Brake fluid
Author
Discussion

leigh1050

Original Poster:

2,431 posts

183 months

Thursday 2nd October
quotequote all
Is there a recommended interval for changing brake fluid,and is it a difficult job to do at home?
Reason I ask is the fluid in mine was changed about 13 years ago when I had braided lines fitted and the brake pedal is feeling a bit spongey now.

itcaptainslow

4,240 posts

154 months

Thursday 2nd October
quotequote all
Most manufacturers recommend every two years. 13 years is definitely pushing it…

Freakuk

4,133 posts

169 months

Thursday 2nd October
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What usage, just road or track?

Do you know what is in there now, i.e. Dot4, Dot5.

I've never done this on a car, but I've done it on plenty of bikes, you need plenty of fluid and never let the M/C get low and draw air into the lines. The routing of the lines can also cause issues if the lines rise then you may get air bubbles high up.

You can do one of a few ways, buy a vacuum pump attach to the calliper and it will draw new fluid through from the MC when you open the bleed nipple. I've had mixed success with this, you can do this yourself though.

My preferred way requires 2 people, one to depress the brake pedal and one to open/close the bleed nipple.

You need to repeat the process on each calliper and keep topping the M/C up throughout to flush out the old fluid and the new fluid will get into the callipers/pistons.

dhutch

17,170 posts

215 months

Thursday 2nd October
quotequote all
I am sure 5 years would be fine for almost all situations.

But if I was fitting new braided lines and didnt know when it had been last flushed, I would be flushing it at the time.

Not worked on a car made in the last 25 years, but certainly on a conventional car its an hour or so work to change the brake fluid.
I do mine using an 'Ezibleed' kit which pressurises the header tank using a car tyre, open the bleed nipple on each calliper, job jobbed.

If you really want, do it once, drive it for a week, and do it again.

See also sucking out the particulate matter at the bottom of the header tank!

LennyM1984

924 posts

86 months

Thursday 2nd October
quotequote all
itcaptainslow said:
Most manufacturers recommend every two years. 13 years is definitely pushing it
On my race car and fun car, I change the fluid regularly but last year I changed the fluid on my daily and at 9 years old and ~65k miles, it was still reading less than 1% moisture (I tested the fluid which came out rather than the fluid that was in the reservoir). As such, I'm not totally convinced that the 2 year recommendation is really relevant these days.

Race type fluid (RBF660, Gulf Racing etc) does start to look manky quite quickly but I suspect that is more to do with the usage than the chemical composition.

To the OP, yes, changing it is very easy (worth buying a pressure bleeder or a one way valve if you are doing it alone) but after 13 years, be careful with the bleed nipples.

paul_c123

1,265 posts

11 months

Thursday 2nd October
quotequote all
Manufacturers recommend a relatively short interval, out of caution.

Most indy garages and car dealers seem to ignore brake fluid unless there's actually an issue with the brakes.

I believe the correct answer is somewhere in between - to test and renew on condition. It is easy to measure the condition (basically, the water content) using a cheap/small probe into the brake fluid reservoir.

dhutch

17,170 posts

215 months

Thursday 2nd October
quotequote all
paul_c123 said:
Manufacturers recommend a relatively short interval, out of caution.

Most indy garages and car dealers seem to ignore brake fluid unless there's actually an issue with the brakes.

I believe the correct answer is somewhere in between - to test and renew on condition. It is easy to measure the condition (basically, the water content) using a cheap/small probe into the brake fluid reservoir.
Indeed.

Add to this the fact that in almost all circumstances it's pretty unlikely you are going to boil the fluid in a modern car driven on the road even if it was exclusively water. At which point the reason to change is to avoid corrosion of internal components rather than anything else.

I expect the OPs sponginess is due to trapped air, rather than absorbed moisture in the fluid.

leigh1050

Original Poster:

2,431 posts

183 months

Thursday 2nd October
quotequote all
Thanks for the replies. I don't think it's trapped air as it was fine for ages, I had to do a bit o f very hard braking last week and the pedal felt spongey!
Is there an order to doing the brakes as I'll be doing on my drive using a jack.

Edited by leigh1050 on Thursday 2nd October 13:05

dhutch

17,170 posts

215 months

Thursday 2nd October
quotequote all
leigh1050 said:
Thanks for the replies. I don't think it's trapped air as it was fine for ages, I had to do a bit o f very hard braking last week and the pedal felt spongey! Is there an order to doing the brakes as I'll be doing on my drive using a jack.]
I use a pair of axle stands, or even some timber blocks, so you can get at least two wheels off the ground at time.

Again, not done a car with ABS, but typically I would do one axle at a time, either way round.

paul_c123

1,265 posts

11 months

Thursday 2nd October
quotequote all
leigh1050 said:
Thanks for the replies. I don't think it's trapped air as it was fine for ages, I had to do a bit o f very hard braking last week and the pedal felt spongey!
Is there an order to doing the brakes as I'll be doing on my drive using a jack.

Edited by leigh1050 on Thursday 2nd October 13:05
Furthest wheel (from the brake fluid reservoir) first, then next nearest etc. So, first two will be rear wheels.

leigh1050

Original Poster:

2,431 posts

183 months

Thursday 2nd October
quotequote all
Thanks, I'll get an eezibleed and get it done.

E-bmw

11,452 posts

170 months

Thursday 2nd October
quotequote all
Just for clarity DO NOT UNDER ANY CIRCUMSTANCES LET THE FLUID RESERVOIR GET EMPTIED.

If you do you WILL have a bugger of a job bleeding the ABS system.

I like to start with 2 litres of fluid which is way too much, but "better be looking at it than for it" is a good one to remember.

the-norseman

14,670 posts

189 months

Thursday 2nd October
quotequote all
I've got one of them testing devices, our Volvo which hasn't been changed for about 5+ years is starting to show amber (green,amber,red scale). Alfa was green and I dont think its been changed since 2017.

itcaptainslow

4,240 posts

154 months

Thursday 2nd October
quotequote all
paul_c123 said:
leigh1050 said:
Thanks for the replies. I don't think it's trapped air as it was fine for ages, I had to do a bit o f very hard braking last week and the pedal felt spongey!
Is there an order to doing the brakes as I'll be doing on my drive using a jack.

Edited by leigh1050 on Thursday 2nd October 13:05
Furthest wheel (from the brake fluid reservoir) first, then next nearest etc. So, first two will be rear wheels.
Not necessarily - some cars have a different order, it’s worth checking for the individual vehicle.

For example; the manufacturer of one of my modern classics prescribes RHR-LHF-LHR-RHF due to the split circuit and ABS block design.

brownspeed

985 posts

149 months

Thursday 2nd October
quotequote all
any tips to avoid shearing the bleed nipples off? apart from "take care"?

paul_c123

1,265 posts

11 months

Thursday 2nd October
quotequote all
brownspeed said:
any tips to avoid shearing the bleed nipples off? apart from "take care"?
https://www.youtube.com/watch?v=mWCiPBD7j2o&t=1766s

20:00 and on, there's good tips of brake bleeding.

leigh1050

Original Poster:

2,431 posts

183 months

Thursday 2nd October
quotequote all
brownspeed said:
any tips to avoid shearing the bleed nipples off? apart from "take care"?
I'll be getting some decent penetrating fluid, not sure about heating them up probably burn th paint off the calipers and not sure if brake fluid is flammable!

E-bmw

11,452 posts

170 months

Friday 3rd October
quotequote all
leigh1050 said:
brownspeed said:
any tips to avoid shearing the bleed nipples off? apart from "take care"?
I'll be getting some decent penetrating fluid, not sure about heating them up probably burn th paint off the calipers and not sure if brake fluid is flammable!
You won't burn the paint off the callipers if you just heat the nipples.

Yes, obviously brake fluid is flammable but it is contained in the hydraulic system and it would need oxygen (that it doesn't have in there with it) to complete the "fire triangle" and actually combust.

Just remember you are just heating the nipple up enough to expand microscopically to "break" the hold of any corrosion that may be there, not to melt anything.

chris1roll

1,826 posts

262 months

Friday 3rd October
quotequote all
brownspeed said:
any tips to avoid shearing the bleed nipples off? apart from "take care"?
Make up a 50/50 mix of acetone and ATF. It will need a good shake before use as it likes to separate a bit.

Wire brush your nipples, the apply your Aceton/ATF mix. Soak some pieces of paper towel in it and make a papier mache mould with it around the nipple and leave for a good while.

Come back, use a 6pt socket, and pray.

I've not failed yet since I started doing this.


Also - I'll just point out that you have no idea of the condition of the 13 year old lines under the pretty braiding...

Peanut Gallery

2,615 posts

128 months

Friday 3rd October
quotequote all
I flushed my 2015 car in about 2022 - so 7 or so years old with full Ford service history for the first 3 years. The fluid that came out was BLACK - took a fair amount of fluid to try get it running more brake fluid coloured. Yes, black is not a water content, but..

I went 2 person route, managed to get a good spray into my face as well and yes it did burn - I was trying to use a non return valve on the end of the hose - and the valve stuck closed.

Please check brake fluid level in master cylinder often - getting any air in the ABS block will be bad.