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Discussion Starter #1
Hit my first real issue with the sts-v. Hopefully one of you can help me out. Started getting the engine hot ac off msg. I know this is normally tstat and car was running fine so I ordered a tstat and kept driving the car until it arrived. Before I could get the tstat in the mail I got a check coolant msg. I brought it to my shop and we checked it out, had a small oil leak that is being dealt with but obviously that doesn't have to do with my coolant. My main reservoir was about an inch lower then where it should be. My other 2 reservoirs that are on the passenger side (small tube and reservoir beside) were completely empty. We filled up the small tube and both other reservoirs to see what happens. It's been about 2 days and the small tube is completely empty again while the other 2 seem to have stayed around the same. Oil cap looks clean so he doesn't think it's leaking into my oil and no coolant drips under car. Where is my coolant going?
 

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2007 STS-V
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The small tube and tank closest to the small tube is for your intercooler not connected to your radiator.keep filling the small tube till it stays full.the rest I don't know.someone else will chim in and try and help you out.good luck
 

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'79 coupe deville, '04 Deville DTS White Lightning
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It can be an up to 1 month long process. Every morning top off on the intercooler before you go by following the instructions in the manual. Eventually all the air will be expelled from the system and you will begin to wake up to a consistently topped off intercooler system. (The skinny neck on the passenger side.)
 

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'06 STS-V, '17 CTS-V
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He was asking about the "ENGINE HOT/AC OFF" message, though. Can THAT message be triggered by a dry intercooler circuit, just as it can be triggered by a low engine coolant circuit? Thought the Engine Hot/AC Off was related specifically to the engine coolant circuit. I guess, but it would be hard to believe, that high IAT's due to a non-functioning intercooler circuit could overwhelm the separate engine cooling circuit...
 

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My ic pump failed and no warnings or lights. Blow the blower up though. You need to fill the tube on passenger side with car running ( fill it fully first turn car on you will need to keep filling ) you can also remove coolant tubes from front of blower and fill that and the tube to speed it up. You could get a bad tstat or the sending unit could be bad to cause that warning again.
 

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2007 STS-V
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You will get a check engine light if the ic pump fails.bought my car, after reading on our forums about you should see coolant flow threw the tube, and I didnt so I bought a new pump, replaced with new pump, tested old 1 and it still worked.3 weeks later I get a check engine light,scanned it saying pump was bad.bought another, replaced it, checked old 1 and it was dead replaced with 2nd new one and check engine light was off.so you should get a check engine light when ic pump when stops working
 

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'06 STS-V, '17 CTS-V
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You will get a check engine light if the ic pump fails.bought my car, after reading on our forums about you should see coolant flow threw the tube, and I didnt so I bought a new pump, replaced with new pump, tested old 1 and it still worked.3 weeks later I get a check engine light,scanned it saying pump was bad.bought another, replaced it, checked old 1 and it was dead replaced with 2nd new one and check engine light was off.so you should get a check engine light when ic pump when stops working
Good to know that the "Check Engine" light is triggered upon IC pump failure, but, just to clarify, that CEL is not the same as the "Engine Hot/AC Off" message, which is what the primary poster questioned, correct?
 

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2017xts vsport platinum, 2011EXT, gt500
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2 inputs. My tstat threw a code 3 weeks ago. If you have onstar they will scan fur codes for free.
I did buy a tstat but when I saw what I'd have to do ,(I'm 70), decided it was much harder to do than my 65 gto so brought it into a trusted dealership. 2.1/2. Hours of labors later it was done. Like 400 bucks
.but codes are done. It did trigger check engine besides the hot engine that's why I had it done.
 

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Discussion Starter #10
Appreciate all the info guys. Now I know what to do for my smaller coolant reservoir but why do you think my main engine coolant would be low? And where is this coolant going? I e attached the codes that were pulled. The o2 sensor one is old and I know I need to replace one of them. The other 3 were new. Thanks again guys for all the info.
 

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'79 coupe deville, '04 Deville DTS White Lightning
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You need to change the thermostat. Bad tstat will throw the engine hot ac off POSSIBLY with a P0128.

You need to do what I said about topping off the i/c.

No message will be given to you by the car if your i/c is out of coolant. You just happened to notice and tell us so I commented on it.
 

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Discussion Starter #13
You need to change the thermostat. Bad tstat will throw the engine hot ac off POSSIBLY with a P0128.

You need to do what I said about topping off the i/c.

No message will be given to you by the car if your i/c is out of coolant. You just happened to notice and tell us so I commented on it.
Oh ya I got that. Will be back to the car tomorrow to top that off. Now I'm just interested in the codes that came up and when my actual engine coolant was an inch low? And why would my intercooler reservoir be so low? Where is all this coolant going? Or just it just evaporate over time.
 

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'06 STS-V, '17 CTS-V
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Oh ya I got that. Will be back to the car tomorrow to top that off. Now I'm just interested in the codes that came up and when my actual engine coolant was an inch low? And why would my intercooler reservoir be so low? Where is all this coolant going? Or just it just evaporate over time.
Coolant systems will evaporate coolant over time as the engine cycles thermally. I have to top off the coolant in all my vehicles every 2-3 years of regular driving. Almost like clockwork I get the coolant low message in each of them. I've had to top off the coolant in my 2006 GMC Sierra k2500 3 times in nine years bc of the low coolant message. An inch low in the reservoir is nothing, as the reservoirs are almost always higher than the top of the radiator, hence the early warning message in the DIC. Temperatures never actually rose in the temp gauge, and when glancing at the coolant during routine maintenance, it always looks full.

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I'd say its nothing, fill it and keep an eye on it. You won't have to fill it again for probably another 50k miles. If it does go down sooner, could be a leaking water pump, or head gasket. If the exhaust smells sweet, and or blows white, it's the head gasket. Test the reservoir with a CO gauge to tell instantly if it's the head gasket.
 
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