Engine overheating - heating on full

Got a 2013 Golf Bluemotion TDI 2l..

Not had any issues at all. My wife told me a couple of times a few weeks ago that the engine STOP light came on and said the engine was overheating. We used to have this on an old MK4 TDI and it was due to a faulty sensor in the coolant tank (we think)

Anyway, she took it easy and got wherever she was going and it didn't happen again, until yesterday. I was coming home from work (about 20m drive) not overly thrashing it.

It was very cold, so I had the heaters blasting my feet. At some point my toes were toasty and I turned off the heater. At some point after that, the engine oil temp went up and the STOP warning came on.

I slowed down to about 45mph and I could see the needle drop a little. I put the heaters back on full in a vain attempt to pull some heat into the cockpit and opened the windows so I didn't boil to death.

The needle dropped rapidly. I started playing around with the heating to see if it was actually making the difference, and it was. The heater off, the engine temperature climbed up quickly. And then turning back off it dropped again.

I had to get fuel anyway so left the bonnet open on the forecourt hoping it might help. Its only about 6 miles from the garage to my house, and with careful driving I managed to get home with no more warnings. It seemed going uphill with a bit more gas made the needle climb and coasting down it dropped...

Any suggestions? We've had the car for a good year with this being my first issue. It _has_ to be related to the massive heating I had pumping out. Surely?

Thanks in advance

The behavior is consistent with a plugged or blocked radiator. Your heater is nothing more than a radiator of its own, and your turning it on high does the job.

Start with the obvious:

Do you have a full coolant reservoir?

Do you have oil?

Are the radiator fans coming on when the engine is at temp?

(If not) Do they come on when the A/C (or defrost) is turned on?

Is the radiator evenly hot once it's at temp?

Is the exhaust blacker than usual?

Does the car feel more sluggish than usual and/or make a whistling nose under load?

VCDS or OBD11 scan will tell if any of the numerous temp sensors or electric pumps are faulty...or anything else...

if you don't have then its a trip to the dealers...as guessing is a waste of time when the engine gets that hot...

You don't really NEED VCDS/OBD11; it may make diagnostics a bit easier but it's not at all necessary. The coolant system isn't very complicated at all. The fact that the heater core can be used to cool the engine would show the ECT sensor is operating properly and point towards mechanical issues. Mostly a lack in ability to radiate heat elsewhere, be it a coolant flow issue (plugged radiator, stuck t-stat), or airflow issue (dead fan, bag stuck to radiator, etc) it shouldn't be difficult to diagnose in a driveway.






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GoatPowder said:

You don't really NEED VCDS/OBD11; it may make diagnostics a bit easier but it's not at all necessary. The coolant system isn't very complicated at all. The fact that the heater core can be used to cool the engine would show the ECT sensor is operating properly and point towards mechanical issues. Mostly a lack in ability to radiate heat elsewhere, be it a coolant flow issue (plugged radiator, stuck t-stat), or airflow issue (dead fan, bag stuck to radiator, etc) it shouldn't be difficult to diagnose in a driveway.



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Exactly this, but also it is the sign of a frozen radiator as well. You need to check you have antifreeze in the system as wind chill at the moment is easily -21c here at speed.

Drove to London and back last night (140 miles round trip) with no issues whatsoever. But only put the heating on 2 max (out of a possible 6) - and it was bloody cold. So I reckon next time it goes in for service I will ask them to check the radiator...

But in the mean time I will have a look under the bonnet for anything obvious. The coolant is fine - not checked the anti-freeze though.

Thanks for help and advice given.