[V6-12v] The Missing Sock Dimension - things you learn about your car

[Tom Christiansen]

Folks,

I have finally found the fourth (or is it fifth?) dimension. The
dimension where the socks disappear to from the drier. The dimension
where all lost nuts, caps, etc. gather to spite us... Read on and I'll
tell you how it happened.

First thank you to everyone who helped diagnose my faulty thermostat. 

About a month ago I noticed that my 1994 90S was running rather cold.
The thermometer would barely show temperatures above minimum except in
prolonged stop-and-go traffic. I was also getting the 2312 trouble code.

Finally, the weather turned for the better and gave me an excuse to work
on the car. I had planned to do the timing belt and water pump now that
I was replacing the thermostat. The timing belt was due in 10k miles
anyway...

The first surprise came when I took the coolant drain plug out. No
coolant came out of the engine!! I scraped the inside of the drain with
a screwdriver and all of a sudden all the coolant escaped at once!
Apparently some sludge had gathered on top of the plug and blocked the
hole until I provoked it with a screwdriver. I was glad I was wearing
eye protection, that's for sure!! 

The second surprise was that the bleed screw on the heater core hose had
been replaced with what appeared to be a short 1/4-20 or so with washer
and nut. Worked fine but was a bit tough to get out of the hose...

When I bought the car 10 months ago I noticed that the cap for the
expansion tank didn't look "audi-like". I thought, "oh, well. Maybe they
changed style" and didn't think more about that. This leads to the third
surprise and discovery of the mystic dimension. When I got the front
plastic covers off, I noticed the original expansion tank cap sitting in
a notch by the A/C compressor. Apparently someone had lost it and
replaced it with whatever they could find. It was a little worn where it
had rubbed against the accessory belt, but was otherwise in remarkably
good shape. I cleaned it up and stuck it back where it belongs.

I ended up not replacing the timing belt because even though I put the
transmission in gear, I still couldn't get the crank locked down
completely. Trying a higher gear helped a bit but I could still turn the
crank at least 10-20 degrees or so. And I conveniently didn't have the
audi tools needed. So I just changed the thermostat without removing the
belt. What a royal pain in the butt. As the thermostat protrudes a bit
from the opening, getting that "funnel"/cover thing off is a major
ordeal. But after futzing around with it for a good 15 minutes I finally
had the thing off. And sure enough, the thermostat was broken it two
pieces and stuck open.

Then I put everything back together, refilled the coolant, and the car
runs smoother than ever. It really helps when the engine is allowed to
reach full operating temp. That Castrol Syntec 5W50 oil I changed to
yesterday also seems to make a rather big difference.

Here's the procedure I used for changing the thermostat:
1) Disconnect battery. Remove belly pan.
2) Take radiator fan out.
3) Remove plastic covers (front, top, timing belt covers) from engine.
4) Take the cap off the expansion tank.
5) Loosen the bleeder in the engine coolant line (5 mm Allen - 15 Nm).
Loosen bleeder in the heater core line.
6) Drain coolant from radiator (red knurled knob).
7) Drain coolant from engine block. Bentley suggests using a special
tool for this, but an 8 mm Allen key works just fine.
8) Once coolant has drained, stick the drain plug back in. (Torque: 20
Nm).
9) Remove accessory belt tensioner (10 mm Allen - 55 Nm).
10) Remove accessory belt.
11) Remove thermostat funnel/cover/housing thing by loosening two 10 mm
hex bolts (10 Nm) and one hose clamp. Be careful not to slide the timing
belt off of the tensioner. 
12) Replace thermostat. The small bypass valve goes on the top. O-ring
on the outside. Install the O-ring on the thermostat before installing
the thermostat. Makes life easier.

When refilling the system with coolant, close the bleeders when coolant
starts seeping out. 

Now I just need to find someone who's willing to rent the tools for
timing belt replacement to me. But I guess I have about a year to find
that someone... If any of you know anyone on-line or in the Seattle area
who has the tools for rent, I'd appreciate it if you'd let me know.

Tom