I'd like to do a coolant flush tomorrow. I'm trying to assemble information from different posts, but I'm not entirely clear.

First question, finding the drain plug. Some make it sound like it's on the bottom of the radiator, another back post made me think otherwise:

* It's an allen head, I believe it's stainless,
* and it's rather shiny. It's the only allen
* you'll clearly see facing you when you're under
* the car.

* The location is behind the oil pan... near
* where the trans and engine meet, on the driver
* side of the flywheel.

Okay so, assuming this is right, now we have to flush out the crap. The same back post suggests using a coathanger to clear any detritus blocking the drain, so after that, another post suggests the following:

* Take a running hose and stick it in the
* reservoir with the plug open and run the car in
* this fashion for about 3 mins.
* Let it all drain.

* Then close the plug and fill with the distilled
* water. Let the car run in this fashion for
* about 5 mins. Drain all the water, and fill
* with the distilled water and the G12 coolant.

Sounds reasonably straightforward. Drain, flush, circulate fresh water, drain again, and top off. Easy enough right? I thought so until I read <a href="http://forums.audiworld.com/general/msgs/13583.phtml">Miktip's back post</a> about bleeding after flushing. It sounds like his process is a bit more thorough than the simpler process I listed above, so I'm not sure if that is what causes the possibility of air pockets.

However, the last thing I want to do is blow a heater core in the process. Is the process I listed above accurate for a basic flush, or should extensive bleeding be undertaken? If so, where exactly is the bleeding screw Miktip refers to, and given the abbreviated process I'd be following, what sort of bleeding would you recommend?

Thanks for any input.

<center><img src="http://pictureposter.audiworld.com/6607/coolpic.jpg"></center><p>
The engine block drain is on the engine, at it lowest point. Underneath, where the engine &amp; gearbox meet, towards the drivers side.

<img src="http://pictureposter.audiworld.com/6607/drain.jpg" border="0">

Depending on how long your cooling system has been neglected, and how bad a shape its in, will determine how in depth you may want to go? If your system is in rather "new" your can probably for-go, a chemical cleaner? My 1993 90 was 6 years old, when I bought her, and her cooling system was in bad shape.

Has your 1997's coolant been changed since 1997?

If your unsure, I'd recommend the Prestone SuperFlush, and follow the direction on the bottle.

Above all, be safe, and allow the system to cool before performing maintenance.

More good info-<ul><li><a href="http://www.mnsi.net/~natwhite/Audi/Coolant%20Flush%20&amp;%20Fill%20Procedure.htm">http://www.mnsi.net/~natwhite/Audi/Coolant%20Flush%20&amp;%20Fill%20Procedure.htm</a</li></ul>

I believe the coolant was flushed this August when the timing belt was replaced by an independent mechanic. Unfortunately, on the way back from the mechanic's the coolant light went off and we topped off the expansion tank with non-G12 coolant. I didn't realize the error until now. So, I want to flush the system.

The instructions you linked are very thorough and should suffice, save for a few questions. I looked under the car but could not be certain about the location of the radiator drain plug and the specific coolant hose the instructions mention. I'm also not exactly clear on the location of the bleed screw, since there are a couple of bleeders in the diagram you posted. Do you have any pictures that might show clearly?

... they must have replaced the coolant. Old coolant does not contain sufficient additives to "prime" newly installed metal parts. If they flushed the cooling system is not clear, unless they told you. They may well have just drained the old coolant and refilled with fresh coolant.

PS: How did the O/C go?

Sounds quite feasible. This place, Woodlawn in Philadelphia, came well recommended by RKA and some of the other Philly area guys, but I'm not sure whether they did the full flush or just drained. I was working and my dad was off that week, so he picked the car up for me, I didn't speak to them.

As to the oil change - almost flawless. I ended up using the 'lifetime' plug which appeared to work fine. Tightened it about 1/3 of a turn past finger-tight with the socket wrench, didn't want to push it any further. I unfortunately managed to knock about 3/4 of a quart onto the driveway while rolling under to install the plug, but let's just forget about that. :)

I pre-loaded the baffles of the filter pretty well apparently, because the oil pressure light did not come on when I started the car to get it down off the ramps, nor when I started it up and idled for a few minutes per your instructions. I drove around the block several times, taking it very easy, and everything seemed okay. Thanks a lot for all of your help, I truly appreciate it.

Check the invoice and see if they charged you for coolant. ;-)

It's nice when the oil pressure light doesn't stay on for 30 seconds when starting the car after an oil change, right? :-) Congrats on your first do-it-yourself oil change! The next one will go even smoother. Oh, and you're welcome!

They charged:

R/S tie rod end $70
Timing belt $65
Timing belt tensioner $48
Roller $59
Water pump $105
Thermostat kit $23
Antifreeze $14
Serpentine belt $28

That was for parts, labor was $325 for the whole timing belt etc. procedure, $32.50 for the tie rod replacement and $97.50 for the alignment. So, no, I presume they simply replaced the coolant.

It was nice when the oil pressure light didn't come on. I don't ever want to see it again! I poured oil into the filter about an ounce at a time, then rolled it around in my hand and let it soak into the baffles. I kept on doing that until it wouldn't soak up any more. I figure that probably helped... of course, I was expecting the light, so when I didn't see it, I got anxious. Then I figured I should count my blessings, no harm no foul right? ;) Thanks again man, I really appreciate you holding my hand through everything. I'm serious, look me up if you're in Philly, let me buy you a few beers! ;)

As I said before, if you have any questions, I'll gladly help as good as I can.

that would be enough antifreeze to do a flush i would think.. so did you ever figure out what the issue was?
i am about to do a flush myself and i was just seaching the archives..:)