[WessenS]

Hello,

For the past two days when I start my car, my radiator fan or engine fan is super loud! like a loud vacuum. It also takes a while to stop once i turn off my car.

I noticed the coolant levels were way low so i topped it off today but it had no effect. I then noticed my AC isnt blowing cold air.
I can't take it to the dealership until Tuesday @ 2pm.
Any tips? (not a car guy btw)


2017 Camaro
V6 2LT RS



Thanks!

[i007spectre]

Bad thermostat.

[S.Macias]

Thermostat. Was $500 here in Cali to replace

[Idaho2018GTPremium]

Originally Posted by i007spectre

Bad thermostat.

Originally Posted by S.Macias

Thermostat. Was $500 here in Cali to replace

How would a bad thermostat cause a loud fan at startup, presumably when the engine is already cool? The thermostat would be in recirc mode, and the radiator fans wouldn't need to be running on a cold engine. That doesn't seem like the problem unless the thermostat has a temperature sensor that went bad (which I've never seen a t-stat with a sensor in it). The issue sounds like something electronic to me; perhaps a bad sensor somewhere causing the control unit to start the fan at a high speed, even though the engine is cold.

[cellsafemode]

So, the default behavior for the camaro when the thermostat temp sensor reads too cold for too long is to assume the sensor is unreliable and to run max cooling.

This disables the AC and keeps the radiator fan on.

You can verify if the issue is actually a bad temp sensor or actually a stuck open thermostat by using an odb2 reader on fresh startup. You will see a temp reading going up but not up high enough (185+ degrees).

If you see temps going up but then after 5-10 min it shows 0 and your fan turns on and all that, then the thermostat is stuck open.

If the temp sensor is always 0, then the temp sensor is bad.

The thermostat gets stuck from dexcool buildup on the surface that the valve slides up and down on to open and close. This usually occurs because the coolant level dropped low (at least temporarily) and your valve oxidized the dexcool. Oxidized dexcool is sticky./gunky.

You can clean your thermostat and remove the residue and it will probably work fine again. Some people even just manually force the valve with their fingers / tools a couple times to mechanically scrape the dexcool residue off and put it back in. Though, I'd suggest a more thorough cleaning or just buy a new one.


note. The coolant reservoir is tricky to read full. So it's easy to let it be too low since you dont usually pay attention to the bottom part. Parking on a steep hill can expose the thermostat to air when it gets cold and all. just some common ways that happens. Intermittant failing / functioning is a strong sign that it's buildup on the t-stat leading to it becoming stuck open. Also, keep in mind, if the car is in this failsafe mode, a ecu check engine code is thrown but isn't going to usually cause the check engine light to turn on. Some odb2 readers can see this code and clear it and the car will re-test the temp sensor and either trigger again or be fine. Otherwise it takes many cold starts to trigger a re-test. While that process hasn't happened, it will default to failsafe immediately.

[cellsafemode]

Originally Posted by S.Macias

Thermostat. Was $500 here in Cali to replace

500 for a 30 dollar part.

I know it's a pita on the V6 to get to the t-stat due to them wedging it between the heads under the intake manifold and oil return lines.

But it's super easy to get to on the V8. Like literally a 30 min job requiring a socket wrench and basically nothing else (maybe some coolant to fill back in whatever you lose disconnecting the t-stat).

doing it on the V6 was super annoying and the t-stat housing is a bit more than the v8's since it's the whole housing. I guess i could see them charging 4 hours of labor if they had to diagnose it as well though. But if you have the patience, fixing this problem could be almost 0 dollars if you do it yourself. The thermostat isn't really bad. It's almost certainly just gunked up with dexcool and can be cleaned.

[S.Macias]

Originally Posted by cellsafemode

500 for a 30 dollar part.

I know it's a pita on the V6 to get to the t-stat due to them wedging it between the heads under the intake manifold and oil return lines.

But it's super easy to get to on the V8. Like literally a 30 min job requiring a socket wrench and basically nothing else (maybe some coolant to fill back in whatever you lose disconnecting the t-stat).

Tell me about it. The fan got stuck on after I drove out of town and didn't have the tools to disconnect the battery to turn the fan off. Rather than deal with it myself like I usually do, I just drove to the nearest dealer and told them to fix it. I was three hours from home with limited options. It was costly but repairs on this are a lot cheaper than my Mercedes or Jaguar.

And I did get a few more tools to keep in the car...

[The Maverick]

An alternate take - I cleared the code that got set when this first happened (there is no check engine light, I found out about the code getting set from other forum posts about the issue). That took care of the problem for months. It happened a second time and I cleared the code again, and the problem did not recur before I sold my 2016 1LT at around 46K miles, which was months after I cleared the code a second time.

So while the symptom is consistent with a thermostat problem, at least in my instance it was only an intermittent issue that I was able to address by clearing the code. Might want to give that a try...

[KingLT1]

Originally Posted by Idaho2018GTPremium

How would a bad thermostat cause a loud fan at startup, presumably when the engine is already cool? The thermostat would be in recirc mode, and the radiator fans wouldn't need to be running on a cold engine. That doesn't seem like the problem unless the thermostat has a temperature sensor that went bad (which I've never seen a t-stat with a sensor in it). The issue sounds like something electronic to me; perhaps a bad sensor somewhere causing the control unit to start the fan at a high speed, even though the engine is cold.

The problem does stem from the thermostat over cooling by about 15-20 degrees. GM programs these newer cars to respond to a situation where the coolant temperature stays too low for too long. Some models the ECU will turn the fan on high and put the car in reduced power, other models it will put the fan on high and say "power steering reduced". Either way if you have Hpt tuning software like I do, you can go in and turn off the code PO128 and the problem will never happen again. I fixed my brothers Z06 by doing this and I fixed my 2017 GMC Acadia 3.6. Or you can replace the thermostat.