I bought a 52-plate Seicento Sporting yesterday.

On the drive home, I stopped with the engine running for about 10 minutes.

I noticed the 'high coolant temperature' warning light was illuminated but it went out again after driving for about a minute.

Back home I popped the bonnet and let it warm up again.

The warning light came back on but the fan didn't kick in.

I could see the water bubbling away in the expansion tank so I turned the engine off and left it.

Where do I start trying to diagnose and repair the fault?

First check that the top radiator hose (and the rad if you can reach in) get thoroughly warm (should take 5 minutes or so). If not, replace the thermostat.

If that's OK, check the fan itself first by jumpering it directly to 12v. If it doesn't come on, replace the fan. Then, identifying the + and - feeds to the fan, and with the engine thoroughly hot, jumper one at a time.

Failure to come on will identify which side of the circuit is iffy. If the + side, it'll just be a simple wiring fault, if the -ive, look for an issue on the earth side (clean up the earths, etc). The circuit -- I think -- is switched on the earth side.

don't like the sound of bubbles in the expansion tank. with the engine cold, remove the cap and start the car, check it for bubbles.

arc said:

Don't like the sound of bubbles in the expansion tank. ..

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What are you thinking?

fingers99 said:

First check that the top radiator hose (and the rad if you can reach in) get thoroughly warm (should take 5 minutes or so). If not, replace the thermostat.

If that's OK, check the fan itself first by jumpering it directly to 12v. If it doesn't come on, replace the fan. Then, identifying the + and - feeds to the fan, and with the engine thoroughly hot, jumper one at a time.

Failure to come on will identify which side of the circuit is iffy. If the + side, it'll just be a simple wiring fault, if the -ive, look for an issue on the earth side (clean up the earths, etc). The circuit -- I think -- is switched on the earth side.

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I can do the first bit alright but I'll have to get someone else to fiddle with the leccy.

Roswell said:

What are you thinking?

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Head gasket. But don't pull the head before you've checked everything else and done a compression test.

Roswell said:

What are you thinking?

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i'm eliminating worst case (failed stat causing overheat, causing blown head gasket)

There's no 'mayo' in the oil and the water seems reasonably clean - it's still a nice green colour.

hg can blow and not touch the oil, if a combustion chamber is leaking into the cooling system then it will blow exhaust into the expansion tank causing bubbles. i don't think its very likely to have happened this time - but it takes 30 seconds to check.

arc said:

hg can blow and not touch the oil, if a combustion chamber is leaking into the cooling system then it will blow exhaust into the expansion tank causing bubbles. i don't think its very likely to have happened this time - but it takes 30 seconds to check.

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Worst case scenario, how much will it cost me if the head gasket has blown?

I have a mate who can do the work for me for beer tokens.

~£80 in parts (gasket, bolts, skim, cam belt, tensioner, waterpump, oil, coolant)

arc said:

~£80 in parts (gasket, bolts, skim, cam belt, tensioner, waterpump, oil, coolant)

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That's not too bad then (compared to fixing the same fault on my Alfa!! )

Well worthwhile cutting in the valves, fitting new valve stem oil seals and re-shimming the tappets while you're in there. That way, the head should be fine for 40 -60k miles.

fingers99 said:

Well worthwhile cutting in the valves, fitting new valve stem oil seals and re-shimming the tappets while you're in there. That way, the head should be fine for 40 -60k miles.

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I think I'll concentrate on getting the fan working first though eh?

Aye.

I'm just spoken to my mate (an ex-Alfa/Fiat technician) who thinks the problem could just be a seized fan. He's going to check it out for me at the weekend.

If it has not done an 'old faithful' water geaser, you are probably ok.

There are two bleed screws, when the engine is cold undo the one between the driver headlamp and the coolant header tank, when you only get water tighten it, it is a little hose stiching out of the inner wing.

Then undo the one at the end of the little hose sticking out next to the heater bulkhead, when you get water retighten it.

Until the fan runs all the time use the heater on hot with the heater fan on max, & dont get stick in a traffic jam. It is best not to use the car at all.

The rad fan should spin freely given a flick from a finger, if it is stiff you need a replacement, but more normally the earth is bad.

Noel

Thanks for all your replies.

I'm going to attempt to drive it 20 miles home from my girlfriend's house later this afternoon.

Roswell said:

Thanks for all your replies.

I'm going to attempt to drive it 20 miles home from my girlfriend's house later this afternoon.

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If you must, make sure the cooling system is filled and bled. Be prepared to turn the heater blower on full with the heat up full as an additional radiator fan and switch it off if you get to a traffic jam.

Cheers

SPD

Hi young David is not being annoying my fan comes on when the car slows to a crawl or stops at traffic lights.

So open the windows and leave the heater fan on all the time, if you are crawling along kill the engine, run the rad fan, re-start the engine only when you need more speed.

The rad is worth about 2kw of heat extraction but you need more when stationary, or near stationary.

Noel