Thread: Low coolant alarm coming on everynow and then?

The coolant leak at the pump could also be allowing air in to the cooling system. It may only take 10-15ml of air to enter the system each time as the engine cools down to cause the level sensor to activate. When started cold the sensor will sound until the thermostat opens and coolant flow is enough to force the air at the sensor to flow down the radiator hose to the radiator and eventually into the coolant reservour. When the engine is still cold and revs up the air pocket may move down the radiator hose away from the sensor towards the radiator and the alarm will go off, as the engine comes back to idle the air pocket will flow back up to the sensor at the highest point in the hose and the alarm will sound.

Fix the coolant leak and you will solve your problem - it worked for me after putting up with it for three or four months. The leak I had was not really evident until I checked the tell tale hole from the water pump (TD5). I never topped up the coolant but there was a stain around the tell tale hole - air was sucking in but very little coolant was leaking out. Sometimes a vacuum test will show up problems a pressure test won't show - air bubbles in your reservour. Bottom line is air is getting in to your cooling system and making its way to one of the highest points which is at the level sensor.



Rick

Are you getting/maintaining pressure at your filling point/expansion tank?
I know you say you have had a pressure test some time ago, but just check after you shut down the engine and release the cap just slightly
(with caution) check the seals on the filler cap (O rings).
Sounds like an air bubble passing over the sensor, possibly caused by the thermostat acting or maybe the sensor is just on the way out. Check the wiring to from the sensor and your light/alarm setup.
Hope some of this helps.

I had that in mine when I changed radiator hoses and the pick up was not perfectly positioned.
I pulled it out and ordered a replacement one to go into radiator where the brass plug usually sits.
Its perfect now and only a slight chime on start up.

Mine does it from time to time - usually goes away one the engine gets warm - usually caused by a small air pocket caused by the vacuum in the system no sucking all the coolant back into radiator when it cools down. My sensor is high in the top hose and at the top of the hose - exactly where the air bubble forms.

I am going to rotate the sensor so it sits at the bottom of the hose (still up near the radiator) and fill the radiator with the car pointing up hill so the air bubble forms at the filler in the radiator.

Seems to work OK.

Garry

Thanks guys

The system has pressure as when the wife got home today I slowly removed the cap and there was a wosh.

Also today I noticed the radiator has a leak at the top above the brass bung and its weeping very slowly, I cannot pin point exactly where the leak/weep is as its in a ***** of a spot.

As for the tap tap sound its more of a rattle like something is in the pump, anyway I ran out of light today so I might take the belt off tomorrow and check the pully for any movement.

Could it be that you are not pumping coolant around your engine?
Or only getting poor circulation?
The noise you refer too could be the impeller not doing what it should.
If you were getting hot spots around your cylinder head and bores it could flash the coolant off to steam/bubbles and this is triggering your alarm.

I think you need to isolate the noise to either the thermostat or the water pump.

Water pump is about $100

Originally Posted by RR P38

Could it be that you are not pumping coolant around your engine?
Or only getting poor circulation?
The noise you refer too could be the impeller not doing what it should.
If you were getting hot spots around your cylinder head and bores it could flash the coolant off to steam/bubbles and this is triggering your alarm.

I think you need to isolate the noise to either the thermostat or the water pump.

Water pump is about $100

The pump was my first thought too, but now that you mention the hot spots around the head Iam little worried as she's done 380k and to my knowledge the head has never been off.I surrpose the only way to find that out is to take the head off

The only reason i mentioned the hot spots is (IF) you are not pumping coolant around your engine it will get hot enough to boil around the hot spots. Take a look in a kettle before it all boils you get those bubbles at the bottom this might be happening around the head and block.
Is your temp gauge normal?
If you think you have a noise coming from the pump i would pull that off before i did the head$$$$$$$$

Im no expert on this im just thinking out loud.

On monday i did replace my water pump and hoses on my p38.