Engine temperature gauge instantly hit maximum
 

Yesterday, after driving for under 5 minutes I noticed my engine temp gauge was at max in the red. So I immediately slowed down, and pulled over with in a minute. I shut off the vehicle and re started. The needle returned to normal, which under the conditions was still cold, just above the blue.

Conditions:

• -17 degrees celsius outside
• engine was still cold prior to incident
• car had only been running ~5min

Based on these facts, I doubt the gauge was accurately depicting the true engine temp.

So could my engine temp sensor be failing? This is the first time this has happened, and it has not re occurred yet.

On a side note, a couple of months ago, I noticed that after 1+ hours of highway driving, my gauge was still not reading out at optimal engine temp, it was slightly on the cold side. Again, faulty sensor?

Thanks in advance for any advice,

Disclaimer: I’m no expert, and I’m new here. Just giving my opinion.

My first guess would be a bad thermostat rather than a temperature sensor. Usually one will fail open so that your car never really gets to operating temperature, but I’ve had one or two stick closed, causing the engine to overheat, while the radiator was still nearly ice cold.
My second guess would be that you have some outside contaminant inside your cooling system that caused the thermostat to stick closed this time, but to stick open previously. Had any work done recently that opened up the cooling system?

No work has been done to the cooling system or anything else for that matter.

I really have no clue about the cooling system, this open/ closed thing is new to me.

Well, what I meant by "opened up" was just work like a new hose, water pump, alternator, heater work, anything that would require the coolant to be drained.

It happened again guys, exact same conditions and scenario.

It did not happen on the way home (was sitting for about 1.5 hours)

I hope this is not going to be a $$$$ issue.

Didn't you replace your engine somewhat recently godfather?

You are correct, however it was almost a year ago.

There have been no problems till now. It already went through a harsh Canadian winter. It is unlikely that what I am experiencing now is attributed directly to the replacement...but then again.

Hey, any other ideas? Any obvious things i should be checking for, or be cautious of? Thanks.

Experiencing any other electrical/low voltage symptoms? A drop in voltage could do that. Most likely it would be the coolant temp sensor however.

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I am not aware of any electrical/voltage problems.

Is there any way to test the coolant temp sensor?

I am sure thermostat or water pump created this problem. This is happened exactly with my previous 528i when it was ~150K miles. I replaced both thermostat and water pump, and the problem never happened again.

He's under the assumption that the engine didn't get to boiling though. If that's the case, then it's reading incorrectly; sensor or gauge.

I had a temp sensor go bad (e34) and it would give all kinds of readings.

In your case it was fairly cold outside so that may have effected operating temp, explaining the tad low reading. A sensor is probably the easiest and cheapest to fix, so I would start there. If your motor is rounding 120k, then might as well do the water pump and t-stat.

I will look into the water pump and thermostat.

Thanks guys.

I am put more at ease knowing the engine isn't actually overheating, or at least I am convinced it isn't.

I am having this EXACT same problem on my 01 3.0i...did u ever figure anything out godfather? Im guessing its my coolant temp sensor...

It was the thermostat. Also the coolant was low very low. But first and foremost the thermostat.

Ok cool thanks...I think I'm going to change both temp sensor and thermostat and maybe even do the water pump while I'm at it since I'm pushing 120k