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SD1too · 11th October 2019, 09:15

Steve,

I'd say that your next step is to look at the two 'O' ring seals on the expansion tank cap. Do they look flat? Mine did, and when I renewed them I didn't have to top-up the coolant every few days just as you are having to do. I didn't get any evidence of loss either.

Whilst you're there, can you confirm that you're NOT filling the expansion tank higher than the 'MAX' tab which should be visible inside the tank and almost at the bottom of it?

After that, if no improvement, look in the 'V' at the clips on the straight plastic coolant pipe joining the water pump with the thermostat housing. Are they positioned fully outwards at both ends, i.e. touching the water pump and thermostat housings? If not, correct that.

The other possibility is that you have an air lock dating back to the last time the cooling system was drained. Have you activated the instrument pack diagnostics whilst driving to monitor the actual coolant temperature? It should be stable in the low nineties, slowly rising to 100 degrees when you're stationary in traffic (air con. must be switched off). The fan should then reduce the temperature to 96 degrees. Can you report back on that please Steve.

Lastly, forget about those gas testers. They always seem to give a positive answer when there are no other symptoms of gasket failure present (as is the case with your car as I have already pointed out).

Simon

11th October 2019, 09:15	#29
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,382 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Steve, I'd say that your next step is to look at the two 'O' ring seals on the expansion tank cap. Do they look flat? Mine did, and when I renewed them I didn't have to top-up the coolant every few days just as you are having to do. I didn't get any evidence of loss either. Whilst you're there, can you confirm that you're NOT filling the expansion tank higher than the 'MAX' tab which should be visible inside the tank and almost at the bottom of it? After that, if no improvement, look in the 'V' at the clips on the straight plastic coolant pipe joining the water pump with the thermostat housing. Are they positioned fully outwards at both ends, i.e. touching the water pump and thermostat housings? If not, correct that. The other possibility is that you have an air lock dating back to the last time the cooling system was drained. Have you activated the instrument pack diagnostics whilst driving to monitor the actual coolant temperature? It should be stable in the low nineties, slowly rising to 100 degrees when you're stationary in traffic (air con. must be switched off). The fan should then reduce the temperature to 96 degrees. Can you report back on that please Steve. Lastly, forget about those gas testers. They always seem to give a positive answer when there are no other symptoms of gasket failure present (as is the case with your car as I have already pointed out). Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.