MiataMark
Club Retro Rides Member
Posts: 2,963
Club RR Member Number: 29
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brake fluid changeMiataMark
@garra
Club Retro Rides Member 29
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Thinking of replacing my brake fluid with Dot 4 or 5.1 fluid (and changing to braided hoses at the same time).
Stupid question, how do I ensure I flush out all the old fluid and replace with new? I've got an eezibleed.
Mark
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1990 Mazda MX-52012 BMW 118i (170bhp) - white appliance 2011 Land Rover Freelander 2 TD4 2003 Land Rover Discovery II TD52007 Alfa Romeo 159 Sportwagon JTDm
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Aug 13, 2012 10:03:33 GMT
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As the fluid is relatively cheap you can just keep pumping it through  Beware you may find your master cylinder may fail, reason is that the seals hit the ridge created due to short movement in normal use and the ridge damages the seals when you are pumping the pedal full strock  |
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MrSpeedy
East Midlands
www.vintagediesels.co.uk
Posts: 4,786 
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Aug 13, 2012 10:13:12 GMT
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One thing you need to be aware of, IIRC* DoT 5 fluid is silicone based and not compatable with the seals in conventional systems. Therefore, if you change to that you will also need to reseal everything in the entire brake system
*Disclaimer; my memory isn't always 100% acurate and as such what follows may be complete tosh!
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MiataMark
Club Retro Rides Member
Posts: 2,963
Club RR Member Number: 29
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brake fluid changeMiataMark
@garra
Club Retro Rides Member 29
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Aug 13, 2012 10:29:03 GMT
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One thing you need to be aware of, IIRC* DoT 5 fluid is silicone based and not compatable with the seals in conventional systems. Therefore, if you change to that you will also need to reseal everything in the entire brake system * Disclaimer; my memory isn't always 100% acurate and as such what follows may be complete tosh!According to the Demon Tweeks catalogue, Dot 5.1 (AP Racing fluid) is non-silicone and compatible with Dot 4 & 3. Dot 4 is synthetic and non-silicone. Maybe Dot 4 is the one to go for. Would the issue with the MC be reduced by using the Eezibleed as your not actually pumping the brakes. |
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1990 Mazda MX-52012 BMW 118i (170bhp) - white appliance 2011 Land Rover Freelander 2 TD4 2003 Land Rover Discovery II TD52007 Alfa Romeo 159 Sportwagon JTDm
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Aug 13, 2012 12:24:38 GMT
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Yer come to mention it the eezibleed is presureized to your right |
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Aug 13, 2012 12:49:00 GMT
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As you're changing the brake hoses you'll need to bleed the system out anyway - once it's bled you can be fairly sure that all the fluid has been changed: IME it takes ~1L of fluid to bleed out a braking system, and the actual capacity is probably around 100mL.
You won't have trouble with the master cyl seals with an eezibleed as you won't be pumping the pedal. That said, if you have trouble getting the last bubbles out, pumping the pedal with the eezibleed attached can help push them out. You don't need a one-way valve or second person to stop air being drawn back in due to the top pressure from the eezibleed. Just make sure that the supply bottle doesn't run out, and that the tyre pressure you are using is 10-15psi: any more and it'll pee fluid everywhere.
DOT 5.1 is a premium 'ordinary' brake fluid - an upgrade to DOT 3 and 4 with a higher specifed boiling point. DOT 5 is silicone and doesn't mix with regular fluid.
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MiataMark
Club Retro Rides Member
Posts: 2,963
Club RR Member Number: 29
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brake fluid changeMiataMark
@garra
Club Retro Rides Member 29
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Aug 13, 2012 13:05:26 GMT
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DOT 5.1 is a premium 'ordinary' brake fluid - an upgrade to DOT 3 and 4 with a higher specifed boiling point. DOT 5 is silicone and doesn't mix with regular fluid. Thanks for the info. So Dot 4 & 5.1 are upgraded versions of Dot 3 (normal brake fluid) with higher boiling points. Dot 5 is Silicone and should only be used in a brake system that hasn't previously had non-silicone fluid in it and with seals that will work with silicone fluid. Mark |
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1990 Mazda MX-52012 BMW 118i (170bhp) - white appliance 2011 Land Rover Freelander 2 TD4 2003 Land Rover Discovery II TD52007 Alfa Romeo 159 Sportwagon JTDm
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MrSpeedy
East Midlands
www.vintagediesels.co.uk
Posts: 4,786
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Aug 13, 2012 17:16:26 GMT
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DOT 5.1 is a premium 'ordinary' brake fluid - an upgrade to DOT 3 and 4 with a higher specifed boiling point. DOT 5 is silicone and doesn't mix with regular fluid. Ahhh, that's what I was thinking of. Not too far off the mark then. |
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Aug 13, 2012 21:49:53 GMT
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I will just reiterate what James said about the pressure of the spare wheel you use. The instructions state a pressure that just blows seals. About 10psi works well for me
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...proper medallion man chest wig motoring. |
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Aug 13, 2012 21:59:47 GMT
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DOT rating isn't necessarily an indicator of the fluids boiling point, I believe it's more a measure of the quality of the fluid in terms of the purity of its composition; it represents its quality, but not necessarily its performance. A reputable make of brake fluid will be able to supply you with information about it's boiling point, and the effects on it of water absorption.
I don't believe seals are an issue with silicon brake fluid, but as said, the system needs to be 100% cleaned of all traces of 'normal' fluid internally before it can be used. Silicon fluids don't absorb water over time like normal fluids do, however the downside is that they can foam/froth from vibration, which will lead to a spongy pedal feel. Because of this they aren't really suitable if you're aiming for performance, and a regularly changed normal fluid will give better results, they're only any real advantage over standard fluids if the standard fluids are allowed to age too much.
As James said, just bleeding the system will generally flush is through nicely, and old fluid if usually discolored, so you'll be able to tell when it's new stuff coming through. As long as you stick to DOT3/4/5.1 then it's 'compatible' with your old fluid (as long as it's not got DOT5 in it at the moment) so no harm will come if trace amounts are left anyway.
(Edited because I'm a clot who can't type, and typos made it hard to read.)
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Last Edit: Aug 13, 2012 22:06:25 GMT by RobinJI
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