Bleeding brakes computer involvement?
Cargo Master
Joined: Apr 2003
Posts: 2,058
Likes: 424
From: Too close to Houston
Brake fluid is hydroscopic ( I think thats the correct term) meaning it absorbs water, and starts degrading after approx 2 years. It also degrades with heat, and brakes get VERY hot.
The degradation happens gradually, and few drivers will notice the fading power of the brakes.
I found this out when I replaced the brake fluid on my dirt bike. I was used to the brakes the way they were, and then I hit the front brake with the new fluid and it almost launched me over the bars. The braking power was literally night / day difference! Most situations won't result in a difference this dramatic, but in my experience the fluid does degrade over time. No way around that.
The degradation happens gradually, and few drivers will notice the fading power of the brakes.
I found this out when I replaced the brake fluid on my dirt bike. I was used to the brakes the way they were, and then I hit the front brake with the new fluid and it almost launched me over the bars. The braking power was literally night / day difference! Most situations won't result in a difference this dramatic, but in my experience the fluid does degrade over time. No way around that.
While I don't see a problem with routinely changing brake fluid I've never noticed a difference from just a fluid change either. I have seen master cylinders messed up by stroking them past their normal wear pattern during brake bleeding. The Speedi-Bleed kit posted above (or something similar) could save a master cylinder from premature failure.
Tuned
Joined: Mar 2021
Posts: 370
Likes: 178
It's a sealed system and won't absorb any water unless it's opened. The gasket on the reservoir cap is designed to displace into the reservoir to compensate for fluid loss into the wheel cylinders during brake application and due to friction material loss so the reservoir doesn't "breath".
While I don't see a problem with routinely changing brake fluid I've never noticed a difference from just a fluid change either. I have seen master cylinders messed up by stroking them past their normal wear pattern during brake bleeding. The Speedi-Bleed kit posted above (or something similar) could save a master cylinder from premature failure.
While I don't see a problem with routinely changing brake fluid I've never noticed a difference from just a fluid change either. I have seen master cylinders messed up by stroking them past their normal wear pattern during brake bleeding. The Speedi-Bleed kit posted above (or something similar) could save a master cylinder from premature failure.
As the air gets pulled in, it also pulls in moisture. As brake fluid ages, it becomes acidic and corrosive...
I wouldn't go every year, but every 5 to 10 years is a good range...
Hotshot
Joined: Oct 2015
Posts: 19,698
Likes: 12,824
From: Wyoming
BMW and other high end manufacturers are recommending a three year interval.
As Norcalpr said, brake fluid is cheap. I do my own fluid flush, so the whole process is inexpensive. Replacing corroded brake lines and other components is not cheap. The fluid from my '91 Ranger (that I inherited when it was 14 years old) was down right nasty. Metal particles suspended in the fluid made me question the reliability of the system. Had it ever been changed? No idea.
Brakes are, to me, the most important system in a vehicle and I treat it that way. I don't go cheap on brakes.
As Norcalpr said, brake fluid is cheap. I do my own fluid flush, so the whole process is inexpensive. Replacing corroded brake lines and other components is not cheap. The fluid from my '91 Ranger (that I inherited when it was 14 years old) was down right nasty. Metal particles suspended in the fluid made me question the reliability of the system. Had it ever been changed? No idea.
Brakes are, to me, the most important system in a vehicle and I treat it that way. I don't go cheap on brakes.
Cargo Master
Joined: Apr 2003
Posts: 2,058
Likes: 424
From: Too close to Houston
How does air get pulled in?
I’m not trying to bash anyone for flushing their brake system. I just haven’t seen the need to flush just for the sake of flushing myself.
For those that do, I’d suggest loosening and re-torquing the compression fittings on the calipers and master cylinder before initiating the flush. That way you will have a much better chance of replacing them down the road without twisting your brake lines. That’s always my worst problem with old brake systems, fittings that have seized to the brake lines.
I’m not trying to bash anyone for flushing their brake system. I just haven’t seen the need to flush just for the sake of flushing myself.
For those that do, I’d suggest loosening and re-torquing the compression fittings on the calipers and master cylinder before initiating the flush. That way you will have a much better chance of replacing them down the road without twisting your brake lines. That’s always my worst problem with old brake systems, fittings that have seized to the brake lines.
Tuned
Joined: Mar 2021
Posts: 370
Likes: 178
How does air get pulled in?
I’m not trying to bash anyone for flushing their brake system. I just haven’t seen the need to flush just for the sake of flushing myself.
For those that do, I’d suggest loosening and re-torquing the compression fittings on the calipers and master cylinder before initiating the flush. That way you will have a much better chance of replacing them down the road without twisting your brake lines. That’s always my worst problem with old brake systems, fittings that have seized to the brake lines.
I’m not trying to bash anyone for flushing their brake system. I just haven’t seen the need to flush just for the sake of flushing myself.
For those that do, I’d suggest loosening and re-torquing the compression fittings on the calipers and master cylinder before initiating the flush. That way you will have a much better chance of replacing them down the road without twisting your brake lines. That’s always my worst problem with old brake systems, fittings that have seized to the brake lines.
Posting Guru
Joined: Feb 2018
Posts: 1,555
Likes: 516
Air enters the system through the caliper piston seals. The seals are liquid tight. Not air tight. There is a brake system phenomenon that can occur where a vehicle has perpetually spongy brakes. They bleed the brakes and get a firm pedal and in a couple days, the pedal goes spongy again. This happens where the rotor doesn't meet standards for parallelism. What this means is the rotor doesn't run true to the plane of the axle and it causes the caliper pistons to pump back and forth. This action pulls sufficient air into the system to cause a spongy pedal. The parallelism issue is why when you remove a rotor, you always clean both the rotor and hub to ensure the rotor runs true on the hub. You can also induce a parallelism problem when turning rotors in the course of a brake job where the machining that is slightly off.
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