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Discussion Starter #1
Just changed my coolant temp sensor now car runs hot and radiator fans stay on at all times bad sensor?
 

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How would air get trapped?
if you didn't fill it properly, it could happen.

if you have an 04 it's less likely with the surge tank setup. i guess it seems to happen more frequently with the 05/06 coolant setup to not have a complete fill and have an air pocket somewhere. you may notice that checking the radiator after running the engnie it will be low, perhaps even significantly low, even though you swore you topped it off when you filled it.

i would fill it from the radiator, engine cold, with the engine running. wait for the thermostat to open, then top it off. it can help to have the front end raised slightly. if you have an 04, do the same process i guess, just fill it from the surge tank.

with a properly filled cooling system, you should get better cooling and your temps might drop.
 

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you could also do the secret menu thing by holding down the "mode" and "set" buttons as you turn the car on with the key. should change the center display on your DIC to diagnostic mode and you can cycle through it with the mode button until it displays engine coolant temperature, in exact degrees. the guage itself is not accurate from the factory.
 

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Check the wiring. -39C means open circuit I believe. Fix it before you foul out your plugs and o2 sensors.
 

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Check the wiring. -39C means open circuit I believe. Fix it before you foul out your plugs and o2 sensors.
yeah, OP's car should be running like total crap if that's the case.

also sounds like it would be intermittent, since his gauge is reporting a high temp in the pic.

how did you check the sensor, OP? scantool? secret menu? backprobe?
 

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Discussion Starter #15
It ended up being the coolant temperature sensor connector for anyone who might have a similar problem.
 

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It ended up being the coolant temperature sensor connector for anyone who might have a similar problem.
Was the clip not in or the actual clip needed replacement? Just broke mine off with the header install so I'm scheduled to do this over the weekend with the rest

Sent from my Pixel 3 using Tapatalk
 

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if you didn't fill it properly, it could happen.

if you have an 04 it's less likely with the surge tank setup. i guess it seems to happen more frequently with the 05/06 coolant setup to not have a complete fill and have an air pocket somewhere. you may notice that checking the radiator after running the engnie it will be low, perhaps even significantly low, even though you swore you topped it off when you filled it.

i would fill it from the radiator, engine cold, with the engine running. wait for the thermostat to open, then top it off. it can help to have the front end raised slightly. if you have an 04, do the same process i guess, just fill it from the surge tank.

with a properly filled cooling system, you should get better cooling and your temps might drop.
I want to share my experiences from this morning with the dreaded air bubble so that maybe it will save someone else the grief I went through.
First, got a "check alternator" warning light. Strange. Shortly thereafter, both the dummy water temp gauge and mechanical gauge started climbing, and then the sweet smell of antifreeze. Pulled over and popped the hood. Found the belt shredded and as a result of no water pump, puked all the water out. Luckily, I am as prepared for such things as one could be. Installed the spare belt and used most of the 1 gallon of water I had. Unfortunately, 1 gallon was not enough, but figured it would get me to a water source. Wrong! Enter air bubble. I did manage to get to a service station where a "cheap" gallon of coolant was purchased, but subsequently puked out when I could not get the dreaded air bubble to pop. I tried at least 6 times to purge. Luckily, I found a water source to supplement the "cheap" coolant. Squeezed hoses until carpal tunnel set in. Jacked up the front end as others have recommended, but you don't get much elevation with trunk jacks. Finally decided it was a lost cause to keep hoping the bubble would pass, and pulled the thermostat housing, removed thermostat, reinstalled housing, removed top hose from the pump, filled radiator until water cam out of the top hose, reconnected, topped off radiator, and crossed fingers. Managed to complete the last 10 miles to work at 170 degrees temp on mechanical gauge. What a friggin nightmare! This is the second serious air bubble I've experienced with my LS2. The first 3 or 4 times, I had no issues. I really dislike the cooling system on the LS motors. Don't like the location of the thermostat. AFAIK, GM dropped the ball on this part. Loved the SBC system however. I don't know if there is a sure fire way to eliminate this from happening, but either what I did is, or I finally got lucky after 2-1/2 hours. I hope this might help a fellow GTO/LS owner in the future.
 
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