Brake fluid flushing procedure

[drgnrdr33]

Preventative maintenance time - need to flush my brake fliud so I referred to my hand Ford Service manual and saw the first step:

1. Connect the scan tool DCL cable adapter into the vehicle datalink connector under the dash and follow the scan tool instructions.

The rest of the steps are familiar but the first one is a new to me. I'm fresh out of scan tools. Is this step required to get a decent flush?

Also, has anyone successfully used a vaccuum bleeder (hand vaccum pump contraption) on each wheel cylinder?

[valleyman]

I used a vacuum bleeder on each wheel cylinder when I put on the KVR brakes. It works fine. Just BE SURE you don't let the fluid in the master cylinder drop too low or (correct me if I'm wrong) a major ABS headach will ensue. :bandit:

[drgnrdr33]

I used a vacuum bleeder on each wheel cylinder when I put on the KVR brakes. It works fine. Just BE SURE you don't let the fluid in the master cylinder drop too low or (correct me if I'm wrong) a major ABS headach will ensue. :bandit:


Thanks for the info. I agree about letting fluid run low. :down:

[jdando]

I have used a Motive Pressure bleeder on my Wilwood brakes.

click me (http://store.summitracing.com/default.asp?Ntt=motive&x=0&y=0&Ntk=KeywordSearch&DDS=1&searchinresults=false&N=0&target=egnsearch.asp)

Works great, one man operation. Sorry I can speak to stock brakes.

jeremy

[Warpath]

You can probably get away without the scan tool. I've done it twice already. The only drawback is that there will be old fluid in the ABS and traction control equipment. Do NOT key on until you are completely done and have no air in the system. The ABS and TC valves cycle when you key on (at least they do on my Cobra).

[drgnrdr33]

All - Thanks for the info above. I tried a vaccuum bleeder but could not get a good seal. Air kept leaking in through the threads on the bleed valve. I couldn't find a balance between the valve being open but tight enough to keep the air from getting in. I went back to the tried and true two-person method. My 14yr old girl pumped the brakes while listening to the radio and pretending to drive. The brakes are firmer now :up: but I still want a brake upgrade.

[Todd TCE]

Why don't you try gravity.

Place a drain pan under the caliper, open the bleeder, top off the reservoir and let it go. Sit back and watch a football game in the garage! Every five minutes or so get up and top off the reservoir again. After three or four fillings close the bleeder and rinse off the caliper with a watered sponge to remove the residue.

Do this on each wheel for about 15m each and you'd be done.

People (or tool vendors) make way too much of brake bleeding. It's not pressure, it's not suction it's just displacement. If you have not introduced air into the upper area of the system all you need to do is move it from the top down. By design bleeders will self purge on cars today as they are on the top where they belong.

[metroplex]

The only problem is that if you rely on the gravity method, the fluid in the calipers (closest to the open valves) are now exposed to air which can contain moisture. Brake fluid (DOT 3/4/5.1) readily absorbs moisture from the air (glycol based). Bleeding your brakes is one thing, but flushing it out with new fluid every year is a much better way to go. Use a vacuum bleeder to suck out the old fluid in the circuit until new fluid comes out. Repeat for all 4 corners every 1-2 years.

[DEFYANT]

Besides, brake fluid is not oil or coolant. When you open the bleeder, it just doesn't piss out. It may drip a few times, but all you've done then is introduce air into the line at the bleeder.

The system needs to be presureized.

For the record, I have never done MM brakes. Perhaps this system is different from the 4 or 5 other cars I have worked on..

[Todd TCE]

While I was not suggesting you do this in the rain, yes moisture can get in there. I'm not banking on much in the short while you do this.

And no, brakes do not need to be pressurized to be flushed. And no, you are not inducing air in the system by opening a bleeder to let it flow. The only air that gets back in there is when it is pressureized and someone releases the pedal allowing the mc to suck fluid back. In the normal sense fluid does not run up hill. IN the case of many race cars where the mc is below the bleed level of the caliper gravity of course will not work. Then you use a piece of clear hose onto the bleeder, loop it up about 8" and down into a botle, stroke the pedal slowly while filling the reservoir about 4 times and then close the bleeder. In this case air migrates to the top of the loop and sucking back (or reverse gravity really) takes a couple of minutes. Ample time to walk back and close the bleeder.

If you choose to invest in all the gadgets that are intended to bleed brakes that's fine. I'm not at odds with that. I'm simply telling you from one who's installed his share of BBKs that it's not necessary. Dont' believe me? That's cool, but try it some time. Think of it as "no pedal required". I can't begin to think of how many solo bleeding projects I've done and I don't even own a 'tool' to do it.

[drgnrdr33]

Back to part of my original question: What does the "scan" tool do when bleeding brakes? Above, Warpath mentions old fluid being left in the ABS module if it is not used. I've torn into a GMC ABS unit and from what I can tell, flushing the brake system would not leave old fluid in the ABS module. I've not opened up a Ford ABS unit so no experience here.

[metroplex]

I "invested" $30 for a Mityvac bleeder vacuum tool (lifetime replacement warranty with Autozone). It can hold vacuum to test old vacuum valves, it can also suck fluids out of reservoirs, etc... as well as bleed flush my brakes.

I talked to a few TRW and Bosch engineers. From what I have gathered, the primary valves work like any regular proportioning valve. The secondary valves are controlled by the HCU. If you get air in there, you may not be able to get the air out even with a scan tool (depending on model/make). They recommended just getting a new HCU if that ever happened. :eek:
I have bled my Crown Vic brakes in the same way I have bled other non-ABS and ABS equipped Fords.