• Yesterday I had to drive 80 miles, which is the longest I’ve driven in ages. So I thought it was worth checking the coolant level, something else I haven’t done in a while. It was fine, but I forgot to put the expansion cap back on. When we arrived at our destination we had to sit in a small queue of traffic to park. After a few minutes I could smell a hot smell and then noticed the coolant was dumping on the ground. I parked up straight away and topped the tank with water and wrapped a crisp packet over the filler neck with an elastic band.
    Today I made an 8 mile round trip and I’ve just checked and the expansion tank is empty again. No dash warning lights or anything. I’ve ordered a new cap which my in laws are going to bring with them when they meet us here on Monday. I don’t need to drive between then and now.
    Is it just a case that the crisp packet isn’t air tight so the coolant (mainly water tbh) has evaporated, or could it be something more serious?

  • i doubt that the crisp packet has made a pressure tight seal.

    There are also some risks with adding cold cooling water to a hot engine but it'll likely be fine when you get a proper cap on the tank.

    what sort of car is it?

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