Water coolant temperature gauge moves rapidly to overheat
Discussion
After driving my car for 4 miles this evening at about 70 mph my temperature gauge went from the normal 90 degree position to 130 and beyond in 5 secs. The overheat warning light and buzzer came on. I took the foot off the accelerator to bring the car to a standstill and the gauge went straight back to the normal position.
Lifting the bonnet there were no signs of overheating and I drive the rest of the journey at 70 mph with no issues.
I don't think the car could have overheated and it would not have been possible for the coolant temperature to rose then fall so quickly. Any idea's as to the cause. Car has done 50000 miles.
It's a 2.0 tdi Golk Mk7.
As an update - driven today for around 200 miles. Apart from one point when the gauge went up from 90 to 110 - and then back again - all seems normal
Lifting the bonnet there were no signs of overheating and I drive the rest of the journey at 70 mph with no issues.
I don't think the car could have overheated and it would not have been possible for the coolant temperature to rose then fall so quickly. Any idea's as to the cause. Car has done 50000 miles.
It's a 2.0 tdi Golk Mk7.
As an update - driven today for around 200 miles. Apart from one point when the gauge went up from 90 to 110 - and then back again - all seems normal
I would suspect a fault in the coolant temp sensor or the wiring to it.
If in doubt whether you have a working cooling system, check the cabin heater is putting out hot air - this confirms you have at least some coolant circulating.
I assume you'll check the coolant level once it's cooled down.
If in doubt whether you have a working cooling system, check the cabin heater is putting out hot air - this confirms you have at least some coolant circulating.
I assume you'll check the coolant level once it's cooled down.
VW coolant temp gauge is "corrected" to display 90 degrees over a temperature range (75 to 105). So it can move relatively quickly if the actual temp goes above 105.
If you say there are no signs of the car actually overheating then as said it's probably a coolant temp sensor. If it were overheating then the thermostat and water pump would be the first things to check along with the radiator fans.
If you say there are no signs of the car actually overheating then as said it's probably a coolant temp sensor. If it were overheating then the thermostat and water pump would be the first things to check along with the radiator fans.
I would be looking at changing this part out before getting snowed under 
My VW Golf MK7 TDI 2.0 Estate Diesel has the same issue, and I research and found someone had the same issue years ago.
My Issue: Coolant Temperature suddenly rise up from standard 90 degree Celsius, when it reached 130, the warning light showed up on the dash display twice then went off.
1st time of the issue: 27th Nov
- Happen last week, parked in layby, opened the hood, engine bay was cool (3-4 degree Celsius weather)
- But the fan was on and fast
- Turned off engine, and started it up, all become normal
- Coolant level in reservoir is fine
- Heating was fine, hot and worked as normal
- Checked Engine Fault Code, no issue has been found
Follow-up: 28th Nov
- Top up some engine oil (which was ok already)
- Tested drive a lot in local carriage way and motorway, could not reproduce/re-create the issue.
2nd time of issue: 01 Dec 2020
- The coolant temperature raised up fast and sudden that issue has come back 2nd time.
- I went to next town, during the return, on motorway, suddenly the coolant temperature raised from 90 degree to over 100 degree in few seconds, and keep rising
- So I slowed down and parked the car in layby, engine bay was not hot at all, but the fan spined fast
- Turned off the engine and started it up, then the problem has gone.
- Coolant Reservoir is fine
- Heating was fine, hot and worked as normal
- Engine Oil temp gauge showed normal between 90-100 degree Celsius before and after the incident.
- Checked Engine Fault Code, no issue has been found
My Thought:
- This issue happen twice only when driving on motorway, not local/ 50mph or below, so far
- After turned off the engine, and restarted, everything is back to normal. If the water pump and thermostat have issue, it should not behave like that
I have no idea what the cause it is, but guess that
70%: Coolant Temperature Sensor
20%: Thermostat
10% Water Pump
Jesus Christ, may God save me this time.
My Issue: Coolant Temperature suddenly rise up from standard 90 degree Celsius, when it reached 130, the warning light showed up on the dash display twice then went off.
1st time of the issue: 27th Nov
- Happen last week, parked in layby, opened the hood, engine bay was cool (3-4 degree Celsius weather)
- But the fan was on and fast
- Turned off engine, and started it up, all become normal
- Coolant level in reservoir is fine
- Heating was fine, hot and worked as normal
- Checked Engine Fault Code, no issue has been found
Follow-up: 28th Nov
- Top up some engine oil (which was ok already)
- Tested drive a lot in local carriage way and motorway, could not reproduce/re-create the issue.
2nd time of issue: 01 Dec 2020
- The coolant temperature raised up fast and sudden that issue has come back 2nd time.
- I went to next town, during the return, on motorway, suddenly the coolant temperature raised from 90 degree to over 100 degree in few seconds, and keep rising
- So I slowed down and parked the car in layby, engine bay was not hot at all, but the fan spined fast
- Turned off the engine and started it up, then the problem has gone.
- Coolant Reservoir is fine
- Heating was fine, hot and worked as normal
- Engine Oil temp gauge showed normal between 90-100 degree Celsius before and after the incident.
- Checked Engine Fault Code, no issue has been found
My Thought:
- This issue happen twice only when driving on motorway, not local/ 50mph or below, so far
- After turned off the engine, and restarted, everything is back to normal. If the water pump and thermostat have issue, it should not behave like that
I have no idea what the cause it is, but guess that
70%: Coolant Temperature Sensor
20%: Thermostat
10% Water Pump
Jesus Christ, may God save me this time.
Stephen-ro9kw said:
Many thank for your kindly reply. I would do the same then and see any help.
Do you still have the sensor part receipt? Is it 04E919501B coolant temperature sensor right?
Don't worry if you dont have record. I just try my luck, because searched online result finding thermostat housing but no sensor.
Many Thanks in advance.
coolant gauges on cars for the last 20 years are just simple ‘wally’ gauges or more technically called ‘stabilised’ which means they just go to the middle despite a fairly wide range of actual coolant temperatures.
Which is why they have been almost eliminated from modern cars and replaced with essentially ‘nothing’ means things are ok.
Of course when the sensor starts playing up - then you get seemingly odd gauge temperatures as the car trys to decide whether to draw your attention to a problem or not.
getting an obd reader and grabbing the actual temperature should identify if the sensor is giving random values
Which is why they have been almost eliminated from modern cars and replaced with essentially ‘nothing’ means things are ok.
Of course when the sensor starts playing up - then you get seemingly odd gauge temperatures as the car trys to decide whether to draw your attention to a problem or not.
getting an obd reader and grabbing the actual temperature should identify if the sensor is giving random values
mawallace said:
On mycar, as I was the person who started the thread, it was the thermostat sensor which was faulty.
Replaced it and its been fine since
Have started to experience the same issue and the garage is struggling to advise on what is happening. Have you also replaced the water pump before replacing the thermostat sensor?Replaced it and its been fine since
Thanks!
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff