99 Eclipse RS, heat barely works.

[9699 RS]

I've got a 1999 eclipse rs my problem is that the heat barely works now.

It worked great last winter (It would literally burn you out of the car)
But now I can just barely feel the heat from it, sometime it even blows cold air.

All of the different speed settings do the same thing, with the highest feeling colder than lowest.
The car is staying at normal operating temperature, coolant levels are in check.

I'm leaning towards heater core or heater hoses? Does anyone else have a better idea?
I'm really needing to get this figured out because the temperature has already dipped into the teens this year, and I cannot make my 2:30 hour drive every week without heat. Thanks in advance guys!

 

[BoostedBeaver]

The air gets colder on higher settings because there is not enough flow through the heater core, therefore the increased fan speed causes the coolant in the heater core to become colder causing the cold air. Increasing the flow (or releasing the blockage) to the heater core should remedy the issue.

I would try to flush the heater core. Remove the inlet and outlet hoses and flush in reverse flow (pressure into the outlet house) using the pressure from a garden hose. A long nozzle hooked to an air compressor can be used to blow out any stuck debree. If the flow is still subpar when trying to flush it, you may also try to use some CLR or simple green to soak the core for an hour or two. Make sure if you decide to use any chemical cleaners that you thoroughly flush/rinse the core before putting it back into circulation.

Flush the core and let us know if the problem persists.

 

[eclipse012]

Agreed with robertbaxley. When was the last time you checked your coolant? I would drain all the coolant out the rad. Flush the heater core and lines. Flush the radiator. Fill it back up with demineralized water and run the car with the heat on high, full blast until your thermostat opens and moves the water through the heater core. Shut it off, wait 20 minutes for engine to cool a bit, repeat until water has no chunks or clean. Then add your mix of coolant/water. You would be surprised how much sediment and crap builds up over the years in the coolant system. Long story short, full coolant system flush to start. See what happens from there. Try to stay on top of maintenance. If you want to go the easy route bring it in to have a full system pressurized coolant flush done. Just make sure they include back flushing the heater core and lines as well.

 

[luv2rallye]

If flushing doesn't work you may need a new radiator or heater core (they do wear out). Also here in Mn we put cardboard in front of half the radiator in the winter to help get heat - works great and costs nothing.

 

[BlackKnight2013]

+1 on flushing the heater core. one of the best flushing chemicals i have used is by BG coolant system cleaner kit. it comes with a cleaner you add directly to your radiator after you remove about 16 ounces of coolant and then drive the vehicle and get it hot for about 15 minutes then you drain the coolant and flush with water a few times and then add the stay cool addative the kit comes with and then add your coolant mix.

another thing to check would be for flow through the heater core. the none intrusive test would be with the car at normal operating temperature, and anything in your way of touching the heater core hoses near the fire wall removed, touch the heater core hoses. the inlet hose should be hotter than the outlet by a couple of degrees. if either of the hoses are cold or slightly warm to the touch then you have a restriction in one of the heater core hose/pipe lines or in the heater core itself. an intrusive test for this would be to remove the inlet/outlet hose (best to do both so you can see if you have a restriction in the heater core) from the heater core and have another person start the vehicle and another person to watch for a flow/gushing stream of coolant coming from the outlet/inlet. if you have flow then you have no restrictions and the water pump is good and providing enough flow. if you have no flow then you have either a restrictions, which you will have to try to find and remove and re-test again; or a bad water pump that isn't providing enough coolant flow to support any heat to the heater core. to fix a bad water pump you would simply have to remove the timing cover and belt and replace the water pump. if you do find its a water pump, i would highly suggest a factory water pump and a gates timing belt kit with the tensioner and all the idlers and belt as it would be the best time and less headach later to go back in and do it again if you have never done one before or know of its service history.

if you have good flow and no restriction in the heater core is free of debrie, then i would suggest a new thermostat of 192*F and gasket.

 

[2slow4now]

Be careful using the DI water method and be prepared to replace parts. It does work well but make sure to not leave any in the system for any extended period of time.
Why I say that is think of DI water as being like a sponge. It is pure water that has plenty of "room" for minerals to be absorbed into it including the metals in the cooling parts.

Long story short a friend had an old truck and put Di water in to flush and clean the system and it absorbed the corrosion, rust, and chemical build ups in his cooling system which caused many leaks. He did run it for several days though. He had leaks around the thermo housing, hose connections, radiator, and even the water pump gasket. His cooling system was "sealed" by corrosion and build up of years of sediment. It was clean when he was done for sure along with some new parts.

 

[BlackKnight2013]

another thing to check is the temp control cable at the heater box to make sure it hasn't popped off and can move the blend door to full heat position.

 

[97 eclenger]

Nothing about the thermostat? A thermostat stuck pen will continuously cycle coolant, not allowing it to warm up. Instead of the temp gauge reading nrmal in the middle, itd show as only a quarter.

 

[Lou98GSX]

try feeling the heater hoses they should both feel the same . if one is hotter than the other then the core is clogged . if they both feel the same then i would make sure the blend air door is working . turn the blend air knob back and forth you should hear a thud if the door is moving properly . if it isn't then the cable could of come off .

 

[CABLODSM]

Mine I like this. I thought it's from my headgasket.
I smell coolant in my exhaust.

 

[97 eclenger]

that sounds like a head gasket if you can smell it and see white smoke. hopefully he figured it out already. if not just a clog or thermostat

 

[abelebd]

Like 97 eclenger suggested I would check the thermostat.

 

[fastfred]

If all the coolant, heater core etc. checks out i'd take a look at the blend door.