how often do you change brake fluid?

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[GTP]

I have a brake fluid testing pen, but it looks with the way the brake fluid reservoir is designed they have the cap offset to where I can’t get it down to the fluid to test it. That sucks!

Agreed.
Just bleed some from a caliper and test that. That's where it is most critical anyway.

 

[Dana Pants]

Live your life however you want, but after 12 months my brake fluid is completely black. So I flush every April before race season starts.

 

[sk47]

Hello; Three years is a decent time goal. More often will not hurt anything except the pocket book.

I have known plenty of folks who never change( flush) brake fluid and do not have issues for a long time. Of course when they do have a problem it can be more expensive in terms of parts and maybe a failure on the road.

Once the brake fluid absorbs enough water my take is the small amounts of water gets hot enough to boil under hard braking. Might be part of the squishy pedal feel the OP likes. I do not like that myself.

 

[5550snotamerc]

I'm going to be the contrarian here and say this: if, like me, you are a Corvette style jort wearing driver whose car sees more cloth diapers than track days there is a strong case to be made that you should not mess with it. It's a sealed system so unless there is a leak, opening it up is the only way water is going to get in.

 

[sk47]

I'm going to be the contrarian here and say this: if, like me, you are a Corvette style jort wearing driver whose car sees more cloth diapers than track days there is a strong case to be made that you should not mess with it. It's a sealed system so unless there is a leak opening it up is the only way water is going to get in.

Hello; I have unsupported notions as to how such a sealed system becomes compromised but will postpone that discussion for now. Thing is over time the fluid does darken which is a visual sign. (NOTE- this includes the first time a new cars system for the first time.) I would like to think you are correct as such would save some effort of flushing a brake or clutch system.
You make an interesting claim which runs contrary to a generally accepted contention, among DIY types and experienced mechanics. That lots of folks never flush the brakes and their cars run OK for years is a clue but not a proof.

I have been flushing brake and hydraulic clutch systems for decades. My 2001 car has been flushed every few years (2-3) since new. I did have to replace a rear caliper about three years ago, so 21 years of service.

Afraid I do not test old fluid when i flush a system so can only go by color. Even in two or three years the fluid is clearly darker from a sealed system. I would be pleased to forgo that chore if you or others can provide some backup for the claim.

 

[5550snotamerc]

That lots of folks never flush the brakes and their cars run OK for years is a clue but not a proof.

Firstly please don't take take this as being contentious. I would never dissuade someone from doing more preventative maintenance if their budget allows. That being said, if the brakes don't corrode or get soft and it's not being tracked, I don't know when one would need to change it.

 

[sk47]

Firstly please don't take take this as being contentious. I would never dissuade someone from doing more preventative maintenance if their budget allows. That being said, if the brakes don't corrode or get soft and it's not being tracked, I don't know when one would need to change it.

Hello; I also see no need to be contentious. if you are correct we all can save some effort and money.
The evidence i am and for decades been aware of shows old brake/clutch fluid becoming contaminated over time. So far as i personally know in every sort of vehicle. Let me go first with one reason I think this is so. As we drive the pads and rotors wear down. Some European cars have rotors which wear down as fast as the pads in the calipers. To the point both need to be changed when the pads wear down. That these things wear down is my point.
When a pad wears (gets thinner) the space behind the pad (behind the piston) in the cylinder becomes larger. To compensate a bit of extra brake fluid drains from out of the reservoir to fill in behind the piston. At least four piston but can be many pistons.
If the system is totally sealed then my take is a vacuum will be created some place in the system. With enough vacuum the piston could be pulled back into the cylinder much too far. I figure as the brake fluid level goes down some how air gets into the system.
Likely at the reservoir and also likely at the top of the system. I would not be surprised to find some sort of rubber like diaphragm involved to help keep the air away from the fluid in a system or two. Maybe inside the cap. Pretty sure the air pressure needs to be equalized somehow.

There is another notion I have about heat cycles, but not right now.

I also get a garage queen car only driven a few miles a year will have a lot less wear on the pads so less of the effect I just described. Afraid I most likely thought the above up and have no links or references to offer. Somewhere in the last six decades I simply accepted the need to flush brakes as a real thing. I may be way off in my thinking.
My truck is about due for a flush, so save me the effort. Explain if you will the reasoning behind your stance.

 

[Ogopogo]

I don't believe I have ever changed brake fluid on any vehicle in the last 50 years except when brake pads/rotors et al need to be replaced. Might be every 5 (or more) years. Seems like an invitation to simply introduce contaminants and/or cause leaks.

 

[markayash]

If you live in an area where the humidity is high change it if you live in an area where its dry your call
I have never changed mine but have a friend who lives on the coast and he said after 3 years his pedal gets mussy and he has it flushed and replaced.

 

[sk47]

I don't believe I have ever changed brake fluid on any vehicle in the last 50 years except when brake pads/rotors et al need to be replaced. Might be every 5 (or more) years. Seems like an invitation to simply introduce contaminants and/or cause leaks.

Hello; You are among many I know. Likely the greater number do not flush brakes on a regular basis than do.
I get do not mess with it if it is not broken idea. Follow such on some things. Helped my brother change the front rotors on his F-150. Put new pads on as well. I suggested a brake fluid flush and he declined. I can change rotors and pads without opening the system on still sound systems. Biggest worry is when compressing the pistons (two in each caliper in his case) to keep an eye of the fluid reservoir so it does not over flow. We got way with the job.
I no longer do such work for others but perhaps 90+% declined a brake flush, so you have plenty of company.

I rarely keep a vehicle less that ten years. Have had some much longer. My take of the threads questions are different I suppose. One is how often a flush is done. The other is if a flush is needed. I land on the side they are needed and like no more than three years. I know well that most folks get by without such flushes for years and lots of miles.
However, on occasion I have to fix such neglected systems. They will eventually fail in some way. The cost and effort goes way up. If a person trades every few years the issues usually are avoided.

Back to my main question in this thread. I laid out my thinking on how air gets into a brake system, however slowly. I agree the systems are sealed so as to not leak fluid but contend air can get in. Had a guy show up one day for a repair. I noticed the plastic can on the brake reservoir was melted. Guy had laid a shop light on it ( the old hot type). He had been driving around that way for a few weeks. The system did not leak. He was a buddy in a tight money spot so I red-necked a fix for that and his other problem.
That said I again ask for some information showing how brake flushes are not needed. I would be fine if I never had to do another for only it is become a regular thing.

 

[tosha]

That said I again ask for some information showing how brake flushes are not needed. I would be fine if I never had to do another for only it is become a regular thing.

Brake systems are not perfectly sealed. Moisture gets sucked in over time and air bubbles are not uncommon thing. Having said that, every brake fluid has dry and wet boiling point. If you believe you could heat it up to the wet point (e.g. you track your car or tow a lot or live in the mountains), then it's better to maintain it fresh. But if you just drive on flat straight highways, it is unlikely that you would boil it in one emergency braking situation.

Ultimately, I wouldn't suggest to test these limits on a performance car, or something big and heavy. Once wheels are off, it takes me maybe 10 minutes with a beer stop to flush it, and it costs 20 bucks. It's a no brainer.

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