Technical Thermostat hose cold car overheating...

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Technical Thermostat hose cold car overheating...

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Quick question, my girlfriends punto (1.2 8v) is overheating quickly and alot!
when it gets half way on the temperature the themostat hose is still quite cold and the car starts to overheat and fan constantly on, is this a thermostat stuck closed i take it?
many thanks, Aaron.
 
Yes, quite possible thermostat failure or severe airlock in the cooling system, replace stat and bleed bleed bleed!

Also, DON'T run the car while in this state, unles you want to pop your headgasket!

Overheating = fan turns on, engine overfuels to keep cool, and usually goes into limp home mode.

Benny
 
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the car only overfuel's when a lamda says its running lean due to a sensor / air leak /failure

OR the temp sensors fails,
The less fuel in combustion creates a leaner burn, the leaner the burn the hotter it is

So when the CTS fails, it burns rich = cooler burn = Saves excessive heat

What i dont get is why they overfuel when cold? Eitherway they do

Ziggy
 
What i dont get is why they overfuel when cold? Eitherway they do

Think of it as an electronic version of a choke.

KH750 two stroke triple middle carb was jetted up one or two to keep it cool iirc.

Not uncommon for supercharged and turbo engines to do the same. But it's really a band aid you're unlikely to find on a pedestrian shopping car.
 
Best explanation I've seen is that at lower temperatures the fuel tends to pool in larger clumps rather than fully combine with air. So, put more fuel in (richen the mixture) to make combustion possible.

Almost there with this one. The pools of fuel do not evaporate well, so do not draw into cylinder as a proper atomised mixture. Extra fuel helps, although lots is lost. Also cold engine needs more push to run. Electronic fuel injection will reduce richness very quickly, just raising the tickover to keep the cold engine running.
 
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