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2009 - X MT - Running hot?

('09-'13)
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57 views 14 replies 7 participants last post by  donkpow  
J
#1 ·
Vehicle Details:
2009 Forester X
Recently, the AC in my 09 X 5-speed has started cutting out when sitting running at idle. If I rev it a little it sometimes cuts back in. When it works it works pretty good. I think this is related to the engine running hot. On my scanner (no gauge) and using an IR thermometer the engine gets up to about 230 at the water outlet just driving around.

Couple things:
  • The entire AC system except for the liquid line and the pressure switch is less than 2 years old.
  • The entire cooling system is relatively new as well.
  • The radiator is a relatively new Megan Racing aluminum radiator. The cap is new OEM Subaru.
  • Both fans were on high and working well. I swapped in the XT style fans (RockAuto replacements) when I swapped the radiator.
  • The system is full of Subaru blue premix.
  • Water pump is a local parts store replacement (I didn't have time to wait at the time).
  • Thermostat is also local parts store.
  • It doesn't seem to run poorly or throw codes or set any warning lights.
I ordered a new OEM thermostat and temp sensor (before I confirmed it was reading right).

I have read now that Subarus are particular about the thermostats. It also seems like 230 is higher than it should run but some posts say that up to 250 is in the normal range? Where do yours run an average?

I know a lot of cars have a safety cutoff for the AC if the engine gets hot. Could not confirm or disprove that a 2009 Forester would do that though.

Thoughts?
 
#2 ·
Engine temp doesn’t matter with your A/C.
Condenser is in front of the radiator. Maybe your aluminum radiator is restricting airflow through the condenser and it’s cutting out on high pressure.
You’d have to use some gauges and see what your A/C pressure is like.
 
#5 ·
Kashlak said:
Engine temp doesn’t matter with your A/C.
Click to expand...
Oh yes it does. If the engine gets too hot the A/C will cut out. ;)

Josh09X said:
Where do yours run an average?
Click to expand...
Mine runs around 203F (95C) normally; when stressed can go to 230F (110C) but would not usually got past 214 (100C). 250F (121C) would really be pushing the limits and I would be pulling off the road to investigate under those conditions.
 
J
#3 ·
I own a set of gauges so I can do that. I've been ruling that out though because the AC worked fine when it was 105+ this summer and has only started cutting out in the last couple weeks when it's been in the low 90s. Makes me feel like this is a new failure of some sort.
 
#7 ·
Lots of threads where the use of a non-OEM thermostat and/or radiator cap caused overheating problems as @bman400 noted, and often the problem has been corrected after OEM replacement.

The AC is a separate system, but the engine ECU can turn off the AC to reduce the load on the engine when it is overheating.

Replace the thermostat with an OEM part as that is a well known problem cause, and it hopefully will also resolve your AC issue.
 
J
#8 ·
bman400 said:
What does 'on my scanner' mean? What scanner? OBDII Scanner? Subaru Thermostats/OEM is critical...aftermarkets are not always reliable or compatible.
Click to expand...
Mid grade Autel OBD scanner. Mine is an X so the dash is just RPM, MPH, and fuel. I can stream live data from the OBD though on the scanner.

Kevin said:
Mine runs around 203F (95C) normally; when stressed can go to 230F (110C) but would not usually got past 214 (100C). 250F (121C) would really be pushing the limits and I would be pulling off the road to investigate under those conditions.
Click to expand...
I was watching the scanner while driving this evening. Outside temp was about 88. It was getting up to about 225 on the highway at steady speed. So shouldn't be an airflow issue. At stops it would creep up to 231. As soon as I started driving it would drop down to about 215. RPM seemed to help a lot, which makes me think that it's a flow issue, so thermostat.

donkpow said:
I'd be looking at the fans. See what is happening. From my 2010 manual:
Click to expand...
I was looking at that same chart in my 2009 FSM. I might try wiring some LEDs to the pressure switch to see what load condition is being sent to the ECM to control the fans. Both fans and all the fan relays are new and I can confirm they were on high speed when it was 230 degrees.
 
#11 ·
I believe that that A/C pressure switch "normal" position is the only load condition reported to the fan control logic. In other words, it's either normal or not. A/C load is probably quantified by the body control computer.
 
J
#14 ·
If I'm reading the FSM triple switch diagram correctly, I think you are correct. The middle pressure switch just determines the load condition for the fan speed based on the chart you posted above and this triple switch diagram. If I read it right, high speed (high load) would start at about 257 psi and stay high until the pressure exceeds 426 psi or drop below 213 psi. If a new thermostat doesn't fix it, I'll dig up my gauge set and check it out.
Image
 
#12 ·
Josh09X said:
... It also seems like 230 is higher than it should run but some posts say that up to 250 is in the normal range? Where do yours run an average?...
Click to expand...
We have the same engine, and I have a dash-mounted ScanGauge that shows coolant temperature. It varies from 180 loafing along, to cycling down off 205 stopped in traffic. The fans cause the cycling.
 
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