Accord1278

I have a '98 Accord sedan, 4 cyl, auto with 127k miles, and just recently like within the past week or so, I'm barely getting any heat in the car. Up until then, the heat used to be nice and hot but now it's barely warm. Not the best thing considering the outside temps been dipping into the teens in NJ!

I'm thinking that my heater core might be the culprit here, either the unit or that it's clogged up or something. My thermostat is fine because the car warms up normally as it has always; the coolant level is good including the reservoir; the water pump is practically new as it was changed recently with the timing belt.

I was thinking that if the heater core is dirty/clogged up, maybe I should start off with flushing out the entire coolant system, which should clean out the heater core as well. If that doesn't work, then go from there, like maybe replace the heater core itself, etc.

So does any have any ideas as to what it can be or how to troubleshoot it?

Accord1278

Ok problem solved. Did a coolant flush as well as changing out the thermostat.

daanno

The first thing I would try is checking to see of the valve on the heater core inlet is opening. I've never looked under the hood of a 98 but every other car I've looked at has one. It's usually a cable actuated valve (like a plumbing ball valve) that's got a triangle shaped bell-crank on top. The cable goes from the lever, through the firewall and connects to the heater knob (usually). Turn the knob and it turns the valve. Some of the newer cars are controlled with vacuum but I don't think Honda does. Turn the knob and make sure the valve lever is moving. It could be dissconnected, stuck or clogged. Usually easy to remove and replace or clean. Also, you didn't mention if your heater/ac fan is working. That is something else to check. Some vehicles have big resistors connected to the blower to allow for different speeds. If one has failed the you may be missing one or more speeds on your blower. So the heat may be working but the blower is not moving the hot air into the cabin.
It's not likely but it is possible to have a massive air bubble in your cooling system. This would decrease heat transfer. There should be a bleed screw on one of your large hose fittings. It should be the highest point of the cooling system. The principle being that the air rises to the top and you loosen the screw to let it out.
I would not suspect the water pump if the engine is not overheating.
If none of the above leads you to a solution then I would try disconnecting both hoses to the heater core (from under the hood) ( if you have room) and connecting a garden hose. If you can push water through the core than your problem is elsewhere. If nothing else, it's a good time to flush it. I'd flush it both way but others might disagree. Some say it causes more problems because it could dislodge mineral deposits if you flush INTO the OUT port. If you save your coolant when you drain the radiator (before you flush), strain it through an old T-shirt. If you get a lot of particulates the you may have a clog.
I hope this help you find a solution and I hope turns out easy. I know I hate working on cooling systems in the winter.

Good luck
dan :10q: