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Marty
Marty, ASE Certified Technician
Category: Jaguar
Satisfied Customers: 55103
Experience:  Bosch Certified Master Technician with over 35 years experience in the automotive industry.
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I have replaced the expansion tank and sensor on my 1998

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I have replaced the expansion tank and sensor on my 1998 car. When I start everything is OK until I have driven about 2 miles and then the LOW COOLANT LEVEL warning light and message appear on the dashboard. I can drive home and the temperature gauge remains in the middle of the scale. After the engine has cooled down, I check the coolant level in the tank and it has not gone down. I use a 50% / 50% mixture of yellow antifreeze and water as recommended by Jaguar. I have also replaced the water pump, some of the coolant / heater pipes and had the system pressure tested for any leaks. None have been found. I am fed up with having to repeatedly keep an eye on the temperature gauge whilst driving. It has taken the fun out of driving an otherwise fine car. Any ideas would be gratefully appreciated.

Hi, my name is***** the coolant level maintaining at all times? Are you suspecting a false indication on the dash?

Customer: replied 6 months ago.
to both of your questions

Ok, was it a new or used expansion tank?

Customer: replied 6 months ago.
All new products were used

Ok, then either there is not enough coolant in the tank or the float in the tank is sticking or there is a fault with the wiring to the coolant level sensor. A simple test would be to disconnect the sensor and bridge the terminals with a jumper lead to keep the light off then drive the car and see if it remains off. If it does then I would say your new tank has a defective float. If the light remains on when the connector is bridged then I would look for a fault in the wiring between the sensor and the cluster. Most faults are found right at the connector.

Customer: replied 6 months ago.
The garage tested the float and it is not jammed. The coolant level is within 6mm of the underside of the neck

Then there must be a wiring fault. The lead to the cluster and to the chassis ground needs testing. It's possible that the cluster is bad but I have never replaced a cluster for this problem. I'd bypass the circuit and see what happens.

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Customer: replied 6 months ago.
I will ask the garage to try your recommendations

Very good. Let me know if you need anything.