Jump to content


Do you replace the brake fluid in your car?

Recommended Posts

I've never replaced mine. Though during work on the brakes or lines i've replaced quite a bit by bleeding them on occasions.

 

Sounds daft to me, though none of my cars have ever needed high performance breaks. :hihi: So maybe it is necessary in some cases ?

 

Glad i've totally cleared that up for you. :D

 

Brake fluid is hygroscopic. When exposed to the air it will absorb water. So after a while brake fluid will build up a level of water content.

 

I've competed in motor sports and you quickly learn to replace brake fluid regularly. Under heavy braking huge amounts of heat are transfered through the calipers to the fluid. At 100 C the water boils and forms steam pockets. The next time you hit the pedal it goes straight to the floor. Not good.

 

I've known folk actually boil up old fluid and drive off the moisture. I'm told it works, but as a half litre of fluid is far cheaper than a new front panel it's not something I'm about to try.

 

By the way. If you leave your brake fluid in an open bottle that you used for bleeding it will absorb a lot of moisture. So keep fluid in sealed cans or bottles.

Edited by SHYTOT

Share this post


Link to post
Share on other sites
No never! Top-up Yes!

 

Why top up ? Does it leak ? I always thought the fluid goes down as the brakes wear then when new ones are fitted it pushes the fluid back up to the level.

Share this post


Link to post
Share on other sites
My VW has it as a service requirement at the 3rd service and every 2 years after that.

 

The explanation is that the operating temperature of the brakes is anything up to 230C and gradually over time minute amounts of water/steam are absorbed into the brake fluid from around the brakes, and this gradually reduces the maximum temperature at which the brakes can function fully. Once that maximum temperature drops down below the temperature at which your brakes are functioning on a busy run, things can go very badly pear shaped without warning (I'm paraphrasing the mechanic I spoke to).

 

So it's basically precautionary, but worth doing every couple of years if it prevents only a very few brake failures.

 

That's about right. The boiling point of water is 100C.

Share this post


Link to post
Share on other sites
My VW has it as a service requirement at the 3rd service and every 2 years after that.

 

The explanation is that the operating temperature of the brakes is anything up to 230C and gradually over time minute amounts of water/steam are absorbed into the brake fluid from around the brakes, and this gradually reduces the maximum temperature at which the brakes can function fully. Once that maximum temperature drops down below the temperature at which your brakes are functioning on a busy run, things can go very badly pear shaped without warning (I'm paraphrasing the mechanic I spoke to).

 

So it's basically precautionary, but worth doing every couple of years if it prevents only a very few brake failures.

 

I agree, this is true.

 

If you don't change the fluid, the brakes will work perfectly and stop you on a sixpence etc. etc. Then one day, when you have been using them a lot in the summer, or going down a long hill, they will get hot and fail completely.

 

This happened to me last year going down East Bank Road. The pedal went right to the floor !!!

The weird thing is, once they cool down they work perfectly again.

 

Post 13 (SHYTOT) is spot on.

Edited by andrejuan

Share this post


Link to post
Share on other sites
It's amazing how some people risk their lives just to save a few£££

 

Welcome to Sheffield :)

Share this post


Link to post
Share on other sites
I've never replaced mine. Though during work on the brakes or lines i've replaced quite a bit by bleeding them on occasions.

 

 

I doesnt cost much more, just to keep pumping and topping up, then it is replaced.

Share this post


Link to post
Share on other sites

Cheers everyone, good to get some consistent advice :hihi:

 

My concern is you pay the garage, they reset the service interval and tell you they replaced the fluid.

Share this post


Link to post
Share on other sites

Yes, brake fluid should be changed to manufacture's recommended intervals for the reasons that have been pointed out already and because it does tend to get dirty and contaminated.

 

My advise to anyone who does suffer brake failure due to boiling brake fluid is to not panic and just pump the brake pedal back and forth as fast as possible to try and regain the use of the brakes. This compresses the air in the system helping to regain the hydraulic force, while its under pressure this also raises the actual boiling point in a similar manner to the cooling system.

Share this post


Link to post
Share on other sites

Never ever changed the brake fluid in any car I have owned, and at the age of 64 I have had plenty.

 

So saying if your car manufacturer has gone to the lengths of giving you a warning light on the dashboard telling the driver that brake fluid requires replacing, it might be prudent to have it changed.

 

Angel1

Share this post


Link to post
Share on other sites

As most above have said you do need to change it.

 

The reason is that brake fluid is hygroscopic and absorbs water from the air. The fluid colour changes from light pale yellow to a deep straw, almost brown colour.

 

Just a small amount of water in the fluid lowers the boiling point and once you get to the boiling point you get steam bubbles in the caliper. This results in a massivly reduced braking effort. You may never encounter this, but as soon as you do you've got almost no chance of stopping.

 

If you are worried about the garage not swapping it, look at the fluid colour before taking the car in and check it gets a lot lighter after the service.

 

As for topping up - you should never do this. The fluid level will fall from the FULL to EMPTY line as you wear down the pads - as the level approaches EMPTY the pads are almost worn out. Once new pads are fitted the level goes up to FULL. If you top up - the reservoir overflows when new pads are fitted.

Edited by Obelix

Share this post


Link to post
Share on other sites

As has been said by others brake fluid absorbs water and should be changed before excess water content in the fluid causes brake failure. However the two year service interval recommended by nearly all manufacturers is for most people is a bit over the top. I bought a brake fluid tester which gives an indication of moisture level in brake fluid and tells you when the fluid actually needs changing, my wife's car is five years old and the tester still shows minimal moisture content. My car on the other hand showed excessive moisture levels, I am currently overhauling the brakes and have already spent £400 on replacement parts.

Share this post


Link to post
Share on other sites

Had mine changed on my last service, part of the lifetime warrany agreement apparently.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.