6 replies to this topic

[Krusty]

Realistically how often should I be changing my brake fluid?
I change it Spring time every year, car is track use only, brakes have been great until last Saturday at oulton where towards the afternoon the pedal went a bit soft, after a few slow laps with little braking it went back to normal. I possibly had got a bit carried away and had done maybe 15 or so laps and there seems to be a lot of braking at oulton. Also I think I've done about 10 trackdays so far this year, what are your thoughts?

[swast4]

I used to leave my fluid, the proper race stuff and didn't change it for about 6 track days but my brakes faded at Oulton also. I managed to change fluid in 3 out of 4 calipers whilst there but couldn't risk striping other nipple while that hot.

After that I have down graded my fluid to AFR blue (or used to be blue) and changed out more frequently, say every other track day. It's really easy to do with a pressure bleeder.

I use a very big syringe with a small hose on the end and remove all the old fluid from reservoir first then top up with new and bleed from each caliper.

I always am unsure if removing the reservoir fluid is necessary as it is the calipers that see all the heat but for the sake of a few quid I think it is better but am interested in anyone else's view?

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Edited by swast4, 21 August 2019 - 06:37 PM.

[blackoctagon]

As a road-only user I find that the oft-recommended 2yr period has never left me wanting.

I suck out the reservoir as best as I can then bleed though.
I use the blue for one change, then something else for the next (Shell Donax is a nice watery yellow colour), then back to blue so I can ensure it's all out.

Sadly, as noted above, any more Blue will be new old stock, so the jig may be up on that one.

Edited by blackoctagon, 21 August 2019 - 08:43 PM.

[RC220]

While this subject is live what brake fluid is recommended for standard n/a brake system...and pads for that matter?  Fast road use with v occasional track days.

Regards,

Roy

[Arno]

I change it Spring time every year, car is track use only

For a track car I'd say get a pressure bleeder and do a quick flush every 3 months or so or every few trackday outings as part of the spanner-check before tracking it.
 
Eg: https://www.sealey.c...bleeding-system
 



Makes it really quick and simple and makes sure you always have good fluid in there.

Regular flush also means you can run pretty standard (cheap!) DOT4 or 5.1 fluid as it will always be pretty 'fresh' and not exposed to water for long and the dry boiling point of all is high enough. No need to run very expensive 'race' fluids in that case, which BTW can be extra hygroscopic to start with and degrade to their 'wet' point and below faster than standard brake fluids.

 

Now if someone could find out how to trigger the ABS 'flush' mode with an OBD tool/OpCom then you'd not even need the bleeder.. Just a big storage reservoir/container connected to the master cylinder, open the bleeders on the calipers to let it pump the fluid through by

itself.

 

 

 

Bye, Arno.

[chris_uk]

easiest way to see if its needs changing is with a brake fluid tester. 

 

 

they measure the moisture levels of the fluid.. 

 

i have left brake fluid in for a couple years, and its been fine, and once on a trackday it boiled. so now i always test it as a pre-trackday test. 

 

[Arno]

Problem is that the brake system doesn't really circulate, so the moisture content of the reservoir doesn't say much about the content on the caliper end where the heat happens and the exposure to water is the biggest.

 

You'd really need to open a bleeder and catch some fluid in a container and then use such a tester.

 

Or just take 10 minutes extra and chuck 1L of fluid through it with a powerbleeder and be done with it 

 

Bye, Arno.