Most people will be suprised to find that the brake fluid needs changing.
Well it does. Brake fluid is hydroscopic – that means it absorbs water. As it absorbs water its boiling point falls. This means that is becomes easier to boil your brakes resulting in scary moments if driving hard or towing. Also if too much water is present to absorb then corrosion of brake components can happen.
How often you change it is up to you really. I never really go out of my way to change the brake fluid (with one exception I’ll come on to later), however when changing pads etc I’ll bleed a fair amount of fluid though topping up the reservoir so that I get clean fluid out, and that way I know the fluid has effectively been changed.
Clutch fluid – This is the exception to the rule above. As the fluid never gets bled out of this system it can get very contaminated. It is not unusual to find a jelly like deposit in the reservoir! What I do is suck the fluid out with a syringe etc, wipe the reservoir clean with some tissue, then fill back up with brake fluid and then bleed the clutch until the fluid runs clean. Note that bleeding the clutch can be a pain! Vacuum bleeding is the key here and if you are lucky I’ll show you how to make a DIY vacuum bleeding system for very little cost.
What fluid to use
Generally you will want dot 4 fluid. There are higher performance alternatives such as dot 5.1 etc however unless you have problems boiling your dot 4 fluid – which you won’t, then there is no point in using it. Infact dot 5.1 absorbs water faster than dot 4. There is also dot 5 fluid which is synthetic. This does not mix with dot 4 or 5.1 so is best avoided. It may also not be compatible with the seals in the standard cars so in my view it is a headache that is best avoided.