draining (and flushing) the coolant system

[Henkjan]

how do I properly drain the coolant system? the main rad is easy, but how do I get for sure all the coolant out off the engine when it's cold (so the thermostat is closed). I want to flush & clean it, do I need to drain it properly to get the cleaning stuff out before I put new coolant in.

[Error404]

I normally take the thermostat out and stick a hose in the radiator top hose and leave it for 15 minutes

[Henkjan]

so you mean thermostat out, housing closed again and then drain from rad?

btw: the heating circuit is always open? so no need to put the aircon on max temp?

is the thermostat the lowest point that is accessable?

[veneto rs2]

so you mean thermostat out, housing closed again and then drain from rad?

btw: the heating circuit is always open? so no need to put the aircon on max temp?

is the thermostat the lowest point that is accessable?

Hi.

Yes: thermostat out an housing close again.
Yes: the heating circuit it's always open
No: the lowest part to drain off it's on the bottom of the main radiator you have a pipe beside the thermo switch closed by a gummy clamped tip (this if you have the original radiator don't know about others kinds/types)

Stefano

[Henkjan]

the thermostat is a pita to get to, even with the aux rad removed so I'll remove it, flusk, clean, flush, flush the system, then put thermostat back and fill with coolant.

the lowest part to drain off it's on the bottom of the main radiator you have a pipe beside the thermo switch closed by a gummy clamped tip (this if you have the original radiator don't know about others kinds/types)

I meant lowest point on the engine. I have an ori rad (nice plastic, with Audi logo on the side) but can't find any drain plug. removing the hose from the rad is probably just as quick

[Henkjan]

change of plan... with the Wagner IM in place, the PAS pump can no longer be moved, making accessing the thermostat close to impossible. but I noticed that the flow towards the heater is upstream the thermostat, thus draining from that side (e.g. using the hose to the afterrunpump) is possible. so thermostat goes back in [edit] tomorrow when I have a fresh O-ring

[Henkjan]

I completed this last weekend: I first did a cleaning with cleaning liquid, amazing how bad this looked when it came out! Then I did 2 rinses with clean water, and then filled her with new cooling liquid.

on the draining: from the hose connected to the afterrun pump, it was nog possible to drain all liquid out, I used a vacuum cleaner (Kärcher) to suck out most of what was left (several liters!) so if you want to exchange the cooling liquid: get yourself one of those, or a large amount of the old&dirty stuff will be left in the system