MkIV Golf - engine runs cold

A few weeks ago the engine warning light came on. The diagnostics picked up two problems "temperature sensor out of range" and "low airflow to inlet 1" - sorry but I don't have the actual codes anymore. My local garage (top guys and really helpful) replaced the engine cover vent pipes (which had split) and the temperature sender unit. They also reset the car's computer.

The car started and ran fine but it was a bit strange that the engine temp gauge only crawled up to about 60 then fell back again. The car heater was also very cool (thank heaven for heated seats!). After about two days the engine warning light came on again.

Back to the garage and now only one problem "temperature sensor out of range" so they changed the temp sender again and reset the computer again. I had the same problem with the engine temp gauge and three days later "hey presto" and back came the engine warning light.

In the good 'ol days this problem would be a sticking radiator thermostat but my garage want to change the temp sender again.

Anyone recognise this problem?

Would sugest cleaning the wiring and check for continuity. Also what color is the coolant temp sensor conector. Note the fault codes and post them on the forum. Good luck.

The idea that three temp senders are defective is far fetched.
Unless you've invented the motor designer's dream of a heatless combustion engine, I would suggest the likelihood of an air lock in the cooling system. The garage should have the means to force-flush the system and so push out any trapped air.

The connector is black (I think). Garage have cleaned connectors and spayed them with de-greaser. So far so good!

And.... nope. Its back. Damn

Hello,

What engine is in your Golf?

Had exactly the same problem myself a few weeks ago. My local service garage replaced the temp sender unit but the problem recurred. He assumed he had been supplied a faulty unit so replaced it FOC, but the problem recurred again. I then disconnected the electric fan, and deliberately tried to overheat the car, but at best managed to get the temp up to 90 after running up a steep mile long hill and then letting the car idle for about 10 mins. As soon as I started moving, the airflow over the radiator dropped the temp back down.

I reported this to my service garage, and requested that he replaced the thermostat - problem cured immediately!

My theory is that when the engine runs at low temp, the emmissions go out of spec which triggers the warning light. Because the temperature is wrong, the diagnostic points to the temp sender unit. When the diagnostic is reset, the problem returns shortly afterwards as the car never reaches running temperature. VW ought to re think the algorithm on this one...

I have this same issue on my 2.0 TDI Golf. However without any DTC's and temp sensors seem to be be reading normally. I've replaced the thermostat and still the engine won't get to temperature. I must admit I didn't pressure bleed the system so wondering if I have an airlock now!