Punto Overheating

Hi guys,

Problems again with the birds punto :(
It's overheating, and the fans not cutting in. I bought a new switch type thing which screws into the radiator (rad switch) and fitted that, but to no avail!!

I can't think what else it would be, as its not that complicated a thing is it..

Theres no more power leads going to the fan, only the ones that have to pass throught this rad switch thing.

Theres definately power before the switch, but none's coming out.. I know the fans working, cos I bridge the switch wires and it worked..

You guys got any idea's??

Thanks in advance...

I assume you've checked that, or are certain it IS in fact overheating and not just a guage fault? Have you checked for leaks? Pressure in the water system? Does the car boil over quickly if you leave the radiator \ header tank cap off? You've checked the fan and the supply to the fan therefore we can eliminate them and check the switch itself, you can test it using a meter\ continuity checker or a test light of some sort, preferably with it's own power supply but either will do. Boil a kettle or pot of water and put the switch in, see if it actuates at ANY temperature then try and get the exact temp it switches at by using a thermometer if poss. Did you check the operation of the fan with the ignition in both off and on positions? Can't remember if the fan stays on or not with ign off, some cars drop the voltage so the fan runs on, some don't, which I reckon is pretty dumb cos the engine is overheating whether it is running or not and needs cooled. Assuming you've done all of the above I'd be looking at the thermostat next. Fiat usually use an in line thermostat which has 3 or 2 hose connections and ain't cheap, but you should be able to check it IS functioning properly by checking the heat in the hoses and the radiator at running temperature there should be little or no noticable difference. Do the rest of the electrical checks, check the switch, ensure you are not getting a false reading from the guage, check for airlocks (pressure\no heater etc) then I'd be checking for internal pressure which, if found is probably a sign of a head gasket problem. Let us know how you get on anyway.

Thanks for all this mate, your a true wealth of knowledge lol

OK it isn't a gauge fault as its getting really hot and I keep burning my hands lol.

the fans got a continuose power supply even with the ignition off (checked with multi meter)

When its hot, and I take off the radiator water cap, theres a bit of hissing and a fair bit of gurgling.

Sometimes the heater in the car comes out hot, other times its blowing out cold even though the cars over heating! You mentioned this and reacon it could be an airlock.

Would completely draining the system, and physically lookig through all the rubber pipes sort this??

To remove an air lock you have to remove the highest water pipe and run the engine till it at normal temp and make sure the water is getting to the pipe you removed. Sometimes you need to back fill them because the air lock is near the thermostat and affecting its normal operation. The easy way to check a thermostat is actually working is to cover the radiator with water so that when the thermostat opens you will see lots of steam coming from the radiator as the heat from the water inside it dries off the water outside it. Really unless there has been work carried out that involved draining the coolant or, if it was run dry, then my guess is your looking at a thermostat or a head gasket problem. The fact all the electrical circuits are working fine would indicate that the thermoswitch is not working because there is no water there to make it work, it can't read air temperature and therefore will not switch on even if the radiator body is above it's working temp. There is most certainly an air lock there, what you need to do now is find out whats causing it. You can have a garage check it with a gas detector which is just a fluid bottle that is held in place of the radiator cap and the fluid turns a different colour if there are combustion gases in the water chamber, which is really the only reliable test for that problem. Only other thing I can suggest is to try a new thermostat, but it's not likely that it's causing the problem.

Theres a bleed cap in front of the heater matrix under the bonnet . Loosen it off and it should bleed ok , the punto is a right get to bleed at times .

Urban