Things We Should Know About Low Coolant Alarms
And Block Temperature Sensors

I am often asked which is the best of the two types of alarm and why.
My  answer is simple and has always been the same:
If you are only going to fit one type, fit a Low Coolant Alarm.

Why do you say that?
My answer is based on the fact that over 70% of engine failures are due to loosing coolant
A Low Coolant Alarm will usually detect this straight away.
By the time an external Temperature Sensor reacts to this the engine can be damaged.
During our extensive testing of Low Coolant Alarms we use a block sensor as
an additional temperature monitor.
In all cases the low Coolant Alarm has been the first to react to coolant loss.

But I have heard that block sensors react to small changes in running temperature and are very sensitive.
So won't that make them the best bet?
An engine has 3 main temperature zones.
1/. The cylinder walls, piston top and inner cylinder head.
2/. The coolant in the jacket surrounding the above.
3/. The shell temperature of the outside metal of the block and head surrounding the coolant.
The best place to measure running temperature is the coolant
That is where manufacturers measure it.
It is right next to the hottest part of the engine.
Unfortunately if the coolant is lost, the sensor can only measure the shell temperature which is less than coolant running temperature and quickly drops when coolant is lost, until heat soak finally gets to the sensor by which time damage can be done.
People who have block sensors regularly say how sensitive they are.
Yes they are, however how many people have tested them in an engine with coolant loss.
I have customers who have experienced this and they tell me the temperature on the block sensor drops just like the factory gauge does and damage is done.
That is not much use. is it?
Also if an engine looses coolant overnight or when parked and is then started & driven away, by the time a block sensor reacts engine damage will probably have occurred.
An Engine Saver® low Coolant Alarm will detect this on start up.

So what use are block sensors?
There are a couple of scenarios where they are very good.
1/. When a thermostat malfunctions and stays closed or partially closed
The temperature will rise rapidly and most factory gauges won't move from the normal position until the engine is very hot.
The block sensor will pick this up straight away.
2/. When an engine suddenly runs hot due to heavy load or a management system malfunction
or an obstruction to the radiator such as mud, spear grass or even a plastic bag.

So what do you recommend to fit to my vehicle?
If you want a reliable level of engine protection fit an Engine Saver® Low Coolant Alarm
as this will warn you almost immediately if any coolant is lost.
Whatever you do, fit something and don't rely on the standard factory gauges to warn you.
Most factory gauges have a dead band built into them for about 10 degrees above and below normal running temperature to stop people worrying about minor variations in temperature.
On a modern engine running high temperatures this ten degree dead band can be an engine killer.

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