One of our '90 ZR1s started using coolant. It was dripping
under the firewall in back of the passenger front wheel. I
checked the area around the heater hose conditions and
everything was dry. Checked the passenger rug and it was
dry. That ruled out the heater core but I could not see how
it could be anything else. Then I thought that maybe GM got
smart and vented the heater box to the outside! That would
be almost as good as moving it to the other side of the
firewall and let it leak on the ground. Anyway it turned out
to be the water pump and the fan was blowing it back to the
firewall but I did not know it and we tackled the heater
core.
Followed the Helms manual to remove the dash but two
things came up worth passing along. One is that there is a
plastic duct going across the front of the heater box with a
snap on short duct going into the heater box. This duct goes
on behind the main console which I had no intention of
dismantling. I was tempted to cut the duct by the console
and get a rubber tube to reconnect it later but restrained
myself from doing this due to the many years (since 1980) of
NCRS training. So I unbolted the heater box and pulled it
out from behind the duct while pulling out on the duct. This
separated the snap on duct that I did not know was there.
Next time I will separate it first. The other thing to
mention is that there are two rivets that look weird and not
like rivets. These I pried up with a screwdriver. Even if I
knew they were rivets, it would be hard to get in there to
drill them out. (Bad design - GM should have spent a few
cents more and used bolts. They could have use rivets to
hold a nut plate on for the bolts.) I did not have the time
to redesign it so I left the rivets out when I put it back
together.
Hint on putting the heater box back together : Slip the
heater box cover back in place but don't bolt it back on.
Take some twine and tie it to the short duct that goes into
the heater box. The twine needs to be long enough the be
pushed down and off of the pipe after it is snapped into
place. Put the tube in the box with the twine coming out
over the duct. Get the fingers of both hands around the duct
and pull the twine until you get the snap end of the inner
duct in place. Put the key on first and snap the two
together. Push the twine off the end of the tube and pull it
back out of the box. I used a piece of spring steel to shove
it off the end of the tube. This maneuver should not take
more than 1/2 hour to get the tube snapped in place. P.S. I
had to take the dash apart three or four times before I got
it together right.
All was not in vain as the heater core had a pin prick in
the middle and a v-shaped stain but had not started to leak
out of the box yet.
The water pump is another story!
