I know from experience this can be a PITA. If I had access to an air line I would do a vac fill but I don't. So I am after best hints and tips. My basic plan is to first flush the system up to the callipers to ensure their is no residual debris in the lines using what ever cheapo fluid then make final hose attachment and start with 'proper' high spec fluid ( car is destined for track days ). This will be by the traditional two man method. Previous experience suggests that this will not be a continuous process but requires some relax time to get the last air bubbles to release.
Given that high spec fluid is expensive I would rather not throw the second pass away but recycle it after any air bubbles are released. Obviously this fluid needs to kept clean and to the extent possible protected from moisture. Is this a no no? Really not looking forward to this so any help would be much appreciated.

I've got a handheld vac kit which you're welcome to borrow (although notice you're somewhat far away!), however, having used a number of different systems to completely flush/bleed some cars, I'd do it using a pressure bleed (the spare tyre kit thing you can buy in halfords for a tenner).

Least effort, and in my personal experience, the most effective.


The way it's done at work on new cars is:
- system assembled dry
- vac pull on master reservoir
- while under vacuum, brake fluid filled into reservoir
- vac pulled 2nd time to remove any air bubbles

A bit impractical unless you've got the kit which is the size of a room!

[Edited on 10/3/15 by PSpirine]

From my own experience a brake system holds a surprisingly small amount of fluid when full.

I do my first fill/flush like you suggest then connect to the callipers and so far been realy lucky such that they have bled themselves by simply leaving the nipples out until I was satisfied that all the air was purged, I bleed that way at a total loss, they hold that little fluid it's not in my opinion worth the risk of saving it.

Those one man brake bleed tools work a charm and cost about £3 (it is just a ball bearing in a tube after all) and make the job so much easier.

I'd start on one corner, work my way around and then do each corner a 2nd time to make sure you get the last of the air out. You'll probably do all that with 500mL so wouldn't bother with the cheap stuff.

i have never had any issues with priming brake fluid systems and only use a basic clear pipe

a little trick i do is simply let gravity do the hard work for you and never have a system where the fluid res is lower than anything else

brake grease the nipple threads to save suck back later on and all pistons all the way home, fill the system, open all nipples (do not pump pedal!) and go make a brew

when the nipples start to drip close them one by one and when all have let a few drips out attach a clear pipe on shortest line and open nipple again watch gravity feed fluid for aroud 30secs and bubbles should be gone in line and close nipple , do each corner in turn working from shortest to longest lines

now press pedal with all nipples closed and it shoud be hard

the key is to alow the fluid to naturaly drain in and push the air out. as pumping or vacum can mix in air bubbles.
i can usualy only waste 100ml fluid on a dry fill system

as for fluids unless your useing silicone base types just use a quality dot 5.1 fluid that has been sat still in a sealed container its not expensive

[Edited on 10/3/15 by baz-R]

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it's not expensive

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Thanks for these tips - very useful. My difficulty in the past is probably due to having floor mounted pedals/master cylinders so I could not use the gravity method. That's what I will try now that I have a top mounted pedal set up.

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Originally posted by JAG

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it's not expensive

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It kinda depends how serious you are about trackdays and brake fluid... have a look at Castrol SRF Brake Fluid

HERE

It has a very high dry boiling point - 325 Celsius and costs between £42-50 per litre.

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there are identical products in the market at around half the cost of that

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Dot 5 absorbs water so easy dont you have to change virtually monthly? Some 5,1's are better but the above is one of the best i have yet found.

Avoid special brake fluids like then plague, racing brake fluids are highly hygroscopic, it is the water contamination in brake fluid that will cause long pedal.
Normal DOT5 .1 or even DOT4 fluids changed yearly are more than adequate fade of the friction material will occur before the fluid boils.

[Edited on 14/3/15 by britishtrident]

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Originally posted by threadbare wallet
Dot 5 absorbs water so easy dont you have to change virtually monthly? Some 5,1's are better but the above is one of the best i have yet found.

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Originally posted by baz-R
i have never had any issues with priming brake fluid systems and only use a basic clear pipe

a little trick i do is simply let gravity do the hard work for you and never have a system where the fluid res is lower than anything else

brake grease the nipple threads to save suck back later on and all pistons all the way home, fill the system, open all nipples (do not pump pedal!) and go make a brew

when the nipples start to drip close them one by one and when all have let a few drips out attach a clear pipe on shortest line and open nipple again watch gravity feed fluid for aroud 30secs and bubbles should be gone in line and close nipple , do each corner in turn working from shortest to longest lines

now press pedal with all nipples closed and it shoud be hard

the key is to alow the fluid to naturaly drain in and push the air out. as pumping or vacum can mix in air bubbles.
i can usualy only waste 100ml fluid on a dry fill system

as for fluids unless your useing silicone base types just use a quality dot 5.1 fluid that has been sat still in a sealed container its not expensive

[Edited on 10/3/15 by baz-R]

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Originally posted by threadbare wallet
Dot 5 absorbs water so easy dont you have to change virtually monthly? Some 5,1's are better but the above is one of the best i have yet found.

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Originally posted by britishtrident

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Originally posted by threadbare wallet
Dot 5 absorbs water so easy dont you have to change virtually monthly? Some 5,1's are better but the above is one of the best i have yet found.

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DOT5 fluid is not hygroscopic, it repels water.
Because isolated pockets of moisture can occur in the system DOT 5 fluid is only really suitable for classic cars which stored by collectors for years without moving.

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Originally posted by v8kid

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Originally posted by britishtrident

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Originally posted by threadbare wallet
Dot 5 absorbs water so easy dont you have to change virtually monthly? Some 5,1's are better but the above is one of the best i have yet found.

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DOT5 fluid is not hygroscopic, it repels water.
Because isolated pockets of moisture can occur in the system DOT 5 fluid is only really suitable for classic cars which stored by collectors for years without moving.

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I think you mean silicon not DOT5?

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Originally posted by britishtrident

Normal DOT5 .1 or even DOT4 fluids changed yearly are more than adequate fade of the friction material will occur before the fluid boils.

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....i knew it was a pain in the arse in some way lol thanks for the info chaps,always good to learn more.

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Originally posted by britishtrident

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Originally posted by baz-R
i have never had any issues with priming brake fluid systems and only use a basic clear pipe

a little trick i do is simply let gravity do the hard work for you and never have a system where the fluid res is lower than anything else

brake grease the nipple threads to save suck back later on and all pistons all the way home, fill the system, open all nipples (do not pump pedal!) and go make a brew

when the nipples start to drip close them one by one and when all have let a few drips out attach a clear pipe on shortest line and open nipple again watch gravity feed fluid for aroud 30secs and bubbles should be gone in line and close nipple , do each corner in turn working from shortest to longest lines

now press pedal with all nipples closed and it shoud be hard

the key is to alow the fluid to naturaly drain in and push the air out. as pumping or vacum can mix in air bubbles.
i can usualy only waste 100ml fluid on a dry fill system

as for fluids unless your useing silicone base types just use a quality dot 5.1 fluid that has been sat still in a sealed container its not expensive

[Edited on 10/3/15 by baz-R]

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Never ! put mineral grease anywhere near brake hydraulics.

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