Thread: Series 3 Cooling System

The thermostat is essential.

Is the radiator new? If not it may be blocked even though it looks fine. A digital laser thermometer is useful for measuring the surface temperature of the radiator, to check for even water flow; it should be cooler at the bottom of course.

Does the top hose feel too hot to touch, when the gauge reads hot? If not then the sender unit may be the wrong one, as you surmise,

Cheers Charlie

Yes the thermostat is essential to proper cooling.

Matching the sensor with the electrical system/voltage stabiliser and respective gauge is critical.

When an engine is overheating it is usually either a radiator blockage or problem in the engine like a blown head gasket.

Now you've identified a problem with the current thermostat, fitting a new one should be your first job.

If it's not blowing coolant out of itself it's not likely to be the head gasket.

Without a thermostat the diesel will struggle to maintain temp at idle,

I'd blame the gauge or regulator but you could also have a failed sender that is going shorting when the coolant finally warms up.


First thing I'd do is check the temp with a stand alone thermometer.

As Dave says - first determine whether it really is overheating. With no thermostat, it would have to have a fairly serious (and almost certainly obvious) problem to even get up to operating temperature.

John

Originally Posted by chazza

The thermostat is essential.

Is the radiator new? If not it may be blocked even though it looks fine. A digital laser thermometer is useful for measuring the surface temperature of the radiator, to check for even water flow; it should be cooler at the bottom of course.

Does the top hose feel too hot to touch, when the gauge reads hot? If not then the sender unit may be the wrong one, as you surmise,

Cheers Charlie

Hoses aren't to hot to touch and I wouldn't say it's overheating. Just worried that the temperature gauge sits midway when vehicle first started but after 10-15 minutes moves up into the red.

The temperature sensor I had put in was a new spare that was sitting in a draw. Can't remember what Landy or Range Rover I'd bought it for but was not for a diesel motor.

Originally Posted by Lotz-A-Landies

Yes the thermostat is essential to proper cooling.

Matching the sensor with the electrical system/voltage stabiliser and respective gauge is critical.

When an engine is overheating it is usually either a radiator blockage or problem in the engine like a blown head gasket.

Now you've identified a problem with the current thermostat, fitting a new one should be your first job.

I would have thought that without the thermostat the whole system would be running to cold. It's not a blown head gasket as system is not loosing any water, running rough or moisture in oil. I'm thinking that it may be just the temperature sensor.

Not true, the lack of a thermostat overcools the engine, using more fuel (particularly when you have an automatic choke) and leading to premature engine wear. Remember the thermostat opens at minimum engine operating temperature so below that temp fuel is more dense and won't vaporise correctly