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
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.
that make them the best bet?
An engine has 3 main
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
It is right next to the hottest part of the
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
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.
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
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.
do you recommend to fit to my vehicle?
If you want a reliable level
of engine protection fit an Engine Saver®
Low Coolant Alarm
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
On a modern engine running high temperatures
this ten degree dead band can be an engine killer.