Some may come across my punto needed a heart-transplant a few weeks ago. Finally I got it back the week before last after an engine replacement.

But the overheating problem is still haunting. The overheating indicator comes up very easily from dim to

bright just within a few miles. So I hardly dare to drive it too much fearing this engne cooked again.

Here is some observations and facts relating to the problem:

Before the old engine cooked, I had the radiator fan swtich changed due to a similar overheating

problem (I suspect the headgast has possibly been seriously damaged then) as diagonized by a local garage. The garage told the fan kicked in but at a higher temperature than it should. A few weeks later, the engine gone.


The garage that did engine swap failed to come up with any idea. They claimed only very dim light was

observed when they tested it. They changed the thermostat, anti-freeze, oil filter, radiator cap etc. They warned of poor radiator condition though.

It blows hot air from air conditions.

Tried to bleed airblock in coolant system. Found two bleed valves totally and a small amount of air seen out.

The fan does kick in after idle for a while. But the overheating indicator remains bright.

No milky sign in oil.

One interesting thing is that, if i leave the car idle for one or two minutes before driving away, the light comes on much slower and keeps dim for long time (actually I havn't seen it become fully bright possibly because didn't drive for long distance). The light comes on within 5 mins and turn bright if I drive away right after I turn on the engine.


I am wondering how to test whether it is just a faulty indicator (i.e. no real overheating problem).

Thinking of testing the swtich and blushing the radiator this weekend before this engine is cooked again.

Any suggestions guys? Thanks in advance.

There's two different types of water temp sensor on these, one for a gauge and one for a warning light if I've got it right. The one for the light is supposed to be a switch, for the gauge a variable resistor (thermistor) so the dim light makes me think the new engine may have the wrong sensor for your dash. Warning light should be either on or off I believe.

On my MK1 punto there is one sensor for the ECU and one for the gauge/warninglight. Anyway, models with the warninglight and gauge does not have the same sensor. My fiat garage gave me wrong and my gauge didnt move.

Since you have a punto with warninglight it would be the opposit. I would expect it to glow brighter the warmer the engine get, which is not the correct way. Since when the punto is in normal temprature it would reach about 30-50% of the gauge depending on traffic, which would make you warninglight light up even when the temprature is not high.

To make things short, I would think you got the wrong sensor for the warninglight .. very easy to change yourself.

Thanks, fixitagaintomorrow and joel,
Any hints on how to find the sensor for the warning light and change it?
Is it the one in the cooling fan switch?
I check the Haynes mannual, but couldn't find any other ones.

On my engine it was on the left side of the engine standing in front of the car. Just behind the oil filler cap. It cost about 10£ at fiat. Think they sell thirdparty aswell, but mine just showed the wrong temprature when using thirdparty so bought a fiat and changed.

Yep, that's the one - near the dipstick on the back of the engine. It's screwed into the cylinder head near the black plastic cam belt cover.

Cooling fan switch is different, that's screwed into the radiator and switches the engine cooling fan on and off.