break fluid change how often?

[Jonnycoupe]

Okay so how does it decide it's cooked at precisely 3 years?

Trend of typical ambient conditions found on planet earth.

That reminds me i need to get my haircut this week as its been 3 weeks and overnight it will instantly gain 2 inches. Unless someone is about to tell me hair is constantly growing?

 

[theone8181]

Permeation through hoses, seals and directly through the reservoir cap typically.

See that makes sense. As an engineer myself I was thinking its got to be reasonably well sealed otherwise youd loose the pressure. I guess the cap isn't a fantastic seal, I'd be surprised at much coming through seals, although not sure what material as I'm sure brake fluid is quite corrosive. I assume it's a case of when it's new boiling point is 190 degrees (quick google), and overtime that slowly reduces and depending on how hard/often someone brakes dictates how hot the fluid gets. My thinking with this is old Doris who hardly brakes would never notice, but young Johnny in his saxo vts will notice it as the pedal is digital in his case .

 

[jaybee]

But fluid requiring replacement is not going to one day like a switch completely fail where you lose brakes. It will typically be a gradual fading and loss of performance, even if you thrash it round a track and boil them to complete fade. Complete loss of braking where fluid spills out, is more going to be something else that has perished like a seal/nipple/line. That's not as a direct result of old fluid generally.

 

[tom_e]

But fluid requiring replacement is not going to one day like a switch completely fail where you lose brakes. It will typically be a gradual fading and loss of performance, even if you thrash it round a track and boil them to complete fade. Complete loss of braking where fluid spills out, is more going to be something else that has perished like a seal/nipple/line. That's not as a direct result of old fluid generally.

Right, but the general car driving public are generally completely oblivious so asking them to get it replaced when they notice a reduction in braking performance would mean most wouldn't replace it until there is no braking performance.

 

[Doobedoo]

It should be tested for during an MOT in my opinion.

 

[jaybee]

It should be tested for during an MOT in my opinion.

Braking performance is tested during an MOT. Testing the chemical breakdown of brake fluid could become a complete swindle and money maker for the MOT stations, plus what equipment would be used to test it? Cost to keep those machines calibrated etc. If the car passes brake performance checks it is deemed road worthy. Whether your fluid is 10 years old or 1 is immaterial.

 

[jaybee]

Right, but the general car driving public are generally completely oblivious so asking them to get it replaced when they notice a reduction in braking performance would mean most wouldn't replace it until there is no braking performance.

That just doesn't happen though. You don't go to a garage with a problem with "no braking performance" and it be the fluid. It would be very rare to be that. Possible air in the lines through some other problem maybe. Pads worn yeah. Calipers warped or sticky piston yeah. Fluid that just got too old..... not really.

 

[JonRGV250]

what equipment would be used to test it?

https://www.amazon.co.uk/Universal-Portable-Precision-Automotive-Diagnostic/dp/B07H5HXNLS/ref=asc_df_B07H5HXNLS/?tag=googshopuk-21&linkCode=df0&hvadid=310744208542&hvpos=&hvnetw=g&hvrand=2394889852419563003&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9045064&hvtargid=pla-562961187008&psc=1

That’s exactly what I used when I was a AA inspector.
Even some of the filthy old brake fluid I tested would still pass.
I don’t agree it should be part of the MOT test.

 

[Doobedoo]

Braking performance is tested during an MOT. Testing the chemical breakdown of brake fluid could become a complete swindle and money maker for the MOT stations, plus what equipment would be used to test it? Cost to keep those machines calibrated etc. If the car passes brake performance checks it is deemed road worthy. Whether your fluid is 10 years old or 1 is immaterial.

Braking performance is tested on a brake tester or even just a tapley meter, the duration of the test is seconds which is not long enough for brake fluid to be a factor unless it’s severely poor.

 

[JonRGV250]

Bear in mind that we can fail brake fluid on a MOT if we can “clearly see the fluid is contaminated”.
Which isn’t particularly easy as we’re not allowed to remove the reservoir cap.

 

[nlel1975]

Just had a thing in the post regarding my three year service plan, they renew the brake fluid during the B service but check it during A and C services.