Type 89 heater core

[THOMAS TAUSKEY]

Joe:

Did heater core last summer in '88  80.  It's a bitch (as you well know)

You don't want to hear this but.....I don't think you can pull out the combo evaporator housing/heater core housing so as to get to the top of the heater core box 
without disconnecting the a/c so the whole (huge) black plastic combo evaporator housing/heater core housing can be pulled off the firewall enough to get remove the top cover of the heater core box.

To disconnect the a/c you need to remove battery - there's an access hole through which (using a 6 or 8 mm allen wrench) you can disconnect the (single) clamp retaining both the a/c inlet and return lines to the evaporator.  OF COURSE you'll have to unload the freon first - and recharge later.  

Also need to disconnect (working from inside engine compartment) two bolts holding the fresh air inlet to top of the evaporator housing.  

Although it is tempting to try to disconnect the heater core box from the a/c evaporator box (several little clips hold the separate assemblys together just outboard of the heater core box) you can only get at a couple of the clips and will only end up butchering the whole assembly - you won't be able to get at the 
clip(s) on the firewall side without pulling the combined units off the firewall.  We did not try to dissassemble those clips - didn't have to since once the combined assembly was pulled off the firewall we could get to the top of the heater core box and the two screws holding the top cover of the heater core housing. 

There are of course lots of plastic tabs and connectors to break .. we broke a vacuum line fitting off the fresh air/recirculating flap valve on the far right-hand end of the evaporator housing.  (and were happy that was all that broke). 

Also... with all the work involved... putting a used core in .... well you'll be experienced when that goes :(   
New core was only about $75.   This seems to be a common type 89 failure.  The list archives used to have a fairly detailed explanation of this job. 

We took over a year to approach this fix and picked July as the month to do it  .... (after the leak developed we had disconnected the heater hose lines and spliced them together with a plastic sprinkler line  90 deg. elbow from Home Depot). 

If there's anyway to defer - put the dash back together and splice the heater hoses as above -  to get home I'd seriouslly recommend that. 

Sounds like you may be in too deep at this point to defer...but a roadside repair it's not.  Best of luck.