Coolant Temp alarm after carwash

[Bret11]

I got gas this evening and then went thru the automatic car wash at the station. I put it in neutral and left the engine running as we went through. Almost immediately after leaving the car wash, I got a high coolant temp alarm and the temp gauge was in the red. I parked it right away and turned the engine off.

Under the hood it was warm but there was no apparent catastrophe. There was a soft hiss coming from the radiator, but that didn't seem like anything extreme. I couldn't find any obvious failure and my mechanic's shop was closed, so I decided to let it cool down for half an hour and took my daughter to the playground. When we got back I turned the ignition to the on position to check the temp on the gauge and it was right in the middle. We weren't far from home so I decided to give it a shot at making it back. The temp was steady and right in the middle all the way home. At home I let it idle for a few minutes with the AC on -- the needle stayed steady.

So it appears that I have no overheating issue?

Is it possible that some water from the carwash got under the hood and was heated by the engine which tripped the coolant temp alarm?

[X53Jay4.8is]

Originally Posted by Bret11

I got gas this evening and then went thru the automatic car wash at the station. I put it in neutral and left the engine running as we went through. Almost immediately after leaving the car wash, I got a high coolant temp alarm and the temp gauge was in the red. I parked it right away and turned the engine off.

Under the hood it was warm but there was no apparent catastrophe. There was a soft hiss coming from the radiator, but that didn't seem like anything extreme. I couldn't find any obvious failure and my mechanic's shop was closed, so I decided to let it cool down for half an hour and took my daughter to the playground. When we got back I turned the ignition to the on position to check the temp on the gauge and it was right in the middle. We weren't far from home so I decided to give it a shot at making it back. The temp was steady and right in the middle all the way home. At home I let it idle for a few minutes with the AC on -- the needle stayed steady.

So it appears that I have no overheating issue?

Is it possible that some water from the carwash got under the hood and was heated by the engine which tripped the coolant temp alarm?

No. More like water got into a connector and caused a false reading that triggered the alarm.

[Bret11]

Originally Posted by X53Jay4.8is

No. More like water got into a connector and caused a false reading that triggered the alarm.

Thanks for your reply X53Jay4.8is. Seems like it was a false alarm -- it's still running at proper temp today

[crystalworks]

Originally Posted by X53Jay4.8is

No. More like water got into a connector and caused a false reading that triggered the alarm.

Yep, especially if using the undercarriage cleaning versions.

The only other thing I could see it being (without actually looking at the vehicle) is an auxiliary fan issue. If that's not working you might experience overheating under certain circumstances. Like going through a tunnel wash with no air moving over the radiator. Not sure if those places use heated water, but that could also contribute.

^I don't think the above is likely. But if you see the needle do the same thing in the future it's something to take a look at. It's a known failure point on the E53.

[Bret11]

Originally Posted by crystalworks

Yep, especially if using the undercarriage cleaning versions.

The only other thing I could see it being (without actually looking at the vehicle) is an auxiliary fan issue. If that's not working you might experience overheating under certain circumstances. Like going through a tunnel wash with no air moving over the radiator. Not sure if those places use heated water, but that could also contribute.

^I don't think the above is likely. But if you see the needle do the same thing in the future it's something to take a look at. It's a known failure point on the E53.

Thanks crystalworks. I'll keep the potential auxiliary fan issue in mind.