Changing brake fluid

maidhc

I bought a Mintex brake box from ebay for my focus.

How does one change the brake fluid, any hints or tips?

(I am completely confident about messing with the brakes in my car btw, but never actually changed brake fluid!)

peasant

If you have to ask, you shouldn't be doing it

crosstownk

Relieve an equal amount of fluid from each nipple - maybe a slight bit more from the rear due to the extra length in the lines.

mickdw

Open bleed nipple, ensure reservoir is continually topped up and gently and smoothly pump pedal. Its best to just push the pedal through the distance it usually travels instead of pushing it to the floor each time. Possible damage to master cylinder seals (on old cars at least) due to slight corrosion of the master cylinder unswept area.
Then when a fair amount of fluid is collected at that wheel, push down pedal and hold down while mate tightens nipple.

Repeat at all wheels typically starting a wheel furthest from the reservoir etc.

This is a safe method for use with all type of brake systems. If you have abs, there may be a small amount of fluid trapped in abs pump but at leat this way you are not introducing any air or additional pressure into the system so you cannot cause any problems

Plug

maidhc wrote: »

I bought a Mintex brake box from ebay for my focus.

How does one change the brake fluid, any hints or tips?

(I am completely confident about messing with the brakes in my car btw, but never actually changed brake fluid!)

You don''t need to change your brake fluid just cos your doing pads. is it due a fluid change?

milltown

mickdw wrote: »

Open bleed nipple, ensure reservoir is continually topped up and gently and smoothly pump pedal.

Pumping the pedal with the bleed nipple open is not a good idea.

mickdw wrote:

...at least this way you are not introducing any air or additional pressure into the system so you cannot cause any problems

Yes you are and can.

Peasant is right OP. Without experience, it'd be much, much safer for all road users if you got this done by a mechanic. Brake system hydraulics are not rocket science but confusing posts like mickdw's are the reason enthusiastic amateurs shouldn't tackle the safety systems on their cars, armed only with what they read on a forum.

No offence intended mick, maybe you just explained what you meant badly.

BTW, what's a brake box and why does it require a fluid change?

Plug

milltown wrote: »

Pumping the pedal with the bleed nipple open is not a good idea.

2 people for that job, a pumper and someone at the brake. It has to be pumped down to the ground about 4 times then the lad at the brake shouts 'hold' and the pumper has to hold the pedal fully down to the ground then the lad at the brake opens the bleed nipple. Its important to start at the furthest point from the brake fluid resoivor and work your way up to it.

maidhc

Plug wrote: »

You don''t need to change your brake fluid just cos your doing pads. is it due a fluid change?

I think 6 years and 100k miles is time.

To those who are of the "if you have to ask you shouldn't do it" persuasion I disagree. I have more or less all the equipment of a garage and I have bled brakes and replaced brake lines before. I am just looking for a few pointers, hints and tricks.

The "brake box" is just a set of pads and discs. My car needs both, I know a fluid change is not required, but there is no harm in it at this stage.

mickdw

milltown wrote: »

Pumping the pedal with the bleed nipple open is not a good idea.



Yes you are and can.

Peasant is right OP. Without experience, it'd be much, much safer for all road users if you got this done by a mechanic. Brake system hydraulics are not rocket science but confusing posts like mickdw's are the reason enthusiastic amateurs shouldn't tackle the safety systems on their cars, armed only with what they read on a forum.

No offence intended mick, maybe you just explained what you meant badly.

BTW, what's a brake box and why does it require a fluid change?

Well,you are not introducing any additional pressure into the system and this is undoubtably the best way for a DIYer to do this job instead of using pressure systems and possibly doing untold damage.

I do it myself with a one man bleed system (tube with one way valve)
I cannot see a problem with this. How do you maintain that this is introducing additional pressure/damaging the system?

cuculainn

milltown wrote: »

Pumping the pedal with the bleed nipple open is not a good idea.


quote]

I have done a partial change of my brake fluid in this way in the past. I think the way it was explained was not very clear.

You need two people for this. one in the car and the other at the cylinder

1. pump brake pedal a few times.

2. Hold on the last pump.

3. person at the cylinder (with a flexible tube attached to the nipple and the tube into some sort of container.) opens the nipple and lets fluid drain out. The pressure on the pedal will reduce and the drivers foot will go to the floor ( or less if you want to be sure you dont damage cylinder due to rust as a previous poster said).

It is important that you close the nipple while the pedal is pressed. this stops air getting into the system when the pedal is released.

4. continue this until you have new fluid coming through.(make sure the reservoir is topped up)

5. repeat on the other 3 wheels. ( this should not take as long as the first as the reservoir will not be full of old fluid)

rebel.ranter

A few tips:

1. If you can get a different colour brake fluid (yes there are colours available) it will let you see that all the old fluid has been drained out.

2. Follow Cuchulainn's process but...Put a piece of wood underneath the pedal so that you don't let the pedal hit the floor.

3. I use a "One Man Brake Bleed Kit" even though there are two of us doing the job. If you do not have one use a clear flexible tube with a jam jar or similar, put some new fluid into the jam jar in case of mistakes tightening up the bleed nipple.

4. Don't over tighten the bleed nipples!

5. If you can afford the luxury do not bleed the brakes at the same time as changing the pads & discs. Allow the pads & discs to "bed in" first.

milltown

mickdw wrote: »

Well,you are not introducing any additional pressure into the system and this is undoubtably the best way for a DIYer to do this job instead of using pressure systems and possibly doing untold damage.

I do it myself with a one man bleed system (tube with one way valve)
I cannot see a problem with this. How do you maintain that this is introducing additional pressure/damaging the system?

There's no danger of damaging the system or excess pressure. The risk comes from your advice to open the bleed nipple and pump the pedal. As others have said, the nipple has to be closed again each time the pedal is allowed back up to prevent air getting in. You made no mention of bleed kits in your post mick.

Ideally it's a two man job IMO. The bleed kits can be a bit hit and miss. OP, if you want tips and intend going solo with a bleed kit, make sure the end of the tube is immersed in a small container of brake fluid so if it does try to draw anything back up, it'll be sucking fluid, not air.

Darragh29

There's a procedure to this OP and you'd need to understand what is going on inside, to confidently be able to do this task...

Also, you'll need someone else to be working with you to operate the brake pedal while you are opening and closing caliper or wheel cylinder bleed nippes, whichever is appropriate. Also, a common mistake is to forget to top up the master cylinder with new fluid as the level is dropping and getting air bubbles into the brake lines on this basis...

mickdw

milltown wrote: »

There's no danger of damaging the system or excess pressure. The risk comes from your advice to open the bleed nipple and pump the pedal. As others have said, the nipple has to be closed again each time the pedal is allowed back up to prevent air getting in. You made no mention of bleed kits in your post mick.

Ideally it's a two man job IMO. The bleed kits can be a bit hit and miss. OP, if you want tips and intend going solo with a bleed kit, make sure the end of the tube is immersed in a small container of brake fluid so if it does try to draw anything back up, it'll be sucking fluid, not air.

You are right,I didnt say about attaching pipe to nipple in first post. I didnt go into enough detail. i.e. close off nipple for pedal return or use bleed tube/kit.

maidhc

Thanks for all the replies.

It all makes perfect sense.

Rowley Birkin QC

Hijacking slightly maidhc, hope you don't mind!

I do most car maintenance myself but brakes are one area I'm not willing to go at. I'm giving my car to a local mechanic tomorrow for pads to be replaced. Would the fluid be replaced as a mater of course or should I ask him to do it specifically??

I would imagine it has never been changed, certainly not in the previous 50k miles.

Plug

Fluid is nothing to do with milage but every 2 years.