Yeah it sounds like a clogged heater core.
You could try to flush it before you replace it. Maybe that's all it needs.
-Drain some coolant out of your radiator (not all of it but you need to lower the level of coolant in your radiator)
- Disconnect the heater hoses at the engine side (not at the firewall; it's easier that way) and run water thru one hose for a few minutes (until the water coming out of the other hose is clear). Then repeat the process with the other hose. Be careful with your water pressure! Too much pressure could damage your core.
-Once you're done flushing the core, pour some coolant in one of the hose until you see water/coolant coming out of your other hose; the reason for that is to make sure there's no air trapped in the core. Reconnect the hoses and refill your radiator with coolant.
-Jack up your car and leave the radiator cap off.
-turn it on and turn the heat on high. Add coolant in your radiator as the level goes down.
-let car run like that for a few minutes to let the air in the cooling system out. (If you have too much air in your system it will mess up your heat and it could even result in overheating). Squeeze the upper radiator hose a little bit to get the air out of it.
-When coolant start coming out of your radiator, put cap back on.
-let car warm up until it reaches normal operating temperature (until the thermostat opens); take it for a short ride monitoring the temp gauge.
-turn car off and let it cool down
-check coolant level and add as necessary. It may take a few times before you get the system completely refilled and all the air out; but once it's done, you should have heat again. If not (one heater hose still cold), your heater core is still clogged at which point you'll need a new one.
If you feel like doing it, it could be a good opportunity to flush the entire cooling system, especially if you never done it before and your coolant is turning brown. You could buy a flush kit with the connector you install in the heater inlet hose.
It's up to you but you may get better result if you do so, and that will help to prevent other problems, such as overheating or clogged radiator.
Hope this help.
Tuesday, December 9th, 2008 AT 9:53 AM