250 Coolant temperature

Discussion in 'Mechanical - Engine, Gearbox, Exhaust etc' started by S4BiT, Jul 26, 2016.

  1. Hi,

    There was a thread somewhere about it, but i didnt find it anymore. So i made a new one, asking whats the normal temperature for the coolant on hot days and where the needle on the dash should sit ideally? Mine seems to sit higher than it should, at least compared with my memories about my old car.


    If its too high, what should be the reason, more related with the coolant temp sensor or faulty thermostat?


    Sent from my SM-A300F using Tapatalk
  2. That's sitting higher than mine usually does, mine usually sits at the second mark from the zero position i.e. one mark lower than in your picture.
    Nigelo likes this.
  3. Is the fan kicking in? With the heat we've had here mines sounded like a truck it's been on so much but the needles stuck around that 2nd bar all the time.
  4. Actually i havent heard the fan kickin in on idle, it was ticking over yesterday quite some time and the temp gauge was like on the picture. Have to put some voltage directly to the fan to see if it works at all.

    Sent from my SM-A300F using Tapatalk
  5. As the coolant temperature in any vehicle is normally in the range of 80C - 120C, depending on the vehicle and various factors the difference in ambient we have here in the UK summer is rarely more than a little over 10 degrees so I doubt it would be responsible for much variation, ( the summer max to winter minimum would be more of an effect of course, but the thrmostat would just open a little later/or earlier to compensate ).

    I would look at the thermostat as a first check, then levels and as suggested Fan operation.

    The actual coolant temperature is available in degrees as one of the Live data from the ODBII port if you have access to that - It's often more precise than the gauge
  6. Same for me.
  7. -Jamie-

    -Jamie- RSM Moderator

    Mine vary between that one and the one before it, The gauges are always just a guide though. I don't pay too much attention to it and go by the actual coolant temp.
  8. I have to find some OBD access and find out what is it showing exactly, as the gauge needle is moving from the "right" place to the place showed on my picture as it wants. As the thermostat price and work for changing it is okay, i may do that anyway to be shure.
  9. I have a bluetooth ELM always in place (cover is on too), and just use something like Torque app on phone to check outputs, I also have an old 7" android tablet (and vent mount), so can have my own extra dials when I want to check things as I drive
  10. Mine is the same middle location as yours, rs monitor usually says between 82-87° C tought it was normal but everyone seems to be lower?
  11. Hi, my 250 RS has the same indication on hot days, I think 31 degrees outside in Italy is a hot day. When cruising 120 km/h on the autostrada's the needle went back to "normal" ... I shouldn't think too much about it.
  12. Seems about right to me!
  13. Same here.
  14. Hi, I know its old thread but I just got my 250. Coolant temperature gauge sits exactly like yours, one bar to the right, maybe 2mm before that bar. I just checked with OBD2 live data and coolant is about 90C, I read that it should be 80. After some hard accelerating it went to 95-97 and fan kicks in and it got back to 88-92. Is it ok or thermostat is bad ? Thanks.
  15. The RS250 thermostat is set to start opening at around 83C and is fully open, if I remember correctly around 90C.
    Most failures of the thermostat are related to staying open, so coolant temps are low - typically lower than 80C. This means ecu sets fueling to "cold start" - hence poor performance, misfires etc.

    In your case it seems a little higher than I experience.
    I've attached some track day logs of coolant temp with my faulty (always open) thermostat and after a new one was fitted.
    As you can see temps aren't that far from what your experiencing, albeit at a trackday.

    If all the obvious things (level, radiator fins, no air traps, etc) are ok, then maybe someone has previously replaced the thermostat with the wrong one.
    i.e. not an 83C opening one, but another Megane (non RS) one - which I believe you can get with a higher opening temp - I think Gates make one at 90+C.
    RS250 Track day with old faulty thermostat.png

    RS250 Track day with new thermostat.png

    View attachment 40961 View attachment 40962
    manugtt likes this.
  16. autronix

    autronix RSM Club Member

    I have same behaviour. at ouside temps around 27 - 30 degs , ECT is 95 to 100 degs. fan is always kiks in low speed when parking , etc. thermostat is oem new , new waterpump , new coolant, system has no air....
    I might have a thermostat malfunction that is not open fully ....
  17. thanks for helping. I asked last owner, he said that he is driving like that last 4 years. Dont know if I should check/change thermostat or just drive lika that..
  18. same as mine, im driving on gauge one bar to the right and when i stop car in traffic or somwherr fans kicks in on low speed. how long are you driving like that? did you ask for others opinion if its alright or not ?
  19. autronix

    autronix RSM Club Member

    I have the car just from 2 months and I drove like this just a few days. I always keep an eye on the ECT values from ECU. I have the ECT on the high side but engine was not overheated. I replaced the thermostat with oem unit from the genuine parts programm I work with. I might have used an 89 degs unit. I have ordered o new 83 degs spec and I will test....
  20. like i sad, previous owner drove car like that 4 years. he was also going to tracky days. he said that temperature gauge is always sitting like that once the car is properly warmed (10mins of driving).maybe owner before him changed thermostat and put 90c. please tell me after your thermostat change. do you have facebook? so i can add you.
  21. autronix

    autronix RSM Club Member

    I will update here no problem.

    (the temp gauge is not very helpful .... from 60 to 100+ will barely move it`s position)
  22. A 265/275 the needle should be vertical. a 250 is lower to the left by a couple of needle width's.

    My 265 one dropped to where a 250 one should be, but i noticed that the fuel consumption was worse, fitted an aftermarket thermostat and it went back to vertial and the fuel consumption was better.
  23. Same thing happened on my 275.
  24. autronix

    autronix RSM Club Member

    so , yes I was using an 89 degs thermostat , oem unit by Thomson , I don`t remember the oem number.
    I replaced with the oem 83 degs version by Calorstat. it comes with no gasket so here are some oem codes in the photos:

    IMG_20230914_122609984.jpg IMG_20230914_122622692.jpg IMG_20230916_214608929.jpg
  25. I did quite the opposite in my 250. The needle use to be a bit on the left of the vertical. When I´d change to a 89º Calorstat went totally vertical, and it always there, normal drive, hard drive, tracks...Like Ian said, the consumption went better, around 8,2 l/100km, 130km/h in the speed limiter.

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