New thread ford fiesta '56 problem

[_georginaamyc]

Basically.

Driving at a steady 30-40 no problems.
Going up towards 50-80 it starts to over heat. However, the temp gauge fluctuates. It'll go right up to the red bring itself down to 3/4 then up a bit then to 1/2 etc
At idle for 10 seconds it went straight into the red, after driving 400 yards it went down to 1/2.

Any idea? Fan works, coolant isnt leaking, hoses are hot etc etc etc

[imagineifyeswill]

Bad earth on engine block, possibly earth lead loose.

[PaulKemp]

Or bad connection to temp sensor
Gauges usually default to max on older cars, newer cars gauges are controlled by ECU

[E-bmw]

Or air lock meaning the sensor isn't always under water.

[Classy6]

To start you need to know you have a good coolant level & good mix of antifreeze/water. You also need to know you have no leaks by checking with pressure tester, although you may not be losing coolant noticably you still may have a tiny leak.

Treat yourself to an infrared temp gun and grab a generic cooling system diagram so you understand how the circulation flow works.

Use it to find out if the cars actually overheating or whether you have a dodgy temp sensor to start with by comparing the temp gun to car temp sensor. It takes time for things to get hot and longer for them to cool down so your car temp gauge shouldn't be moving erratically.

From there, run it up to temp ,for arguments sake ~90* odd and use the gun to check the temp of all the hoses as it warms up - top & bottom hoses (in/out of radiator), also check in and out of heater matrix pipes. Use it across the face of the radiator (where accessible) to check for hot spots/blockages.

Using the gun you can begin to tell what's happening, whether the thermostat is opening by taking temp of either side & using top/bottom hoses, when it's up to temp 90* the Fan should be cutting shortly after to regulate temp @ idle.

At this time (at operating temp) the hoses should be reading similar temperatures give or take 10* or so to indicate that the water pump is circulating the coolant correctly and you have no kinks/blockages. If everything is fine when tested at tick over, pick up the revs or go for a drive until something happens that you can rego over the process to find the fault.

The only other thing I may advise on above that has caused me strange faults in the past is a block test to ensure no combustion gases are getting into the cooling system.

HTH

[_georginaamyc]

I had a new temp sender, thermostat and water pump fitted. Flushed the system a few times are we're back in business

[PaulKemp]

So know we don't know if it was the temp sender, thermostat or pump

[_georginaamyc]

It wasnt the pump as i had that changed first
The thermostat was still working they just swapped it
So it wouldve been temp sender