low water alarm intermittently going off

[bear3103]

Have you tried pulling the sensor out and cleaning it or maybe the sensor is faulty.???.

[Cuppa]

Have you tried pulling the sensor out and cleaning it or maybe the sensor is faulty.???.

The ’sensor’ is only a machine screw screwed into a plastic sleeve.

Whilst in contact with the coolant it maintains an electrical circuit. If the electrical circuit is broken the alarm goes off. So whilst a dirty ’sensor’ could cause the problem, it would be very unlikely for it to be intermittent. It would also seem not possible for it to be faulty. I would think that a faulty connection/internal break in a wire might be the most likely cause, but the fact that revving the motor stops the alarm sounding points more to the ’sensor’ losing contact with the coolant.

[Stropp]

Yes that's what I thought cuppa but I have loosened that sensor a few times and let the coolant fluid out but never had air come out, also after doing that the alarm does not go off for a few weeks.

[NP99]

What about the earthing system? Is it tight and clean? Just guessing now....

[Stropp]

Yeh checked it and it looks good

[nissannewby]

I'm with cuppa in thinking it could be the water pump. On the machinery I work on I have seen a similar thing where the coolant flow is low give it a rev and all good. This is really kinda grasping at straws as you should see other symptoms if a water pump is on its way.

[threedogs]

On the water pump theory have you grabbed
the water pump to see if any play in the shaft,
any signs of coolant under water pump shaft, or further down if dripping.

[kevin07]

try descaling the probe this causes alarms going off in buses they need to be cleaned regular and a specific coolant to stop this happening

[Stropp]

ok will pull the sensor and check it and look for the other bits with the water pump but ihave never seen any leaks.

[Cuppa]

I wasn’t thinking in terms of leaks. Reason I asked if you had run water rather than coolant was thinking about the possiblity that the impeller (or whatever it has) of the water pump may have become pitted or rough, potentially causing diferent swirl patterns/cavitation ................ but it’s a pretty long shot, & not really the basis for dismantling the pump.

Another thought, & I haven’t looked at any diagrams or the real thing, so it’s only a shot in the dark ....... the sensor screws into the thermostat housing. Is it possible that Stropp might have a ‘sticky thermostat’ causing the problem? .... Anyone? Stropp does the alarm go off after a good run, or only whilst the motor is still warming up?

You could also try putting a longer sensor in to see if this makes the problem go away. If it stops the alarm going off you’ll know it’s not an electrical connection issue.

Cuppa