When to do a Brake Fluid Flush?

How often do you flush your brake fluid? And what are the indicators you need to do so? I have a 2020 Off Road with 50k and haven’t done a brake flush. The pedal isn’t soft or mushy but it doesn’t firm up with each push either. Does a brake fluid flush improve “pedal feel” and prevent brake fade?

 

5ok is good time to do.

 

Brake fluid is very hygroscopic. In addition to color I have a battery powered H2O concentration meter I use to check routinely.

 

The Canadian maintenance booklet up to about 2012 used to specify brake fluid replacement every 48 months. Later it was reduced to every 36 months.

 

I have one of those meter “pens” recommended by the Car Care Nut and it reads solid green. Just wondering if a firmer pedal feel can be achieved by a flush.

 

Thanks All. I’ll schedule the flush. Think $150 US is a fair price to have it done at the dealer? I know there’re lots of DIY videos out there but need it done in a couple weeks for a trip and I just don’t have the time.

 

It'll probably be charged an hour of labor, that's a fair price for a dealer but since nothing is weird about the 4Runner as far as brakes go, you could probably get a better price on an equally decent job at an independent shop.

I wouldn't expect a firmer pedal in your case. My SO and her family's Honda's have been speccing brake fluid changes (Honda's have this maintenance minder thing that tells you what to do) at 3ish years I believe. I'm planning to do them all (around the same age) and loop in my 4Runner too within a year.

I'm going to likely go more by time than mileage but whether I'll go for every three is a very good question.

 

Not likely. Soft pedal feel and long pedal travel is a characteristic of 5th gen design. The caliper pistons were upsized compared to 4th gen but the master cylinder not so much.

 

Exactly this. While not particularly well balanced as a system due to the 4th gen master cylinder, panic braking software if you ever come across the scenario will show you just how much brake force it is capable of.

Experimenting with pads and rotors can provide a little more early "grab" which for me is what was lacking stock.

 

You guys read my mind. Soft pedal feel and long pedal travel is what I was alluding to. I’ve forgotten what my 5th Gen. should feel like. Considering I’ll be on some steep off camber shelf roads in a few weeks some early “grab” would be preferable. Definitely getting the fluid flushed still though.

 

Even if there is moisture in the system it should not affect pedal feel under normal conditions as water is a liquid and will not compress. The problem with moisture is corrosion if left for long enough and it lowers the boiling point of the fluid thus causing problems under hard, repeated braking.

 

No the water turns to steam and compress like a gas into the hydraulic fluid which will effect pedal feel. The corrosion is just a secondary effect.

 

Larger caliper cylinders in comparison to the master cylinder will slow the initial "grab" but will actually increase the force of the cylinders in the calipers. The PSI remains the same but there are more square inches to act upon. It's basic hydraulics, the cylinder piston moves slower but has more force once it encounters resistance. The inverse also holds true.

On early front disc brakes for early '70s Norton Commandos, sleeving or replacing the the master cylinder results in better braking due to higher multiplication of the force of the hand lever. Again, basic hydraulics.

 

This is correct.

 

Did you read all of my post? I specifically addressed moisture lowering the boiling temperature under hard braking. Under normal driving where brakes are only used occasionally this is not a factor. Water can't turn to steam unless it boils.

As a mater of fact the boiling temperature of water rises with pressure. At 300 PSI water turns to steam at over 400°F. Imagine what it would be at 1,000 PSI.

 

Well it may be correct I did address that issue in my original post. Seems that people only read what they want to read.