The air conditioning in my vehicle began running hot at intervals, then I noticed that the temperature gauge began bouncing between the hot and middle mark. I was advised to change the thermostat and sensor and also had the radiator completely serviced (nothing unusual was found with the radiator).

The problem now is that the water level in the radiator is still dropping as I have to top it up, and the water bottle level remains constant. What can the problem be?

  • Does the temperature stay in the normal range? It sounds like you could have air in the system, but I would expect that the level in the coolant tank would drop or the engine would run hot. Does the heat work?
    – Eric
    Nov 8, 2016 at 3:13

1 Answer 1


a list of things to check:

  • check your oil for white goop. This probably means you have a blown head gasket. This would also explain the fluctuations in temp, it could be sealing then opening back up again.
  • difficult to check but it could be a crack in the block leaking water into the cylinder or the head gasket blew in such a way the water only gets into the cylinder. in these cases you will not find white goop in the oil but you can test for exhaust gasses in the coolant. if you go to a smog shop they may "sniff" your coolant for you with their smog machine and if it registers any exhaust then that is probably your issue.
  • do you have coolant spilling on your driveway or seeping after you stop?
  • does coolant drip while the car is on? both of these mean you have a leak somewhere and could be why the water is getting low. it can also make the engine heat up if the water gets below the top of the heads.
  • is our radiator cap loosing pressure? This could let the coolant boil causing all sorts of strange temp readings. Check the cab for cracks in it seals.

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