gmc15 Posted January 12, 2015 Share Posted January 12, 2015 2002 1.3 duratec water light coming on. Replaced thermostat housing, same problem. Replaced water pump which was damaged, same problem. Replaced expansion cap, same problem. When the car is stationary, with a few revs the water heats up and heater gets nice and hot, the thermostat opens and the bottom hose gets hot, fan kicks in and out as it chould - whole system works fine. As soon as I go for a drive the temp light comes on. When I stop the bottom hose is cold. If I then put a few revs on the car and feel the bottom hose the thermostat opens and the bottom hose gets hot again. As soon as I drive off, within a few miles it appears that the thermostat has closed and the temp light comes on. What I cant understand is how the system works fine when the car is stationary but not when it is moving! Any ideas? Head gasket leaking from cylinder to water system causing pressure build up? Graeme. Quote Link to comment Share on other sites More sharing options...
DieselPig Posted January 12, 2015 Share Posted January 12, 2015 If the head gasket is blown the expansion tank will blow hot water out and the water should turn a murky colour, have you changed the thermostat? Quote Link to comment Share on other sites More sharing options...
gmc15 Posted January 12, 2015 Author Share Posted January 12, 2015 The thermostat unit has been changed.The header tank fills up but it has no actually blown out yet. As soon as the thermostat opens the water level falls to a normal level. Quote Link to comment Share on other sites More sharing options...
DieselPig Posted January 12, 2015 Share Posted January 12, 2015 Could be an airlock in the system the water level should remain constant. Quote Link to comment Share on other sites More sharing options...
gmc15 Posted January 13, 2015 Author Share Posted January 13, 2015 Checked that all the air is out of the system by starting up from cold with header cap off. Can't understand why it works pefectly when on my drive but not when out on the road. Quote Link to comment Share on other sites More sharing options...
btmaldon Posted January 13, 2015 Share Posted January 13, 2015 It does sound odd as you appear to have done everything you could. is the system still holding the pressure. Once cooled down are the pipes still hard and do you notice the system releasing pressure when you undo the cap. If its not holding the pressure it would restrict circulation and the coolant will boil at a lower temperature. If pressure in system is ok then all I can think is that there is a blockage in the radiator which you may be able to flush out with a hose. Quote Link to comment Share on other sites More sharing options...
gmc15 Posted January 13, 2015 Author Share Posted January 13, 2015 When it has cooled down and I undo the cap pressure is released so it is holding pressure. The radiator has been backflushed and appears to be OK. When the car is stationary and the thermostat is open the radiator gets nice and hot from top to bottom and the hoses are all hot through to the thermostat housing. Not sure why the thermostat shuts when I drive the car which I think is stopping the flow and causing a pressure build up which pushes the water into the expansion tank. Quote Link to comment Share on other sites More sharing options...
gmc15 Posted January 13, 2015 Author Share Posted January 13, 2015 I am not sure how the thermostat opens, is it just down to physical water temp touching it or is it electronically controlled ie a sensor tells it when to open? If there is back pressure in the engine would this cause the thermostat to close? When the thermostat is open the whole system appears to be working as it should, so I wondered what might be causing the thermostat to close? Quote Link to comment Share on other sites More sharing options...
DieselPig Posted January 13, 2015 Share Posted January 13, 2015 The stat opens by hot water being in physical contact, did you fit a pattern or genuine Ford part? The original Ford parts had a small bleed hole to allow water/air to bypass the stat when cold. Quote Link to comment Share on other sites More sharing options...
gmc15 Posted January 13, 2015 Author Share Posted January 13, 2015 I am not sure as my local garage fitted it, but they had to take the old one off to get the serial number off it. Funny that it works fine, nice and hot and everything flowing but when I drive the car the thermostat appears to close! I am stumped. It has also had a new temp sensor fitted - on top of the thermostat housing. Quote Link to comment Share on other sites More sharing options...
troy45 Posted January 13, 2015 Share Posted January 13, 2015 Pressure in the coolant system when the engine is cold isn't a good sign in my experience, Focus ST cracked cylinder liner etc :( however this was combined with the car using water and not throwing up any temp faults, though if you'd have run it empty it would have! Only thing which changes when driving the car is air flowing through the radiator - sounds like the thermostat is working the wrong way round, if such a thing is possible? Is it possible to fit it the wrong way round and cause the issue? If it's possible to get a schematic of your coolant system that may give some other ideas to work through. Quote Link to comment Share on other sites More sharing options...
DieselPig Posted January 13, 2015 Share Posted January 13, 2015 You can't fit a stat the wrong way round and it would still open when hot. The only thing I've seen cause this is the water pump impellor spinning on the shaft but this has been changed. Quote Link to comment Share on other sites More sharing options...
gmc15 Posted January 13, 2015 Author Share Posted January 13, 2015 The thermostat is built into the housing so you buy the complete article, I don't think it is possible to fit anything the wrong way round. I even tried covering part of the radiator to restrict the cold air flow when driving but the thermostat still closed. I disconnected the cooling fan and ran it like that for a short while but still had the same problem. I got the whole system nice and hot and everything flowing as it should then went for a drive and within a few miles the temp started to rise so I stopped, the bottom hose was cold again as if the thermostat had closed, and the header tank level went up a fair bit. I disconnected the fan to stop it cooling, let the car idle with a few revs and kept feeling the bottom hose. Eventually the thermostat opened and the water started to flow and the level in the header tank fell to normal. Everything was then working as it should! I drove back home a couple of miles and bottom hose cold and header tank high again!!! Quote Link to comment Share on other sites More sharing options...
gmc15 Posted January 17, 2015 Author Share Posted January 17, 2015 Had enough of it so part ex'd it for a Toyota Yaris. The garage will just put the Fiesta to auction and then someone else can have a play with it!! Quote Link to comment Share on other sites More sharing options...
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