Technical Punto 2001 Temperature problem

[jte]

When the engine is warming up, it works ok.
First time when it reaches normal temperature, which is
little below half way mark, it goes down two and half small mark in
5 seconds, stays there about 10 seconds and goes back up in 5 seconds.
It does this few times and when engine is fully warm, it goes down only about
one small mark. It didn't done this last winter. Thermostat has been changed a few years ago.
What could it be?

 

[flisko]

it is probably bad thermostat or air in cooling system, usually if you got air in it wont blow hot air
had same on my mk2, no matter how many times i tried to bleed it, it would still do what you are describing, changed thermostat, bled it again and it was all good, temp gauge sits on middle and doesnt move when its warmed up

it would be wise to change antifreeze at the same time

 

[jte]

I have bled the system and there is no sound under the dash.
Thermostat is not original Fiat part.

 

[flisko]

doesnt matter if its original or not, they should work, just fake ones have a reputation of failing faster

 

[Twotoncarman]

Just change the thermostat. AND the coolant,
The coolant is probably carrying all sorts of crap around.

 

[flisko]

thats why head gaskets go, look at that old antifreeze


https://www.fiatforum.com/punto-mk1...mk1-1-2l-8v-fire-similar-radiator-system.html

 

[jte]

Now I have changed thermostat (original), coolant, coolant temperature sensor, and bled the system, but temperature needle do the same thing.
Few weeks back I read temperature from the OBD socket and temperature dropped 10 degree when needle dropped.
I don't know anymore what could it be.

 

[flisko]

Now I have changed thermostat (original), coolant, coolant temperature sensor, and bled the system, but temperature needle do the same thing.
Few weeks back I read temperature from the OBD socket and temperature dropped 10 degree when needle dropped.
I don't know anymore what could it be.

are you sure you bled it properly?
do you got hot air from vents?

https://www.fiatforum.com/punto-mk2-2b-guides/347158-coolant-renewal.html
https://www.fiatforum.com/punto-mk1-guides/43906-bleeding-cooling-system-8v-16v-petrol-engines.html
https://www.fiatforum.com/punto-mk1-guides/90237-bleeding-cooling-system-mk1-punto.html

 

[jte]

I pressure bled the system and there is no any sound behind the dash.
Hot air is coming from the vents.

 

[flisko]

did you check after new thermostat if temperature drops when temp gauge goes down

 

[jte]

No I didn't.