Coolant loss

My friend’s 2003 Ford Fiesta 1.4, petrol manual has gone through one litre of coolant over a period of about two months. I had a good look underneath the car and around the engine and I cannot see any obvious leaks and the engine is surprisingly dry for its age and 110,000 miles. Since getting the car, it has been trouble-free apart from a broken window regulator. The aircon blows hot and cold air and doesn’t overheat.

What should be my next step in trying to identify the cause of coolant loss? I wondered if it might have something to do with the head gasket and, if so, how could I check that? I know there are some tester kits available on ebay, but are they reliable?

I am also planning to service the Fiesta and have already started soaking the spark plugs in penetrating fluid as they appear to have not been touched for a long time and look rusted to the engine. None of them would move when I tried to undo them to see how they look. Have you advice on how to remove them safely?

Finally, does this manual Fiesta have level and drain plugs in the gearbox, so the transmission fluid can be changed? I could not see any obvious ones while under the car.

Starting with the coolant loss, checking inside the vehicle for any leaks from the heater matrix would be the next step. You may not necessarily have puddles forming in the footwell, as the coolant might evaporate as it leaks, but there should be signs of the leak in the form of stains around the matrix or the lower vents. It would also be worth checking the thermostat housing for any staining, which might indicate a slow release of coolant from the base of the radiator. If one litre is escaping in two months, it could well be evaporating as quickly as it leaks out, which would explain why no drips are present under the vehicle. Another potential point of the leak is from the water pump. This might be hidden from view as it is tucked back behind the cambelt cover, and again the coolant may be evaporating before it pools on the floor.

I haven’t personally used any of the kits available on ebay, but the principle is very simple and they should work effectively. Most of them work by using the liquid in a vessel in the coolant filler neck. The vessel seals off the system, ensuring that any escaping gas is vented through the vessel. By placing a chemical in the vessel, which is sensitive to exhaust gases, the liquid will change colour if gases are in the system. This will be an indication of either a leaking head gasket or a crack in the cylinderhead. In the workshop, we use an exhaust gas analyser placed just above the coolant header tank to detect the presence of any gases. Before doing this test, though, we use a pressure tester to put the cooling system under pressure, possibly exposing any leaks.

The spark plugs can be very troublesome to remove and pre-soaking them is the best step. I usually try to remove them after the engine has been warmed up and is just starting to cool. This means that a small amount of expansion and contraction has taken place, giving the best possible chance of success.

The filler and level plug is at the front of the gearbox, just above the gearchange mechanism, hidden behind a plastic shield protecting the mechanism. The gearbox does not have a drain plug because Ford claims it’s filled for life.