Brake bleeding

[Alun450]

I've had my front brakes off the car,
I'd like to replace fluid with Dot 5.1 so I will have to expel all the old fluid including removing from pistons.
So if I pump the old suff out of the master cylinder and completely drain the system so will I have to bleed the master cylinder after filling it or just fill and bleed the brakes. I'm going to try gravity, open both rear bleed valves and wait until fluid comes through. Then the fronts then use a bleed kit.
Does that sound plausible?
Do I need the engine running when bleeding brakes ( pressing pedal) to expel any air?
I done it before but about 30 years ago.
Anything else I should be aware of would be greatly appreciated.

[rigga]

Bleeding brakes on your own won't work unless you use something like a gunson eazi bleed kit which I found worked well, no pumping of the pedal as you use air pressure from a spare tyre to push the fluid through the system from a container filled with fresh fluid, no engine running either. Why completely drain the system unless you have dot 5 in there already as dot 5.1 is comparable with dot 4 which is commonly used.

[Alun450]

Ok, thanks Rigga, I've got the non return valve type bleeder, I'll get an easy bleed kit.

[spend]

It is wise IMHO to consider flushing as much as you can out of the piston area (it could have 20 years of boiled/baked st in there!)

I open the bleed valve and push the pads back to expel that area whenever changing pads ~ no flow so getting rid of the heated fluid and topping up seems a good trade off. You can do this whilst bleeding through several times to try and' wash out' the caliper areas, but I'd question whether its just easier to remove & rebuild the calipers? I'd also pull the reservoir off and clean it out when empty if you want a thorough job.

The easy bleeders are not always so easy to get to seal at the res cap and even then you have to let the tyres down to @20psi IIRC.
If you have a compressor the air 'suckers' are great and the same for oil extracters which will do brake bleeding (there are compressed air and manual operated versions) , so you pull it rather than push it out IYSWIM.

[rigga]

I quite often use a large syringe and back bleed the brakes from the caliper end....mainly bike's but I've done it on car's too that were difficult to remove the last few bits of air.

I take spends point about flushing out as much of the old fluid as possible, but my point was the compatibility of now using 5.1 and what as in there before.

Edited by rigga on Tuesday 6th May 09:59

[brett84]

have you got a compressor mate?
I've just bought this
http://www.ebay.co.uk/itm/SEALEY-VS020-Brake-Clutc...
And some blue brake fluid so it's easy to see when your getting fresh fluid through
http://www.eurocarparts.com/ecp/p/car-accessories/...

[spend]

rigga said:

I take spends point about flushing out as much of the old fluid as possible, but my point was the compatibility of now using 5.1 and what as in there before.

Not disagreeing, just pointing out common service procedures / advices don't really cater for 20yr old systems... Also if folks are looking to put 5.1 in because they've cooked the brakes on track I'd guess getting as much fresh 5.1 in the areas that get hot is vital & I suspect just flushing fresh through from res to bleed valve leaves the unsuspecting with mainly old stuff where it matters most in the caliper.

Service & restoration are quite different so it's upto the owner to decide how far they want to go and whether simple service is enough to get brakes back to new condition or not IYSWIM.

[Alun450]

Thanks gents, I'm going to remove calipers to expel all old liquid anyway.
My friends just informed me he has the vacuum type that I can borrow.
I've only got standard brakes and not really aiming to do many track days but would like the better fluid.
So I should take off M Cyl to clean out old fluid.
Maybe I should just use Dot 4 for now. I'll be putting better brakes on it in the future so might just wait until then to change to 5.1. And do the complete system as described. Thanks again boys. Al