My MRS3 Trophy 275 reaches a water temp. of only 70-73°C (158-163°F) when cruising with part throttle to the job in the morning. With such low load, she could reach easily about 90-93°C (194-200°F) to save fuel and heats a bit more when cold outside. In summer, when I raced on the track and stopped in the paddocks, she got about 108°C (226°F), I cooled her down by idling some minutes. On the german Autobahn, she gets even in Summer when hard driving max. 85°C (185°F). She has no trouble with dealing high loads, but as mentioned, I think with low temps. outside she should get warmer. Probably you guys can tell me your experiences, maybe by water thermostat isn´t ok entirely.
I would change the thermostat as a first call, my temp stays the same what ever i do, track day, cruising, or driving around town, it was slow to get to temp and always sat low, once i changed it it never moves.
its smack on the 4th mark, once there never moves, on the rs monitor hasn't gone over 99 degrees as the fan cuts in just before that.
Today I spoke to my dealer, he confirmed that 70+ °C is usual, the cars (only RS) are running that cold. Basically it helps to avoid knocking, I would agree with high load driving with big charge pressures, but in part or low throttle it makes no sense. Due to the simple thermostat (mechanical with expansion stuff inside) maybe it´s not possible to control the water temperature as quick as possible once pushing the pedal hard suddenly. An electronic control unit as nowadays usual in modern cars would be able to match the temp to the engine loads and would high part throttle temps make work together with low temps with wide open throttle. A bit more consumption, worse heating.....it is like it is....
The opening temperature of the thermostat is 89°C, you are right so far. But that is not to say that the coolant temp stays with 89°. First the temp raises to about 90° or so, and along with the increasing flow of the coolant the temp drops down a bit after the thermostat startet to open. On older cars, you can watch this on the temp gauge. On modern cars, maybe as well on the Megane, the gauge is mostly a bit cheating to keep the driver relaxed once the temp varies. Some engines are running with 105° and elder guys are not used to this cause their old school engines were running more in the 85° range. With a 89° Opening temp. it´s possible that the engine will run with 82-85°. But we agree that 70° C is really a bit strange. In spring I have to replace my timing belt, then I will replace the Thermostat as well to check out the influence. I assume that the temp. gauge in the R-Link (big display in the middle of the dashboard) shows the reality and is not cheating. In contrast, the oil temp in the display doesn´t measure the real oil temp, it just calculates it by some algorythms ( maybe from water temp / engine load / outside temp..etc). The coolant temp should be reality, at least I hope...
It was just above the 3rd mark on the gauge, car didn't feel quite right, must have been running very slightly rich.
