Do I really need a brake fluid change 2nd service?

[jthspace]

12 hours ago, Maurice Mynah said:

Pedant alert - it's hygroscopic.

I do err on the side of safety and change it myself 2-2.5 years.

Hence the "?" in my post 😂🤣

[Gren]

Given that the fluid is hygroscopic, how does the moisture get in there?  Surely the moisture in the air at the top of the reservoir is miniscule, and as the system is sealed how could any more get in?

[Yaris_Cross]

8 hours ago, Gren said:

Given that the fluid is hygroscopic, how does the moisture get in there?  Surely the moisture in the air at the top of the reservoir is miniscule, and as the system is sealed how could any more get in?

When we were in our teens we all ran cars on a shoestring the only time we changed brake fluid was when we had a leak due to a seal going (usually rear brake cylinders) i can honestly say i  never noticed any difference after it was changed, changing it every two years is a con i don't care what they tell us. 

[ronnyb]

As well as a Yaris cross I’ve a 21 year old mk4 golf I’ve had virtually from new. It’s never had the brake fluid changed and will still stop on a sixpence.

[Mojo1010]

Never changed it in all the cars I've had, no issue. Next service is major on current car so it's included otherwise would not bother.

[anchorman]

Most modern cars have a two year brake fluid cycle but thats dictated by the brake system manufacturer, not necessarily the car manufacturer.   What should it cost?  Well I only use DOT3.  DOT4 is 100% compatible and has a higher boiling point but as discussed elsewhere, boiling fluid is virtually impossible these days for normal use cars.  I use DOT3 because it is quite oily by comparison and kinder to rubber components (according to a manufacturer I was once associated with).  I pay less than £10 a litre for either so a dealer buying a case of it won’t pay much above a fiver.  What troubles me a bit is the amount they use.  I once bought a full service kit at a dealer at a customers request and they appeared with 500ml.  It’s interesting but I’ve never been able to find the capacity of a brake fluid system in any documentation but I have extracted the best part of 500ml out of numerous reservoirs so if you then add an ABS pump, several valves and cylinders, a raft of pipes and a bit for purging, I am fairly certain 500ml won’t cut it.  The comment “well that’s all we ever use” didn’t exactly give me a nice warm feeling so I’ll be changing my own when it’s due.  They use the ABS pump to purge the rears on modern hybrids so a half decent mechanic might take half an hour on a lift and his “500ml” of fluid….  I don’t think £50-70 and the dreaded VAT should be a surprise.  

[anchorman]

17 hours ago, Gren said:

Given that the fluid is hygroscopic, how does the moisture get in there?  Surely the moisture in the air at the top of the reservoir is miniscule, and as the system is sealed how could any more get in?

The system has to breath Ken or it would cause a vacuum in use.  It definitely does absorb moisture and in high humidity by quite a lot over time.   For those bragging about not changing it with no problems, it depends how long you keep it.  There will come a point where there is enough moisture and wear debris in it to cause a problem but that’s the point, you won’t know when that is but if it does gubber up an ABS pump it’s going to make you eat your words and if it causes a fault and you or someone else gets hurt there are further implications.  If we said £70 (£84 inc VAT) over 2 years or even 3 is probably ok, I spend that on toffee crisps and some folk spend considerably more on !Removed! and vapes and tats and and and.  I’ll be doing mine at 2 years.  If you ignore brake fluid, why not ignore engine oil.  You won’t know that’s ruined the engine until it’s too late.  

[anchorman]

4 minutes ago, anchorman said:

The system has to breath Ken or it would cause a vacuum in use.  It definitely does absorb moisture and in high humidity by quite a lot over time.   For those bragging about not changing it with no problems, it depends how long you keep it.  There will come a point where there is enough moisture and wear debris in it to cause a problem but that’s the point, you won’t know when that is but if it does gubber up an ABS pump it’s going to make you eat your words and if it causes a fault and you or someone else gets hurt there are further implications.  If we said £70 (£84 inc VAT) over 2 years or even 3 is probably ok, I spend that on toffee crisps and some folk spend considerably more on !Removed! and vapes and tats and and and.  I’ll be doing mine at 2 years.  If you ignore brake fluid, why not ignore engine oil.  You won’t know that’s ruined the engine until it’s too late.  

The snowflake filter has removed the totally inoffensive slang word for cigarettes.  I presume it doesn’t like savoury ducks either 🙄

[anchorman]

On 10/17/2024 at 12:57 PM, Mjolinor said:

That is probably why it has not happened since I stopped messing with old Minis. before disc brakes were common. 🙂

 

Some disc brakes could cause problems with boiling but that’s the point was when they had solid discs and the fluid crossed the bridge to an out piston or pistons.  The pistons were also full of fluid but these days there are one or two pistons inboard of the brake and the outer pad is applied by the reactionary force of the piston/s via slide pins.  There is no fluid crossing the cooler ventilated disc.  Furthermore, the pistons are inverted and fluid acts on the back of them - a good 50mm from the inner pad.  If you boil the fluid back there you’ve got big problems at the pad/disc interface.  It’s not impossible on a race track but very very unlikely on a road car.  

[Madasafish]

I use DOT 4  antifreeze.

Our Mark 1 Yaris had a complete fluid change when ten years old.

Have not bothered since - it is now 21 years old. Still runs OK an fluid looks OK

  (I did inspect and change one rusty hose clamp)