproof. I think it is still possible to get air trapped in pockets just outside the fluid flow - like in a cylinder.
Just like mountainbike, I prefer the tube in a bottle method. Not only can I do this by myself, but it moves the fluid rapidly enough to dislodge bubbles of air. The only drawback is that you have to push enough fluid through the tube on the downstroke to prevent the bubbles from coming back into the bleeder on the up stroke…
Ditto Mountainbike, cheap and easy, almost foolproof. Rocketman
I don’t know if its cross connected or what but my Chiltons for my Pontiac has a definate sequence of RR, LF, LR, RF. Not always accurate but usually are just plagerized from the factory manual. That’s how I did it anyway for a fluid flush and worked well.
Nothing wrong with following the procedures in the service manual.
How exactly does the bleeder screw work? I assume there’s a hole in the bolt stud on the other end. Why does it not matter how much you exactly turn it? Does loosening the screw move the location of the shaft hole higher, so it’s now in the fluid? Or does turning the screw position to shaft hole to FACE the fluid in the right direction? This doesn’t make sense, b/c another 90* turn would close it off, but that doesn’t happen.
You sure you’re looking at the bleed screw? It looks like a grease zirk. You can slip a hose on the nipple to direct the brake fluid into the jar. Yes it has a hole in body. You unscrew it a half to 3/4 turn and it is open so that pressure in the line comes out the center hole into the tube. Then close it again. Should be fairly self evident.
I personally prefer the vacuum bleed method. You can get a hand help bleeder fairly cheaply and it allows you do do the bleeding without a helper. I have also never had any air pockets left behind with this method.
“How exactly does the bleeder screw work?”
It’s essentially a needle valve with a hollow passage for the fluid: