I'd normally be worried about our car showing 3/4 - 2/3 on the temp gauge if it wasn't for the fact that the electric fan turns OFF at 3/4 reading.

This implies to me that the gauge is simply reading high?

I presume the fan & the guage use different sensors?

Anyone else get a high reading with 1.1's and does anyone agree my 'can probably ignore it' feeling?

I have back flushed the rad & refilled, & it doesn't get through water.
Comments please!

all things must pass.

my punto always reads just under half way on the dial that woried me when i first got it. Don't forget to use anti freeze all year round or you will damage engine.

A common misconception, the gauge must be wrong.
Bad news, the gauge is right.
On all Puntos the fan has a 2 stage drive (except the GT which has 3), in an attempt to limit the fluctuations of heat in the cooling system the fan comes on at 1/2 speed when the temperature reads about halfway. If the temperature increases to approx 3/4 the engine panics and to save its worthless hide will ram the fan on full pelt in a last ditch effort to bring the temperature down.

The problem is the temperature really only reaches that sort of level if the water is low (so won't cool the engine no mater what) or there is a problem in the system (blocked pipe, water pump fins broken or the all to common thermostat swich just not switching).
When the engine is started cold the water bypasses the radiator to let the engine build up a good operational temperature, when the water reaches a set point it will divert it around the radiator to regulate the heat. If this doesn't switch the water continually gets hotter. The way to check this is to remove the thermostatic switch and emmerse it in boiling water to see if it clicks, if it doesn't its knackered.
To add to this problem I believe the fan has 2 fuses and is prone to wiring problems, so in your case, the temperature reaches 3/4, the fan kicks into full blast but doen't work because the wiring or fuse is shot.

Interesting, thanks for that.

Just for clarity, when you speak of a themostat switch, do you mean the themostat itself (the thing that blocks or opens the water flow to the raditor via the top hose), or literally an electrical switch somewhere of which I am unaware (if so, where is it please, and what function does it control again?).

In case it helps, the radiator water is getting hot (via top hose) which is why I have concluded that the themostat is opening - but perhaps late or not fully?

Didn't know about the 2-stage fan though - definately am not getting 2 fan speeds. However the real issue is the high temp reading at motorway speeds, when there is enough airflow not to need a boost from the fan.

Am I right in thinking that to replace the thermostat it's the 2 (?) bolts under the ignition pack, and that it's an integral part of the housing (so that you have to buy it from FIAT)?

all things must pass.

Have you air-bled it to make sure there's no airlocks after you refilled?

Pete.
Cinq sporting 1242cc
Cinqs&Seis Yahoo group
Clubcento

Yes, bled it Ok thanks - got air out OK & then drained off some fluid just to be sure. Dead handy that bleed valve - good thinking on Fiat's part (or at least their radiator supplier!).

all things must pass.

BTW, have seen no mention of 2 speed fan in the Punto haynes manual.
I'd change the thermostat and antifreeze first, if that doesn't fix it change the temp sensor. If the zigzag cooling fins are rotted off the radiator, that makes a considerable difference as well.

Pete.
Cinq sporting 1242cc
Cinqs&Seis Yahoo group
Clubcento

It must be the thermostat not opening properly or the water pump.

Haynes manual! It has no mention of the 1.2 sporting, 1.4 GT, 1.6 sporting and the cabriolet. Lets just say the haynes is a good guide but not the bible.

Yup, I've decided the logical course of action is to change the thermostat & see what happens.
Radiator looks in good nick (back flushing yielding no crud) fins in good condition and not blocked with road-kill.
Absolutely no signs of leaks.

This is a job for Saturday - I'll post the upshot.

EvilP:- this 2 speed fan thing - any guidance on most likely places to seek fault on the lower speed? (eg: where fuse located, where sensor located etc?). Also have Haynes manual (well, will do on Sat when car back)but if not featured ......

all things must pass.

BTW, I made the mistake of asking in Halfords how much a gauge temp sensor was before you guys helped me realise it 's probably the thermo, and they list about 7 different temp sensors (all special order) and couldn't tell me which one I needed for the gauge (now there's a surprise!).

Anyone got any info on where it actually is and how to identify it?

all things must pass.

The fan fuse is in a small cluster of "things" nest to the battery (connected to the inner wing), You may want to check the continuity of the wiring between the fuse(s) and the fan with a multimeter.
The fan is run off the same sensor that does the temperature gauge in the car so we know that works because the gauge is going up.
Could still be the water pump (right side, below and to one side of the coil packs), couple of bolts out and check the pump fins, if these have corroded or sheared the flow rate will be reduced.

Do you have a copy of the Fiat Punto parts CD, sounds like you need a copy (email me, [email protected])
Or you can go to Fiat with your VIN number, they can use that to pinpoint what part number you will need.

Thanks for that EP - might as well peek at the pump vanes whilst it's drained down to change the Thermostat.

Thanks even more for replying at 3 o'clock in the morning!

Don't worry about the part number CD - I'll make my Fiat dealer do the work!

I'm impressed with your knowledge of Punto workings -(this and other posts) - can I ask how this comes about?

all things must pass.

It was 3.46 in the morning
I work nights as an Engineer for Docklands Light Railway.

Supreme punto knowledge comes from owning one for 4 years, doing all the mech work yourself because the Fiat garage near me is poor (show me one that isn't) and picking up info from other Punto owners.

I am a member of 3 other Punto forums but for some reason I am only clever in this one

Sorry this proubly to late for matts dad but for anyone else punto thermostats are not a fiat dealer only part, I got one from wilco the other week for £12.
I find wilco usualy lot cheeper than halfords eg head gasket set with new bolts for 1.2 punto £24.99 in wilco £37.00 in halfords both the same make (FAI).
TO find a wilco near you go to www.wilco-fastfit.co.uk

Where has this site been over the weekend - I couldn't reach it ... the virus problem perhaps?

Temp problem solved - it was the old thermostat opening both late and not fully. New one (£13 from motor factors)does the job a treat.

Didn't inspect the water pump since discovered it meant removing the timing belt & I don't have the appropriate tools to ensure correct tension on replacement.

Although when I was exploring a new pump I found Fiat price £75, motor factors price £23!! Some difference.

For info, my model (94 1.1 SX) definately has a single speed fan and is switched by a sensor in the radiator, not from sharing the temp gauge sensor.

Many thanks for everyone's help and advice - this is a good forum!

all things must pass.

Matts Dad,

Right at the beginning you were concerned the fan only turned off at 3/4.. Has this changed since you replaced the thermostat?

Evil-Punto,
I've got a 55s with overheating problems. I want to connect a guage to monitor the temperature as I can't stand the red "warning" light as its basically too late when this comes on. Is there any way to connect an aftermarket or 55sx temperature guage to the factory fitted 55s sensors?

Can somebody tell me where on my Punto the thermostat and temp sensors are located? Is the warning light driven off one of these sensors or from the ECU?

Thanks,
Martin.

-
95 Punto 55s

Martin
Yes - the fan is now coming on about 3 or 4 needles width's about half-way, and goes off before dropping back to reach half-way. Normal running is now 1 needle-width above half, although motorways are still higher - but nowhere near 2/3.
My only explanation for why the fan operating point seems to have changed is that maybe in flushing the rad I've improved the fan sensor's thermal connection to the water, maybe it was insulated with gunge previously and so needed a higher water temp to get the fan switch to trigger?

Dunno - can't really explain it - easy answer is that I was wrong about where the fan came on & off previously!

I'm told the temp gauge sensor is the blue plug underneath the inlet manifold (view from nearside of car) - seen it but I haven't confimed that's what it is.
Not sure what you mean by Thermostat sensor - the above gauge measures water temp, and the thermostat is self-contained (no sensors).

On my car, the fan works from a switch on the radiator.

No idea what makes the warning light come on, or whether the ECU uses different sensors - all I know is that Halfords found about 7 different temp sensors listed for the 55SX!


all things must pass.

Thanks, and the thermostat is where? What tools are required for its replacement? Do you have to drain/replace the coolant?

Cheers, Martin.

-
95 Punto 55s

The thermostat is at the engine end of the top hose feeding the radiator - the hose actually connects onto it.

It comes as a complete assembly (metal housing & all) and is fixed by 2 bolts to the engine block. Access is easier if you remove the plastic shroud around the ignition pack which obscures the view otherwise.

Yes, I drained the radiator but I guess if you are prepared to put up with a horrible mess you could just unbolt it & wait until the water stops gushing out! It is on the high end of the water system anyway.

By the way, there are 2 bleed valves to use when refilling. One is obvious on the radiator (top, other end to top hose) and the other is well hidden - a screwdriver slot in a 'cap' that is screwed into one of the hoses that feeds the heater matrix. This is most visible when peering at those hoses from the drivers side behind the air intake (may find a torch useful). This valve is in the 'high point' of the system & the spot that air is most likely to be trapped after re-filling.

It's not a difficult job - probably the greatest danger is the temptation to overtighten the bolts which feels like it could easily strip the threads - so use some sealing compound to remove the temptation to 'bolt it down like a good'un'!

all things must pass.