help with focus overheat problems
Discussion
mk1 1600 petrol focus , had the dash lights come on yesterday on the motorway , luckily dived down a slip road almost straight away and switched off
the coolant tank was full the cap and spiting out coolant , after it cooled it had lost around half an inch or so
got towed home , and pulled it apart thermostat works in a hot saucepan, water pump impeller isnt lose /damaged
refilled it and ran it up again , seems the engine gets hot and the fan comes on after a normal amount of time yet the coolant tank and hoses are still cold , the passneger side rad hose was warm
so in a nutshell...engine hot, rad cold , heater works fine
the coolant tank was full the cap and spiting out coolant , after it cooled it had lost around half an inch or so
got towed home , and pulled it apart thermostat works in a hot saucepan, water pump impeller isnt lose /damaged
refilled it and ran it up again , seems the engine gets hot and the fan comes on after a normal amount of time yet the coolant tank and hoses are still cold , the passneger side rad hose was warm
so in a nutshell...engine hot, rad cold , heater works fine
If the coolant tank is staying cold then you probably have a blockage. This could easily prevent the system from degassing so you could have built up an air lock. Once that finds its way to the radiator it'll cripple the cooling system. It would also prevent the system from filling properly if you needed to top it up after your overheating episode.
small 90 deg elbow on the back of the head that connects to the small bore hose to the header tank was blocked or at least partially blocked
its all getting hot like it should now , driven it around town for an hour and no mishap's , will keep an eye on it
one strange thing though , the temp gauge shot from normal to max instantly then back again after say 5-10 seconds , it did this a few times , too fast to be a true reading ,more like an electrical glitch
its all getting hot like it should now , driven it around town for an hour and no mishap's , will keep an eye on it
one strange thing though , the temp gauge shot from normal to max instantly then back again after say 5-10 seconds , it did this a few times , too fast to be a true reading ,more like an electrical glitch
its still randomly shooting the temp gauge from normal to red for a couple of seconds then back like its a elec problem
ive got a scanner jobbie but i dont really know what im doing , i can watch the cly head temp sensors reading raise which im told in turn is what triggers the rad fan , but unsure at what temp it should trigger at?
ive got a scanner jobbie but i dont really know what im doing , i can watch the cly head temp sensors reading raise which im told in turn is what triggers the rad fan , but unsure at what temp it should trigger at?
If the coolant temp sensor is not sitting completely immersed in water because of underfilling or an air lock then it can't actually register a proper temperature. In fact it's possible for the engine to be melting and the temp sensor to register stone cold. Random fluctuations in the gauge can be because an air lock "burps" its way free letting some water to the gauge for a minute (temp goes sky high if water really is that hot) and then air builds up again and gauge drops back.
It seems strange not to have the coolant temp sensor immersed in coolant, but I don't know that engine. The coolant temp sensor is almost certainly a thermistor which is wired into a voltage divider circuit within the ECU. With this type you can see what the sensor reading it by measuring the voltage across the sensor while it is connected to the ECU, or by measuring the resistance across the sensor while it is disconnected. You could use either approach to find whether the sensor is actually reporting the wide temperature swings your gauge shows. (Doing it while connected would be slightly preferable since it would avoid causing fault codes at the ECU.)
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