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I had mine tested and it was at 1% water in it.

Going to test again at 50000 miles.

What is your opinion on a full change ?
 

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Good idea to get it changed in my opinion.

Brake fluid just kind of sits in place and when water content builds up in it, it can cause rust in brake lines, the brake pad pistons and cylinders and cost $$$.

They have a machine at most dealers that can flush the entire system at each wheel and replace with fresh fluid. If I keep a vehicle for 5 years or more I have it done. By that time, it is due. I am about ready to do it to my truck.
 

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Not "recommending" this, but just for some perspective here: been maintaining my cars for 30 years now, approaching 1 million miles driven with 5 vehicles, and only replaced brake fluid *once* - on my Taurus - and only because the master cylinder had to be replaced at 200,000 miles!

So - probably a good idea to do it, but my experience says - at least here in the warmer Southeast, not really necessary unless you're doing it as part of another repair.
 

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Usually when I replace the brake pads I'll flush the fluid. I mean, heck you're already in there so why not?
 

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Colt Hero said:
So - probably a good idea to do it, but my experience says - at least here in the warmer Southeast, not really necessary unless you're doing it as part of another repair.
Is temperature the cause of need to change, or is it humidity ? I vote for humidity - but wouldn't bet my life on it.

I'm with you though. When I get bored, I think about changing it, but seldom do it. I've driven cars for up to 20 years with no brake line rust issues.

Also, I think that time is the trigger for need to change, not miles - but again, just my opinion.

Any educated thoughts ???
 

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I did it at 5 yrs (82,000) on my 2010 Traverse

On my 2003 Trailblazer did it at 5 yrs and I think it was 100,000.

Simply because of age.
The good thing for me-- is that its super easy.
Takes 20-30 min.

Opening the the bleeder is also easy. No rust whatsoever.
This is what my brake parts looks like at 5 yrs....
they still look the same now.
the bleeders have a rubber cap over the tip.. (thus the shiny metal)

 

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I don't have any rule of thumb, but if I do it, it's with a brake pads or calipers. I did my truck recently (110K miles and 10 years) because my calipers were pretty bad and one had seized up. I emptied the reservoir with a turkey baster and refilled with new fluid. At that point, I just let it "drip" out mostly and then purged the air.

I've only ever done it sporadically and never felt a difference. I have had brake lines rust out, but I'd say it was mostly from the outside in.

I live in the north though, and deal with really "dry" winters, so I mostly have only done it because the fluid looked dark or contaminated. Humidity is the enemy of brake fluid. It absorbs moisture, and it lowers the boiling point of the fluid, which gives the spongy feeling when your brakes get hot. Ive heard that you shouldn't buy more than you need either. Any bottle that has been opened is suppose to be used up in a short period. Likewise for the reservoir, don't take the cap off any more than you need to.
 

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Supposed to be every 2 years.

I did mine - really easy job with a helper to pump the pedal.
Less than half an hour to do all 4 and put stuff away.
Easier to access fronts if the wheel is turned out.
No jacking or ramps needed.

My fluid was 3 yrs old and was pretty dirty.

$8 for a litre of DOT3 ... why not?
Peace of mind re longevity of components.
Wasn’t for a safety related concern for me ... just keeping everything working like new longer.
 

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Supposed to be every 2 years.

I did mine - really easy job with a helper to pump the pedal.
Less than half an hour to do all 4 and put stuff away.
Easier to access fronts if the wheel is turned out.
No jacking or ramps needed.

My fluid was 3 yrs old and was pretty dirty.

$8 for a litre of DOT3 ... why not?
Peace of mind re longevity of components.
Wasn’t for a safety related concern for me ... just keeping everything working like new longer.


If your car is a GM model and has antilock brakes (ABS), a complete brake fluid change includes activating the ABS module shutter valves with the GM TECH 2 device, to ensure all of the fluid is exchanged.
 

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My fluid was 3 yrs old and was pretty dirty.
Brake fluid is in a closed system, so it should never encounter any dirt. However, moisture will permeate through the rubber hoses, and contaminate the brake fluid by adding water to it. Then it could freeze - unlikely, but it could help to rust the brake lines from the inside out. It will also lower the boiling point, which will reduce the braking efficiency when you do a lot of braking.
 

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Fresh brake fluid is clear and becomes dark as it absorbs moisture. I typically replace it whenever I have to open the system, or if it gets really dark.
Nuts - I knew that, and didn't say it. Thanks for adding that in. Basically, his fluid wasn't "dirty", it was contaminated with water (moisture).
 

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If your car is a GM model and has antilock brakes (ABS), a complete brake fluid change includes activating the ABS module shutter valves with the GM TECH 2 device, to ensure all of the fluid is exchanged.
True enough.

However I sucked out the reservoir, refilled it with fresh, and purged each wheel till the colour went clear. Has abs, and was able to flush just the same. If there was some remnants in the abs module still it’s way better than leaving it. And I spent a total of $8

Fluid was,darker for sure. Looked sooty in the jar on this vehicle as opposed to the usual reddish colour when old. Have had flakes in it on other vehicles. Rust particles in lines or pistons. System hasn’t been opened, but it still got contamination over the years.

Just info for anyone considering whether to leave it or dyi vs dealer.

Personally, I’ve seen enough of my own vehicles results over the years, it’s a regular maintenance item like oil changes for me. However you approach it, it should be on the to do list.
 

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Brake fluid is in a closed system, so it should never encounter any dirt. However, moisture will permeate through the rubber hoses, and contaminate the brake fluid by adding water to it. Then it could freeze - unlikely, but it could help to rust the brake lines from the inside out. It will also lower the boiling point, which will reduce the braking efficiency when you do a lot of braking.
Yep, it was moisture I’m sure. However have had particles in past vehicles. This time though I feel maybe some brake dust came in past the piston o rings maybe ?? Colour was a bit golden from moisture. Also Smokey grey. Didn’t notice it in the bleed tubing. But collectively in the jar it wasn’t just transparent.

Good thing now is it’s clear again, and fresh.

Braking effect is subtly better. The light pressure pedal modulation is ‘smoother’ or more progressive now.
 

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that reminds me--- the Nox is nearing 5 yrs.... in Sept-- and ill be doing the 'purge' .
 

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Our 2013 Denali at 72,000km (45,000mi) operating in Vancouver wet and traffic DID NOT really need pads (worn to 50%) but the fluid was green. Used a hand pump vacuum device to pull in two bottles of brand new DOT4 fluid. This really improved the stiffness of the brake pedal response. But, I was unaware of the need to pump through the ABS system fluid as well --- after one has gone out for a joyride and hammering on the brakes' ABS pump for a while. Hmm... back to the car jack again to finish the flush.
 

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Have a vacuum bleeder and it wouldn’t suck like it’s done on other vehicles. Had to go basic with a friend pumping the pedal.

Sucking out resevoir ... turkey blaster at $ store. Then toss it. :)
 

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I Would Say It's More Age, Than It is Miles. I Had Low-Mileage Harley That Had Years on it. After About (5) Years it Kept "Failing" the Rear Brake Light. I Put in a Brake Light Switch About Every Year (It Connects Right to the Outlet of the Brake Reservoir) I Flushed/Changed the Rear Brake Fluid. (It Was Black) & Never Had the Problem Again. Also, On Airplanes After a Period of Time Small Pieces of Debris in the Fluid Would Get Between the "O" Ring on the Caliper & Cause Leaks. These Sometimes Could Be Flushed Out With Pressure By "Pumping" the Brake Pedals Numerous Times to Flush the Particle. Sometimes Grit Gets on Between Caliper & O-Ring. Will Keep You From Having to Change the O-Ring. Problem Usually Never Came Back. My 2 Cents as One Poster Says.
Good Luck! Let Us Know How It Goes
 

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Used some thread seal tape on the bleeder screw thread before pulling vacuum. That stopped the vacuum leak through the threads. However, this car does take a long time to pull fluid through it on mitey mite vacuum pump. BTW, the same pump is great for emptying the reservoir of old fluid too.
 
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