Brake Fluid Procedures

[beanjr]

Have read many of the post concerning the brake recall, general brake problems, and do-it-yourself brake work. It is my understanding that bleeding, draining, and flushing are all very different procedures. Bleeding at each wheel is basically making sure there is no air in the brake line to that wheel. Draining is all that is required by the recall notice. This procedure does not remove all fluid from the brake system. Flushing will remove all old fluid but requires special equipment that not all Workhorse Service Centers have. Make sure to specify what you expect done when your brakes are serviced. If my understanding is incorrect I would appreciate other clarifications as I know that brake discussions are a very important subject and that everyone should be aware of these differences.

[DriVer]

Quote:

Originally Posted by beanjr Have read many of the post concerning the brake recall, general brake problems, and do-it-yourself brake work. It is my understanding that bleeding, draining, and flushing are all very different procedures.

Bleeding will immediately remove the majority of contaminated fluid in the caliper and any trapped air. Draining or "Gravity Bleed" has been used on vehicles since the golden ages and is simple but time intensive to accomplish. Open the bleeder and wait. Flushing can be done without any special equipment other than a vacuum recovery bottle which is used to pull out the old fluid in the Hydro-Max booster. The rest of the process is basically a bleed until the fluid runs clear at the wheel end.

[peskyfeller]

Quote:

Originally Posted by beanjr Have read many of the post concerning the brake recall, general brake problems, and do-it-yourself brake work. It is my understanding that bleeding, draining, and flushing are all very different procedures. Bleeding at each wheel is basically making sure there is no air in the brake line to that wheel. Draining is all that is required by the recall notice. This procedure does not remove all fluid from the brake system. Flushing will remove all old fluid but requires special equipment that not all Workhorse Service Centers have. Make sure to specify what you expect done when your brakes are serviced. If my understanding is incorrect I would appreciate other clarifications as I know that brake discussions are a very important subject and that everyone should be aware of these differences.

Hi, No special equipment is needed to bleed or flush the "Workhorse" brakes. Basically all that is needed is a person to push the brake pedal, a 3 foot section of clear 1/4 inch hose, a jar to catch the old fluid and a wrench that will fit the bleeder valve. Get the clear tubing from Lowe's.

It can be done by one person if you have a vacuum bleeder, a pressure bleeder, speed bleeder valves or one of many after market kits.

The workhorse chassis has a electric pump that pressurizes the brake booster when the pedal is pressed even if the engine isn't running. There is no need to pump the brakes.

I am not a fan of gravity bleeding brakes because there is no way to know if all the old fluid and air is out of the system. You can get clear fluid from a bleeder but with gravity bleeding but there is no assurance that air has not gotten back into the line. Gravity bleeding is basically opening the bleeder valve and allowing fluid to run...drip from the valve. There is no pressure applied to the fluid from the master cylinder to force any contaminants from the brake lines. I had my calipers replaced a few weeks ago and they were gravity bled. When I got home I flushed the system and you can see in the picture what gravity bleeding left in my brake system.

The only difference between bleeding and flushing brakes is that flushing removes ALL the old fluid and replaces it with new fluid. Bleeding only removes part of the fluid and is usually used when brake calipers or a brake line has been disconnected and replaced. Pressure or Vacuum bleeding removes air and old fluid and debris in the brake lines by forcing or sucking it out. Unless you completely flush the system you have no guarantee the fluid in your system is clean and dry "no moisture in the fluid".

Here are the basics: To bleed the brakes first make sure the reservoir is full of fluid. Put the cap back on the master cylinder becaue the fluid may splash out when the pedal is pressed and released and it will eat paint! Go to the caliper that is the greatest distance from the master cylinder passenger side rear. Doing this with someone pressing the pedal you will need someone inside.

I use tapping to communicate with my assistant. Put the clear line over the bleeder after cleaning it with a rag. Put the other end in a jar. Have the assistant press and hold the brake pedal. (one tap on the frame is easier for them to hear than yelling) Open the bleeder valve and watch the fluid flow through the tube. Make sure the assistant knows the pedal will go to the floor but not to let the pedal up until the second tap. Close the valve and have the assistant let the brake pedal up (2 taps on the chassis). Have the assistant press and hold the pedal again...open the valve and let the fluid drain. Continue this sequence until there are no bubbles in the fluid. Then do the same thing on the driver side rear, the pass side front and finally the driver side front. You may not see any bubbles in the lines except on the wheel you worked on. During this process keep checking the reservoir and never let it get less than half empty. When you finish fill the reservoir to the top and put the cap on tight.

Flushing the fluid follows the same procedure with a couple of exceptions. When flushing brakes the first step is removing the old fluid from the reservoir. This can be done with a turkey baster but I prefer siphoning the fluid out. Use a clear hose and you will see when the fluid is coming down the tube and this will avoid a nasty experience "brake fluid is toxic and taste bad!"

Once you get the old fluid out of the reservoir refill it with new fluid. It will take a little over a quart of fluid to fill the reservoir. Follow the same procedures for bleeding except this time watch for the clear new fluid to come through the bleeder before going to the next wheel. It will take a little over three quarts to completely flush the system. It is extremely important to keep the reservoir at least half full during this procedure. If you drain the reservoir and the pedal is pressed air will get in the line. A major no no.

Jerry Newberry

[jdsr]

Quote:

Originally Posted by beanjr . Draining is all that is required by the recall notice. This procedure does not remove all fluid from the brake system.

Thats right. It seems that not even wh believes in flushing the system or I would think they would provide just "ONE" more qt of fluid. It will be very hard for wh to use that for an excuse in the future if they fail again. Speaks volumes to me.