Technical Overheating problem

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Technical Overheating problem


New member
Jan 18, 2005
After covering 14 miles of a 15 mile journey to work this morning in my Seicento sporting. The temperature light lit up on my dash. Not having seen this light before I pulled over to try and find the cause. it was 6am and dark, I could just manage to see a small amount of steam coming from the coolant filler cap. I opened it up after a lot of hissing and bubbling to find the coolant level near the bottom of the expansion tank, had a look underneath the car and could not see any leaks. I then drove to the garage nearby and brought 2 2 litre bottles of water. I filled the expansion tank back up and drove to work. when I left work this after noon I checked the expansion tank and it was empty I put about 3 litres of water into the tank to fill it back up. I then drove home stopping half way to check the level and it was still full. I checked the level once I got home and it was still full.
Does anybody have any idea what has caused this? Possibly the head gasket gone?
Oh and while I am thinking about it I have not heard the electric fan for a while! is there a way of testing this?
Thanks in advance.
it could be the expansion tank lid, sometmes they play up and dump the coolant out as steam.

There are ways of testing the fan, what type of eninge do you have. Mk1 SPI, or mk2 MPI ?
To test the electric fan leave the car running and listen for it cutting in as it will even just on idle after a while. If nothing then you know it's toast! Sounds like the fan has gone though and the car overheated, you might be lucky and not have blown the head gasket but only a compression test will tell you this for sure.

Hope this helps,

if the fan is suspected as not working, then i wouldnt test it like that. you're only gonna end up overheating the car again. not a good idea!
Good point you can tell it's nearly the end of the day!

Can you put 12v across it to see if it spins up? Also can you imerse the sensor in boiling water to see if that is working?

arc said:
There are ways of testing the fan, what type of eninge do you have. Mk1 SPI, or mk2 MPI ?
How do i tell?
SPI has a rectangular grey airbox on the top of the engine, an MPI has a circular black airbox.
arc said:
SPI has a rectangular grey airbox on the top of the engine, an MPI has a circular black airbox.
I have the SPI engine then. What are the list of checks i should be carrying out now?
okie kokie.

first of all, with the engine off - check that fan spins freely. that there is nothing jamming it.

If that is fine then turn the igintion on, and go to the front of the car. Looking at the rad, there should be two wires that go into it, around the middle of the right hand side. Unplug the connector. Using a random bit of wire, or metal - joing these two connections together. It might spark when you do this.

If the fan spins up, then the fan is working. Although the temperature switch in the radiator could be faulty. These cost around £10 new from FIAT.

If it does not spin up, then its time to check the fuse. The fuse on the Seicento is behind the battery. It is a big spade style fuse.
If the fan was running when i switched the car off a lot of the time it would keep in running (the fan) and would not switch itself off, until i switched the ignition back on and waited for the fan to cut out and then turn the ignition off.
Does anybody else have this problem?
with the fan switch being in the rad, when you turn the engine off, the water stops flowing. It can take a while to cool the contents of the rad down enough to turn the fan off. The fan kicks in around 92c, and off again at 87c ish - it can take a while to cool that without any water flow in the rad
Ive had a quick look under the bonnet. I can see a spray coming from behind the oil filter can't pin point it. The timing belt seems too be kicking up a lot of spray. so the fluid has found it way in there some how. It is looking like a leak at the moment. any ideas what could be leaking in that area? As soon as the light came on i stopped the car. Do you think it would have an effect on the head gasket?
should be ok if it didnt severly overheat.

could be a hole in the rad. there isnt any waterpipes over there, bar the ones that go from the expansion tank
I have now got the Seicento in bits on the drive. I have tested the fan and it is working. Does this mean the temperature sensor is faulty? When it overheated I had just come off a fast dual carriage way which I had been on for about ten miles. I would of though the fan would not of needed to on along this stretch of road.
I have been looking for this leak and it seems to of disappeared and the top of the expansion tank does look very wet.
If the engine had of overheated due to the fan not working could it of boiled the coolant forcing it out through the expansion tank cap? as opposed to blowing any gaskets etc?
I have just been quoted £41.23 by Fiat for a new temperature sensor :eek:
Is the coolant temperature sensor a different part to a radiator fan switch?
Cone on arc give me the answers im looking for :worship:
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You say the top of the expansion tank is wet? Try buying a new expansion tank cap, filling and bleeding the system and then let it heat up.

Cooling systems run under pressure, this pressure keeps the boiling point higher. The exapansion cap is meant to vent this pressure if it gets too high (stops a pipe blowing off). If the cap is faulty, the system will not seal properly, will create no pressure and the coolant will boil to early before coming out the cap as steam, condensing on the top of the tank / area.