(G) Fiat Uno Fire heating question

Hi Everyone,

I'm Reuben from Malta and I own a Fiat Uno Fire 1989 model. Lately I had some problems with water vanishing from my radiator and my mechanic discovered that we had to face the cylinder head and do some welding on it too. The water was entering the exhaust system. We changed the thermostat too. Today I went to pick up the car and noticed that while driving it back home the temperature would go up somewhere near 90 and stays there. After around 15min driving it I hit some traffic and was noticing that the fan would turn on for a while and then sets off until I managed to avoid the traffic. My question is .... is it normal to have the temperature set around 90 while driving normally ? Or should it be lower ?

Reuben

Hi there if you are sitting in traffic then sitting at 90 is not uncommon but if it starts to creep above this i would be a bit concerned.

But is it ok that while driving i'll be somewhere in between 80 - 90 ?

Yes.

About 90 is the correct running temperature. The needle should sit at halfway on the gauge. That's what FIAT always aim for.

This seems to catch out Japanese car (and probably older English car) drivers, who expect the gauge to register about 1/3rd during normal running - to leave 'plenty in reserve'. That's a throwback to the days when cooling systems were really inefficient and struggled with the new stress of motorway driving.

These days, cooling systems are efficient and, actually, the heat lost from a radiator increases with the temperature differential - that is, more heat energy can be lost if the coolant is at 90 degrees rather than if it is at 70 degrees. The thermostat restricts the flow through the radiator to achieve the correct engine temperature. If the temperature increases, the thermostat opens some more, and the radiator radiates more heat. As the temperature drops, the thermostat closes.

For some cars, the correct temperature is as high as 100 degrees (remember that the pressure cap of the cooling system raises the boiling point to 120-130 degrees).

Regardless, you should find that the temperature hardly increases at all, however fast you drive. It should be really steady. On the Uno Turbo, if the turbo is working hard, it tends to contribute a great deal of heat energy (the turbo is water-cooled). Perhaps for this reason the standard running temperature of the Uno Turbo is a bit lower to allow for the increase.

On the Uno, the radiator fan comes on when the gauge needle goes a bit over halfway. That's normal too. It should go off after 30-60 seconds, and then come on again about a minute later. The fan switch (screwed into the radiator) has 'hysteresis' - it turns off at a lower temperature than what it turns on at. Sometimes the switches seem to lose this hysteresis and then the fan turns on and off for a few seconds at a time. If you have this, it's easy to fix - replace the switch.

-Alex

Thanks a lot for such help

I have noticed today that the fan starts to operate at around 100 ..... and works in sort bursts. I don't really know if that's ok or not. It keeps operating until the needle sits a bit above 90.

Sounds about right - the 'short bursts' should be about 20-30 seconds though. As long as they are more than 3-5 seconds, I'd say that would be OK. As I mentioned, when the switch fails, the fan tends to go on and off every three seconds.

-Alex

Thanks a lot Alex ..... you have been of great help to me.

I have changed the fan switch as for some reason it wasn't working as it should be. Now everything is good. The fan starts to work at around 92 and colls down to around 87.

That's better Good work.

-Alex