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Re: Heater Core

Jerry wrote:

>I believe that it is time for a heater core-
>symptoms:  losing coolant (lots), sweet smell inside from ventilation
>system, no visible leaks under car, runs too good to be a head gasket
>(fingers crossed and I've left the requisite 3 broken systems intact on the
>car to satisfy the Audi gods)
>question:  I've been looking for some definitive guidance on how to do this
>The car is an 86 5KS with 160K on it.
>Search of the archives has been not real helpful and somewhat confusing.
>Some archive letters say a total dash disassembly is required to remove the
>Others suggest  that a total disassembly of the heater blower box will give
>me access.
>I have already gathered that its a major PITA to do, but hey, its an Audi.
>This 60 degree weather ain't gonna last forever in Syracuse!
>Any BTDT's ?


    Your symptoms are indeed those of a leaking heater core. Lift your front
floor mats and look under them - if you are losing that much coolant through
the core it should be running through the footwell heater duct and pooling
on the floor. Many years ago I replaced a heater core on a '86 5ktq - I
assume you have the same electronically controlled heater/AC system in your
car. You have to pull the heater box out of the car and take it apart to
replace the core. While you are in there, you might as well replace the
blower motor.
    A wire bundle runs from the heater box through the firewall to a block
connector which plugs into the back of the AC control head. This connector
is designed to come apart so you can pull the wire bundle back through the
firewall and remove it with the heater box. To get at the connector, you
have to pull the side panels off the centre console, but you do not have to
remove the dash.
    Aside from the usual drain the coolant, disconnect everything in sight
advice, the biggest PITA with this job is actually getting the box out. It
is stuck to the firewall with a self adhesive gasket which you may have to
loosen by working a thin blade through the gasket between the heater box
flange and the firewall. After about an hour of poking, prying, cursing,
grunting, and straining, you (and an optional assistant) should be able to
pull the box out of the car. Pull the front of the box up first to clear the
front section of firewall, and wiggle it out. The hole to the inside of the
car is quite impressive.
    You will need a new gasket to re-install the box.
    Some of the screws holding the box together are cleverly hidden in deep
recesses, so if it doesn't come apart easily, look for more screws. Mark the
position of the internal flaps before taking the box apart. The Bentley
diagrams are helpful here. The new core must be sealed to the box with
silicone at the end with the hose connections.
    When re-installing the box, make sure you re-attach the rubber boot
inside the console which attached the box to the heat duct to the rear seat.


Fred Munro
'91 200q  263k km