Heater core.........

[racedvl]

Well, I went to check my oil this morning and noticed anti-freeze leaking down my firewall near the heater core hoses. I will of course check the hoses for tightness, but if I need a heater core, what is involved in replacing it? It does not have a/c. Thanks. 1986 GMC.

[Zilverado]

Replacing the heater core is no big deal, just takes a couple of hours. Did mine last fall (on an A/C truck). Just a few comments.

• The heater core is located inside the distribution box which is inside the cab, behind the glove box.
• Remove the glove box for access.
• All but one of the fasteners for the box are removed from the engine side of the firewall. There is one (I think) which comes off from inside the cab.
• Once the distribution box is loose, you just have to finesse the thing out.
• Be careful when disconnecting the heater adjusting cables and any vacuum hoses. take note of where they come from so you can reinstall them correctly. I had one vacuum hose which came from the top of the box. Kinda tricky to get at, just take your time.
• Once the box is oout, the core is a piece of cake.
• Reinstallation is the reverse (of course).

Just be sure you pressure test your new core - even if it's just with a garden hose. The first new core I tried, I just held the hose to one inlet on the core and covered the other with my hand. This was enough to identify a bad solder joint.

Anyway, that's about it. I'm sure you'll get more input and advice. So have fun with it and chalk it up to experience.

[rolson1039]

ok call me over cautious, but when i took apart the vacuum lines and cables and all i went and labelled it all. it made it easier when i put it all back together.
Also when you put the bolts back into the heaterbox, you have to not overtighten them cause my friend did his in a rice burner and he overtightened and cracked the heater box
Hope all this helps

[PHOENIX]

All i need to say is changing a heater core on one of these trucks is ALOT easier thena car. I have a non-ac truck and can help you out if you run into any problems.

My truck had 3 nuts on the firewall that I had to take off. They are the 3 that are on threaded bolts. I believe the only nuts near that area. Becarefuly though my nuts were stuck on the bolts and I ended up bending a bolt or two. Still went back together though. In other words what Im saying is dont remove any bolts from the engine bay on the non-ac models, just remove those three nuts.