[Kyle]

So, got a quick question. Got a 2004 Subaru and after 15–20 minutes of driving the temp gauge goes to red then will go back down to halfway no lights on dash coolant level is fine radiator hose is warm while running, I heard possible thermostat or water pump malfunction.

[Mike]

Sticking thermostat.

[Matt]

I had a 99 Outback a long time ago.

I was having that issue with the temp climbing up and going back down. It was the head gaskets. It was a hairline break, causing exhaust to leak into the coolant.

You’re going to need to check your coolant for exhaust.

It won’t show up unless you can get it to overheat.

[Adrian]

Take it off and put it in water and heat the water to boiling and see if it opens.

[Chris]

I’m thinking thermostat or engine coolant temp sensor. Both not too expensive to replace to see if they fix the issue.

[Gary]

Check your pressure cap.

[Author]

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