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Tech info and how to guides for ASV users


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Removing trim429 views1989 Astro Heater Core Replacement.

The smell of antifreeze when I used the heater told me that it was past time to change the heater core in my 89 Astro. It's a job I dreaded due to previous experiences with other vehicles, but it wasn't too bad actually. In fact, disassembly is a snap, but I had to get a touch creative to get it back together.

I removed the engine cover first; don't know if it's necessary, but it always seems like I have to do it no matter what I'm up to. Hey, that's the mighty 305 all nestled in the engine bay, by the way.
Next, remove the four Phillips headed screws that hold the heater trim piece in place and then remove the trim piece. Actually, it will fall off when the last screw is removed. Lay it and the screws out of the way.
I failed to get a usable photo of the heater box cover removal, but it's the black object with the louvers you see behind my hand. Four 7mm hex headed screws hold it in place. You'll have to get at floor mat level to see them all, but they're not bad to get at. Unscrew those fasteners and remove the heater box cover. Once that's off, you still won't see the heater core, though. That's because it's behind the heater core cover, located on the right of the heater box, and is held in place by three screws, also 7mm headed. An upcoming photo will give more detail on the location.
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Connections at firewall494 viewsUnder the hood, on the passenger side of the firewall, you'll see the heater core hose connections. Drain the radiator (it holds about 6 quarts) and remove the heater hoses. You will probably also have to remove the heater blower motor relay and fuel pump relay bracket to make the hose removal easier, as I've done here. By the way, the silver relay is for the blower motor; the back relay is for the fuel pump.
Another note: I drain the radiator by use of a small hand pump. I snake the suction line of the pump down past the transmission cooler in the radiator tank until the hose bottoms, then I pump the coolant into a container. Sure beats trying to catch the antifreeze in a basin of some type after opening the radiator drain. And I'm getting old, guys, so I don't care to wallow around on the ground searching for the radiator drain if I don't have to.
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Heater core exposed marked412 viewsAnd here's the heater core after the cover has been removed. The core itself is also held in place by two
7mm headed screws, which I've circled here in orange. Remove these screws, lift away the metal bracket that secures the core tank, and pull the heater core towards yourself. It may resist a bit, but if you've removed the heater hoses it'll come out. Don't tip it too much on removal as there is always antifreeze waiting in the core to leak onto the carpet. I've put a shop rag on the floorboard to catch any that does leak.
Note the black plastic tab above the heater core; it's job is to fasten the defroster duct in place. It does a great job of that, but it does an even better job of making reassembly of the heater core cover a real nightmare.
More on that in a moment.
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Heater core363 viewsHere's the heater core, in this case, it's the old leaky one I removed. Notice the small round post between the two heater hose nipples. That post must be placed into a hole in the heater box during the assembly of the new heater core. If you don't get it lined up correctly, you won't get the heater core to seat all the way into place and the screws for the heater core won't match up with their holes in the heater box.
Don't ask me how I know this.
Once the heater core is secure in its place, I'd suggest reconnecting the heater hoses and filling the radiator. After that, start and warm up the engine. Check for leaks; you sure don't want to have to tear back into all this in case something is wrong.
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Heater core cover344 viewsThis is the heater core cover. In this photo, we are looking inside at the rear of the cover; note that there is a channel here that continues on both sides of the cover. This channel's purpose is to engage a tab in the heater box and thereby seal the heater core in place. It's a nice idea, but that defroster mounting tab mentioned earlier will be right in the way of lining the cover up. In fact, I'd say that the tab makes lining the cover up almost impossible. So, after fighting that tab for a while, I did the only sane thing—I cut the tab off with a hacksaw blade, making sure I made the cut so I could reattach the tab later.
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Heater core strap mod408 viewsHere you see the offending tab spliced back into place by use of a brass strap and another screw. That's the heater core cover it's screwed to, by the way, and it's all back in its original location.
You need only add the heater box cover, the trim piece, and the engine box cover and this job is finished.
You've probably noticed that this heater box is sealed with white foam. The original black foam was a sticky mess, so I cleaned it all off and replaced it with the white foam I got from the hardware. It seems to work fine.
   
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