Of coarse they are blaming it on the owners and not changing the fluid every 2 years. IMO 2 years is a ridiculous service interval on what is a closed/airtight braking system. Some only get a few thousand miles in 2 years. Do any of you guys bring your car into the shop for brake fluid change every 2 years??? They are just gonna scare owners of non recall bikes into bringing their bikes in for un-needed brake service and that will pay for the recall on the ones that have faulty parts.

davej wrote:
Of coarse they are blaming it on the owners and not changing the fluid every 2 years. IMO 2 years is a ridiculous service interval on what is a closed/airtight braking system. Some only get a few thousand miles in 2 years. Do any of you guys bring your car into the shop for brake fluid change every 2 years??? They are just gonna scare owners of non recall bikes into bringing their bikes in for un-needed brake service and that will pay for the recall on the ones that have faulty parts.

I change mine every 2 or 3 years

Does brake fluid have a 2 year shelf limit in the stores? After all, it's still able to absorb moisture. It's no more sealed than in your brake system. If you buy a bottle that is a year old, is it only good for a year in the vehicle you put it in?

How about a 1/2 empty bottle that is sitting in your shop. Is it no good after 2 years?

I do not use open bottles of brake fluid, if the vehicle I'm working on needs brake fluid they can buy a sealed bottle for 10$. To my knowledge most brake systems are not sealed, they are usually vented at the reservoir cap otherwise the fluid level would not drop if you cannot let air into the system.. Which is where the moisture enters the system. They make brake fluid testers that measure water content of the fluid, 3% water and the system requires fluid replacement. I change my brake fluid when my fluid tester says my fluid fails. the people that don't change their brake fluid usually regret it when they blow a brake line and they are forced to replace a working caliper just because the bleeder snapped or stripped.

daveto wrote:
I do not use open bottles of brake fluid, if the vehicle I'm working on needs brake fluid they can buy a sealed bottle for 10$. To my knowledge most brake systems are not sealed, they are usually vented at the reservoir cap otherwise the fluid level would not drop if you cannot let air into the system.. Which is where the moisture enters the system. They make brake fluid testers that measure water content of the fluid, 3% water and the system requires fluid replacement. I change my brake fluid when my fluid tester says my fluid fails. the people that don't change their brake fluid usually regret it when they blow a brake line and they are forced to replace a working caliper just because the bleeder snapped or stripped.

What do you do with the brake fluid you don't use when topping off a master cylinder? Do you throw it away? or set it on the shelf to top off the next one? If you are that strict on the use of brake fluid why not save it for the next car or to top off a system and test it with your tester and use it if it is good according to the tester? I have never used a tester how often is a fluid change needed when checked with a tester? Is the interval the same in the rainy state of Washington or humid state of Florida as it is in Az or Southern CA?

Being in the automotive repair business for a whole career I never had anyone bring a car to me for a brake fluid change. I have used a power bleeder that replaced fluid when changing a component but that was a rare occurrence. At 60 years old and owning a bunch of vehicles I have never changed the brake fluid in any of them just to change the fluid. I'm not saying that you shouldn't if you feel the need to do so and it absolutely can't hurt anything as long as you use the proper fluid for the vehicle when changing. I'll just keep doing things the way I have for all theses years and will likely never have an issue just like in my first 60 years.

BTW any venting for the MC is going on above the rubber seal on the cap. The flex in the rubber seal movement does the rest. Moisture thru a cap vent never gets to the fluid.

Dave, every car / truck I have ever worked on used the same isolation method. A rubber (or synthetic) barrier between the fluid and the cover / vent. The majority have had an accordion fold to allow reduction of fluid in the reservoir while limiting air / moisture contact.

I'm with you on this one.

I will try to answer by starting from the top, when I am replacing brake fluid I usually take 2 bottles per vehicle, I flush 1 3/4 thru system by vacuum bleeding with the engine off. I keep the 1/4 bottle in case there is a leak once I start the engine and I have to pressure bleed and top off. Once the car is off my hoist I dump the unused 1/4 into the dirty oil bucket.

As far as the tester I believe they are newer technology (only had mine for about a year and never heard of them the day before I bought my tester). I normally replace dirty fluid long before it fails the moisture tester.

I would suspect if you are in a damper climate your fluid would get moisture inside quicker. I have only worked in Ontario Canada as a mechanic for 20 years so I cannot confirm my suspicions. Here the fluid reads 2-3% moisture after about 10 years sitting outside in the rain and snow, garaged vehicles the same age are still passing here with 1%or less.

If you live in a cold climate you can actually feel the moisture in the brake line causing a much stiffer pedal feel than normal. The moisture won't blow lines because the brake fluid won't actually freeze and the flex lines allow for slight expansion of the fluid in the lines. We have even had some vehicles with push button starter that the pedal pressure gets so high parked overnight that the customer cannot push the brake pedal far enough to start the engine.

I forgot about the boot under the cap on gm vehicles. I work on imports that just have a overflow channel in the plastic cap, no boot on our set up.

Did I miss anything?

fixed above post, not sure what I did wrong

daveto wrote:


As far as the tester I believe they are newer technology (only had mine for about a year and never heard of them the day before I bought my tester). I normally replace dirty fluid long before it fails the moisture tester.



I have only worked in Ontario Canada as a mechanic for 20 years so I cannot confirm my suspicions. Here the fluid reads 2-3% moisture after about 10 years sitting outside in the rain and snow, garaged vehicles the same age are still passing here with 1%or less.


This is exactly my point about 2 year change intervals. 2-3% after 10 years according to a fluid moisture meter.

Changing fluid due to being dirty (as you referenced above) is closer to my way of doing things not because of moisture concerns.