Does one really have to gut the cab to replace the heater core in one of these trucks?

 

Depends on the climate control box/housing. I managed to change a heater core on a 1988 Chevrolet C-2500 pickup, as it had just enough room with the lower part of the box removed to work it out. That sure saved me lots of time and work.

 

My truck has recently started losing coolant and I THINK it's narrowed down to the heater core. I searched a bit for replacement cores and a few U Tube videos came up. After watching a couple of them it looks like every piece of plastic forward of the seats has to come out (and go back in). Looks like an eight hour job even if all goes well. Must be a $500+ project labor wise if hired out.

I'm currently considering other options. Running without a heater is one. This is a work truck, and I don't use it too much in winter months anyway. I can easily survive without a heater if I could keep the windshield clear.
I'm thinking about cutting a hole in the firewall, trying to get it out through the front, then patching that back in. Cosmetics are of little importance here. It's no show truck to begin with. Not sure if that's possible, as I haven't actually studied it from that angle.
Also considering gutting the air conditioning and using the evaporator as a heater core. I never use the A/C anyway. It works, but I've probably turned it on less than five times in four years. That might be enough to take care of the windshield.

 

I'd look into using something like Bar's Leak or Alumiseal, if you can't get to the heater core somewhat easily. Maybe even use some Block Sealer to stop it if that doesn't work. Are you pretty sure its the heater core, like smelling anti-freeze in the cabin? Is there any coolant on the ground when your park it hot? It would be coming out of the A/C drain hose near the bottom of the firewall, if so, unless it's a very small leak.

I got real lucky with that 88' C-2500 and the fact that it had enough room to get all the screws out of the bottom of the climate control box, but I did have to use a flexible 1/4 inch drive socket to get them all out. The unit had no corrosion at all, but Chevy tried building the heater core with crimped-on plastic tank ends, like they still use for radiators, as well as the plastic inlet and outlet tubes. Thankfully, by then they went back to full-aluminum heater cores and tubes, which I installed. No more heater leak!

 

I've never been a fan of "stop leak" products. My experience has been they plug holes you don't want plugged, and leaks just keep leaking on.

My diagnosis consists of the following -- It started a few days ago when I noticed the temp gauge was reading much higher than normal. That's happened a few times and it's always been the thermostat. I've changed probably three in the four or five years I've had it. So I stop at NAPA, pick up a thermostat, go home and park it. Next morning I change it out. In previous changes I loose maybe a pint of coolant, that's all. This time it takes nearly a gallon. Red flags here. I top it off and run it that day. It acts as usual, the gauge reads as normal all day. Next morning I check coolant again cold. Down some, maybe a pint, maybe less. It never uses coolant (at least not until this week). I check the radiator every now and then, it's always right at the top. So something is different. I top it off again and drive it another day. Next morning I check it...down again. This time I had slipped a piece of clean cardboard under it when i got home and left it over night. It was slightly wet on one side with water/orange antifreeze mix. No visible leaks under radiator, water pump, hoses, anything engine related. I pinched off both heater hoses and topped it off again and drove it that day. Yesterday morning I check coolant and it's still full. Drove it today and will check again in the morning but I suspect it will still be full. If so, my money is on the heater core as the problem.