car overheats after long drive temp guage goes up and down hot no ac opened overflow bottle car running bubbles were coming up
May need a new thermostat. Make sure the fans are working also. If some work had bed done that you had to drain the coolant down, then it may be that the cooling system needs to be purged from air pockets.
Subaru t-stats are extremely durable. Due diligence indicates checking for radiator and heater hose blockages, but historically the highest probability is that you've an inner head gasket breach, resulting in the infamous "percolation" of combustion gases superheating the coolant; pockets of this gas slip past the thermosensor, causing the bouncing needle. Quick determination can be made by "sniffing" the bubbles for HC content. If positive chase a "new" used motor, as blocks are usually too-stressed by the superheated coolant to last long after a HG replacement job. Sorry.
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