Thread: cooling fans

So I haven't posted in a few months. Summer was crazy lol. I have an 06 gxp 122, xxx. Just replaced water pump due to a leak not that hard but time consuming. So I'm proud to say no more leaks but I have noticed my fans don't kick on unless I use the ac. My car will go alittle over half like 217 F and then come down to 195 and keep cycling through this. Its a gradual process not a fast up and down. When I use the ac I hear a low speed and high speed I guess but when I turn thw air off high speed stays on low turns off and then after about 5 min the high speed will turn off. No fans will cut back on unless I turn the air on again. So I unplugged the coolant temp sensor and they stay on. I'm not sure where to go from here. Do I need to replace the temp sensor?

Originally Posted by GXPrunner06

So I haven't posted in a few months. Summer was crazy lol. I have an 06 gxp 122, xxx. Just replaced water pump due to a leak not that hard but time consuming. So I'm proud to say no more leaks but I have noticed my fans don't kick on unless I use the ac. My car will go alittle over half like 217 F and then come down to 195 and keep cycling through this. Its a gradual process not a fast up and down. When I use the ac I hear a low speed and high speed I guess but when I turn thw air off high speed stays on low turns off and then after about 5 min the high speed will turn off. No fans will cut back on unless I turn the air on again. So I unplugged the coolant temp sensor and they stay on. I'm not sure where to go from here. Do I need to replace the temp sensor?

not to far out of whack however still high. with that mileage have you had the coolant flushed, also has the t-stat been replaced??. take care of the maintnence issues then try cleaning the temp sensor make sure theres no sludge built up on it.

First thing I'd guess is air in your cooling system. When you changed the water pump you must of drained the majority of coolant out and had to refill after your project correct? if there is a big air bubble in the block it can create hot air near your coolant sensor and you will get a high reading. Sometimes its difficult to get the motor to "burp" so I've been prefilling the block with coolant by taking off the thermostat housing and t-stat and pouring in the coolant to the top. Are you sure your fans don't come on eventually without the air on? You may be able to get the air to bleed out with the bleeder screw on top of the t-stat housing also. I'm assuming your LS4 has a bleeder screw on the housing like my L67?

The thermostat has not been replaced I heard it is a bit of a nightmare on the ls3. The cooling system had been taken care of at 100, 000. Boughr rhe car used at 115, 412. To my knowledge I don't think the ls3 has a bleeder screw. My other question was about my fans not turning on, any ideas?

No ls4 do not have. Bleeder screw. Our system bleeds through the steam vents which go to the top of the filler neck on the block. To make sure you can unscrew the cap and run the car for. Little while to make sure you have no air but I doubt that's your issue. If you're on a factory tune your fans will hit 30% around 210 degress sowhat youre seeing is normal. The thermosat isnt that bad if you go from underneath.

The fans kick on around 217??. If I run the heat or air my car will stay where its suppose to be. I'm assuming because the fans are on. Half way on the gauge is about 210-212? Right?

Yep sounds normal to me for a stock PCM. A lot of us reprogram with a 180 t stat and lower temp setting for the fan turn on.

Originally Posted by GXPrunner06

The fans kick on around 217??. If I run the heat or air my car will stay where its suppose to be. I'm assuming because the fans are on. Half way on the gauge is about 210-212? Right?

yep, right about that temp, the heat just helps the temps because the heater core is acting like a second radiator.

here is a stock 06 fan turn on temp vs fan percentage power, notice our fans wont kick on regardless till 192degrees regardless. getting a 180degree is pointless stick with the stock 187degree replacment thermostat if you go that route


Coolant temp
Labels 192 196 199 203 207 210 214 217 221 225 228 232 235 239 243 246 250
Fan Desired 0.0 6.0 12.0 16.0 18.0 20.0 25.0 32.0 39.0 46.0 53.0 53.0 53.0 53.0 53.0 53.0 53.0

Originally Posted by tms8582

Yep sounds normal to me for a stock PCM. A lot of us reprogram with a 180 t stat and lower temp setting for the fan turn on.

for the LS4 and other gen 4 v8's our only option is to turn up the fan power at 192 degrees and scale it from there.

Oh yeah forgot I was in the LS4 section lol On a naturally aspirated engine the cooler running temp is not as important anyway.