Evans (Zero-pressure) coolant

[Igor Kessel <e6941tb@ix.netcom.com>]

Hello, Club!
          
Several people have asked me about the results of the coolant sys
conversion on my 200TQ.

In short - I am happy.

I replaced the heater core when I pulled the heater box out in order to
do the blower fan. The core was OK, but since it was made out of the
famous Audi plastic (although sometimes I suspect Audi uses papier-mâché
instead), I decided not to penny-pinch 60 bux and replace it. Especially
given the PITA associated with the heater box removal.

Pros:
1. Zero-pressure operation. The cooling sys should last forever. Bye-bye
blown hoses and torn rad and aux water pump nipples.
2. Subjectively speaking, a somewhat higher heat transfer ratio. The car
is no longer a dog on a 100°F+ day.

Cons:
1. $27.50/gallon.
2. May NOT be mixed with water! Unless you want to imitate an Icelandic
geizer from under the hood in the middle of an Interstate.
3. Old Ethylen Glycol based antifreeze has to be flushed out with water.
        Afterwards water has to be thoroughly evacuated:
        a) disconnect heater hose @ the firewall. Juck up the front of
        the car. Drain comepletely.
        b) remove the thermostat. Juck up right rear of the car. Drain
        completely.
4. Even after the most thorough evacuation you'll end up with ~1 to 2 L
of water in the sys. It_will_be boiling out giving white water vapor and
driving you nuts for a week. Ignore and add Evans little by little, just
enough to keep the floating sensor in the expansion tank happy, untill
the boiling and vaporisation of residual water stops.
5. You_will_need a modified expansion tank cap. I used a VW part from a
junk yard. It was real easy to modify: just break out one of the two
check-valves, to let it ventilate the pressure freely into the
atmpsphere.

BTW, I have also installed an all-metal heater valve and the SOB does not
close completely (it blows warm air on a 20°C day with the CC set on 20°C
in the *econ* mode). Anyone has this problem with the non-OEM valves?
I installed it into the sys without taking into account the direction of
flow. Does the flow direction *really* matter?

--
Igor Kessel
'89 200TQ - 18psi (TAP)
'98 A4TQ - already in the port of entry (Boston). Any day now.
Philadelphia, PA
USA