Technical Warm little Punto - TOO WARM!!!!!

[JSAMacLean]

Hello,

I've got a 99(T) Punto 60, old shape, and it's been giving me grief recently. Its gotten to the point where the 10-mile commute every day is a nerve-wracking experience[V].

I bought the car used in the summer of 2002, and it was fine until this summer, when sitting in traffic I looked down and the temp gauge was solidly buried in the red. Doh!

So I took it to Mr.Local Mechanic who re-gasketed it, refaced the head, and put a new Thermostat in. Fine.[^]

I was out of the country for a month, and I've come back and all hell's broken loose. The radiator is fine, as the level stays constant (i.e. doesn't leak), and when I'm moving on the Motorway at 70 in 5th the temp gauge sits between 1/2 and 1/4. However, it used to (before the overheat) start up and go to 1/2 and just sit exactly there all the time. Now, as soon as I'm doing less than 40 the temp starts rising.[xx(] If I'm sitting in traffic it just keeps going up - thus far it's not gotten to the red, but it has been above 3/4 frequently.

I thought the fan didn't work, as I didn't remember hearing it - so I did a DIY test and short-circuited the fan switch (and yes it does work). Then I thought the fan-switch might be bust, but when I was in traffic today watching it get to 3/4 temp the fan came on for about 30 seconds - and then went off again!!!B)

Anyone got any bright ideas?[?]

Cheers - JSA

 

[FiatExpert]

Sounds to me if you have had head gasket done, that either you,ve got a sticky thermostat or a air lock in the system, or a bad h/g job done

 

[JSAMacLean]

Well, I could buy any of those, except it can't be the thermostat, because there's plenty of cooling at high speeds, and it can't be the head gasket, because it doesn't lose any water.

Handily I work for an Automotive Design company, so I'm going to get some help from the electrician to wire in a fan-relay bypass switch, so I can turn the fan on at will from the cabin. Fingers crossed that'll solve the problem.

 

[Enzo]

I think this problem's due to a blocked radiator, of course I assume the thermostat to be good and no air inside the cooling circuit!Try to empty the circuit and to use a flushing product and then refill it with distillate water and a good antifreeze (50/50%) to avoid calcium deposits[8D]!

 

[poggy]

Hi,

I think it is the thermostat. It doesn't matter that at high speeds it cools OK as the thermostat would close more then due to the increased air flow cooling the water in the radiator. When in traffic the thermostat needs to be fully open. The fact you are getting different readings at different speeds, does point to the thermostat. Also if the fan isn't coming on much, it proves the hot water is not getting to the radiator as it is not tripping the fan switch.

I had this problem in another car after replacing the head gasket and the thermostat.

Poggy

 

[thefishdude]

hi i had a similar problem on my last car. 93 vauxhall. head gasket once blew i had it and teh radiator replaced. few months later as soon as i stopped car moving engine would over heat. i asked my mechanic who i had used for years, he tested the fan it was fine. so he suggested either the head gasket was badly replaced ( he dint do last one) or he had known of the impeller blades on water pumps to wear down and corrode so much that it did not push the water around quick enough to cool engine. my car was booked into to get water pump replaced but week later i wrote car off so never did find out for sur i knwo your car is newer but just thought i would say

 

[JSAMacLean]

Cheers all.

Fingers crossed, I've decided to replace the thermostat and the fan relay switch, seeing as both require dumping the coolant. I was going to just do the switch, but ya'll have convinced me that the thermostat could be to blame as well.

I'd be shocked if it was a blocked rad, seeing as the car's only done 34.5k miles, and the sudden change from working fine to overheating seems more electrical/mechanical than the slow build-up of crap.

I'll let you know how I get on.

 

[Brava GT]

Sounds like jammed water pump.

**
Italiana

 

[JSAMacLean]

Good news. After an afternoon spent cursing Fiat design, I've installed the new fan relay switch and thermostat. On the way home got stuck in traffic for 30 mins and the temperature got to just over half and stayed there. So I think we'll call that a success then. Fan came on and helped stabilise the temperature, which it wouldn't have done before.

For those planning to do any DIY on the cooling system, be warned. The fan relay switch is about a 29mm hex head and is right next to the expansion tank, so you can't get a spanner down there. It's got the sensor plug on it so you'd need an extra-deep 29mm socket (which is really obscure sizing and you'd never use again). With a bit of cajoling I managed to get the old one off with an adjustable wrench, but it took me ages. Also, the standard Fiat hoze clamps are really crap, and you have to prize open two bits of pressed-on metal to free them. Took ages, and once you get them off you can't reuse them, so have some good old jubilee clips ready.

Thanks for all your help!