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Coolant level going up and down?

Discussion in 'MK3 Toledo' started by Cosmo, Jul 31, 2014.

  1. Cosmo

    Cosmo Guest

    Hello All,

    The Coolant level/temp warning light and audible warning went off yesterday in my Mk3 Toledo. The engine was not over-heating but when I checked the level in the expansion tank, it was well below the "minimum mark". I topped it up with coolant to about 1mm below the "max" mark. When I first drove the car after doing this, I only got about 0.5 kms before I got the warning again. I pulled in, checked the level and it was back down well below the "min" mark again.

    I drove straight home parked it. A couple of hours later I checked the level again and it was still below the "min" mark but this time I noticed that when I removed the the expansion tank cap to top it up again. The level immediately rose back up to just below the "max" mark. Does anyone know if this is normal and if so, how are you supposed to gauge how much coolant to put in?
     
  2. vroomtshh

    vroomtshh Full Member

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    That's normal. You should measure the coolant at cold, when there's no pressure in the system
     
  3. Cosmo

    Cosmo Guest

    Thanks for the reply. Yeah I figured as much but my problem is that when the car is cold the level showing in the expansion tank is below minimum. That's until I open the cap on the expansion tank, which causes the level to rise up to the maximum. So when I go to top it up the level is already at maximum. Therefore, I have no way of accurately gauging how much to put in.
     
    #3 Cosmo, Jul 31, 2014
    Last edited by a moderator: Jul 31, 2014
  4. vroomtshh

    vroomtshh Full Member

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    So if you go out first thing in the morning and open your coolant cap, the level raises?
     
  5. Cosmo

    Cosmo Guest

    As far as I can tell, yes.
     
  6. vroomtshh

    vroomtshh Full Member

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    You have a problem then. The system should never be pressurised when cold
     
  7. w1ll0711

    w1ll0711 Active Member

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    I would try changing your filler cap on the radiator, it works as a pressure relief at around 15psi, when the pressure hits this it vents the excess coolent (expanded liquid from heat) into the expansion tank via the relief pipe so if its seized shut the pressure cannot escape the radiator and system becomes heavily pressurised, the only way for it to escape is to go back up the feed tube when you tank the expansion tank cap off. Thats why the coolent level increases when you take the overflow cap off. Its the first (and cheapest) thing to check really. Hope this helps!
     
    #7 w1ll0711, Aug 2, 2014
    Last edited: Aug 2, 2014

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