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Hello, recently I noticed the heater in my 2011 Hyundai sonata is not as hot as it was. I didn't put too much thought behind it because it would get the job done. Due to the cold weather I've been experiencing on the east coast with single digit temperature or the teens, the heat sucks now. Someone suggested to me that it could be a heater core but when I looked online to diagnose a heater core issue, all the symptoms for a faulty heater core, experiencing none of it. Any feedback will help.
 

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Hello, recently I noticed the heater in my 2011 Hyundai sonata is not as hot as it was. I didn't put too much thought behind it because it would get the job done. Due to the cold weather I've been experiencing on the east coast with single digit temperature or the teens, the heat sucks now. Someone suggested to me that it could be a heater core but when I looked online to diagnose a heater core issue, all the symptoms for a faulty heater core, experiencing none of it. Any feedback will help.
My Sonata's gauge is one notch lower than center...is your car in that range? If it's not you may need a new thermostat.
 

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My thermostat is fine, I replaced it three years ago because it was over cooling the engine. From what I been reading coolant that have particles can clog up the heater core which can affect the heating over so I may just need to get the cooling system flushed.
 

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Make sure you have the HVAC setup to recirculate the air instead of using fresh air in extreme hot or cold weather. trying to cool 100F air with the AC will only get it down to around 60F (maximum efficiency of a basic AC system in a car). Same goes with heat, if its 10 degrees outside and your heating the air with 170F coolant be prepared for not so hot heat. Recirculating the air will allow the car to reheat / recool the same air over and over allowing for hotter heat, or colder AC.
 

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The heater core should be OK. Hyundais 180F thermostats don't heat the motor up enough to deal with good heat with below 0F temps.

I just put a 190F t-stat in my Accent. It's much better but I have not seen the below 0F temps yet with it.

The higher temp t-stat perfectly matches the fan turn on and off speeds though. Before with the standard 180F t-stat the fan would seldom if ever come on. Fan turn on is 204F and off at 194F but this is only when not moving.

A piece of cardboard covering the front will help quite a bit.

The thermostat I used is a Stant 48469 190f Xactstat for the 1999 Accent 1.5L. Probably fits a lot of Hyundai 4 cylinders. It will fit my Gen Coupe 2L also.
 

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The heater core should be OK. Hyundais 180F thermostats don't heat the motor up enough to deal with good heat with below 0F temps.

I just put a 190F t-stat in my Accent. It's much better but I have not seen the below 0F temps yet with it.

The higher temp t-stat perfectly matches the fan turn on and off speeds though. Before with the standard 180F t-stat the fan would seldom if ever come on. Fan turn on is 204F and off at 194F but this is only when not moving.

A piece of cardboard covering the front will help quite a bit.

The thermostat I used is a Stant 48469 190f Xactstat for the 1999 Accent 1.5L. Probably fits a lot of Hyundai 4 cylinders. It will fit my Gen Coupe 2L also.
wut? :blink:

ten degree open change between t-stats will net you no more than 3-6 degrees out of the vent. And no, they are not the same t-stat
 

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Make sure you have the HVAC setup to recirculate the air instead of using fresh air in extreme hot or cold weather. trying to cool 100F air with the AC will only get it down to around 60F (maximum efficiency of a basic AC system in a car). Same goes with heat, if its 10 degrees outside and your heating the air with 170F coolant be prepared for not so hot heat. Recirculating the air will allow the car to reheat / recool the same air over and over allowing for hotter heat, or colder AC.
On my car, you can only use recirculate with A/C...it's de-activated for heat. May be when you are in defrost mode (because the A/C is on) it will work?
 

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Recirculating the air when it is very cold out will fog up the windows in less than 5 minutes.

And the AC will not come on when the temp is below freezing.

And judging from the pictures of the Sonata thermostats it does appear they are the same size. So the 190F Stant for the Hyundai 1.5L should fit and give you a nice boost in heat while staying within the ECU cooling fan on/off parameters.

Here is my account of trying the higher temp t-stat in my Accent.

http://www.hyundai-forums.com/mc-2006-2011-accent/609385-so-how-well-does-your-heater-work.html
 

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The coolant gauge is one notch below half...how different is that than anyone else's? We've had extreme cold here and I have to turn it down after heating for about 10 min.
 

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It appears the Stant 190F t-stat has a .2" larger diameter bypass sealing disc. This is used when the t-stat is fully open. It may or may not fit in the back of the thermostat location on the engine.

But the end sealing disc looks like it can be changed pretty easy on my OE t-stats. Just a clip holding the spring and disc on.

OE Sonata dimensions for 2L and 2.4L

Temperature (F): 180
Design: Bottom By-Pass
Flange Diameter (in): 2.12
Height from Flange (in): 0.97
Depth from Flange (in): 1.6
By-Pass Flange Diameter (in): 1.1
Jiggle Pin: Yes

Stant 190F LC Accent t-stat. 48469
Temperature (F): 190
Design: Bottom By-Pass
Flange Diameter (in): 2.12
Height from Flange (in): 0.97
Depth from Flange (in): 1.52
By-Pass Flange Diameter (in): 1.3
Jiggle Pin: Yes
 

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The coolant gauge is one notch below half...how different is that than anyone else's? We've had extreme cold here and I have to turn it down after heating for about 10 min.
You really cannot judge the actual temp by the OE gauge, other than hot or cold. You need an OBDII scanner to see what the ECT sender is sending to the ECU.
 

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My thermostat is fine, I replaced it three years ago because it was over cooling the engine. From what I been reading coolant that have particles can clog up the heater core which can affect the heating over so I may just need to get the cooling system flushed.
Low coolant level can cause similar issue.

3 year old thermostat could've failed again. So, without an OBD scanner, how do you know its FINE?

Asian coolants don't clog heater cores. They don't have silicates.

Heater core flow can easily be checked. So, pull the hoses and go from there.

I'd take the advice that the others provided concerning the thermostat. Replace it. It has a tolerance that can be out of spec, or be slowly degrading.

Stock thermostat isn't fully open until 203F
Valve opening temperature : 82 ± 1.5°C (179.6 ± 2.7°F)
Full opening temperature : 95°C (203°F)
Valve lift : 8mm (0.3in.) or more at 95°C (203°F)
 

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You really cannot judge the actual temp by the OE gauge, other than hot or cold. You need an OBDII scanner to see what the ECT sender is sending to the ECU.
Yes, but it should give you an approximation from car to car!
 

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Yes, but it should give you an approximation from car to car!
Maybe, at best you are still only knowing if it is hot or cold. It's a dumbed down gauge and I prefer the red and blue lights as they are rather precise. The OE temp gauge on my Gen Coupe is worthless.

No way will you know what temp the thermostat is opening at.
 

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No way will you know what temp the thermostat is opening at.
My only point, is a reference from one to the other: I have adequate heat at this point in the gauge, what does your's read. :rolleyes:
 

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My only point, is a reference from one to the other: I have adequate heat at this point in the gauge, what does your's read. :rolleyes:
My Accent does not have a factory gauge. It has a blue light when it's below ~66C. But I do have an Ultra Gauge connected all the time. It is accurate to 1C.

And bad ECT sensors or connections to it will affect the reading.
 

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My Accent does not have a factory gauge. It has a blue light when it's below ~66C. But I do have an Ultra Gauge connected all the time. It is accurate to 1C.

And bad ECT sensors or connections to it will affect the reading.
Ah, but the OP has the same car as I do...hence compare readings!
 

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Ah, but the OP has the same car as I do...hence compare readings!
Yes but what are you comparing. On my Gen Coupe with a temperature gauge it does not move between 160F and 190F. Unless you know what the ECU is actually reporting seeing the gauge is just an idiot gauge and good for laughs maybe.
 
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