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What Temperature is your Heat? 240 Degrees?

5.6K views 33 replies 12 participants last post by  Cciman  
#1 ·
Hello Everyone, first time poster, long time reader.

My 2010 3.8L Town and Country with 116,000 miles has me confused. The Heat coming out of the vents gets up to 240 degrees on full heat! The temp gauge never goes over halfway, but if the heat coming out of my vents is 240 degrees, doesn't the motor temperature have to be 240 degrees also?

A couple more facts, I believe the thermostat works, because my top radiator hose is measuring 175 degrees. I would like there to be more pressure on the top hose though, is seems pretty limp when the car is running, I thought these things were supposed to have some pressure while the cooling system is hot.... The thermostat housing measures about 190 degrees and the top of the engine right next to the thermostat housing measures about 215 degrees (when measured by a temperature gun) The engine has been smelling slightly hot, but not too bad. I recently did a coolant spill and fill. I put in the correct G05 antifreeze and I used an air lift system to burp the air out of the system while both the front and rear heaters were on.

I don't know what the next step is, 240 degree heat seems way too high even though the rest of my gauges seem in range.

Do you guys have any ideas? What temperatures do you guys have with your heating system?

Thanks!

Ben B.
 
#3 · (Edited)
Exactly, unless I still have an air bubble in there and that air bubble is getting up to 240 degrees. The air coming out of the vents is HOT! Like, its hard for me to hold the heat gun at the vent exit because my hand starts getting very very hot.

I have also used my temp gun to check the heat temp out of our Camry vents and Chevy Traverse vents, about 170 to 180 degrees, would not get ANY hotter.
 
#4 ·
Interested to hear the outcome of this.
Not at all saying your wrong in your observation, but 240 seems almost impossible to believe.
Hot tap water has scalding potential at +/-140..
you can smoke a pork shoulder at 250 and make some fine pulled pork lol
 
#6 ·
Top Heater Hose is 180ish, bottom hose is 100 or so. It takes a LONG time for my heater hoses to get any temperature at all in them. I was getting 230 degree heater vent temps and my hoses were pretty cold. The hoses did not feel pressurized, so I took the radiator cap off with the engine still running. Keep in mind, the engine had ran for 25 minutes and the heater temps were 230, yet the hoses were not that warm and I was brave enough to take off the radiator cap, which I know is dangerous, but the front of the coolant system is acting almost independent of the heater core.
 
#8 ·
Something doesn’t add up. The heater hoses should both be 195 or so. One hot and one cold usually means the heater core is plugged, but that would cause less heat. I still question that the air coming out is that hot — a real thermometer might give a different reading.

I don’t think a radiator cap will change anything.
 
#10 ·
Coolant is always flowing to the front and rear heaters, there are no control valves in these systems.

The heating system operates regardless of the thermostat being open or closed. Many times, while driving, the thermostat is closed but your heater is providing heat, acting like a radiator. If the thermostat is stuck closed, the heater can get very hot and your engine temperature should be very hot as well. The coolant system keeps everything operating at an acceptable temperature and from overheating, that's basically what it does. The heating system can operate on its own, to a point
 
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#18 ·
Your temperature gauge should be showing an overheating condition when coolant isn't circulating and cooling properly. Also dash lights will be flashing and you will know there's an overheating condition if bad enough.

What's the temperature on the heater lines where they go through the firewall? Heater can't get any hotter than that.
 
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#12 ·
I am going with the t-stat not opening, or at least not all the way. In the past year with similar aged vehicles, we went through 3 bad t-stats in a row. Two didn't open at all and the other wouldn't close after it did open. Then, out of disgust, we put one in from Chrysler which costed $16 more than after market rip offs & all is well now. Can you use your heat gun and scan all the areas of the radiator after warm up to see how uniform the temps are. I know from the front the condenser is in the way and shrouds & such from the rear. There is almost nothing on any newer vehicle that isn't buried behind a bunch of crap! Good Luck! :(
 
#16 ·
PVC plastics melt at 320-400 degrees. I cannot keep my hand in front of the vent, it gets burning hot and I have to move my hand out of the way. The Heat Gun was accurate on the other cars, 170-180 degree heat output at the vent. My exhaust manifold measured like 500 to 550, I haven't googled to see if that is a standard reading.
 
#17 ·
Temp gauge reads normal.
Vehicle operates as normal.
Rad hoses are normal to cool.
Heater hoses are 180F at most.
All responses here tell you it's not running above 240F.
You say the air vent can burn you. Skin burns at anything over 130F.
Removing cap when hot does not result in boil over. 50/50 mix boils at 226F without a rad cap. You believe coolant temp is well over 240F?

The only thing you have saying the temp is 240F or more is the heat temp gun. What does logic tell us here?
 
#21 · (Edited)
Why worry about the temp of the heater air? You've got a good heating system.
Don't turn it up so high. Is this a real problem?

What are you trying to troubleshoot elsewhere in the cooling system?

Heater core flow is on the hot side of the thermostat-- independent of the thermostat and beyond. If you run both heater cores, full blast with cold cabin air, no load on the engine, you may bypass the cooling system (radiator) completely, as you don't reach temp to open the thermostat.

I don't trust your reading. I think you need a meat thermometer in the vent for accurate readings. Try that to confirm what you think the temp is.
 
#22 ·
I am going to try the meat thermometer in the vent and compare it to my heat gun numbers.

I'm just trying to not blow up the motor. I don't trust the factory gauges anymore since losing my Tacoma engine under very similar circumstances.

I really appreciate all the help! The Y hose reading and meat thermometer will hopefully show my van is operating correctly. Fingers crossed.
 
#24 ·
Made progress today, the Meat Thermometer is showing the infrared Heat Gun is not accurate. I did not test my van yet, but I did compare readings on our Camry and readings on my mom's 2008 Dodge Caravan with the 3.8. On my mom's 08 Caravan, the Heat gun showed 215 while the meat thermometer showed 160. I'm guessing my 2010 van will show 170 out of the vent with the meat thermometer, but I still need to verify this. I took some additional readings from under the hood of my mom's 2008 Dodge to compare to my van. My moms van showed 200 at the top of the motor and her radiator hoses were 180 Top, 120 Bottom.

So, I'm confident my vent temp is not actually 240 degrees! I do think my vent temps are hotter than my mom's and top of the motor temp has proven to be 10 degrees hotter than my mom's, so I fell like I still have an issue, but not as big of an issue I originally thought. Whoever first said an infrared temp gun struggles to get vent temps was spot on! I will continue to troubleshoot to see if I can get my head temp and vent temps down to my mom's temp range. Maybe 10 degrees is an acceptable variance?

Thanks for the input, help and ideas everyone!
 
#26 ·
Just point it at the thermostat on your kitchen wall. :)
 
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#30 ·
Hello Everyone, first time poster, long time reader.

My 2010 3.8L Town and Country with 116,000 miles has me confused. The Heat coming out of the vents gets up to 240 degrees on full heat! The temp gauge never goes over halfway, but if the heat coming out of my vents is 240 degrees, doesn't the motor temperature have to be 240 degrees also?

A couple more facts, I believe the thermostat works, because my top radiator hose is measuring 175 degrees. I would like there to be more pressure on the top hose though, is seems pretty limp when the car is running, I thought these things were supposed to have some pressure while the cooling system is hot.... The thermostat housing measures about 190 degrees and the top of the engine right next to the thermostat housing measures about 215 degrees (when measured by a temperature gun) The engine has been smelling slightly hot, but not too bad. I recently did a coolant spill and fill. I put in the correct G05 antifreeze and I used an air lift system to burp the air out of the system while both the front and rear heaters were on.

I don't know what the next step is, 240 degree heat seems way too high even though the rest of my gauges seem in range.

Do you guys have any ideas? What temperatures do you guys have with your heating system?

Thanks!

Ben B.
Don't drive it at 240F

1. Change thermostat - 195F. Plenty of videos how to on YouTube. And its 20 bucks.
2 . Burp, bleed air with a funnel with radiator attachment. - also 20 $ on Amazon and plenty of videos.
3 change cap - hose should be very stiff and hard under normal operation.
4 Check internal sensor temperature against gun temperature.
10-20-30$ max wireless ( Bluetooth) OBD "scanners" on Amazon - no need to spend more + the free Torque Pro app and you have a perfect " phone" OBD scanner , code eraser / lookup.
5. When all changed and closed up you should see thermostat fully open at 195F and top radiator hose getting warm ( even a bit before)
6 Run parked for a while - at 220- 225 max you should see radiator fan blowing on high.
And hose getting stiff

If that is not happening - mayyy be a bad water pump , but you would see other signs of that. Noise, leak, drip.

If you suspect " clogged" radiator it's easy to check - but unlikely unless your previous coolant looked like oatmeal or you used one of these " seal a hole" liquids from auto stores.