VW polo (1999) overheating problem

[dave4563]

My 1.4 VW polo has suddenly developed an overheating problem from the beginning of this week, which i noticed whilst sat in traffic, just after coming off a motorway, I glanced at the temperature gauge to see that that car was running at 110 degrees, which has never happened before! As I was only a short distance from home, I carried on driving and turned on the heaters to try and cool the engine down, which thankfully worked.

Once I got home, I checked the oil and coolant (both of which were fine) no coolant loss or oil in the water. I also waited for the engine to cool down, and then started it up again and let the car idle on my driveway. I waited for the car to warm back up to normal temparature to see whether the fan kicked in. It didnt, and the car started to overheat again up until the warning light came on.

I don't know an awful lot about this kind of thing, but am pretty sure its unlikely to be a head gasket as there is no oil in the water or vice versa, or the water pump as I had it replaced last year). Researching the problem online has led me to believe it is likely to be a thermostat or a fan switch... Any other possibilities? I have also checked the fuses for the fan and they all seem to be fine. Are these easy problems to fix? I have a haynes manual and would like to fix the problem myself if possible!

Any help greatly appreciated! Cheers.

[dave4563]

I have also been using the car since monday and it is still overheating, but hasnt lost any of its coolant. Turning the heaters on when it overheats in traffic cools the engine down, but this isnt ideal in the middle of July!

[calistheman]

I have also been using the car since monday and it is still overheating, but hasnt lost any of its coolant. Turning the heaters on when it overheats in traffic cools the engine down, but this isnt ideal in the middle of July!

It will be the thermostat....I've had to replace mine 2 or 3 times on the same model polo. Way to test is to pop it out and place in to a cup of boiling water....if it doesn't open, it will need replacing. About £3-4 from any decent motor store.

[dave4563]

Thanks! I've just replaced the fan switch (which wasn't the problem) and bought a thermostat as well just to be on the safe side. The bottom hose is sone cold while the top one is really hot, car is still overheating and the fan still not kicking in. Gonna put the new thermostat in later and hope it works!

[calistheman]

The cold hose coming out of the radiator also points to a failed thermostat.

[dave4563]

I have now changed the thermostat and the fan switch and took the car out for a drive and it started to overheat again straight away, c@£*!. The fan definitely works, have tested it on both speeds, but still doesnt seem to be kicking in when the car starts to overheat, strange... Any more suggestions? This is about as far as my very limited mechanical knowledge goes, unless theres anything else obvious and simple wrong with it, then I'm going to admit defeat and take it to the garage and part with large amounts of money.

[dave4563]

The bottom hose is a bit warmer now as well...

[witblitz]

This is a long shot but could be a blocked radiator core or faulty waterpump.

[dave4563]

Latest update as I'd given up messing about with this one, called the aa out today, first time I had used the car after being away for a week, and it overheated within minutes! the mechanic quickly diagnosed as a faulty replacement thermostat which didn't open, as the bottom hose was still cold. Removed this and going to get a replacement soon. Was told its ok to run the car with no thermostat for the time being. Thanks for all the help and suggestions guys!