lower rad hose temp during winter

iliketoyota · 01-03-2013, 01:02 AM

Ive been trying to determine my problem of my heater only blowing 100 degree air. Ive replaced the heater core and all the flaps are working correctly. The control valve is working too. One thing i noticed is after 30 minutes of driving in 20 degree temperatures the lower radiator hose was still about 50 degrees. Is this normal for this time of year? Because it kind of had me suspecting the water pump not circulating well after noticing that. The motor is running at 180F as tested by a heat gun at the thermostat housing and ive put 2 different ones in it.

A few days ago i spent half an hour bleeding the system with the front raised up and got it to blow a litter hotter but not as hot as it should be. There shouldnt be any air bubbles i would think.

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timothy47129 · 01-03-2013, 08:23 AM

If its 50 degrees coming out of the rad it sounds like its doing its job very well.I went with a 190 degree t-stat and drilled a small hole in it so the is always a little coolant flowing trough it and it helped quite a bit.Is your fan clutch disengaging when cold?I had to bend the spring on mine a tad so it wouldnt run when it was cold out.when i start mine in the morning you can hear the fan run for about 30 seconds untill all the fluid in it gets flowing to unlock it then it stops.

rworegon · 01-03-2013, 03:10 PM

Are you using a Toyota OE thermostat?

Similar issue solved with a Toyota t-stat

jerry507 · 01-03-2013, 07:12 PM

I don't understand your obsession with the lower hose temperature. The heater circulates fluid from the block and not from the radiator. In a perfect world there isn't continuous flow through the radiator. Cold fluid from the radiator is pumped into the block until it heats up. The thermostat opens after the fluid reaches a certain temperature and flushes it into the radiator which pushes cold fluid in. The coolant temperature inside the engine looks like a ramp going up and down.

The fluid in the bottom radiator hose SHOULD be cold, or you're flushing hot fluid into the engine to cool it. Obviously counterproductive. IIRC you mentioned in your last post that you used an IR thermometer to measure the temp of the upper hose outlet and it was 180 or 190deg F. If your dash temp gauge has it sitting about middle, and the outlet was the right temp, then your engine coolant system is probably working just fine.

Most likely you have a blockage or restriction preventing fluid from getting to the core. What is the temperature of your heater hoses right by the control valve?

01-03-2013, 03:10 PM	#3 (permalink)
rworegon Contributing Member Personal Sales Rating: (0) Join Date: Nov 2010 Location: Columbia River Gorge, Oregon...east side Posts: 2,782	Are you using a Toyota OE thermostat? Similar issue solved with a Toyota t-stat __________________ 95.5 Tacoma 3.4L Auto, bought with 0.8mi. FSMs TSBs P/N & diagrams (source for OEM parts on east coast) PNW OEM Parts source - Titus-Will, Tacoma, WA

01-03-2013, 07:12 PM	#4 (permalink)
jerry507 Registered User Personal Sales Rating: (0) Join Date: Jun 2011 Location: Twin Cities, MN Posts: 151	I don't understand your obsession with the lower hose temperature. The heater circulates fluid from the block and not from the radiator. In a perfect world there isn't continuous flow through the radiator. Cold fluid from the radiator is pumped into the block until it heats up. The thermostat opens after the fluid reaches a certain temperature and flushes it into the radiator which pushes cold fluid in. The coolant temperature inside the engine looks like a ramp going up and down. The fluid in the bottom radiator hose SHOULD be cold, or you're flushing hot fluid into the engine to cool it. Obviously counterproductive. IIRC you mentioned in your last post that you used an IR thermometer to measure the temp of the upper hose outlet and it was 180 or 190deg F. If your dash temp gauge has it sitting about middle, and the outlet was the right temp, then your engine coolant system is probably working just fine. Most likely you have a blockage or restriction preventing fluid from getting to the core. What is the temperature of your heater hoses right by the control valve? __________________ 95 Pickup, 22re, 4x4 regular cab

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01-03-2013, 08:23 AM	#2 (permalink)
timothy47129 Registered User Personal Sales Rating: (0) Join Date: Apr 2012 Posts: 180	If its 50 degrees coming out of the rad it sounds like its doing its job very well.I went with a 190 degree t-stat and drilled a small hole in it so the is always a little coolant flowing trough it and it helped quite a bit.Is your fan clutch disengaging when cold?I had to bend the spring on mine a tad so it wouldnt run when it was cold out.when i start mine in the morning you can hear the fan run for about 30 seconds untill all the fluid in it gets flowing to unlock it then it stops.

01-03-2013, 07:12 PM
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