Are these the leon cupra 345mm brakes or the fr ones like the gti?

[Teutonic_Tamer]

fitting mine in about 3 weeks time.

TT......is 1 litre of fluid enough to do the full fluid change?

For a straight-forward BFC in a manual car, then 1 litre should do - as the official specs just state purging either 200ml or 250ml from each nipple.  However, if you have a manual, then you should also bleed the clutch too!    So by a couple of litre cans just to be safe.  But the crucial issue is to only use "ESP" specific fluid - and obviously the genuine VW fluid is just fine (and it actually out-performs many of the so-called 5.1 fluids too  )

[Teutonic_Tamer]

Do you need to do a fluid change?

No, you don't need to completely change the fluid - but rather just bleed the new calipers.  But unless the calipers are "pre-filled" with brake fluid, there will be an aweful lot of air to get rid of.  So invariably, it may use more fluid than during a conventional routine BFC. 

When I used to fit 312's I would leave the cap on and just swap the pipes over.  You'll obviously get air in the line but the fluid won't all leak out.  As long as you make sure to keep the resoviour topped up you should be ok. Bleed them all round when you are finished.

Yup.  Some sound advice there. 

Another couple of tips - try to get a brake pedal depressor, then before you actually swap the calipers, crack open a bleed nipple, press the brake pedal to the floor, and clamp the pedal in this position.  Then remove the resvoir cap, top up, and before screwing the cap back on, use a CLEAN freezer bag or similar over the resevoir opening, and refit the cap (the freezer bag acts as a secondary seal).  Just make sure you remove the freezer bag BEFORE releasing the pedal clamp. 

Dropping all of the fluid out can cause you a headache unless you have a decent pressure bleeder.

Dropping all the fluid can be an utter ball ache, irrespective of how you bleed! 

[Teutonic_Tamer]

Do you need to do a fluid change?

When I used to fit 312's I would leave the cap on and just swap the pipes over.  You'll obviously get air in the line but the fluid won't all leak out.  As long as you make sure to keep the resoviour topped up you should be ok. Bleed them all round when you are finished.

Dropping all of the fluid out can cause you a headache unless you have a decent pressure bleeder.

Can I get away with not changing fluid?  it was only done 6 months ago at the dealer mind you. we're using the conventional route of pumping the brake pedal rather than using spare wheel/eezibleed to pressure bleed the system.

but if we can avoid fluid change then that would save time!

In theory, you shouldn't actually need to "change" the fluid, but being as the brakes use a diagonal "split-circuit", I would stronly advise on bleeding the rears too.

Another important issue - should there be the slightest doubt of air entering the ESP modulator, then this will need to be "cycled" during the bleed process.  VAG-COM can do this, but if you dont have it, then just bleed everything to the best of your abilities, bolt everything up, and go for a <cough> test drive <cough>.  Now on the test drive, it is important to "excercise"  the ESP modulators.  This can be done in a number of ways, by getting either the ESP, ABS or traction control to kick in a few times.  A wet grassy playing field really makes this easy  , but if one isn't local, then try to find a deserted lane, complete with grassy verges - and get the traction control and ABS to operate - both sides of the car would be good, to get all ports in the ESP purged.  Then after your play test, go back and re-bleed the brakes.