Piston Slap: Liberal Bleeding, Flushing Brake Fluid

Sajeev Mehta
by Sajeev Mehta

Gregg writes:


I have a 2006 Tacoma with 50K miles and anti-lock brakes. I feel it is time to change the brake fluid as a preventative maintenance measure. I have the tools and have bled numerous non-antilock brake systems and have done some research into what it would take to fully refresh the fluid. Some forum people suggest the usual bleeding procedure followed by causing the antilock feature to react by stopping quickly on a dirt road or similar circumstances and then re-bleeding the system. Also mentioned is using a code reader to actuate the antilock system.

Personally I wouldn’t mind paying for a lower end code reader if I knew it would do what I needed, but I certainly am not going to spend big bucks for one. Do you or any of the readers know what will activate the anti-lock system with minimal expenditure?

I also noticed that there is a hose about 3/8 inch ID attached to the master cylinder reservoir that appears to be the return form the anti-lock system. I could easily make up a catch container to keep the return fluid from mixing with the new fluid I would put in the reservoir.

What do you think about using DOT-4 fluid?



Sajeev answers:

Because modern braking systems are a far cry from the old days, this is a time when RTFM is abso-Fing-lutely mandatory for everyone’s safety.

Either buy the factory manuals, or be a forum junkie ( like reading this) as they regularly cover these concerns. The forum suggests flushing brake fluid without the tool is no biggie, but honestly, the “correct” procedure doesn’t look that hard if you buy the right tool or its cheapy laptop alternative.

This loaded task implies you’re forgiven for taking it to a shop with the proper tools, like this cool sucky brake fluid machine. Time value of money and all that.

I can’t quickly Google the factory brake fluid for your truck, but regarding DOT 4: it interchanges with DOT 3 with a higher boiling point. But it doesn’t keep the boiling point higher for as long as you might think. That said, everything suggests DOT 3 systems can be flushed and replaced with DOT4 and it is good idea if you flush DOT 4 on a regular basis. DOT 5 is different, its silicone (not glycol) based. DOT 5.1 is glycol, but I haven’t read anything conclusive about replacing older fluid designs with it.


Off to you Best and Brightest, especially those with more firsthand experience in various types of brake fluid.

[Image: Shutterstock user Nor Gal]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

Sajeev Mehta
Sajeev Mehta

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  • Mopar4wd Mopar4wd on Oct 16, 2014

    I think flushing every 1 to 2 years is a little crazy. Yes it attracts moisture but it takes a while I remember when I worked for a dealer group in the 90 ,s it was a running joke among the techs that vw actually printed a schedule. I think part of the reason was you usually had to open the brake system for service every 50k miles or less which meant at least part of the fluid got changed. My wife's Durango is the only car I ever took out fluid that looked like crap most look very good. My Toyota pickup. Had brand new looking fluid when I did a brake job at 160k. So yes change it but I have to imagine every 2years is a bit crazy

    • 3Deuce27 3Deuce27 on Oct 16, 2014

      It is not just a boiling fluid problem when brake fluid collects water. The moisture collected, due to gravity, sits at the bottom of the bores in master, brake, and caliper cylinders(also clutch systems). If those bores are iron, they start to rust, eventually causing seal failure and can significantly harm the equipment making them not rebuildable. When you have seen as much of this damage as I have over the past fifty years, you change your brake fluid.

  • Speedlaw Speedlaw on Oct 19, 2014

    BMW, before the fallacy/travesty known as "Lifetime Maintenance", recommended every two years. What comes out isn't clear, so for the guy with 700k plus, you are running sludge.... I get to mine every 3 years or so. A quick flush till clear when doing pads/discs is usually adequate. I stick with OE fluid, not because it is the best, but why introduce questions...also, I'm not smarter than the OE, usually.

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