Changing "Coolant Level" sensor in Coolant Tank
(base vehicle '02 TD6, may be different on other / later models)

Over time, the sensor (Part number PCJ000020) can stop working, or just become a bit over sensitive, and alert to low level of coolant even when coolant level is fine. You need to change the sensor.

It is located at the bottom of the coolant tank, found at the front on the left hand side of the engine bay, where you put coolant in (left is always from the rear of the car)

Typically (for an FFRR you can't easily see what you are doing with the coolant tank in place, so I have one out on the bench!

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My new sensor has a black plastic sleeve on the long narrow but that goes in the tank, is this removed before fitting? 2012 4.4TDV8 VSE
2004 TD6 132k miles- SOLD
1995 Land Rover Defender 110 Tithonus Ex Military
1995 Land Rover Discovery 3.9i V8 manual

Well done Tim

Nice and easy too.....come on Sir Stan, wiki it quick as we all know someone bound to ask in 6 months how to change it !  If it dont work.......burn it!

If the IId tool cant fix it.......burn the FF.

If the FF cant be fixed......buy a Land Cruiser!

If the LC cant be fixed..............................................BUY a horse !!

yee of little faith...already in the wiki.. ... - .- -.




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I would add that it is possible to do similar on the TDV8.

I had my tank out recently with minimal coolant loss. the only hoses running to the tank are the main feed hose at the bottom of the tank and the small top breather/bleed hose.

I used a couple of brake hose squeeze off clamps to stop all the coolant leaking off while the tank was out, but other than that it was straight forwards. A top tip when re fitting the 10mm bolts holding the tank in is to wedge them into the socket you are using with a bit of tissue paper that way you don't drop the bolts into the engine bay!

didn't take the level sender out but from what i remember it was in a similar position and should be easily removable in a similar way.  There is nothing that can't be fixed with a hammer😜😜
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I changed my sensor, when I took it out no fluid came from the bottle yet I could see coolant in it, it was full to the correct level. When I drive the car over 60 mph I get the bong of the coolant level again. It seems bizarre, anyone have any thoughts before I remove the expansion tank. 2012 4.4TDV8 VSE
2004 TD6 132k miles- SOLD
1995 Land Rover Defender 110 Tithonus Ex Military
1995 Land Rover Discovery 3.9i V8 manual

Methinks the "sight glass" inside the tank becomes occluded, hence the sensor cannot detect the level/concentration (all done with light?) Only resolution so far is a new tank  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
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Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

What's strange is it did not leak any coolant when I took the sensor out the bottom! I think I will try a new tank. It's bloody annoying. My RR maybe used a little less, got myself a defender for summer.

Joe, i hate to state the obvious after the event but from memory (and it could be for the TDV8) a brand new coolant tank with sensor fitted is only a couple of quid more than the cost of just the sensor!

Makes far more sense to change the whole thing due to the issues above... And obviously the plastics etc will degrade over time so makes sense to change it all for not much more!

This 'sensor' is nothing more than 2 thin steel strips that normally are not touching each other to complete a (low power) electric circuit. They are encased in a glass tube for support and protection. When a magnet is close enough both pieces of steel become magnetised in the same phase and they attract each other to close the circuit [edited to invert wrong logic in original post ]. Being magnetically 'soft' they loose their magnetism as soon as the external magnetic field is removed and spring back apart.

Inside the expansion tank there is a donut shaped float which has a donut shaped magnet attached. This is fitted to a hollow tube coming up from the bottom of the tank which houses the 'sensor'. When the float is high the magnet doesn't effect the 'sensor', but when it drops lower it does.

The magnetic sensor is also known as a reed switch and can be purchased for about $1. 60 seconds with a soldering iron can swap a new one in place of a broken one. If that is the fault , use a multimeter and a magnet to check (a fridge magnet will be strong enough at close range). Of course it is just as likely that the magnet has fallen to the bottom of the tank . Does anyone know of a glue that works under antifreeze?

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ref: posts above from me and Cam Tech Craig

If the problem is with the "float" or internals then no amount of fixing the sensor will make any difference.

However it really helps to understand how it all works


Any glue should do as the sensor and sensor housing is not "in" the coolant  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

bgennette wrote:

This 'sensor' is nothing more than 2 thin steel strips that normally are touching each other to complete a (low power) electric circuit. They are encased in a glass tube for support and protection. When a magnet is close enough both pieces of steel become magnetised in the same phase and they repel from each other to open the circuit . Being magnetically 'soft' they loose their magnetism as soon as the external magnetic field is removed and spring back together.

Inside the expansion tank there is a donut shaped float which has a donut shaped magnet attached. This is fitted to a hollow tube coming up from the bottom of the tank which houses the 'sensor'. When the float is high the magnet doesn't effect the 'sensor', but when it drops lower it does.

The magnetic sensor is also known as a reed switch and can be purchased for about $1. 60 seconds with a soldering iron can swap a new one in place of a broken one. If that is the fault , use a multimeter and a magnet to check (a fridge magnet will be strong enough at close range). Of course it is just as likely that the magnet has fallen to the bottom of the tank . Does anyone know of a glue that works under antifreeze?

Click image to enlarge

I've added a label to the original poster's picture. Just snip the wires to remove a faulty reed switch and solder a replacement in.

Joe90,
to quote you "If the problem is with the "float" or internals then no amount of fixing the sensor will make any difference. Crying or Very sad " Well, I am glad to inform you that you were "wrong"

first thank you for the post on how to remove the switch and wayneg explaining how the switch works.

after that it was clear that the switch is a sturdy little device and short of contact being corroded or broken, switch was probably OK. so that left me with the "floating dougnath". out with expansion tank and as can be sean in the picture my was dirty and oily.

 .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Thanks for all the contributions on here to this thread,Ill get onto this at the w/e, having to use RR DAILY JUST NOW DUE TO MY CAR BREAKING A ROAD SPRING ...MORE JOBS !