Ford Fiesta Mk 4 - Overheating Problem - Help Please

[AndyT955]

I have a Mk 4 Fiesta 1.6 , it overheats after about ten minutes. I have drained and refilled the coolant system I have flushed the radiator, I have today changed the Thermostat and still overheating. The radiator seems to flow ok when flushed with water. When I removed the thermostat it was definitely faulty could this have caused damage to the water pump ?

I appreciate this only leaves two suspects I think, either the radiator or the coolant pump ? the other clues are the radiator hoses are cold when the car is very hot, turning the heating on the car on reduces the temp reading on the engine, and the hoses running to the heater matrix are very hot. Also when the temp guage is in the red the header tank is only warm and car is not losing any coolant. Defintely a problem with flow but what to do next ?

Any help / experience appreciated ?

THanks

Andy

[Justin S]

Sounds like lack of water moving if the rads cold and you have changed the stat. if the heater pipes are also cold, I would suspect the water pump. Some have plastic impellors, which can fall off the end of the shaft. That would probably be the next port of call.

[AndyT955]

Well the saga continues, pump now changed and still temp off the guage, I am going to try and change the sender unit tomorrow and if that doesn't do it , then I'm really stumped ! any suggestions ?

[S1_RS]

Most likely the heater control valve. It's a common problem on the Mk4 & Mk5 Fiestas I believe.

[AndyT955]

OK, but the heater is working fine, how does this affect the flow through the head / radiator ? and the temp guage ?

Thanks in advance.

[diesel piston]

AndyT955 said:

OK, but the heater is working fine, how does this affect the flow through the head / radiator ? and the temp guage ?

Thanks in advance.

As far as I can see the valve sticks creating a system air lock.
On his 1.25 Fiesta My youngest son took the heater control valve apart and cleaned it and hasn`t had any more trouble

[turbopug]

I can't see the HCV causing an overheating issue, the only problem it would cause is a luck of heat inside the car. Is it possible that you overheated it and warped the head?

[AndyT955]

OK Sender Unit changed, rad flushed again, now car does not overheat but it now goes right to the edge of the normal range on the temp gauge before it starts on a downward cycle, looks like the thermostat opens at a very high temperature , it looks like the new thermostat from Ford is set to open too high or the internal gauge is out of calibration. Even when the car is nearly on the red I have opened the header tank and it does not appear that hot, the car is not losing coolant and is not overheating but its quite alarming to watch the gauge get so hot !

Would the heater control valve cause this ?