[Sarahlarain]

I have a 2008 Kia Optima that I bought last year. The heat has stopped working. Comes out a little warm at best, even after driving for a long time. Thermostat has been replaced, plenty of antifreeze in it, heater core checked for clogs (someone put something in the lines that the mechanic couldn't identify but it's been flushed out, they assumed it clogged the heater core but someone else tested it and it flowed fine). Antifreeze does not get hot. I can drive for 20 minutes and you can take the cap off the radiator and put your finger in it. It'll be lukewarm. The heater hoses were taken off when we checked the core for clogs and I was told to start the engine. Water trickled out of the lines straight out of the heater core but I was told it should be gushing. The car does not overheat, whether driving or idling. There are no leaks. I'm wondering if it might be the water pump. I wanted to check if it could be something else before sinking money into replacing the pump. Thank you for any input you might have! As a woman, I often get suspicious taking it to a shop because they could tell me anything and I wouldn't know if it was true or not.

 

[Sarahlarain]

You can physically grip the hoses that carry the coolant to and from the radiator, and see if they stiffen up or get warm when your engine gets up to operating temperature. I'd say do that first.

Make sure the radiator system is actually working.

So does your car overheat when you let the engine run long enough? If the water pump is bad, then your car would overheat if you let it run and build up heat. The coolant would start to boil and you'd see the billowy steam coming out.

No overheating, even after driving for a long time. One of the hoses will get hot, the other will remain cold.

 

[Sarahlarain]

Cooling system filled to top? What does the engine temp gauge show, bars?
Have old thermostat to test. If the car never overheats or gets hot, I'd say thermostat.
If the pump wasn't circulating water properly, the engine would overheat.

Thermostat was replaced last week with a brand new one. Also topped it off with coolant, and no apparent leaking. After we did that the heat worked for about twenty minutes then started blowing cool again.

 

[Sarahlarain]

Thermostat was replaced last week with a brand new one. Also topped it off with coolant, and no apparent leaking. After we did that the heat worked for about twenty minutes then started blowing cool again.

Also, the temp guage has been normal, climbing to the same spot it always has. Not even a little bit of overheating.

 

[Sarahlarain]

That's impossible if your thermostat is working. Are you sure you are letting the engine reach full operating temperature to where the thermostat opens so hot coolant can flow through both tubes?

Your thermostat is NOT opening if the other hose remains cold but the engine is at operating temperature.

Can you do this test: after driving around to where the engine is fully warmed up, park and let the car idle with the engine running. Do both coolant hoses get warm/hot then, or does one stay cold?

According to the temp gage it gets to operating temp. I've driven it down the highway a couple times at 60+ mph for a good six miles, parked and turned it off and checked the hoses and one is significantly cooler than the other, but I'll try letting it idle for a while as well. The actual mechanic I took it to also said the same thing, that one hose is not getting hot but he could only take a guess that it was a clogged heater core. Not sure what all tests they did there.
I'll also try using compressed air to clear out the heater core, if I can convince my stepfather, who helps me (or rather I help him), that it could still be clogged. He used a water hose to test the flow but he also poured coolant into one of the hoses and it flowed right out of the heater core. A little bit of gunk still came out even after having it flushed at the mechanic back in January. Chunky yellow-brown stuff that nobody could identify. So maybe there's still some left inside the core. We also tested the old thermostat that we replaced by placing it on top of a wood stove and it opened just fine, so I don't think it was bad, I think the coolant just wasn't getting hot enough to open it. What else affects the temp of the coolant? The first issue I had with the heating (only have had the car a little over a year) was the it wasn't working on the passenger side. The air blew out just fine, but heat only came out of the two driver's side vents. Had some sort of motor replaced and a pulley system plus a little flushing and it worked, just not as well as on the driver's side. Now there's no heat anywhere and it's winter in WV. I don't know a whole lot about cars but it seems if it's usual issues like thermostat or water pump I should have some overheating and leaking, right?

 

[Sarahlarain]

I just drove it a good forty minutes down the highway and back, pulled into the driveway and checked the hoses as it idled. One hot and one barely warm. The fan kicked on while it was idling and very cold air was blowing from the radiator onto the engine, which I understand is it's purpose, to cool the engine, but wouldn't it be a little bit warm at least?

 

[Sarahlarain]

Could it still be the heater core, even if water from the hose went through effortlessly? Can there be other issues with it besides clogging?

 

[Sarahlarain]

What hoses are you touching, one hot, one warm, heater core or radiator?
Also, the Ford bomb, running water through the heater core did nothing, it was no different
than the water pump pushing water through, but when I hit it with compressed air through
the out hose, a lot of crap came out into the container.

The heater core hoses. I brought up the compressed air to my stepdad but he insisted it would damage the heater core. But the thing with him is he knows everything without actually knowing everything, and trying to convince him he might be wrong is impossible. So I'm going to look for someone else to do it.

 

[Sarahlarain]

Ok, I've found some info online about thermostats being stuck open. Engine runs cooler, warm air barely comes out while sitting still but blows colder while driving, a drop in gas mileage performance. These are all spot on issues I've been having. The one thing that confuses me is my temp gauge climbing up to normal, whereas I read an open thermostat will cause it to climb slower. So, what causes a brand new thermostat to stay open?

 

[Sarahlarain]

The wnv

Not certain as to where you live, but if a cold environment, if the stat wasn't closing, the temperature gauge would never rise. Have seen cars w/o a stat, let's say engihe temp 180, but when driving in a cool environment, the gauge goes down to nil, it will never heat up.
As far as compressed air, I wouldn't blow 150 psi into the core. When I did mine, I hit it when relatively low and kept giving it a shot as the pressure got higher and when the junk came out stopped.
[/QUOTE

That's what I was picturing when you described using the compressed air. I was thinking there's a way to use lower pressure without full-blasting the core right outta there.
The weather has been pretty cold the past couple of weeks, averaging in the 30s to low 40s during the day. I'm going to take the thermostat out tomorrow and see if it's open. My fingers are crossed that the old one was worn out and this new one is just faulty.

 

[Sarahlarain]

I'll stick my neck out and say you'll find nothing wrong with the stat. At 30 degrees, if the stat
was stuck open, the engine temp would never rise to normal.

You are correct. I took it out and it was closed. Held it over a hot wood stove to open it then let it cool and it functioned just as it should. We also ran the hose through the radiator to make sure it wasn't clogged as it does not get hot either. My stepdad is convinced it's the water pump going bad and not circulating things properly. What I thought was my serpentine belt coming loose and chirping he said could be the pump causing the noise. I was very much hoping it was the thermostat because I have to help him work on it and I do not relish the thought of going after the water pump.

 

[Sarahlarain]

Sorry for the disappearance but I did finally get it into another mechanic. They checked everything, blend doors included, replaced thermostat again, and the water pump. They had it for a week and could not get the heat to work. They were sure nothing was clogged but they flushed it. Then flushed it again. Then a third time. They got solid stuff to come out of the heater core. Somebody but a ton of stop leak in there. At one point they test drove it and the heat worked for a minute then the coolant reservoir got so pressurized it literally blew up. The heat works now, but basically I paid almost $800 to flush out what was probably masking and holding together a leak in the head gasket. You really never can trust a used car salesman, no matter how many good reviews his business gets. You are all very much appreciated for your advice. I have a feeling I have even bigger issues coming my way.