If you had one of those split, it's probably time to tackle the rear heater hoses behind the right rear wheel. Nobody really looks at them because they're pretty much out of sight. Just like the oil cooler lines, they're available from GM as a complete line set with the rubber section crimped on.... Alternatively, you can cut the crimps off and use the hose clamp of your choice and just replace the flexible hose. If you drop the spare tire, you have access to cut the original crimp off, or simply cut the metal pipe and use a compression fitting to convert to a hose barb in a more convenient spot. The 90° elbow off the bottom of the heater core..... It's a 3/4 quick disconnect x 5/8 hose barb.... I've only found them available by Dorman.
Above the spare tire
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And behind the rear passenger tire
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Those 90° fittings can be found here:
Dorman Heater Hose Connector
https://a.co/d/a0fmrD0
And The originals removed at 170,000 miles
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The hoses themselves and the original 90° fittings are exposed to whatever gets thrown up by the rear tire, as well as heat from the exhaust. So yeah, if you have a t connector on the firewall which is protected from road spray finally get brittle and break, you might want to pay attention to these ones as well.
If you go the route I did with a compression fitting on the original pipe, that pipe is 1/2 inch outside diameter.
After dropping the spare tire, here's what you're looking at. The two crimped hoses closest to the camera that look like they've been sleeping are the heater hoses. You can carefully cut the crimps off, and there's a hose barb under there. Or simply cut it off a little shorter and have more room to work with for future replacement.
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This is all you need, in addition to 5/8 heater hose.... I used silicone heater hose for this.... And hose clamps of your choice. I prefer the oetiker clamps.
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