[V6-12v] [Bulk] Re: Thermostat lifespan

Thu Jul 6 20:45:00 EDT 2006

James,

Drain plugs: One on the port side, lower of the radiator. One on the
port side, aft of the engine (I believe it's a 8 mm socket head).
Bleed screws: One in the return line from the heater core. One in the
hard coolant line port side, aft of engine (by the EGR valve). 5 mm
socket head.

Fill procedure:
1) Close all drain plugs.
2) Open all bleed screws.
3) Add 50/50 mix of Audi G12 (red) coolant and distilled water.
4) Close the bleed screws when the coolant starts coming out. For
obvious reasons this means that the lower bleed screw is closed much
sooner than the top bleed screw.
5) Fill the expansion tank to the MAX mark.
6) Replace expansion tank cap.
7) Start engine and run at idle until the rad fans have come on at least once.
8) Fill expansion tank to MAX if needed. Be careful with the hot
coolant. Note that the system is under pressure.

Note that if your cooling system had anything other than the red Audi
G12 coolant in it before, you need to flush it thoroughly at least
twice before adding G12 coolant.

There's some debate about whether you should use the G12 or use any
long-life coolant. I'll leave it up to you to make that decision.
Similar for distilled water vs deionized water vs tap water.
Basically, you want water with a low mineral content. If your local
tap water fits the bill, you can probably use it. I, personally, use
Audi G12 coolant + tap water.

I've never been able to get any coolant to come out of the top bleed
screw (the one in the heater hose). I don't know if it's because I
don't have a super level piece of road to park the car on or what.
When I have bled the system I've ended up having to fill the expansion
tank to the point where the fluid no longer sinks below the max mark,
then start the engine and let it idle. Once the fluid heats up it'll
expand and drive the air out of the system through the top bleed
screw. Once coolant (now rather hot coolant may I add) comes out the
top bleed screw, I close it and continue to allow the engine to run
until the rad fans come on. Then follow step 8) above.

Above has worked for me. Your mileage may vary.

Tom

On 7/6/06, James Whitehouse <james_whitehouse1 at yahoo.co.uk> wrote:
> Hi Tom,
>
> Glad your thermostat problem is solved. I have to do mine shortly. The only
> thing that your excellent procedure, and the workshop manual I have, doesn't
> describe in detail is the correct bleeding procedure for the coolant refill.
> Any pointers here?
>
> Best regards,
> James
>
> > -----Original Message-----
> > From: v6-12v-bounces at audifans.com [mailto:v6-12v-bounces at audifans.com] On
> > Behalf Of Tom Christiansen
> > Sent: 06 July 2006 17:12
> > To: v6-12v at audifans.com
> > Subject: [Bulk] Re: [V6-12v] Thermostat lifespan
> >
> > Austin (et. al):
> >
> > The old thermostat (BBT brand) was broken in two. The new thermostat
> > ($30 at the stealership) Wahler brand fixed the problem.
> >
> >
> > Tom
> >
> > On 7/5/06, Austin Franklin <austin.franklin at charter.net> wrote:
> > > Hi Tom,
> > >
> > > But...did replacing the thermostat solve the problem?
> > >
> > > Regards,
> > >
> > > Austin
> > >
> > > > -----Original Message-----
> > > > From: v6-12v-bounces at audifans.com [mailto:v6-12v-
> > bounces at audifans.com]On
> > > > Behalf Of Tom Christiansen
> > > > Sent: Wednesday, July 05, 2006 12:42 PM
> > > > To: v6-12v at audifans.com
> > > > Subject: Re: [V6-12v] Thermostat lifespan
> > > >
> > > >
> > > > Folks,
> > > >
> > > > Quick recap: It took for ever for the engine in my 1994 90S to warm up
> > > > and I had no heat at the vents. Only in stop & go traffic would the
> > > > engine warm up (in 60-70 deg F (15-20 C) weather).
> > > >
> > > > I shook the expansion tank cap and it did not rattle. This can be a
> > > > sign of a stuck valve, which, according to several list members can
> > > > cause the system to show the symptoms I describe. A new cap was about
> > > > $6.50 at the dealer so it was worth a try. Unfortunately, it did not
> > > > fix the problem.
> > > >
> > > > So I replaced the thermostat, which on the AAH/AFC engines can be done
> > > > without removing the timing belt. Here's how I did it:
> > > >
> > > > 1) Remove belly pan, top engine cover. Drain coolant and dispose
> > > > of it properly.
> > > > 2) Remove radiator fans to give you more room.
> > > > 3) Remove front plastic cover on engine.
> > > > 4) Remove accessory belt and tensioner.
> > > > 5) Remove timing belt covers. Be careful as the plastic can be
> > > > rather brittle.
> > > > 6) Remove the coolant hose at the thermostat housing.
> > > > 7) Remove two 10 mm bolts that hold the housing. One is above the
> > > > idler/roller for the timing belt, the other is under the large pulley
> > > > at the top (use a 1/4" drive socket, universal joint, and a short
> > > > extension).
> > > > 8) Wiggle the thermostat housing out from underneath the timing belt.
> > > > 9) Replace thermostat and the O-ring around it.
> > > > 10) Assembly is reverse of removal.
> > > >
> > > > Remember to bleed the system when you fill it with coolant. Getting
> > > > the thermostat housing out is a real chore as the thermostat gets
> > > > caught on it. But it is possible to get it out (the Bentley Manual
> > > > even says so). It took me around 15 minutes to get it out. 10-15
> > > > minutes to get it back in. The whole procedure took 1.5 hours. Add 30
> > > > minutes for bleeding the system (waiting for the engine to heat up)
> > > > and tool clean-up.I took the time to make sure the timing belt was
> > > > clean and I rotated the engine a couple of revs by hand before putting
> > > > the covers on. Just as a precaution.
> > > >
> > > > Relevant torques:
> > > > Thermostat housing bolts: 10 Nm
> > > > Accessory belt bolt: 55 Nm
> > > > Bleed screw in the hard coolant line by the EGR valve: 15 Nm
> > > >
> > > >
> > > > Tom
> > > > _______________________________________________
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