98 Subaru Overheating


Asked by Feb 05, 2016 at 06:14 PM about the Subaru Outback

Question type: Maintenance & Repair

I have a '98 Subaru Legacy outback, a couple of
months ago it started overheating randomly once a
week or every other week or so. Now, before you all
aske like everyone else, I check my fluids once a
week every week. Since the overheating began I
check them everyday to make sure the coolant is
draining out of the reservoir to attemp to avoid the
My coolant reservoir would overflow and not drain
back into the radiator, then would drain it
completely dry and take a little bit more into the
radiator and I would refill the reservoir to the cold fill
line. Now it is rarely draining all of the necessary
coolant back on its own (It returns some but not all)
and I'm having to remove my reservoir and pour the
remaining coolant that was overflow into the
radiator. Very rarely am I having to add more
coolant to the radiator.
It has now begun to overheat everyday in the
morning and at night, however, driving the same
distances and exact same roads in the middle of
the day it does not overheat 90% of the time.
It has a brand new water pump, timing belt, and
There are no tell tale signs that it is the head gasket.
No sweet burning smell, no smoke, and not losing
The coolant is clean, no dirt, not oil, no residue. And
my oil is clear from all signs of there being a coolant
leak into it.
My check engine light is on and the codes reading
are a malfunctioning knock sensor and a misfire in
cylinders 3 and 4.
We are stumped to say the least.

6 Answers


Niece to see all that you have done, So has the air ben bled out of the cooling system when you changed the water pump & thermostat when refilling the system? Also probably replace the radiator cap with a new one.


Yes the air was bled out. I will try that today The newest curve it's throwing... Just overheated but heater was blowing cold air...


Heater blowing cold air is a good indication of a air pocket. You may have to go to a garage where they have a machine to bleed out cooling systems. Some cooling systems are very hard to purge from air.


Thank you!


Here is a way to try and bleed system before taking a shop. Remove cap from over flow tank fill with anti freeze to full mark leave cap off start vehicle and let idle and reach operating temp anti will start to back up in tank this is normal once t- stat starts to open anti freeze level will drop in tank refill with anti freeze back to full mark then put cap back on. This will remove all air that is if there is not another problem.


I think you may need a new radiator cap. Use some Subaru anti- leak in the radiator for good measure.

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