Cutty Dyer
Active Member
Possibly the thermostat failed in the closed position causing the engine to get hot, the previous owner then removed it. Best replace, as it will help the engine to heat up to the optimum operating temperature (also supply heat more rapidly to the heater matrix)
West Slope Rover
Well-Known Member
Usually because the car's been running hot for whatever reason. Which could be caused by anything from leaks in the system, a clogged rad, a bad water pump, bad pressure cap, etc......
DEFENDER90-DAZ
New Member
Keep a good eye on the temp gauge 
Daz
Daz
West Slope Rover
Well-Known Member
+1keep a good eye on the temp gauge
daz
Removals01
Active Member
Maybe the previous owner didnt have the right sensor for the conversion and it was constantly on Hot?
West Slope Rover
Well-Known Member
If it's in I'd cautiously drive it to see if I had an issue with overheating. Keep an eye on the gauge.
Why were you replacing the thermo in the first place?
Without a thermostat you have no chance of maintaining (or even reaching) the correct running temperature, if it is getting hot then you have a bigger problem than a missing thermostat which has been removed to cover up the problem and not cure it.
A thermostat allows the engine to warm up by keeping the coolant in a closed system circulating it around just the jacket & heater, at this stage it is not flowing through the radiator. As soon as the operating temperature of the thermostat has been reached the thermostat opens and allows the (now hot) coolant to flow through the radiator which lowers the temperature to below the operating temperature of the thermostat so it closes again thus allowing the coolant to warm up. This goes on all the time the engine is running and maintains a constant water temperature.
If you have no thermostat fitted then there is every chance that the engine will never get up to the correct operating temperature as it is constantly being cooled (over-cooled in fact) but if it is then you have a fault which needs to be sorted rather than being covered up.
Is the engine actually hot or does the gauge just say it is?
Is the rad the correct size and if it is, is it blocked or the fins damaged?
Is the coolant circulating & pressurising correctly?
As already stated, it might (hopefully) just be that it failed for some reason and the previous owner couldn't be bothered to get a new one (worrying as what else might they have done in the name of "maintenance"?).
Keep an eye on it and perhaps check the gauge accuracy.
A thermostat allows the engine to warm up by keeping the coolant in a closed system circulating it around just the jacket & heater, at this stage it is not flowing through the radiator. As soon as the operating temperature of the thermostat has been reached the thermostat opens and allows the (now hot) coolant to flow through the radiator which lowers the temperature to below the operating temperature of the thermostat so it closes again thus allowing the coolant to warm up. This goes on all the time the engine is running and maintains a constant water temperature.
If you have no thermostat fitted then there is every chance that the engine will never get up to the correct operating temperature as it is constantly being cooled (over-cooled in fact) but if it is then you have a fault which needs to be sorted rather than being covered up.
Is the engine actually hot or does the gauge just say it is?
Is the rad the correct size and if it is, is it blocked or the fins damaged?
Is the coolant circulating & pressurising correctly?
As already stated, it might (hopefully) just be that it failed for some reason and the previous owner couldn't be bothered to get a new one (worrying as what else might they have done in the name of "maintenance"?).
Keep an eye on it and perhaps check the gauge accuracy.
DEFENDER90-DAZ
New Member
Needle should be 1/2 way on the gauge at normal running temp if the gauge and sender are good. Have a search on how to bleed the coolant - if you're not 100% sure how to do it properly.
Daz
Daz
West Slope Rover
Well-Known Member
What's your weather like today? Cool and moist, or warm and sunny?
Mind you I drive a 4.2 petrol, but my gauge stays just shy of half way all the time so if it's coldish outside you may have an issue if it's sitting at 3/4.
Like I said in my earlier post, is it actually getting hot or is it just a gauge reading and if so, how do you know the gauge is accurate?
With an engine transplant the sender & gauge may not be matched.
Diesel man
New Member
Is your heater hot? If so it should be circulating ok, you could feel the back of the head see if it's hot etc.
The gauge if you pull the temp sensor wire off and put to earth ignition on it should sweep over to hot and stay there without jumping about or dropping, this will give you some idea how well it works.
Water pump impellers can throw a blade not trying to worry you this would not circulate properly.
The gauge if you pull the temp sensor wire off and put to earth ignition on it should sweep over to hot and stay there without jumping about or dropping, this will give you some idea how well it works.
Water pump impellers can throw a blade not trying to worry you this would not circulate properly.
