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I have an issue with my 04 Forester 2.0XT MT, it kind of overheats, but not never reached red, it goes a bit over the second third of the gauge.

A little bit of background, last summer after a longer trip I saw that I had a bit of oil in my expansion tank, my guess was that it was the head gaskets even though I had a rebuild about 20k km before; but I drove the car with too little coolant because a hose started leaking.

I have replaced the head gaskets, installed ARPs, brand new coolant hoses, but the oil was still there, turned out my radiator broke on the inside and the oil in the coolant system was from the gearbox (there are two hoses that go from the gearbox to the bottom of the radiator for cooling or heating).

After I saw that, I bought a new aftermarket radiator installed it, flushed the coolant system and the gearbox (because coolant entered). After a million flushes for both, everything came out clean.

Engine is running fine, under normal driving conditions coolant needle is fixed just a bit over the first third of the gauge, but when I'm in stop and go traffic, or just idling after about 15-20 minutes it heats up to 96C(~205F), then both fans start and it gets cooled down to normal, then the fans stop, if I keep idling this process will start again.

Hoses, radiator cap, thermostat (opens at 74C/165F) are OEM, only the radiator is aftermarket. I've checked recently if the thermostat was installed correctly (it was), changed coolant, burped the system but the problem is still there.

I've only noticed this once before the rebuild but still does not seem normal.

Should the fans start individually? They only start both when it reaches 96C.

Any ideas are highly appreciated. Thanks!

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  • Welcome to Motor Vehicle Maintenance & Repair!
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Feb 7, 2020 at 14:32

1 Answer 1

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It seems to me the system is running as it should. The only thing you could do is to have the tune changed to start the fans sooner (at a lower temp). As soon as the fans start, the temp goes down ... that sounds fairly normal to me. If it never overheats, and by overheats I mean blows its top, then I'd suggest the system is running as designed.

The thing you could check is to put an OBDII reader on it and see where the computer is seeing the temperature is at (compare it to the gauge). If the computer is seeing the temp as lower than it actually is, then it might be turning the fans on late. This could mean your temp sensor is not showing the correct temp to the computer. In that case, a new one would be in order. Your dash gauge is only an indicator. In most cars they are not reliable enough to give you very accurate temperature reading.

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  • Thank you for your reply! I have a cheap ODB2 BT dongle, that's how I got the exact temperature when the fans start. Still, shouldn't only one fan start? then both if conditions still make temp rise. Only both? I'm a bit nervous about summer, I think this will be worse when it's hot outside.
    – sebastian
    Commented Feb 7, 2020 at 14:53
  • There are two fuses, one for each fan. Check to see if one of the is burnt out. Not sure if the second one forces the first, but it might be a place to look and see if the first fan might not be getting power when it should be. They'd be 1 & 2 in this diagram in your underhood fuse box.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Feb 7, 2020 at 15:01
  • Changed out both fuses and all 3 relays.
    – sebastian
    Commented Feb 7, 2020 at 15:41
  • I wouldn't think 205 is overheating at all. I agree that your system is working properly. To find out if both fans are supposed to turn on it may be helpful to find a cooling system electrical diagram. There are many configurations on different vehicles that decide which or when fans are commanded on.
    – Jupiter
    Commented Feb 7, 2020 at 16:56

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