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No heat after changing temp sensor

855 views 4 replies 3 participants last post by  PMI 
#1 ·
I finally got around to changing out my coolant temp sensor (the one near the thermostat). This cleared up my flaky dash gauge (it was intermittent - mostly never reading anything). However, now I'm not getting any heat from the car. I'm afraid that I may have air in the coolant lines to the heater block, if this is possible, since I lost a lot of coolant by removing the heater hose to gain access to the sensor.

The good news - my ACC seems to actually try to make the interior warm up (blower is on strong), making me think that the sensor is also used to tell the ACC that the engine is warmed up. Before fixing the sensor, my ACC would not turn on the blower, thinking that the engine was always cold.

I am not sure that I got the car hot enough to open the thermostat and force coolant through the whole system, but I'm a little scared to run the car if there is a possibility that there is air in the system and it could create hot spots in the block due to air. Should I be worried? I should probably also drain and flush the whole system - it's been a while.
 
#2 ·
Just idle the car for a few minutes, and keep you eye on the instrument panel temp gauge and on the level in the overflow tank. If the level in the tank goes down, top it off with fresh coolant. It should take about 5-7 minutes to warm up (in moderately cold weather).

Thermostat opening temp: 89 +/- 2C
Temp gauge at mid point (9 o'clock) 85-115C

When the engine has warmed up and the temp gauge is at 9 o'clock (center of the gauge range), turn the ignition off and carefully touch the hoses going to the heater core. They should both be warm.

Oh, and reset the ACC, mine gets confused about once per year, and does strange things.
 
#3 ·
Your thermostat should have opened at minute 4 or so; but as the system is air bound, this will not happen. I'd add more coolant thru one of the hoses - probably the upper...

The coolant system is self purging - this will eliminate the remaining air.. The temperature transmitter sends a signal to the ICE ....this signals the instrument cluster...
 
#4 ·
I think you've got it, Earthworm...that makes sense. I topped off the coolant reservoir and expected to have to add significantly more coolant once the thermostat opened, but the level didn't drop significantly even once really warmed up.

I'll add coolant through one of the upper hoses to see if I can get the thermostat covered in liquid and try again.

PMI: how do I reset the ACC?

thanks!
 
#5 ·
sejman said:
PMI: how do I reset the ACC?
Press AUTO and OFF simultaneously, and hold for a couple seconds.

FYI: Our thermostat has a small air hole on the top edge. The hole is open even when the 'stat is "closed", meaning cold. As the coolant pump forces liquid coolant into the engine, air trapped in the top of the engine escapes through that hole.
 
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