Fan tested.Works OK but not cutting in when it should, so water boils after 10k in hot Malta.

Electrician says it is a sludged up/blocked thermostat. Is a new one the simplest answer or is unblocking the existing one not too labour intensive?

I have no handbook. It's a 1994.

Any advice appreciated.

they are only cheap anyway so personally wouldn't bother trying to unblock it

If the thermostat is blocked, the hot water never gets into the radiator and then of course the fan never cuts in. So if this always happens after a while, even if you're driving at some speed on main roads, the thermostat is the likely suspect.

If boiling only occurs when idling/queuing it could be the fan sensor that is broken.

I wolud recommend a new thermostat and a housing (at least if the Favorit has the same plastic housing as the Felicia). Also give the whole system a good rinse and fill it up with recommended mix of water and anti-freezer. Even if Malta's climate is mild, anti-freezer also prevents corrosion.

If the thermostat's sludged up, so will at least some of the waterways and radiator cores be.

Not only do you need a new thermostat, but the block and radiator flushed, then refill with water and 25% G12.

Could also be the fan switch has lost it's efficiency. I'd be looking at replacing the fan switch in the radiator and the thermostat using a hose to give the cooling system a good flush through.

If the thermostat's sludged up, so will at least some of the waterways and radiator cores be.

Not only do you need a new thermostat, but the block and radiator flushed, then refill with water and 25% G12.

If the sludging has managed to get up as high as the thermostat, you have got problems

If the sludging has managed to get up as high as the thermostat, you have got problems

Oh yes, but I was working on the basis that in most liquid flow systems sludge accumulates first at stagnant points and restrictions.

Well, does the radiator get hot? I mean properly hot - should be seriously uncomfortable to touch, all over its surface. If so, there's nothing wrong with your thermostat. By far the most likely cause of overheating like this is the fan switch, which does in fact fail eventually on most cars. It costs about £5 (or the equivalent in Maltese!) and if you're quick and don't mind getting dripped on can actually be changed without even emptying the coolant, though you'll lose some. It's very easy to get at on a Fav.

I've got this issue too but nothing appears to have sludged up just the fan not cutting in when it should be.

We've just wired up a switch so I can switch the fan on when I feel it's needed.

We've just wired up a switch so I can switch the fan on when I feel it's needed.

Mate, just replace that radiator fan switch! Sooner or later you'll forget the manual switch, boil badly and bend your cyl. head!

We did replace the fan switch but that didnt cure the issue.

The fan stilll doesnt kick in until its a little too late

it's not a good idea to run the fan for long periods, the motor isn't designed to run at 100% duty