Coolant level
I am confused as to where the maximum level is on the coolant expansion tank in my Rover 75. It has 99,000 miles and needs a top-up quite frequently, which I hope is not a sign of head gasket failure sometime in the future. The car was bought with no service history, but the temperature gauge stays at nine o’clock on all journeys carried out so far.
According to the owner’s manual, the level markings can be viewed through the filler neck, whereas on mine the marks are on the side, similar to the illustration given in the Haynes manual for a V6 engine. With a tank which has become opaque and the marks on the wrong side, they no longer serve any useful purpose. Inside are fins which I assume assist in cooling. My local mechanic has told me that the fins should be covered in order to top-up correctly, but according to my measurements, this would be way above the maximum mark. Using a home-made dipstick, the maximum level is about halfway below the fins, which to my mind does not make sense. WHA Burgess
The most important point to remember is that the header tank is an expansion tank. It ensures that the cooling system level is maintained at an optimum height, while allowing sufficient room in the system for the coolant to expand when hot. If the level is too high, it will discharge the excess coolant when hot; if the level is too low, air could enter the system and cause problems.
With the coolant tank in your Rover, the fluid should be kept around the level of the visible seam in the tank – this will maintain a sufficient amount of coolant while allowing for expansion space. The actual level markers are inside the header tank and are not the visible fins at the sides, but two tags which are revealed when the level drops. The tags are marked ‘MIN’ and ‘MAX’ and the optimum level is just below the ‘MAX’ mark.