Changing thermostat in 1998 Forester

[Doctor John]

My wife's Forester is sitting at a truck stop in zero degree weather (we are
in quite a cold snap here in Colorado) - it started overheating all of a
sudden and no obvious leaks existed. I think it may be a stuck thermostat,
so I'm heading out tomorrow with my tool box and a replacement. Can any of
you folks give me a quick summary of how to replace the thermostat on a 1998
Forester, 2.5 L 4 cylinder, with AC? I glanced under the hoof when I went
to pick her up, and it sure doesn't look like the old Chevys I'm used to
where the top radiator hose terminates on the engine block at an easy to
remove inlet port with the thermostat underneath. I hope this isn't a long
task as the temp isn't supposed to get above 10 degrees tomorrow! Thanks
for any help.

John

 

[Edward Hayes]

To change the thermostat you first need to remove the undercover.
Remove 4X 12mm bolts and two plastic push clips (one on each side).
The thermostat is under the engine on the drivers side. Remove the
coolant hose and remove the two 10mm? bolts and drop the stat.
Remember to replace the o-ring gasket and align the jiggle pin toward
the front of the car. Top up coolant and away you go. I hope it is not
a head gasket problem. Ed

 

[johninKY]

Only familiar with my 95 2.2 but it is probably the same on your 98. The
thermostat housing is located where the bottom radiator hose joins up with
the engine block. Prepare to crawl under the front of the car. The 2
bolts are either a 10 or 12 mm. An extension helps> Entire job
shouldn't take more than 15 minutes. Also need a screwdriver for the hose
clamp.

 

[Doctor John]

Thanks all - Looks like a fairly easy replacement, if I don't freeze to the
parking lot!

John

 

[johninKY]

Forgot to mention/comment about air pockets. You'll probably create one
changing the thermostat. Keep checking the coolant level on the way home
as it will probably go down on you.

 

[Carl 1 Lucky Texan]

Thanks all - Looks like a fairly easy replacement, if I don't freeze to the
parking lot!

John

In that weather, I suspect either some type of coolant loss or the
t'stat - BUT, since it overheated while stationary, you should confirm
the radiator fan comes on when the temp gets to normal.

Carl
1 Lucky Texan

 

[Doctor John]

Thanks again all for the info. It's 11 degrees below right now so I've
delayed the trip to fix the Subie until tomorrow. What happened was my wife
was on the interstate in below freezing conditions when her temp gauge
redlined - she pulled into a truck stop and found anti freeze all over the
engine compartment. She let the vehicle cool off, added more antifreeze and
drove a few miles and the same thing happened. She went back to the truck
stop and ran the engine while another guy looked it over and neither could
see any leaking hoses and the fan belt was intact. As the engine rapidly
warmed up coolant would come out of the overfill hose (which was lose).
When I got there the temp was dropping rapidly so I did a quick look over
and decided to come back the next day with a thermostat, which by my
diagnosis seems the most likely problem. I think that at these cold outside
temperatures, the fan would have little effect. If you all have any other
ideas I'm sure appreciative of the input. As it stands now I'm heading out
tomorrow with a thick blanket to lay on, tools, hose clamps, anti-freeze and
a replacement thermostat.

John

 

[Mickey]

Thanks again all for the info. It's 11 degrees below right now so I've
delayed the trip to fix the Subie until tomorrow. What happened was my wife
was on the interstate in below freezing conditions when her temp gauge
redlined - she pulled into a truck stop and found anti freeze all over the
engine compartment. She let the vehicle cool off, added more antifreeze and
drove a few miles and the same thing happened. She went back to the truck
stop and ran the engine while another guy looked it over and neither could
see any leaking hoses and the fan belt was intact. As the engine rapidly
warmed up coolant would come out of the overfill hose (which was lose).
When I got there the temp was dropping rapidly so I did a quick look over
and decided to come back the next day with a thermostat, which by my
diagnosis seems the most likely problem. I think that at these cold outside
temperatures, the fan would have little effect. If you all have any other
ideas I'm sure appreciative of the input. As it stands now I'm heading out
tomorrow with a thick blanket to lay on, tools, hose clamps, anti-freeze and
a replacement thermostat.

John

A couple things to consider. Only use OEM tstat. When I replaced
mine sub'd a Beck Arnley I picked up locally and not dealer in town.
The cost was a high as factory tstat but found out the hard way the
tstat opening was only 50% of factory model which kept the temp on the
edge of having the fan on most of the time.

Second, as has been mentioned, BIG need to purge the air out of the
system. Factory procedure is to run engine at high idle for 15-20
mins until bubbles stop in the overflow tank. What I did was not
quite fill the radiator completely full and left the cap off. Ran
until tstat opened and coolant made initial drop. Then topped of the
radiator, put the cap on ran the engine until cooling fans cycled
twice. By then I didn't note any bubbles in the overflow tank. When
the engine cooled off there was little draw from the overflow tank.

Mickey

 

[Jim Stewart]

To change the thermostat you first need to remove the undercover.
Remove 4X 12mm bolts and two plastic push clips (one on each side).
The thermostat is under the engine on the drivers side. Remove the
coolant hose and remove the two 10mm? bolts and drop the stat.
Remember to replace the o-ring gasket and align the jiggle pin toward
the front of the car. Top up coolant and away you go. I hope it is not
a head gasket problem. Ed

Now I'm confused. I thought sure I replaced the
thermostat on my '99 Outback with the 2.5l engine.
And it was behind the water pump which was behind
the timing belt which was behind the timing belt
covers. Not a 15 minute job at all.

 

[Edward Hayes]

Yes, it is somewhat behind the timing belt but, the stat is under the
water pump.

 

[Carl 1 Lucky Texan]

A couple things to consider. Only use OEM tstat. When I replaced mine
sub'd a Beck Arnley I picked up locally and not dealer in town. The cost
was a high as factory tstat but found out the hard way the tstat opening
was only 50% of factory model which kept the temp on the edge of having
the fan on most of the time.

Second, as has been mentioned, BIG need to purge the air out of the
system. Factory procedure is to run engine at high idle for 15-20 mins
until bubbles stop in the overflow tank. What I did was not quite fill
the radiator completely full and left the cap off. Ran until tstat
opened and coolant made initial drop. Then topped of the radiator, put
the cap on ran the engine until cooling fans cycled twice. By then I
didn't note any bubbles in the overflow tank. When the engine cooled
off there was little draw from the overflow tank.

Mickey

Probably need to make sure the temp selector is on heat. Some folks have
luck doing the procedure on an incline - nose up. Do check the rad and
o'flow tank for a couple drive cycles afterwards.

Carl

 

[Doctor John]

Yikes! Is this the location of the tstat on a 1998 Forester 2.5 l ? Quite
a few folks responded and told me it was easily accessible from under the
engine where the lower radiator hose connects. Which is it ?????

John

 

[Edward Hayes]

After you remove the undercover you will see the thermostat housing
with the two cover bolts facing toward the ground.

 

[Mickey]

Probably need to make sure the temp selector is on heat. Some folks have
luck doing the procedure on an incline - nose up. Do check the rad and
o'flow tank for a couple drive cycles afterwards.

Carl

I did that a time or two before giving it some thought. Water exits
the engine between fwd and rear cyl. When on an incline, the front
cyls are higher than the water exit point. Good chance air could be
trapped at the front of the engine.

When I had to do this the last time I was on the first leg of a 4k mi
trip. When I finally returned home, there sill was no need to add any
water to the overflow tank. No more elevated position for me when the
cooling system needs changing.

Mickey