low water alarm intermittently going off

[Stropp]

as the title says, i have a low water alarm and it goes off now and again and i cant work out whats wrong, if i rev it it goes away, have bled it numerous times and even resorted to topping up the overflow bottle when it was above the full mark. I even loosened the sensor so coolant was coming out when it was warm to try to see if there was an air bubble but still no result, it doesnt do it all the time just sometimes and it has me stumped.

[MudRunnerTD]

Bugger! Silly question from me time! Is that after market or one of the dash lights I have never taken notice of? Is there an audible alarm also?

Have you bled the cooling system? Cap off, funnel, heater on, fast idle, go have lunch.?

[threedogs]

Parking nose up with inverted Coke bottle cut in half
placed in the radiator will raise your fill point and hopefully purge any air out of system

[Stropp]

Bugger! Silly question from me time! Is that after market or one of the dash lights I have never taken notice of? Is there an audible alarm also?

Have you bled the cooling system? Cap off, funnel, heater on, fast idle, go have lunch.?

yes its one with the light and alarm, when i swapped it over i got the car warm so the coolant had slight pressure and when i removed the plug to insert the probe the coolant started to come out so i didnt think any air got in there but as i said i have undone the probe a couple of times so its loose and started the car to see if air comes out but all i get is coolant so unless it has an intermittent fault its got me buggered.

[janderson]

Mine dose it sometimes to. One prob I found was a cracked cap (yellow) on the overflow bottle. $12 from Nissan. Hasn't done it now for a while, but found that if you take any of the caps of that release the pressure it'll will go of ever now and again for a while.

[Cuppa]

I'm still not sure if it's factory or aftermarket. I have an aftermarket one with alarm & light that I fitted in my DX, the sensor screws into the bleed screw hole. Where is yours mounted?

[my third 256]

there is another sensor on the right hand side down low on the radiator this can cause this problem also
(the main battery side)
img001.jpg

[Stropp]

I'm still not sure if it's factory or aftermarket. I have an aftermarket one with alarm & light that I fitted in my DX, the sensor screws into the bleed screw hole. Where is yours mounted?

Yep that's the same as mine

[Cuppa]

Yep that's the same as mine

Hmmm, that would seem to rule out the mounting position then. I haven't experienced the issue you describe.
Clutching at straws .... Is it possible your water pump needs looking at? It's possibly a long shot, but I wonder if there has been any 'corrosion' of the water pump causing cavitation .... Potentially an early warning sign of future problems. Have you used water rather than coolant? How long does the warning last for?

I'm sure you've checked electrical connections. Alarm goes off when circuit is broken, so an intermittently poor connection would give you an intermittent alarm.

The sensor is screwed fully in isn't it?

Can't think of anything else.

Cuppa

[Stropp]

Hmmm, that would seem to rule out the mounting position then. I haven't experienced the issue you describe.
Clutching at straws .... Is it possible your water pump needs looking at? It's possibly a long shot, but I wonder if there has been any 'corrosion' of the water pump causing cavitation .... Potentially an early warning sign of future problems. Have you used water rather than coolant? How long does the warning last for?

I'm sure you've checked electrical connections. Alarm goes off when circuit is broken, so an intermittently poor connection would give you an intermittent alarm.

The sensor is screwed fully in isn't it?

Can't think of anything else.

Cuppa

Yep can't think of anything else, may have to go through everything again!