The recommendation is one should do a brake fluid flush and fill every 2 years. I had that done once 2 years ago after I first acquired my 2009 4S cab. So it was bugging me that this had not been done in a while so I bought this tester and it indicates moisture content is at 1% so I'm thinking flush and fill may not be needed at this time. What is the collective wisdom on this?

 

Those gauges are renowned for their inaccuracies. My questions would be ...

1. Do you track the car? If so the temperatures the brakes transfer to the fluid are extreme and a low water % is critical.

2. Do you drive in canyons, twisties, mountains, on long downhills? See 1 above.

3. Do you have a lot of moisture in your air? More moisture equals more transfer into the fluid.

4. Do you care about not getting corrosion into your braking system? Water induces rust.

A brake flush can be messy. I use lots of plastic, towels, and rags when I flush. I hate handling brake fluid. But then I put on my adult underwear and realize it's a quick job that needs to be done, usually.

 

If you don't track your car you can change it every 4yrs or so ...No big deal .... I am going on five and I plan to do it at the end of this season ...

 

I bought one and because I had old but unused fluid in my basement, figured I should test it out because I was skeptical that I needed to change the fluid in our X5. It just looked way too clean.

Put a bit of fluid into small cup that I was tossing out, measured zero water content. Used a dropper to add a drop of water in and it picked it up (went to <1%).

Was it a perfect test? No. It was used on an open bottle of brake fluid that I should've tossed a while ago.

Did the water content reading change after adding a very small amount of water, yes.

 

Wayne Smith, no tracking, no canyons, average humidity (Michigan based), average about 1000 miles per 8 months , stored winters. Thought about the paper test strips but they only come in large quantity. Never did a flush and fill on any other vehicle owned , some up to 20 years.

 

We never did brake fluid flushes when I was a kid. But we replaced brakes every 40K miles, including full rebuilds on all components. So that effectively included a flush ... about every 4 years, or less.

In the San Francisco area, I see an extra .5% increase in water content per year in my driven cars. By the time the water reaches 2%, it levels out. That's with a gauge that I've already mentioned that I don't trust. But if I believed it, I could go 4 years or more in between flushes without any problem.

Additionally, I don't drive hard anymore, so I don't heat up the fluid a lot. So, looking at the graphs indicating boiling temperature as a function of % water, flushes are just to make me feel good. If nothing else, I tell myself I'm reducing corrosion in the system.

Since you've never done a flush before, you might want to do one just to get a feel for it. The equipment you need is a minimal investment. If you go with the Motive Bleeder, my recommendation is to do it dry. Brake fluid left in the pump over time will destroy it. Petza will disagree (he flushes wet, with fluid in the pump), but he'll bleed his entire fleet at the same time, so the hassle of cleaning the pump mechanism amortizes over several cars. For that matter, he could throw out the bleeder after each use!!!! Doing it dry means a risk of running the master cylinder out of fluid. Do not do this. Use a baster to empty the master cylinder into your capture vessel. Mark the vessel accordingly. Refill the master and as you flush, never get near your mark before you empty the vessel and refill the master cylinder. It's a hassle and involves a lot of pressure release at the pump and pumping it up again. But this way, the pump stays dry, there's minimal clean up, and you're ready for the next time. If you opt to flush wet (brake fluid in the Motive pump), then put that pump in a plastic garbage bag for safety as you flush, in case it leaks. Use lots of towels, rags, and plastic ... think Dexter setting up a kill room.

Did I mention I hate handling brake fluid?!?!?!

 

Thanks Wayne Smith, yes I forgot about flushes that occur when replacing brake hardware. Great advice, thanks but I too hate brake fluid so I will probably leave it to the Indy shop.