4.2 coolant refill w/o VAG special tool VAS 6096 ?

[monkeytronic]

I'm in the process of replacing the '02 A6 4.2's coolant expansion tank & temperature sender after draining out the old coolant.

Now fresh new G12++ coolant needs to go back in but, according to the ElsaWin service docs, a suction jet pump doohickie (special tool VAS 6096) is called for to create a vacuum in the closed cooling system which will the suck in the mix of new G12++/distilled water while bleeding air from the system at the same time. The only bleeder valve I can find in the engine bay is a small manufactured hole in the upper heater core hose which is intended to match up w/ a bleeder hole in the pipe when said hose's clamp is loosened and said hose pulled back sufficiently enough.

I'll admit that after wrenching on a few decade-old Fords, GMs, Volvos, and, of course, VW/Audis (mainly 1.8Ts), this is the first time I've come across such an involved refill procedure. I've looked through ElsaWin at other engines and it seems that only the 4.2L V8 is this way, esp. among C5s.

So, the question, isn't there a more DIY-friendly approach to refilling & bleeding the 4.2's cooling system?

[Audi_Tech]

You can purchase an airlift coolant tool ( https://www.google.com/search?q=airl...e=off&tbm=shop ) that performs the same function. You insert it into the coolant reservoir or fill it and drive it. Pull over to add fluid when the t-stat opens and she runs hot.

[rollerton]

Bah!
I'll admit I've never done a full flush on a 4.2, but other than the extra two cylinders I don't see why it'd be special as far as simply filling the coolant. Fill it up! hopefully you want even need to bleed the heater core.
If it was me I'd just keep an eye on the coolant for a few days.

[02 A6 2.7T]

Bah!
I'll admit I've never done a full flush on a 4.2, but other than the extra two cylinders I don't see why it'd be special as far as simply filling the coolant. Fill it up! hopefully you want even need to bleed the heater core.
If it was me I'd just keep an eye on the coolant for a few days.

^^ x2. I recently replaced the thermostat in my 2002 S6 (along with the WP & TB service) and didn't use any special tools or procedures or even bleed the heater hose. After initial filling with coolant, I ran it to operating temp with the heater on high, then let it cool down completely and topped it up. Took two "running/cool down & top up" cycles to get it to the correct level, and has been fine ever since. It helps to measure the amount of coolant drained from the car so you have a good ballpark quantity of new coolant required...

[mithril]

VW and Audi are self-bleeding systems, that's why the expansion tank is at the highest point in the system, Fill procedure:

1. On cold engine, fill through expansion tank until max fill line.
2. With expansion tank cap off, turn on car and let idle until the engine comes up towards temp.
3. Once thermostat opens, coolant will enter rad level will drop.
4. Top up coolant, idle for another minute or two.
5. Shut off engine, refill to max fill (if required) and put expansion tank cap on.
6. Monitor coolant level over next couple days and top up coolant as needed.

This procedure will bleed almost all air from the system most of the time. Occasionally there will be a couple air bubbles that don't bleed up to the expansion tank immediately that work their way once then gets a longer run under load, this is why you need to check it for the next couple days. The amount you need to ad will be negligible assuming your coolant system isn't leaking.

[Scotty@Advanced]

Holy shit I've been doing all wrong!!!!

I've done coolant services on 4.2 for 10+ years and never needed a special tool.

Wait for engine to cool, then either remove lower rad hose or use drain port on radiator.
Drain radiator
Drain engine with the little water jacket drain.
Fill with appropriate amount of undiluted coolant through upper rad hose.
Fill upper rad hose with water until it level appears in the hose (note coolant should drip out of upper radiator hose port.
Clip upper rad hose back on.
open coolant reservoir cap.
Fill with water.
Start car and warm up.
Fill with water when level drops after engine warms up.
Put cap on drive around.
Wait a few hours for engine to cool and check coolant level.

Some people recommend use distilled water however I've never done so.