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What happens when you overfill the radiator reservoir tank?


  1. Himpalapotamus says:

    If you overfill the reserve tank, then as the water in your radiator expands it will overflow out the reserve tank’s overflow tube (not a problem – perfectly fine) then when you stop the engine and the radiator cools down, the water will contract and it will begin sucking from the reservoir tank and the next day you will notice that your reservoir tank is no longer full.

    The full/max line of your reservoir tank is the expected level when the engine is COLD, and the empty space above it is meant for the expansion. If the level is below the full/max line you can add some water/antifreeze mix into the reservoir up to the max line. If you go over the max line it’s not a big deal but you will be spilling the excess coolant and just be wasting it.

    An overfilled reservoir will not stay overfilled after the first expansion cycle and cannot be the cause of your engine running funny.

  2. idonlikeveg says:

    basically if you overfill the coolant, the pressure and heat will simply just push excess fluid out the overfill.

    as for the overheating try bleeding air out of the cooling system.

  3. bungee says:

    don’t worry about it. it will correct itself<<

  4. pliw says:

    Overfilling the reservoir tank will not affect your engine. It will just overflow. Himpalapotamus above explained it correctly.
    The cause of engine running differently may be due to the previous overheating of the engine. Use radiator coolant to cool the engine.not water. Coolant is costly and you have to experiment the mixture if you do not want it pure.Begin, say a 50/50 mixture. then adjust it to say 60/40( 60%coolant/40% water). and so on. If the engine is not overheating anymore, change engine oil. It might be burned.

  5. dudeman says:

    it makes a mess

  6. Binxtaroo says:

    overfilling the reservoir wiil make it possibly overflow when it heats up, but won’t change the way the car runs. if you find the reason for it overheating it will probably give you a clue as to why its running differently.

  7. baldie says:

    once the radiator cap releases, the water won,t have anyplace to go but out on the ground. better get that water out and get some anti-freeze in there. water will boil and rust your cooling system.

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