After a few miles the water hose coming from behind the engine feels very warm,but not hot,whilst the hose that fits into the water pump only feels warm,and the water in the expansion tank is cold...what is the problem...I have been chuffed with my 2002 2.0 tdci 130 zetec estate which is 500 miles off 200,000,it has served me very well as a work horse.

What's a few mile 2-3? If that's the case I wouldn't expect anything other than what you describe if it over 10 miles then something may be wrong. My expansion tank never gets hot

Have you just fitted a new thermostat, then it may be an airlock

Hi Pete,thanks for the reply...I did wonder if it is an airlock...this morning I was sat in slow traffic and the temp. guage sat on normal for the first time in ages...I haven't changed the thermostat,but I did change the coolant temp. sender unit the other week but made no diff. to the reading on the guage...have squashed the hose leaving the thermo. housing and no bubbles seen in the expansion tank...I am going to change the thermostat because if it is opening too soon then that would be the problem,I guess...and I will check the opening temp. of the existing one in a bowl of hot water with a liquid thermometer.Do you know at what temp. the thermo. should open at?

If, in this weather, you tend to have the cabin heating turned up, what you describe is quite normal: the engine only makes a certain amount of excess heat, and you use most of that heating the cabin.

And, to your original question: Usually, no. Well, you can make almost anything fit with a hammer, but the usual arrangement is that the thermostat will not fit unless it is the right way around. And, even if you did fit it the wrong way around, it would probably work more-or-less normally unless you are giving it some stick, and then it might overheat. So, it doesn't seem likely as a cause, particularly as you seem to be saying that it hasn't been touched.

Hi BOF, thanks for the reply,but why are the pipes each side of the thermo. housing of very diff. temperatures....also using a long shaft screwdriver I can hear the water pump whirring away so I presume that it is working o.k....I am at home next week so will investigate more.

Hi BOF, thanks for the reply,but why are the pipes each side of the thermo. housing of very diff. temperatures....also using a long shaft screwdriver I can hear the water pump whirring away so I presume that it is working o.k....I am at home next week so will investigate more.

If they're different temperatures then the thermostat is closed.

The hot side will be upstream.

If you give the pipes a good squeeze (like honking a clown horn) you'll soon know if there's any air. It'll squelch as you do it. The air will tend towards the highest point when the engine isn't running.

Sean,thanks for your reply..I have squeezed the pipes and watch the water swirl into the expansion tank with no bubbles.Clearly the thermostat is not opening properly so I presume that is why the radiator fans are on most of the time even if the air-con is switched off?

Was it a genuine Ford part, ir aftermarket?

My old Punto went through a couple of thermostats - and I know if many others that did the same. The one thing in common with them was cheap ebay purchases.