03 Jetta Cooling system

I recently bought an 03 Jetta. Seems to be OK apart from 2 issues which maybe linked.

  1. Cabin heat doesn’t work. The dealer claimed they had fitted a new heater core, they seemed equally incompetent as they were dishonest.

  2. Radiator fan doesn’t seem to work. The car seems to warm up at a red light and cool again when moving. Temp gauge is right in the middle while driving, goes 2/3 way to the hot side and seems to go back down. Haven’t seen the fan turning when I checked under the hood with the temp gauge in the middle.

So, a couple of questions here

  1. At what temp on the gauge should the fan kick in ? Maybe it just wasn’t hot enough yet.

  2. Any chance the two problems are related, or am I barking up the wrong tree ?

Might the thermostat be a good place to start ?


The thermostat would be the cheapest, quickest place to start. I bought an 86 Firebird back in the day that would not warm up at all. Turns out the thermostat had been removed. I have noticed on my 4 cylinder that the fan doesn’t run if parked/idling.

If the temperature goes to the “hot side” it could be a partially clogged radiator or a sluggish thermostat. I suspect this car had virtually no cooling system mainteance during its life and you might need a new radiator.

The dealer did obviously the bare minimum to make the car saleable.

It’s important not to let it overheat. A good independent shop specializing in cooling system service will test the system. They will also soon determine whether the dealer was lying to you.

In any case be propared for some serious money; If this was my car and I wanted to keep it, I would be spending $600 or so at least to correct these problems.

I would also determine when the timiung belt was last changed; if it goes than all the money you spend on the cooling sysyem will be wasted. A 2003 VW should be on its second timing belt and nearing its third1!

Pleas also tell us how many miles on the car and if there are any maintenance recoprds.

Thanks, no service records yet. I have just done some googling and found the details of the previous owner. Hopefully she will talk to me and we may know something. Car has 126,000. So I would definitely like to get some history from her. I pulled off the top timing belt cover and at a total guess thought the belt looked too new to be from 03.

We knew it was gamble, the car was super cheap compared to others advertised. If it turns out we aren’t due for a timing belt and water pump and a thermostat fixes it it may have been a killer deal. If it cost another $1,000 to get it right possibly not so much.

I can’t resist a gamble.

Now you know why it was super cheap. You’ll be lucky if it hasn’t already overheated and warped a head.


“thought the belt looked too new”

You shouldn’t make assumptions like that

Last year I did the timing belt on my car, because the belt was 9 years old, due by mileage

When I pulled the top timing cover, the old belt itself looked great. Not glazed, no cracks, no chunking, etc. It didn’t look much different than the new belt. However, I know it was the original.

However, by the time I removed the lower timing covers, I could see that the water pump was crusty. Had I not continued digging, I wouldn’t have seen that.

Totally agree, hence the attempts to contact the previous owner. I might find out it was done at 100,000. If I can’t find anything I will probably have to do it, preferably before the 30 warranty runs out.

Anyway does anyone know approximately where the needle on the temp gauge should be when the fan kicks in and whether or not the thermostat may have anything to do with it ?


On most vehicles the temp gauge is roughly at the halfway mark, or a little less

You probably have 2 electric fans. The ac condenser fan should come on anytime you have the ac engaged. The other fan, the radiator fan, might not come on until the engine is running hot. It might not come on until the needles is at the 3/4 mark.

Many manufacturers now play a game with the temp gauge, and I know VW is amongst them. The gauges no longer read linearly. That is to say a slight increase in heat, above normal, will not raise the needle on the gauge. This allows the gauge to continue reading right in the middle despite actual fluctuations in the coolant’s temp. The theory is that the driver doesn’t need to know about such small variations. Bottom line: fan coming on based on gauge reading is not the way to go.
A simple way may be to just let the car idle on a hot day (?) until it gets hot enough to kick the fan on. Or not.