Strange K-series cooling system behaviour
Discussion
Just had the head gasket replaced on a standard 111S (K-Series VVC). The water pump and thermostat were also changed. The cooling system has been bled.
Prior to this work, the engine would warm up quickly and then hold a rock solid 88 degs whilst in motion. At idle/stationery the temp would slowly rise and stop at 96 degs in winter and trigger the fans in summer which would bring the temp down to 96.
Since the work the temp fluctuates between 88 and 92 when cruising at constant speed and throttle - fair enough, maybe the new thermostat is slightly lazy. What's more worrying though is that once the engine speed rises above 4000, the temperature starts to drop. The longer the engine spends above 4000 the further the temp drops. After 15-20 seconds the temperature has reached 71 degs and the display disappears. I can only assume the temp continues to drop. This happens regardless of throttle position or road speed. It happens on the lightest throttle opening necessary to maintain >4000rpm in second gear, and also at high throttle openings in a high gear.
Has anyone any theories on what is happening and where the problem lies? I'm thinking thermostat, but can't get my head round what would cause the thermostat to display this behaviour.
Grateful for any ideas.
Prior to this work, the engine would warm up quickly and then hold a rock solid 88 degs whilst in motion. At idle/stationery the temp would slowly rise and stop at 96 degs in winter and trigger the fans in summer which would bring the temp down to 96.
Since the work the temp fluctuates between 88 and 92 when cruising at constant speed and throttle - fair enough, maybe the new thermostat is slightly lazy. What's more worrying though is that once the engine speed rises above 4000, the temperature starts to drop. The longer the engine spends above 4000 the further the temp drops. After 15-20 seconds the temperature has reached 71 degs and the display disappears. I can only assume the temp continues to drop. This happens regardless of throttle position or road speed. It happens on the lightest throttle opening necessary to maintain >4000rpm in second gear, and also at high throttle openings in a high gear.
Has anyone any theories on what is happening and where the problem lies? I'm thinking thermostat, but can't get my head round what would cause the thermostat to display this behaviour.
Grateful for any ideas.
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