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SD1too · 16th October 2021, 07:55

Hello Julian,

My first thought is an air lock. Was the MG Rover refilling/bleeding procedure followed exactly the last time work was carried out on the cooling system? If you are in any doubt drain it completely, including the cylinder block plug, and start from scratch. Don't take any short cuts and note that the bleeding screw is only removed during the initial filling. It must be refitted before starting the engine.
In the summer I visited a member's KV6 with exactly your symptoms and this was all that was required. No parts were purchased.

Idling the engine for an hour is a waste of time. The car must be driven to put the engine under load so that it reaches proper running temperature. According to the IPK diagnostics, is it staying within the range 92 to 100˚ (when the low speed fan should start and lower it)?

Is the expansion tank filled no higher than the internal 'MAX' marker? A common mistake is that owners fill to the top of the fins.

Simon

16th October 2021, 07:55	#3
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: 20,386 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Hello Julian, My first thought is an air lock. Was the MG Rover refilling/bleeding procedure followed exactly the last time work was carried out on the cooling system? If you are in any doubt drain it completely, including the cylinder block plug, and start from scratch. Don't take any short cuts and note that the bleeding screw is only removed during the initial filling. It must be refitted before starting the engine. In the summer I visited a member's KV6 with exactly your symptoms and this was all that was required. No parts were purchased. Idling the engine for an hour is a waste of time. The car must be driven to put the engine under load so that it reaches proper running temperature. According to the IPK diagnostics, is it staying within the range 92 to 100˚ (when the low speed fan should start and lower it)? Is the expansion tank filled no higher than the internal 'MAX' marker? A common mistake is that owners fill to the top of the fins. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.