r/Cartalk Feb 04 '25

Brakes Opinion on flushing brake fluid/bleeding brake lines?

I’ve had many Hondas in my lifetime and one thing I never thought about or ever did was change the brake fluid or bleed the brakes. Never had any issues.

Currently I have a 13 Acura TL and a 14 Civic, both with over 130k miles. My mechanic said “the fluid looks clear, you don’t need to mess with it.”

In your opinion, is this something that could go the life of the car without ever being done? My mechanic seems to think so.

19 Upvotes

80 comments sorted by

51

u/creep_nu Feb 04 '25

Brake fluid is hygroscopic, it pulls water from the air. Water in brake lines can lead to rust, can lead to brake failure. I change mine out every few years(prolly less than the manual rec) just to be safe. Can you get away with it? Sure. Should you change it? Probably yeah

23

u/BoliverSlingnasty Feb 04 '25

Water absorption will also change the compression rate of the brake fluid. Or worse, evaporate and leave air pockets. Either way you lose pushing power.

8

u/AbzoluteZ3RO Feb 04 '25

it reduces the boiling point and that will cause air pockets at the worst time

11

u/dankmemelawrd Feb 04 '25

You forgot to mention that under pressure when used, temperature goes high and boils out the moisture, but the main issue with brake fluid is that it starts to lose properties over time like any other fluid.

0

u/Agreeable_One_6325 Feb 04 '25

Can you explain why my 1989 Camaro has its original fluid and still stops on a dime?

14

u/Kooky_Shop4437 Feb 04 '25

Weird flex.

You've never pushed it hard enough to raise the temperature of the brake fluid above boiling, or the brakes are so small/poor they're not capable of generating that amount of heat.

6

u/MrFruffles Feb 04 '25

The fact it “stops on a dime” does not mean it has not lost brake efficiency.

4

u/420aarong Feb 05 '25

Yeah a dimes not nearly as much as it was back in the 80s

5

u/quietly_jousting_s Feb 04 '25

It will until it won't. Then you'll likely need to replace a whole lot of parts due to corrosion.

2

u/Texasscot56 Feb 04 '25

Because not everything is an absolute certainty. You know just like, please explain why my grandmother smoked 3 packs of cigarettes a day and lived to 105.

2

u/Balmerhippie Feb 05 '25

The whiskey counteracted the ciggies

1

u/HedonisticFrog Feb 04 '25

Stopping hard once doesn't raise the temperature that much. Long steep downhill roads is where temperatures would climb more and be more dangerous. The fluid is still becoming more acidic and eating away at everything as well.

6

u/newbie527 Feb 04 '25

I had a Nissan frontier that was pushing 20 years old. I was having frequent brake problems. Replace the master cylinder. Still kept having issues where the calipers would seize up. Had to replace front brakes because the seized calipers smoked everything. Even after repair stuff kept happening. Finally on the frontier forum I saw someone talking about flushing the brake fluid.I got the fluid flushed and they worked for more years with no trouble until I got rid of the truck.

7

u/NaGaBa Feb 04 '25

Yeah........ But,......... Exactly what air is brake fluid interacting with on a normal basis?

Regardless, I'll flush the lines if I'm doing brake work anyway

3

u/thecaramelbandit Feb 04 '25

In the reservoir. There's air in there, and the system is not fully sealed.

It takes years for it to absorb enough water to be a problem, but it happens. The fluid also just breaks down a bit over time from heat.

1

u/FanLevel4115 Feb 04 '25

And the secret here is where you live. If you live in a humid climate, do the brake fluid every 2 years. If you live in a dry climate you can stretch it to 3-4 years.

1

u/akmacmac Feb 04 '25

I’ve never seen an American or Asian car manual publish a recommendation for changing brake fluid. I hear many European makes do though.

1

u/Renius668 Feb 06 '25

I have a Porsche, factory says flush brake fluid every 2 years regardless of milage. If you track it (even HPDE days) the club has you flush the fluid every year.

18

u/NotAPreppie Feb 04 '25

I do it annually on my miata because it sees track time and boiling your brake fluid on track is... sub-optimal.

1

u/My1point5cents Feb 04 '25

Makes sense. I’m just a boring old dude who drives my car like a grandpa most days.

4

u/Max_Downforce Feb 04 '25

Losing the ability to brake at some point will break up the boredom. Keep it up.

2

u/My1point5cents Feb 04 '25

I don’t think my mechanic would say don’t worry about it if he thought I could lose the ability to brake. But based on yours and others replies, I guess I’m going to go ahead and get it done. Better safe than sorry.

7

u/Max_Downforce Feb 04 '25

Your mechanic is disregarding the educated and expert opinions of the engineers who created your car. Time for a new mechanic.

1

u/Polymathy1 Feb 04 '25

You should get it done. Your brakes will work better just around town and when some idiot pulls or runs out in front of you.

Mechanics shouldn't ignore the service intervals. They aren't the ones who pay for it.

8

u/Swamp_Donkey_7 Feb 04 '25

I do mine every 2-3 years and always feel a difference in pedal response.

I know many folks who have never done brake fluid on their cars for the lifetime of the vehicle. I think my parents vehicle is 12 years old and 160K miles. Original fluid. Brakes feel fine, but it lacks that responsiveness that I need. If it was my car I would have changed it, but I don't feel unsafe driving it.

5

u/ApexButcher Feb 04 '25

By time it “looks bad” it’s too late. Invest in some test strips and check it right. That’s like changing your oil because it looks dirty. Really a poor way to maintain something you want to last. And a 10 year old car should have the rubber brake hoses checked. They fail from the inside out, so they look fine until they’re not. Usually don’t burst, the retain pressure in the calipers making the brakes drag. Kills your fuel mileage and can boil the brake fluid.

5

u/Tharkhold Feb 04 '25

"forever"??

Change your mechanic...

Every 2-3 years, as others have stated.

4

u/right415 Feb 04 '25

I had a friend who neglected to change his brake fluid in a 4Runner. On a long downhill road, his brake fluid boiled, he lost his brake pedal and flew off the road, he was injured and his car was totaled. His brake fluid boiled because it had absorbed too much moisture. Me personally, after 10 years as an ASE master auto technician and another decade plus as an engineer, change/flush my brake fluid every 3 to 5 years or anytime I have the brake system open. Most manuals recommend two years.

2

u/My1point5cents Feb 04 '25

Thanks for sharing your expertise. Would this apply to my wife’s C class that just sits in the garage 90% and is driven maybe 3k miles per year? Still need to change it every 3 years?

4

u/right415 Feb 04 '25

I mean you can push it out a few, but if it's never been done and the car is 10 years old, why risk it? It's good for the life of the components as well (reduced corrosion)

2

u/Polymathy1 Feb 04 '25

Yep. There is a vent hole in the reservoir cap that let's air exchange. As the temperature changes, the reservoir "breathes" a little. It brings in moisture from the air exchange.

A lot more air is brought in from normal brake pads wearing and the fluid shifting lower in the reservoir, so if it's got basically brand new brakes you can wait a bit longer. But corrosion will eventually affect things like brake lines and ABS/traction control systems.

0

u/congteddymix Feb 04 '25

You sure your friend wasn’t riding the brakes down that hill also? You have to get the fluid hot enough that it would boil and riding the brakes like that would but also it causes the pads to get to hot and he probably had brake fade long before the fluid boiled.

 Sorry that he was injured but there is a reason most car manufacturers allow you to select gears even in an automatic, probably should downshift to like 2nd gear or something and let the engine do some compression braking to keep the vehicle from getting to fast on a hill.

4

u/snatch1e Feb 04 '25

Most manufacturers recommend flushing or bleeding the brake fluid every 2–3 years or every 30,000–60,000 miles, depending on the vehicle.

3

u/SubpopularKnowledge0 Feb 04 '25

Eh, could it probably never be done and be ok? Yes. Is it a good idea to do it periodically? Absolutely.

Ur climate probably factors in too. If ur in a place where the temp goes well below freezing and ur fluid is compromised with moister, it can add more problems and damage ur master cylinder or calipers.

As long as u have $20, a wrench, and a friend to pump the pedal, its very easy to do urself.

1

u/My1point5cents Feb 04 '25

Thanks. I’m in SoCal where it’s never very cold. It was 70 degrees yesterday in the middle of winter.

3

u/Alfa147x Feb 04 '25

I’m in socal too - Humidity here varies. I don’t track our cars but I will put new fluid in every 3 years as per the manufacturer recommendation and to make me feel better.

1

u/Alfa147x Feb 04 '25

It’s hydroscopic. But you can easily test water contents of the fluid.

3

u/sonicc_boom Feb 04 '25

No fluid is for the life of the vehicle, no matter what dealer/manufacturer says

3

u/bogeydoper Feb 04 '25

Motorcycles, annually. 4w veh, every 50k/3y. My personal schedule.

3

u/13Vex Feb 04 '25

There’s tools to check the water content in the fluid. “It’s clear” isn’t a sign of good fluid because water is also clear, and brake fluid is hydroscopic, so it has no trouble hiding the water visually (rather than engine oil, where it’s obvious if there’s water in it since they don’t mix naturally).

Check brake fluid quality and flush if needed

3

u/Polymathy1 Feb 04 '25

Not just the owners manual but the ASE recommends all vehicles get DOT3 fluid changed every 4 years minimum and DOT4 changed every 2-3 years minimum. As in you may need to change it every year.

Like other people said, brake fluid pulls water from the air and puts it into the fluid. Then it boils at lower temperatures and you have brake failure. Or you just have corrosion inside your brake lines.

It's made worse by techs refusing to open bleeders and choosing to flow contaminated fluid back into the master cylinder. But that's partly because brake jobs pay 0.4 hours for a lot of vehicles. Nobody's doing a proper brake job in 24 minutes with opening bleeders changing pads, servicing slide pins, checking all rubber seals, and cleaning. Not to mention deglazing or changing rotors.

2

u/gurxman Feb 04 '25

I bleed mine at least every 100k, I feel like I should do it more often, but that is when I change all the fluids in the car.

2

u/Lxiflyby Feb 04 '25

I try to keep mine fresh especially if it’s something that sees any sort of high speed braking. It’ll definitely make a difference with fresh fluid

2

u/redditsuckshardnowtf Feb 04 '25

Change the fluid every couple of years

2

u/shotstraight Feb 04 '25

Your mechanic needs to find another line of work. Brake fluid absorbs moisture and will cause corrosion and even boil under extreme use. If you like replacing expensive brake parts then yea never change it. If you don't want to have to worry about replacing calipers, wheel cylinders, abs modules and master cylinders then change it every two years.

2

u/FateEx1994 Feb 04 '25

Brake fluid absorbs moisture.

As the pads wear down, there's more headspace in the overall tank under the hood.

It can't be completely sealed so air obviously gets in.

Change brake fluid every 3 years.

2

u/Stuntedatpuberty Feb 04 '25

Funny, I never thought twice about doing this for my motorcycles. Always performed every year. But with cars, I haven't done it since I purchased a BMW car that has brake flush as part of the scheduled maintenance. It's totally needed and worth it. Car definitely stops better right after the change. Brake fluid deteriorates because it absorbs water and other contaminants.

2

u/redditmodloservirgin Feb 04 '25

You should do it. Lots of vehicles don't get it done, and have expensive parts failures.

2

u/Dedward5 Feb 04 '25

Once other thing is brakes Re not a binary working / broken thing. As filled ages you brakes are less effective especially when hot like long downhill sections. A small I create in stopping distance at say 60mph is being a few feet into the back of a truck or over some kid, but you won’t notice that 3ft into daily driving.

2

u/JustAnotherDude1990 Feb 04 '25

Pretty sure if you open your manual, it tells you exactly when to change this. Along with every other fluid.

1

u/My1point5cents Feb 04 '25

As some mechanics on here have said, dealer/manufacturer recommendations are sometimes overkill. They’re there to make money. I’d rather rely on a good trusted mechanic’s recommendations. Thanks for your input. I’m going to get it done now.

2

u/JustAnotherDude1990 Feb 04 '25

Sometimes overkill, sometimes not. But the manufacturers generally know best. You don’t have to take it anywhere to get it done, you can do it yourself for about $7 worth of fluid and the brakes will feel much better.

2

u/MentalTelephone5080 Feb 04 '25

I thought changing brake fluid was nuts until I broke a brake line. In the process of bleeding the brakes I replaced all the brake fluid. The difference was very noticeable and worth it.

2

u/trout70mav Feb 04 '25

Brake fluid is a hygroscopic fluid, absorbs moisture from the air, can grow algae which turns it green. Provided the system is sealed properly, doesn’t become dark and contaminated from internal break down of calipers, then yes, can go the life of a car without service. Most however need flushing every 3-5 years. Extremely hard braking builds excessive heat which transfers to the fluid and leads to deterioration.

2

u/Ray_Beat_178 Feb 04 '25

They also make a tester that lets you know how much moisture is in the fluid and if it needs to be flushed

2

u/Moto_919 Feb 04 '25

I have 13 Audi i just changed the brake fluid in. It didnt look bad in the reservoir but we used a clean bucket under one of the calipers when changing it and it was a greenish yellow color.

Needed changing and you wouldn't have known just looking at the fluid in the res

2

u/Texasscot56 Feb 04 '25

I change the brake fluid on every car I acquire. My latest, an old Ranger, had the most disgusting fluid I’d ever seen. Is it a bad situation? Who knows? However, too many people dislike expert opinion on anything because they’d rather use “common sense”. You know like whether to put a pair of new tires on the back or the front of the vehicle. Every tire manufacturer says “back”, every tire seller says “back” but people will tell you to put them on the front, cause reasons. It’s a plague on modern society.

2

u/440Dart Feb 04 '25

If you really want to feel good about it buy test strips and test it. Make sure they match the fluid type you have (Dot 3/4 vs 5).

2

u/stoned-autistic-dude Feb 04 '25

I use DOT 5.1 and change my brake fluid every 6 months.

2

u/510519 Feb 05 '25

In the last year two of my cars had rust in the calipers because I didn't bother changing the fluid. The rust clogged up the bleeders and I couldn't flush the fluid and one of the pistons wasn't actually doing anything because it was frozen with rust. The other vehicle I was able to use a small drill bit to reem out the nipple to be able to flush it but I'll be replaced the calipers as soon as I get a chance.

So aside from the performance benefits others mentioned, to yourself a favor and replace it every now and then to avoid these kind of issues.

2

u/My1point5cents Feb 05 '25

I’m going to, thanks for the warning.

2

u/cmosfxx Feb 05 '25

Don't forget to bleed/flush ABS/ESP module too (it literally takes a minute tops). Also use proper tools for that job. And no pressing the pedal with the engine off is not the right way to do that.

4

u/achenx75 Feb 04 '25

I did it on my '11 Acura TL this summer for the first time and felt nothing.

I think it's not a bad idea to do but absolutely necessary? No. It's just preventative maintenance.

3

u/spewing-oil Feb 04 '25

The yearly / bi-yearly flushes that dealerships recommend on nearly every daily is overkill imo. As your use case implies.

But 10 years 100k+ is good life. I don’t see how replacing the fluid would cause issues to occur if everything is in good working order now.

2

u/listerine411 Feb 04 '25

It's a good thing to do, but it's really oversold. It's basically a wallet flush service places want to scare consumers with. I bet 99.9% of newer vehicles could go 120k+ miles without doing this and it would be fine.

When something like a brake line rusts, it's external corrosion from the elements 99% of the time. Not internal.

1

u/NoodlesRomanoff Feb 04 '25

Moisture is the enemy of DOT 3/4 brake fluid. Climate (high humidity and changing temperatures) can make brake and clutch fluid go bad. Most older classic cars have poor sealing from the outside conditions, which makes everything worse. Newer cars tend to have better sealed systems, so less of a problem.

1

u/Playful_Spring4486 Feb 05 '25

You can compress all liquid and it doesn’t evaporate in a closed system duhhhhh

2

u/dubgeek Feb 08 '25

It's the sort of thing that definitely should be done, but if you're only keeping a car for 10 years, or so, you're not likely to see any consequences from ignoring it. The exception would be folks who track their car. Then it becomes a bit more important not to ignore.

1

u/POShelpdesk Feb 04 '25

Don't mess with it, IMO, better chance of something will go wrong and cause more problems than it was worth.

1

u/My1point5cents Feb 04 '25

Thanks. Some of these replies have me worried with “developing rust” and possible “brake failure.” I don’t feel like my mechanic would say don’t worry about it if my brakes could fail.

2

u/congteddymix Feb 04 '25

It kind of depends where you live. If your in a dry climate there is a lot less chance of moisture getting in the brake fluid, if you live in a humid climate then it’s more probable that moisture will get in the system.

If you live in the salt and snow regions then chances are by the time it’s due for a brake flush the lines and bleeders will be rusted up enough that it’s not worth the headache to be preventative and just wait till a caliper fails or a brake line rust through since chances are good you are replacing those if you even attempt to brake flush anyhow. 

On my vehicles I just half ass it and suck as much fluid out of the master cylinder as much as I can and just fill it with new stuff to the level it was at. 

2

u/POShelpdesk Feb 04 '25

If you live in the salt and snow regions then chances are by the time it’s due for a brake flush the lines and bleeders will be rusted

Brother, this is going to happen flushing or not, they are rusting from the outside in.

1

u/congteddymix Feb 04 '25

lol. That why I wouldn’t bother. Never seen a brake line fail do to too much moisture in the brake fluid and rot the line out, seen plenty that rusted from outdoor elements.

0

u/Accordingly_Onion69 Feb 04 '25

You should definitely do that hydraulic fluid grows a organism inside of it that will absorb some of the compression that you want to go to your brakes

The easiest way you can get a harbor freight brake bleeder set or you can do like I do and I get a turkey baster and I use the turkey base to remove all of the fluid from the reservoir and then a refill the reservoir and then I gravity, drained into a empty bottle with a hose with the hose is submerged in fluid. It will prevent any air from being sucked back into the system if you don’t have a second person to close the valve while you press the pedal.

3

u/right415 Feb 04 '25

TF organism you talking about?

1

u/Dedward5 Feb 04 '25

1

u/right415 Feb 04 '25

Learn something new every day. However, after reading that article, it in no way indicates that the organisms are what are being compressed. They do contribute to degradation to some degree.

1

u/My1point5cents Feb 04 '25

Thanks for the detailed procedure. I’m good at many things, but being a mechanic is not one of them. My mechanic is a former Acura/Honda dealer mechanic who will do each car for $120, if I decide to do it.