Just like the title says. . . the heater core doesn't leak and everything else seems fine. What else could cause the loss of heat? It's not a big deal now, but at some point I'm going to be freezing my butt off.

 

low coolant level, blockage in flow, or maybe a stuck air door

 

coolant level is good.

brand new Stewart WP Stage 1

180* t-stat

185* JET fan switch

All doors seem to work fine.

 

sounds like ya might have a plugged heater core..

 

Yeah, yank the hoses off and see if you can shove water through the heater core with a garden hose. If it's plugged up almost nothing will flow through. It should be able to flow almost everything the garden hose can deliver with only a modest restriction. For the sake of the heater core's longevity don't disconnect the hoses from the core itself- you could damage the heater core. Just take them off their fittings on the engine or wherever the other side of the hose hooks up and hold the end of the garden hose up to the hose end as tight as you can with your hands to do the flow-test.

Also, most (all?) 3rd gens have a heater core bypass valve in the heater hose system that bypasses coolant through a 3rd hose so it doesn't pass through the heater core (the valve is located under the hood). This valve is vacuum-actuated via the HVAC controls in the dash and shuts off flow to the heater core whenever you turn the hot/cold selsctor all the way to COLD (or in some cases, when you switch to Max A/C). If the valve is stuck or is being supplied vacuum at all times for some reason you won't get much flow through the heater core, and no heat, obviously.

 

that idea about not taking the hoses off the core itself...GENIOUS!! i love it little things that i overlook make me happy i cant wait to see if my core is plugged now that i have an easy way to check!!