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Rich, Technician
Category: Car
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Experience:  ase certified, mitsubishi certified, kia certified and landrover certified technician
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how do I flush out my ABS brake fluid completely from the system

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how do I flush out my ABS brake fluid completely from the system myself.
I have done everything but that & it’s a 1993 RX7 FD with very old fluid.
Thank you

Hi Steve,


Flushing Methods:

The brake pedal method:

This can be done with two people or one with a one man bleeding kit. The one man bleeding kit has a check valve that you attach to the wheel cylinder so air does not get drawn back into the system.

Everyone knows about this method, but few know how bad it can be. Normally the piston, which is connected to the brake pedal, only travels so far in the master cylinder. When using the brake pedal flushing method, the piston can travel much further down in the master cylinder and contact an area that has never been touched by the piston or its sealing O-ring. If the area has corrosion in it you can ruin the O-ring in just one pass and then you will need a new master cylinder. This is most likely going to occur in a vehicle where brake flushing has not been done as often as it should have been. If it has been neglected then you should only have it power flushed.

Knowing that and you want to proceed you should check the shop manual and make sure that your brakes can be flushed this way. Some GM cars cannot and they can only be flushed with a special computer that interfaces with the ABS system.

Determine how far down the brake pedal normally goes and put a block of wood under it to prevent it from going further down to prevent O-ring damage. Next using a NEW turkey baster, not a used one so you do not contaminate the brake fluid and system. Our use my favorite, a large sterile medical syringe. Clean the outside of the master cylinder and reservoir to make sure no dirt can get into the brake system. Remove the cap and use the turkey baster to remove as much of the old fluid as you can and top it off with new fluid from a factory sealed container. Then go to the wheel cylinder that is furthest from the master cylinder. On most cars

that will be the right rear wheel. Apply a 10mm box end wrench to the bleeder valve and a clear tube that goes into a collection container and you are ready to start.

Tell your helper to apply pressure to the brake pedal while you open the bleeder valve. Have your helper tell you when the pedal is against the block of wood and hold it there until you close the valve. Let him know to let the pedal up. It is important that he allows it to come all the way up for a few seconds while the master cylinder refills. Keep going until you see nice new clear fluid free of bubbles coming out of the bleeder valve. Stop and move to the next closest wheel to the master cylinder and so on until you get them all. It is very important that you never let the level in the master cylinder reservoir drop below the MIN mark or you may get air into the system and have to start all over again. Once you complete the last wheel, top off the reservoir and go for a careful test drive. If the brakes are mushy that means you got air into the system and have to do it again until you get it all out. Now you are done until next year.

Here is another nifty idea. There is a company called Speed Bleeder that sells a replacement bleeder valve that has a check valve built right in. It looks like it would speed up the bleeding process especially if you had to do it by yourself. The only thing is that for the speed bleeder to work properly the threads would have to remain air tight so the valves would have to be removed from time to time to apply more thread sealant.

Power Flushing:

Power flushing is the ticket for flushing the brake system and you do not have to worry about damage to the master cylinder like in the brake pedal method.

The professional power flushing systems have a big aluminum gadget that looks like a beer keg. It has two chambers in it that is separated by a diaphragm. One side of the diaphragm is the new brake fluid and the other is compressed air. A hose is clamped on to the opening of the master cylinder reservoir to supply the reservoir with fresh fluid. The tank is hooked up to the shops compressed air line and puts about 15 PSI on the diaphragm which forces the new fluid into the master cylinder reservoir and keeps it under positive pressure. Then all your have to do is go around to the different wheel cylinders and allow the fluid to flow out until you see nice new fluid coming out of the bleeder valve. This works really well, but the equipment is expensive and you need shop air to drive it.

I just found a power flusher tank that works really well for the do it yourselfers.

It is available from Motive Products and it sells for $49.95 for model PBU101.

It works the very same way as the professional power flushing systems, just on a smaller scale. You connect the hose with the universal adapter to the opening of the master cylinder reservoir and dump two quarts of new fluid into the tank and pump it up to 15 PSI and then run around and bleed it out of the wheel cylinders. It is fast and really easy to use. For the money it is a must have item. Many shops charge well over $100 to flush a brake system. You can get one of these tanks and do it yourself for $49.95 for the tanks and $20 in new fluid. From then on all you need is the fluid.


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