Loosing coolant/ overheating

Discussion in 'Mechanical - Engine, Gearbox, Exhaust etc' started by CR41G, Feb 14, 2015.

  1. Ok so a long with everything else that is going wrong with the Megane it seems the car is overheating. So I checked the coolant. When I ipen the reservoir the coolant refills the reservoir after the pressure releases and then starts to drain away again and you can hear it down where the hear linkage is. When I start the car from cold you can hear water in passenger footwell which in assuming is the heater matrix. And also the heating in the car seems to be freezing and the temperature gauge shoots up and down. So not sure if this is related to my engine misfiring or things. (See other thread)

    any ideas?
  2. Thermostat
  3. I changed the thermostat about a week ago.
  4. Sounds like you've got a air lock in the cooling system, have you bled it up correctly?
  5. A coolant hose was leaking a few days ago and the mechanic changed it and also bled the system. So I guess so.
  6. It's certainly something I would be checking as that could easily cause your symptoms only takes 5 minutes to do
  7. What do I need to do this? Cheers
  8. I mean how
  9. Theres a bleed point on side of thermostat housing.

    Whilst cold makesure the coolant header level is good and remove the cap and then remove the bleed screw. Once you get a steady flow of coolant (no bubbles) re fit it.

    Then start the car and run it up and every now and then just crack the bleed screw a little to let any air vent. This is what i do and ive never had any problems bleeding the F4R or F4RT
  10. Tree is also a bleed nipple on a pipe at the back of the engine, easy to see and get to, I'm sure you can do it from there as well, like he says get it running then open make sure water comes out, no air in there then
  11. That'll be the matrix pipe, tbh I've never bothered with that on that 225'd 197 I last did as I've never had trouble but with him having probs you'd better do that too :wink:
  12. Sorry to revive this, i think i’ve got this exact problem. Fitted new thermostat a few weeks ago just as precautionary and not really driven it since due to lockdown.
    From garage to home, coolant needed topping up a bit which I did.

    So did a supermarket run today and and while taking shopping out was just letting the car run and cool down. Coolant temp had shot up to max with an engine failure hazard on dash. Plugged this tech thingy into OBD and temps got to about 115 on coolant

    checked coolant reservoir again and probs needs topping up a bit to get back to max line. I’m thinking air lock as suggested in this thread?

    will give it till tomorrow morning - can someone point out where this bleed nipple is? Do i need to take anything apart in engine bay to access/get to it?
  13. There is a bleed valve on the hose that is at the back of the engine bay, it's for the cabin heater, don't do it when hot or it's still got the filler cap on, top up the tank if its only just on the full mark hot, there is also one on the radiator on a mk3, if it's a mk2 there is one on the top hose, bit difficult to get to though.
  14. This got fixed in the end - overheating was due to fan not kicking in and this was a result of the wiring split for the fan from fuse to relay

    got rewired and fan is working as it should now

    Seems a one off but updating thread in case anyone has similar problems in the future

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