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MK2 Heater core replacement! w/AC! & Heater core bypass!
jtanguay:
Well I finally got around to posting how its done. If anyone has suggestions feel free to add to this post, but please only relevant info to keep it clutter free. Thanks
First off, both lower access 'panels' must be removed. On the passenger side there is a strap holding everything together. This has to be cut. Next the glovebox has to be removed. Now the center console must be removed. The radio and other bits have to come out as well to make it easier to unhook certain ducts and replace the foam. Once you remove the duct for the two center vents, it should look something like this:
As you can tell from the picture, the foam has all rotted due to age and coolant spray. I also discovered why I get air out of all vents regardless of selector position; the gear on the vacuum controller broke under stress from some sticky residue. A little glue and its all better.
At this point you should disconnect the A/C lines. I suggest using a short stubby wrench as it is very tight in this area.
Now, if you have turbo you need to remove the heat shield to access these two nuts on the firewall.
Going back into the car, there is a bolt up under where the glovebox was. In the picture below It's removed.
Now it takes time, patience, and a lot of wiggling to get the whole unit out. After a big struggle, I was able to get it out. Notice the clean floor mat ;D To separate the heater box, there are little metal clips. The plastic clips can be wiggled free, or broken. Tape could be used on the joint to seal it up.
Time for some cleanup, etc.
Now for some new foam!
Here's the new heater core installed. Make sure to put the adhesive foam that comes with it on as the fins will catch and get bent on installation without it, and it just makes a good seal!
And installation is reverse! ;)
Another issue is that the heater core always has hot coolant running through it. If you didn't want to take the time to replace the foam on the different flaps, you could always run a bypass system. This would give nice cool air on an old beater during the summer, and even cooler a/c as well. I'm definitely installing this mod! The two main components that you need can be purchased from rockauto (that links you to a cart already filled with the two main components)
The vacuum solenoid:1990 CHEVROLET ASTRO 2.5L 2474cc 151cid L4 TBI (E)
Emission : EGR Vacuum Solenoid AIRTEX Part # 2F1120
(EGE Valve Vacuum Bleed Valve Solenoid)
And the bypass valve:Heat & Air Conditioning : Heater Control Valve
FOUR SEASONS Part # 74809
The rest of the hookup is pretty easy. All you need is a vacuum tee going from the solenoid to the bypass valve with vacuum from the engine, and a solenoid switch on the dash somewhere to activate flow when you want it. Also, some 3/4" cooling hose might be needed, and some clamps as well. Be sure to have the system hooked up so that hot coolant is only flowing when vacuum is applied to the bypass valve. Now might freeze, but you won't have to pull over for another blown heater core
fdnyguy:
I coulda used this $700 ago... ;D ;D ;D ;D
Stay safe, stay well. Jimmy.
jtanguay:
;D there might also be a way of just removing the heater box for some of you guru's out there... maybe theres just enough room with the help of a mirror to get the rear metal clips? but anyways, i hope this helps people out!
dieselherb1:
I have pulled a A/C-Heater unit out of a 81 pickup. Wasn't too bad only 2 nuts holing it to the firewall-dash that I remember. Is the MK2 that much different? If so then sounds like main work installing into a MK1?
Herb
truckoSaurus08:
I just tore the whole dash out. wish i would have known about this little trick sooner. That strap must be the giant zip tie thing on the evaporator box. Right?
I remember having trouble with those dang speed nuts.
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