2008 Subaru forester. I have to add coolant to reservoir every 50 miles or so. I get very little heat from inside the cars vents. I don't have any oil loss or any water in the oil. I have not been able to find a leak anywhere but I smell antifreeze from under the hood when I stop. What can cause this?

  • 2
    Some plastic coolant reservoirs can split and only leak when hot...
    – Solar Mike
    Jan 15, 2019 at 19:46
  • Or any other flexible part of the cooling system ... Jan 15, 2019 at 19:47
  • It may be going out the exhaust. Either a head gasket leak or cracked cylinder head.
    – Moab
    Jan 15, 2019 at 19:58
  • A small drip on a hot engine can evaporate (and smell) and not create a puddle. A mechanic can pressurize the system to find leaks like that.
    – mike65535
    Jan 15, 2019 at 20:28
  • Or even a bad seal with the radiator cap. These are especially tricky, because the pressure test comes back fine ... since the pressure tester replaces the radiator cap. I had a Bronco that I chased this problem forever. New cap didn't help, it seems the sealing surface for the rubber on the cap was warped and distorted slightly in the radiator neck. Sealed fine with the tester, but leaked on old and new radiator caps.
    – SteveRacer
    Jan 16, 2019 at 3:02

1 Answer 1


You are having poor heating because of the low coolant, without enough coolant in the system you won't get enough circulating through the heater core to provide sufficient heat. You will need to fix the coolant leak to solve your heating problem.

There are four places engine coolant can go

  • The ground (includes the floorboard of the vehicle). This is a crack in the system somewhere that results in the fluid escaping the system to the outside. This seems most likely since you smell coolant from under the hood.
  • Out the tail pipe. This is a failure of the head-gasket allowing coolant to pass into the combustion chamber.
  • Into the transmission. This is a leak in the transmission cooler that sits inside the tank of the radiator.
  • Into the engine oil, this is a failure of the head-gasket allowing coolant to pass into an oil passage between the head and the block.

Check the oil and transmission fluid to look for milky residue.

Pressure test the cooling system and look for leaks on the ground or on the floorboard under the passenger side of the dash.

Finally use a headgasket tester to see if it's going out the tailpipe. See my answer here for more info about that.

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