Coolant and Heating bleeding system
updated 2013 Simon Baxters new bleeding information 
Coolant system takes 8-9L of coolant (for 50:50 mix) +8-9L of water approx 16-18 L in total
Bleeding the cooling system on a T25 - here's the proper way....... Assuming you have an empty system, open the header tank, and fill up, put your hand over the top of the tank, and squeeze the rad pipes, moving the water around and letting the air out, keep doing this until no more water will go in, then....... Put the van up your car ramps, or jack the front up at least 12"(or park on a hill!!) the shape of the cooling pipes makes it a scientific impossibility! Put the heater on HOT, and undo the filler cap on the expansion tank, Run the van up to temp, so the thermostat opens, then increase the revs to 2000 rpm, top up the expansion tank, and undo the bleed screw in the radiator, and then the one in the engine bay(if it will, do NOT force it) Keep topping the expansion tank up, ignore the top up bottle(behind the number plate) and keep topping up until only water comes out of the radiator bleed screw, should take about 20 mins, then put the top on the expansion tank, close the rad bleed screw, but leave the engine bay bleed screw open(if you opened it) then reduce the revs to tickover, leave for about 2 mins then switch the engine off, go have a coffee for about 20 ins, then come back, start it up, increase revs to 2000 rpm, open bleed valve in rad, and if you have a caravelle with rear heater, open the bleed valve in the top of that too(by the in/out pipes)take top off expansion tank and repeat bleeding until no air, only water comes out of the rad bleed screw, when you think it is all done, then put the top on the expansion tank, close the rad bleed screw, the engine bay bleed screw open(if you opened it) then reduce the revs to tickover, leave for about 2 mins then switch the engine off. Job done......
It takes about 15mins longer than you think it should, and you always need to do it one more time than you think you needed to....in short, when you think you have finished, go have a coffee, come back and do it again.
whenever Ive replaced bits of me cooling--hoses or what ever--I jus place a bucket underneath--change pipe--filter contents of bucket thru stocking into jug---pour back into main coolant tank-(leave lid off)-start engine---loosen bleed bolt on rad--till bubble free water flows out-tighten-brim coolant tank---done-check level in top up tank after run----If you want to drain & refill whole system--you wont empty it completely unless you undo drain plugs on engine(not a good idea imho)disconect large hoses at lowest point & stick hose pipe in--this should push old coolant out & leave you with about 6 litres of clean water in system--do up pipes--then pour 8.5 litres of neat antifreeze into coolant tank(heater on full)bleed screws open--start engine wedge pedal for fast tickover--top up tank with water as reqiured---when bubble free water pours out of rad bleed screw-tighten--tighten bleed screw on thermostat--brim coolant tank---if you want to run front wheels on ramps & repeat proceedure-you can--
Hacksawbob probably better to put coolant in first then top up with water that way you know who much coolant is in there, if you dont get it all in, then top up with neat till you have put your full 9 litres in. Avoid removing cylinder head drain plugs if you can avoid it as to get to them you need to remove the push rod protection plates. These are bolted to the exhaust manifold which will most likely be corroded unless they are under 2 years old, and the exhaust stud will probaly snap off leaving you with a blowing exhaust.
Bleeding the system on a diesel or GTI engined van is much easier. Fill the system as much as possible, then start the van, raise the revs to about 2K and top up the expansion tank while you have the revs elevated. Put the cap on and gently drive about half a mile. If the temp starts to climb over the mid-point on the gauge stop and re-fill with water. The half mile drive should open the thermostat. Now with the engine running crack off the radiator bleed at the front. Raise the revs to about 2K and allow it to bleed until no further air bubbles come out. Now switch off and top up as necessary on the main expansion tank. If you're suspicious repeat this bleed process again, but it shouldn't be necessary. Wait for everything to cool down and top up the tank behind the number plate.