I have Fiat Uno (diesel 1.7) which has an overheating problem. When the temperature reaches near 100 degrees centigrade, water in the coolant reservoir starts boiling and overflowing from the cap, and very soon the temperature needle is above hundred. My mechanic says there is nothing wrong with the cooling system: he says thermostat is fine and was replaced a few months ago, radiator was just serviced, we also replaced the fan which looked faulty, replaced a bad gasket a month ago too. The cooling is better but the car still overheats after driving around 10-15 kilometers. I have to stop for at least half an hour and fill reservoir again before starting again.

The only funny thing I can notice is water overflowing from the coolant reservoir cap as soon as the temperature nears hundred. I've sometimes even stopped it at 95 and seen water overflowing from the reservoir. I think this may be the problem - the water starts leaking out when the car is near 100 and once enough has leaked out, it heats up even further.

My questions:

- Is it normal for water/coolant to leak out of the coolant reservoir cap when the temperature nears 100 degrees? Could it be something wrong with the cap? I read that it's supposed to maintain pressure in the system, whatever that means.

- No coolant, only water for now since all the coolant leaked out due to earlier overheating. I've since had the radiator serviced and fan replaced. Could adding coolant solve the issue?

- Could this mean my engine is damaged or something? That's what my mechanic seems to think.

hi,
the coolant MAY help..but I doubt it..,
basically your radiator cap is supposed to hold-back pressure to a certain amount ( around 1.5 bar.?)

it is this pressurised system that stops the water actually boiling as the car operates up to @ 110'C,
however a blown cylinder head gasket will also over-pressurise the cooling system = forcing out the cooling water..,

does the car start and idle well when cool ..??

charlie

Thank you for your response!

My mechanic reduced something he called the "engine speed" a few days back since it normally used to heat up while idle (using a small bolt on the engine) ... Since then, it has some extra vibration and I need to press the accelerator a little bit to get it to start when cold. Other than that, it appears fine.

maujood said:

Thank you for your response!

My mechanic reduced something he called the "engine speed" a few days back since it normally used to heat up while idle (using a small bolt on the engine) ... Since then, it has some extra vibration and I need to press the accelerator a little bit to get it to start when cold. Other than that, it appears fine.

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Get a new coolant cap a friend of mine had the same problem with his Vauxhall vx220 replaced cap problem went. Hope this helps.

Got a new coolant tank cap today. Water does not leak anymore, but the temperature needle would still cross 100 and reached till 110 by the time I reached back home. It was back on 100 once I slowed the car down.

I know it used to stay below 100 while driving earlier. What might be the problem now?

Hi again,
check the water / coolant levels,
you MAY have introduced some small air-pockets with it over heating previously,
I Would recommend - if it appears water-tight after 1 weeks of driving , to dump the Water in the system and replace with a coolant mix,

Charlie