Thermostat or Pump?

[Headlight Fluid]

Hi everybody,

1.6 TDCi (115bhp) Zetec 5d 2014

I have recently noticed that my car has been going through a lot of coolant. I first noticed that my car heaters where only blowing cold air. I checked and seen that the coolant was low so topped it up.

I checked it a couple off days later and the coolant level had dropped again. I cannot see any sign of leaks. When I first start my car, although it's still cold it tries to pump coolant from the reservoir. When I turn the engine off I can hear a whining noise coming from the area of the water pump.

I think it could be the that it could be that the thermostat could be stuck open.

Has anyone else experienced this, know what tests I can do to find out what is causing the issue or what else could be causing this?

Thank you

[stevemcs]

Its really common for the thermostats to fail, just get a genuine one from ford, they are not that expensive at all.

[Headlight Fluid]

Thank you

[Gary C]

But a stuck open thermostat wont cause the system to loose coolant, maybe a stuck closed, but not stuck open.

[stevemcs]

True, but the plastic housings leak.

[Gary C]

stevemcs said:

True, but the plastic housings leak.

But no sign of leaks ?

[Headlight Fluid]

Thank you for all your feedback.

I can't see any signs of leaks.

If I have the heater on full pelt it holds coolant, but if I don't use the heater it goes through a lot of coolant and it drops below the minimum. Does that indicate a thermostat fault?

The whining noise appears to have stopped now, I think it may have been due to the lack of coolant. Does the pump use the coolant as a lubricant?

[Gary C]

if its using coolant, its going somewhere. I could be leaking when hot, and therefore not seen as it escapes as a vapour.

Is the temperature indicated higher than normal when driving, and falls to normal if you put the heater on full ? if so it could be the thermostat and the coolant is leaking when it is too hot.

You can change it, if there is doubt as its a cheapish part but if the housing is known to leak as posted above, ensure the seals are replaced too.

[Poynter87]

I've had two mk7 zs tdci and both had the plastic thermostat housings fail as well as the plastic housing on my mk1 focus rs failing so it would be a good place to start and obviously replace the seals and thermostat at the same time.