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Micra boiling coolant out radiator

  • 27-08-2013 1:41am
    #1
    Totofan99
    Registered Users, Registered Users 2 Posts: 1,597 ✭✭✭


    My trusty little '97 Micra has developed a problem.

    It seems to be fine at lowish speeds but when I go over 100-110kph, it starts to overheat and blows water out the radiator cap.

    I thought it might be the thermostat so I changed that myself. Hasn't solved the problem.

    Just wondering if anyone here has any ideas? I'm thinking head gasket but I'm hoping it's not. :(


Comments

  • #2
    Andrewf20
    Registered Users, Registered Users 2 Posts: 3,251 ✭✭✭Andrewf20


    Any signs of white gunk in your oil (check oil filler cap) or oil droplets in your rads expansion tank?

    Also, what are the water levels like in your expansion tank when the engine is cold?


  • #3
    biko
    Registered Users, Registered Users 2 Posts: 81,220 ✭✭✭✭biko


    If you turn the heat on max it shouldn't boil, can you check this?
    Park car with engine running, take cap off and notice the difference between blasting heat inside and not.


  • #4
    Totofan99
    Registered Users, Registered Users 2 Posts: 1,597 ✭✭✭Totofan99


    Okay, so today I noticed that only half of my radiator is hot when the engine has been on for a while. The radiator must be blocked. I'm changing the radiator because I have one handy from a scrapped car. I'll see if that makes any difference.

    Can't see any white stuff through the oil. When I was driving it yesterday and it overheated I noticed that the water level in the expansion tank had gone up, and it didn't go back down when it cooled.

    I haven't tried running it with the heat on/off. The problem is that it doesn't overheat with the engine just running. It only does it when travelling at speed.

    Thanks for the suggestions anyway. We'll see if the radiator makes any difference.


  • #5
    Andrewf20
    Registered Users, Registered Users 2 Posts: 3,251 ✭✭✭Andrewf20


    Usually the hot water returns from the engine at the bottom of the rad so it should get cooler towards the top due to the fan blowing air across it. This is normal enough.

    If the temperature sensor is reading as overheating it suggest the flow of water passed it may not fast enough due to a restriction somewhere. The fact that your expansion tank isnt returning to normal levels seems strange. Maybe check the drain pipe from the expansion tank for lime scale build up / clogging and look into any ports where the hoses connect. Maybe in the past there was too much tap water added and not enough coolant, causing scale to clog the water channels.

    You say it only happens at speed, but if you turn on the engine and remove the expansion tank cap do you see a steady flow of water into the expansion tank. It should increase with revs as the water pump spins faster. You may have to wait a few minutes until the thermostat starts to open as the engine heats up.

    Strange that the overheating only happens while driving at speed. It should also happen in the driveway if reving the engine as the cooling system is under more stress then (as theres no 60mph rush of cool air past the rad).


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