Bleeding necessary when chaning coolant?

[iqbad]

Hello, I have driven my s4 for about 15000km now and its time to service it for the first time during my ownership (the car has about 85000km on the odo). I have changed the oil, oil filter and air filters now yesterday and tomorrow I am planning to change also the engine coolant. I am wondering if anyone has done this before and can give me some hints? Is there are a drain plug/valve somewhere? Is it necessary to bleed the system after I have refilled the new coolant?

Is there maybe a guide somewhere?

[doug97gxe]

get a lisle funnel

[S4'ed]

Easy way : Get a vacuum coolant refill tool (Ebay $60), then no air bleeding is needed. That is how the factory fills the coolant system when the car is built.

Hard way : http://www.audizine.com/forum/showth...r-AMS-or-stock

[iqbad]

Hello guys, thanks for your reply. I don't know if we have those lisle funnels here in Sweden I haven't seen one before, but I can probably buy myself a vacuum filler.

So, if I want to use the vacuum filler is this the correct way to do this?
1. Drain everything first from the cooler drain valve until the system is empty.
2. Then close the drain valve and install the vacuum pump on the expansion tank.
3. Suck out all the air until I have reached pump specified under-pressure.
4. Refill in expansion tank through the vacuum pump filler valve.

Will I have to bleed anywhere else anyways after this procedure?

Best regards Eric.

[S4'ed]

No bleeding anywhere, if the vacuum fill tool is used.
When you drain the old coolant out, you should open the bleed points (three I think, 2 on the intercooler, and one at the heater feed hose, at the base of the windshield).

[iqbad]

I did the coolant replace now this morning. It was actually quite hard to get all the coolant out from the system, and I am not 100% sure I really got everything out.

Opening the drain valve in the bottom corner of the cooler only drains out about 4L. Then opening the bottom oil cooler hose (the one bolted to the motor) drains out about 1.5L more. I could not locate a motor drain plug, but maybe it is there somewhere? I pressurized the reservoir slightly and got maybe 0.5L more out, but that was it. I hardly think the total volume is only 6L, on my M3 (that has no water cooled intercooler or anything like that) it was over 8L if I remember correct.

Anyways, I uses a vacuum pump and pumped down the pressure to -0.8Bar and then let it suck in new coolant. It worked pretty good and I have now taken it for a long test drive and tested so the cooler and the internal heating is working.

If anyone knows where the engine drain plug is located, please share so i can change out more of the fluids next time.