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2002 Forester 4 speed auto
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29 Posts
Discussion Starter #1
Hi everyone, I just rebuilt the engine in my 2002 Forester with a new short block and machined heads. All new gaskets and seals. I’ve had a CEL since the rebuild and the car starts really hard and idles high/misfires when cold. Runs/drives good when warmed up but still starts hard. Here’s the codes I got from Autozone

P0118 -Coolant Temp Circuit High Input
P0327- Knock Sensor 1 Circuit Low Input (Bank 1)
P0336- Crankshaft Position Sensor A Circuit Range/Performance
P0741- Torque Converter Clutch Solenoid Circuit Performance or Stuck Off
P0113-Intake Air Temperature Sensor A Circuit High Input

I did forget to plug in the coolant temp sensor when I first started it, but that works good now and it reads accurate until it spiked today when driving and the car overheated. I did change the air filter and fuel filter, and I replaced the trans filters/fluid. Any ideas?
 

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Registered
2003 Forester 2.5X 5 MT & 2009 Impreza 2.5i 5 MT
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68 Posts
Not sure about the other stuff, but for the overheating issue did you put the factory Subaru thermostat back in and made sure the jiggle valve is in the right location? Check that first. Then have the radiator cap tested. If bad replace it with factory Subaru radiator cap. You can go quality aftermarket OEM parts for many of the parts on a Subaru, but the thermostat and radiator cap should definitely be factory Subaru and nothing else.
 

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2009 Legacy
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912 Posts
It could be that you have an air bubble in the system. Subarus are notorious when it comes to burping the coolant system. It can be a bear, if you've replaced all the coolant. Air tends to get trapped so it doesn't circulate.

Park the car on an upslope, like ramps or a curb.
Open the radiator cap and put this this type of funnel in the filler neck. It is /the/ best tool for this job.
Start the car and fill the funnel. Turn the heat on. Let it run, squeezing the upper and lower radiator hoses.

Keep the funnel filled. Keep an eye on the temperature. If you have an OBD2 reader, read it out and graph it, if you can. Do not let it overheat, obviously. It shouldn't spike or go above 220 degrees or so. When the thermostat opens, you'll notice a bunch of coolant draining from the funnel. Don't let it suck air in. Again, keep the funnel filled.
Once it won't take anymore, stop the car and put the radiator cap back on.
 

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Registered
2002 Forester 4 speed auto
Joined
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29 Posts
Discussion Starter #4
Not sure about the other stuff, but for the overheating issue did you put the factory Subaru thermostat back in and made sure the jiggle valve is in the right location? Check that first. Then have the radiator cap tested. If bad replace it with factory Subaru radiator cap. You can go quality aftermarket OEM parts for many of the parts on a Subaru, but the thermostat and radiator cap should definitely be factory Subaru and nothing else.
It could be that you have an air bubble in the system. Subarus are notorious when it comes to burping the coolant system. It can be a bear, if you've replaced all the coolant. Air tends to get trapped so it doesn't circulate.

Park the car on an upslope, like ramps or a curb.
Open the radiator cap and put this this type of funnel in the filler neck. It is /the/ best tool for this job.
Start the car and fill the funnel. Turn the heat on. Let it run, squeezing the upper and lower radiator hoses.

Keep the funnel filled. Keep an eye on the temperature. If you have an OBD2 reader, read it out and graph it, if you can. Do not let it overheat, obviously. It shouldn't spike or go above 220 degrees or so. When the thermostat opens, you'll notice a bunch of coolant draining from the funnel. Don't let it suck air in. Again, keep the funnel filled.
Once it won't take anymore, stop the car and put the radiator cap back on.
The car does a new rad, rad cap, water pump and thermostat. Not sure on the brands because they were before I got the car. I temporarily fixed the overheating issue. I believe it was the heater core since the one hose was cold and there was a major flow restriction (top hose swelling and bottom hose cold). I bypassed the heater core and removed the thermostat and it hasn't overheated yet, and I'm getting good flow everywhere. I'm gonna have a shop reinstall the thermostat and bleed the system when I take it for inspection since I've been having bad luck so far.
 

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2004 FXT 4EAT
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609 Posts
before replacing the heater-core, try back-flushing it. Remove both hoses from the heater core and attach a garden-hose to the return pipe of the core. If you're lucky, it will push out the blockage. If you're NOT lucky, there are deposits on the inside of the core and you'll have to replace it.

I've heard of people putting chemicals into the core and letting it sit overnight. But you need to be careful. Some chemicals will just eat through aluminum...
 

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Registered
2002 Forester 4 speed auto
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29 Posts
Discussion Starter #6
Well I bypassed the heater core and removed the thermostat and the car isn’t overheating anymore. I had the radiator to a shop and it checked out good. But I’m getting bubbles in the radiator when I remove the cap. Even after 20 mins of sitting with the front jacked up/rad cap off idling I’m still getting periodic bubbles. I’m starting to think I messed up the head gaskets. Any ideas?
 
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