Changing brake fluid

[Vyse]

When changing brake fluid would it be ok to flush all the old fluid out with some new but cheap brake fluid? Then when all the crap is removed draw out the new cheap fluid and replace with brand new good quality stuff.

Whats a good way of figuring out when the new good quality fluid as completely replaced the cheap stuff?

Thanks

[andyiley]

In reply to your first question no. If nothing else, for the same reason that you ask your second question.

Ideally you need to fully drain the old fluid and then fill with fresh fluid, and then bleed the full system as normal.

with completely clear hose on your bleed nipple, you should be able to tell when the old stuff is out.

You will rarely need more than 1 full litre of fluid so there is VERY little to be gained by using half of it as cheap cr@p.

[Steve_D]

Do you have an airline?
If so get one of these.
http://www.ebay.co.uk/itm/Car-Van-Air-Automatic-Br...

It will suck out all the old fluid leaving you with a completly empty system ready for refill.
Fill with new and use the kit again to pull the new fluid through.

Steve

[ViperDave]

Why would you empty the system? vac out the reservoir yes, but the whole system? just bleed through enough to be sure you have fresh everywhere, as has been said a liter should be plenty, even decent stuff is cheap, but if you want to do it properly look up in the service manual and it should/may tell you how much to bleed out of each caliper for a complete refresh. Alternatively get one of the alternate colour fluids.

[BritishRacinGrin]

ViperDave said:

Why would you empty the system? vac out the reservoir yes, but the whole system? just bleed through enough to be sure you have fresh everywhere, as has been said a liter should be plenty, even decent stuff is cheap, but if you want to do it properly look up in the service manual and it should/may tell you how much to bleed out of each caliper for a complete refresh. Alternatively get one of the alternate colour fluids.

This. Why would you want to completely fill the system with air first? Suck the fluid from the reservoir, clean the reservoir up and refill with fresh fluid. Bleed fluid from the calipers until the fresh stuff is drawn through. Top up reservoir and done. Don't forget to do the clutch fluid too.

[ViperDave]

And another thought, if you get air into the ABS module, some of them require the manufactures scan tool to activate and run through the purge program to properly bleed the ABS module.

[Sardonicus]

ViperDave said:

Why would you empty the system? vac out the reservoir yes, but the whole system? just bleed through enough to be sure you have fresh everywhere, as has been said a liter should be plenty, even decent stuff is cheap, but if you want to do it properly look up in the service manual and it should/may tell you how much to bleed out of each caliper for a complete refresh. Alternatively get one of the alternate colour fluids.

This no need whatsoever to empty the system thus possibly causing bleeding issues from a DIY point of view syringe or vac out the reservoir including any black silt fill with fresh fluid then bleed till it runs nice and clear repeating the 4 wheel pattern, i generally find the clutch fluid in awful condition when done at the same time because many garages dont change it

Edited by Sardonicus on Wednesday 5th November 09:12

[stevieturbo]

Sardonicus said:

his no need whatsoever to empty the system thus possibly causing bleeding issues from a DIY point of view syringe or vac out the reservoir including any black silt fill with fresh fluid then bleed till it runs nice and clear repeating the 4 wheel pattern, i generally find the clutch fluid in awful condition when done at the same time because many garages dont change it

Edited by Sardonicus on Wednesday 5th November 09:12

Exactly, it's a simple process.

Empty reservoir. Fill with new fluid.

Bleed all 4 corners as normal until clean fluid comes out, topping up reservoir throughout as required.

Job done.