Flushing brake fluid / brake system

Fourth Generation Honda Prelude topics

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Prelude Model: 1995 Si w/mods
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Flushing brake fluid / brake system

Postby RedRacer » Tue Apr 10, 2007 4:25 am

** You may want to read my other sticky about brake fluid first, before reading this post. You can find it here:

First off, flushing and bleeding are done using the same basic procedure, but are done for different reasons. Bleeding is done to remove air from the system after it has been opened. Flushing is done to completely change old fluid out and put new fluid in.

The most important reason in my book for flushing or changing your brake fluid is because brake fluid is hygroscopic. That means it absorbs water. A secondary result of brake fluid absorbing water, is that this water will cause brake lines to rust. Rust flakes off and gets in the system. Sediment like this in your braking system is not a good thing.

Some say do this every 30,000 miles, some say every two years. Some actually say never. I say at least once a year, especially if you autocross or drive hard. Think about what this stuff is and what it does. It STOPS your car from slamming into things. You need to take care of your brake fluid and braking system and it will take care of you. So to get rid of that water and sediment, you want to flush the brake fluid periodically.

If you can swing a wrench, you can replace your own pads, bleed and or flush your own brake system. You can do this alone or with the help of a friend. We are going to talk about the old method that requires a friend. And the friend has to know nothing about cars or mechanics, just how to follow directions. They won't even get dirty. So a girlfriend is acceptable. Or boyfriend....depending on your gender or your preference, but lets not get into that here.... :wink:

Speed bleeders eliminate the need for a friend and all that I am about to get into...so if you're using a speed bleeder, stop reading now.

We are not going to discuss or even think about bleeding or flushing the ABS system. You should leave that to the professionals with the right equipment so they can cycle the pumps and valves correctly and not ruin or cause your ABS to fail next time you put it into action. So we won't even get into ABS.

Your regular braking system is independent of the ABS on your Prelude and you can safely work on this system without fear of screwing up your ABS system. Don't be afraid.

You will need the following items to do this:

A small boxed end wrench that fits the bleeder bolts on your car. I won't give sizes in case someone other than a Prelude driver is reading this article.

A turkey baster or large syringe.

A length of rubber tubing, like aquarium tubing, about 12 inches, which will attach snugly to the bleeder bolt.

A small open container or a clean, dry, water bottle in which to collect the used fluid.

A couple of new metal containers of brake fluid

A friend.

Regardless of what method you use to flush/bleed the system, watch the brake fluid reservoir at all times and make sure you don't somehow drain all the fluid out. You don't want to suck air in via the master cylinder.

Raise the car and support it on four jack stands. Remove all four wheels.

NEVER count on a tire or floor jack to hold a car up. When working under a vehicle, ALWAYS use quality jack stands to support it.

Brake fluid INSTANTLY destroys paint. Do not allow it to get on any painted surface of the car or you WILL be sorry.

Now, first thing, to flush the system, get the turkey baster or syringe and draw out all the old fluid from the reservoir on the master cylinder. Once you get as much out as you can, use a micro-fiber or lint free rag and wipe out the remainder of the fluid and any sediment from the reservoir. (if you are just bleeding air from the system you don't need to do this step, just watch the reservoir and make sure it does not run dry)

Now fill the reservoir back up with a good quality brake fluid from a NEW container. Do not use brake fluid from any container that has been opened and left sitting around. Remember what I said earlier? Brake fluid is hygroscopic. It absorbs water from the air. Open bottles are no good and my personal opinion is that plastic bottles are no good either, even when new and unopened, because some plastics also absorb water. Get the good stuff that comes in a metal container. (Of course, if you can't find brake fluid in a metal container, you can use the stuff in the plastic bottles. It's not a necessity, it's just my personal preference.)

Let me repeat, make sure you fill the master cylinder up to maximum and remember to check the fluid level after you're done at each wheel.

Next, pour enough brake fluid into your catch container or bottle so that the end of your rubber tubing will be submerged in brake fluid. This IS important. You don't want air being sucked back up into that tubing if your friend makes a mistake with the pedal, and having the tubing submersed in fluid will prevent this from happening.

Have your friend get in the car...on the driver's side...duh and you go to the right rear wheel with your wrench, tubing and bottle. Attach your wrench to the bolt, put one end of the tubing over the end of the bolt and the other end in the container, submersed in fluid.

Tell your friend to push DOWN on the brake pedal and HOLD IT DOWN until you tell them different. Let them know that the pedal is going to sink to the floor when you open the bolt.

With their foot firmly on the pedal, you now turn the wrench a quarter turn. The pedal will sink, fluid will come out of the bolt end and through the tubing and into the bottle. When no more fluid is coming out, close the bolt and tell them to release the pedal.

They may have to pump the pedal once or twice after you close the bolt to get it to return to a "high" position. If not, it may stay at the floor and no fluid will be expressed from the system the next time you open the bolt.

Repeat this process of pedal down, hold, loosen bolt, let fluid release, tighten bolt, release pedal. Do this at each wheel until the fluid coming out is CLEAR and has no air bubbles.

Repeat again at the left front wheel, then the left rear, then the right front. Keeping an eye on that reservoir and make sure it does not go below half full.

When all four wheels have been done, spray the bleeder screw and any other parts that might have gotten brake fluid on them, with brake cleaner and then wipe dry with a clean rag. Leaving the areas where you worked clean and dry, will make it easier to spot leaks through visual inspection later. Try to avoid spraying the brake cleaner DIRECTLY on any parts made of rubber or plastic, as the cleaner can make these parts brittle after repeated exposure.

Test the brake pedal for a firm feel. If it is still sitting at the floor, you did something really wrong or left a bolt open, etc. The pedal should not be any worse than it was prior to your doing this procedure. Check the bolts and make sure nothing is leaking.

Put the wheels back on and tighten the lug nuts.

With the car on level ground and the engine off, apply and release the brake pedal several times until all clearances are taken up in the system. During this time the brake pedal feel may feel a bit tighter or higher, but it should be at least as firm as it was prior to the procedure.

Take the car for a test drive to make sure all is working as it should be and to ensure that the brakes feel right to you. USE CAUTION THE FIRST TIME YOU DRIVE YOUR CAR AFTER DOING THIS OR ANY BRAKE PROCEDURE! DO NOT PULL OUT INTO HEAVY TRAFFIC OR TAKE OFF AT HIGH SPEED!!

Properly dispose of the old brake fluid. Don't pour it in the gutter, sewer grate or on the ground. Our planet is in bad enough shape without you doing irresponsible things like that! Bottle it and take it to a fluid center or bottle it and store it. But don't dump it!

Bleed sequencing reminder:

Right Rear, Left Front, Left Rear, Right Front

** see my sticky here about brake fluid specs, etc.

Last edited by RedRacer on Tue Apr 10, 2007 3:30 pm, edited 1 time in total.

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Postby spiffyguido » Tue Apr 10, 2007 9:27 am

This is great stuff. And I should note, a similar process works for 3rd generation preludes as well.

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Re: Flushing brake fluid / brake system

Postby Crash_Control » Sun Oct 05, 2008 11:53 am

But what if I have a RHD prelude ??

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Prelude Model: 1991 SE-SR
Location: Alberta, Canada

Re: Flushing brake fluid / brake system

Postby spiffyguido » Sun Oct 05, 2008 10:20 pm

Crash_Control wrote:But what if I have a RHD prelude ??

Should be the same process.

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