Brake fluid flush for low-use vehicles

[JHZR2]

Lots of cars that get daily use never get a change. Just additions when it gets low or a brake job is done.

That doesn’t mean it’s right.

Question really is how much it gets moisture and dirt from the atmosphere versus use dry, versus use wet.

I’d say if 2-3 years is typical, 4-6 is fine for low use vehicles, but I generally just do it every few years anyway when I’m doing oil and messing around with the vehicles.

 

[Arc]

You don't have to change it at all. Plenty of 20 year old cars on the road with factory installed fluid and they stop just fine.

 

[ripcord]

You don't have to change it at all. Plenty of 20 year old cars on the road with factory installed fluid and they stop just fine.

It's a semi self regulating problem. Don't change the fluid. Then calipers and cylinders corrode and start to leak. New fluid gets added when the level gets low and when brake components get prematurely changed.

 

[ecotourist]

I had some routine maintenance done on my 4 year old Tesla recently. I asked them to change the brake fluid. The Tesla techs tested the fluid and said it didn't need changing yet. That tells me that brake fluid in my combination of weather, garage storage and driving only needs changing every 5 years or so.

I understand the comments about not just changing the fluid in the master cylinder (and I would never do that) but there is something here that doesn't make sense. If clean brake fluid doesn't defuse along the brake lines, how does water contaminated brake fluid get to the calipers in the first place. Water is not getting in at the caliper ends. Either contaminated (and uncontaminated) brake fluid defuses along brake lines or it doesn't.

 

[ripcord]

I had some routine maintenance done on my 4 year old Tesla recently. I asked them to change the brake fluid. The Tesla techs tested the fluid and said it didn't need changing yet. That tells me that brake fluid in my combination of weather, garage storage and driving only needs changing every 5 years or so.

I understand the comments about not just changing the fluid in the master cylinder (and I would never do that) but there is something here that doesn't make sense. If clean brake fluid doesn't defuse along the brake lines, how does water contaminated brake fluid get to the calipers in the first place. Water is not getting in at the caliper ends. Either contaminated (and uncontaminated) brake fluid defuses along brake lines or it doesn't.

The same reason that oil floats on top of water. Water has a higher specific gravity than brake fluid, so when it falls out of suspension due to over-saturation of the brake fluid, it tends to migrate to the lowest point in the system.

 

[Lubener]

You don't have to change it at all. Plenty of 20 year old cars on the road with factory installed fluid and they stop just fine.

Very true. My 2003 G.M. I did its first brake fluid change last year. No problems as well. With any of my three vehicles, I don't recall seeing brake fluid flush and replacement in any of the owners manual maintenance schedules.

 

[ecotourist]

The same reason that oil floats on top of water. Water has a higher specific gravity than brake fluid, so when it falls out of suspension due to over-saturation of the brake fluid, it tends to migrate to the lowest point in the system.

Good explanation. Thanks.

 

[Arc]

It's a semi self regulating problem. Don't change the fluid. Then calipers and cylinders corrode and start to leak. New fluid gets added when the level gets low and when brake components get prematurely changed.

It keeps the parts stores in business plus it's a chance to paint the brake calipers and clean everything.

 

[NibbanaBanana]

I had some routine maintenance done on my 4 year old Tesla recently. I asked them to change the brake fluid. The Tesla techs tested the fluid and said it didn't need changing yet. That tells me that brake fluid in my combination of weather, garage storage and driving only needs changing every 5 years or so.

I understand the comments about not just changing the fluid in the master cylinder (and I would never do that) but there is something here that doesn't make sense. If clean brake fluid doesn't defuse along the brake lines, how does water contaminated brake fluid get to the calipers in the first place. Water is not getting in at the caliper ends. Either contaminated (and uncontaminated) brake fluid defuses along brake lines or it doesn't.

Because when you're driving in the rain it's like a fire hose being blasted right on your calipers. The seals aren't perfect. They let a few molecules of water in and over time you get a drop here and there that causes corrosion.

 

[ordinarybloke]

It's hilarious what you can find on forums.

Two pages in, and it's still the gift that keeps giving:

It's a semi self regulating problem. Don't change the fluid. Then calipers and cylinders corrode and start to leak. New fluid gets added when the level gets low and when brake components get prematurely changed.

This is my favorite.

The same reason that oil floats on top of water. Water has a higher specific gravity than brake fluid, so when it falls out of suspension due to over-saturation of the brake fluid, it tends to migrate to the lowest point in the system.

Then again this is golden too. We need more of these. Seems in the world of BITOG no one notices he's joshing with you all.



Ahem...

Made with glycol - look it up - brake-fluid is hygroscopic / water miscible. It's made to be water-miscible exactly to stop most of what's written in this thread from happening or even being possible. Brake-fluid doesn't behave as you all seem to think it does.

Doubt these words? It's written in the DOT standard.

Only this is BITOG. and we're two pages in on the BS. The rectum is in full force.

"What?... read the DOT Standard. A chemist wrote that, what would he know?"

How it ACTUALLY works - and WHY the DOT Standard is there:

Fluid gets wettest and degrades fastest where the heat-cycle is greatest - at the caliper. Fluid will not mix / circulate via the reservoir to get where fresh fluid is most required. There's nothing to make it move that far.

This means accurate fluids tests require sample(s) from the caliper. And testers.... (if electrical) must be calibrated to your brand of fluid. Such a tester will be very pricey. This is why the good testers work by heating to the boil-point. Dip-strips are a fair way to good, but cost about the price of brake-fluid. And by the tme you've tested at the caliper - you might flush?

If you think you can test fluid - or flush - soley at the reservoir end, and still maintain you're doing some good, change your library book.
Because whilst a flush is best - do what the rest of the world does. Whn you wait long enough, fluid goes to acid. Thus acid enough to corrode and tear seals. Messrs eBay has a new caliper / ABS unit for you.

If instead of changing fluid - and it's cheap enough - you're set on a mickey-mouse fluid test there's a pyramid selling / ponsi scheme / time-share for you.

maybe a special doo-dad, for 150mpg and 700bhp. Only $30.

Read the standard... most of what is written here is at best ill considered, or worse actually impossible. Brake-fluid doesn't behave as you all seem to think it does

 

[nthach]

The same reason that oil floats on top of water. Water has a higher specific gravity than brake fluid, so when it falls out of suspension due to over-saturation of the brake fluid, it tends to migrate to the lowest point in the system.

Except the DOT3/4/5.1 standards dictate a glycol ether brake fluid and glycol ethers are already hygroscopic. DOT 4/5.1 adds borate esters to bind to water - though CCI, BASF, Clariant and KD Finechem(a Korean firm who supposedly suppliers HyunKia) have been working on borate-free fluids and have them on the market. There is the possibility of the fluid absorbing water beyond its means, but it’s likely to come out of solution as steam once the brake system approaches the boiling point of the fluid.

Now, if we’re talking HSMO used in older Rolls-Royce/Bentley brake/suspension systems, for the rear brakes of some 1980s-1990s era Jaguars and currently in bikes(Shimano/Tektro, Magura and Campagnolo - SRAM and Hayes use DOT fluid), yes whatever water enters the system will sink to the lowest point. Same deal with silicone DOT5 fluid but water floats on top of it.

 

[Nessism1]

Just flush the brake system on my Honda Civic. So. Calif. living, so mild climate. Four years since last flush. Low mileage vehicle, largely stored in a garage at night.

Even low use vehicles in a mild climate should be flushed. Note the dark colored fluid sitting on top.

 

[Nessism1]

Oh, and I had a quart of fluid but started to run low. So walked down to 7-11 and picked up a couple bottles of their store branded DOT3! How's that for splitting hairs on what fluids to put in your vehicle!