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"Souparu" 05 OB XT
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Discussion Starter #1
This might be a long shot, but any advice is appreciated.

I bought this 2005 Subaru Outback XT last April, not having owned a Subaru before. This car drove great until I took it on a road trip the following August. The engine overheated while going 80 mph in 100 degree weather. No coolant leaks, fan still working. Assumed that the problem could be related to bad head gasket, water pump or thermostat- as car did not cool down when out of gear, only when in gear and driving slowly/low RPMs.

Decided to test my luck and tackle the cheapest option. Replaced the thermostat on the side of the road and found that the thermostat had been open- pried open so that it was stuck permanently 'open'. I assume that this had been done by the previous owner and not a malfunction.

Got back home and decided to do a compression test (to check the head gasket). First 3 cylinders were all at 125 psi. Unable to get the fourth spark plug off, found that it had been glued to a cracked coil. Was told by a friend (that has worked on cars for several years) that the car may only be running on 3 cylinders. Did not look into this.

Reached out to the previous owner and was told that the car overheated in 2018 and the head gaskets were replaced. The water pump was replaced shortly after. I do not have the paperwork, but the Carfax records seem to line up with this timeline. I did not drive this car for a few months, but found no problems with the engine or overheating when I started it in January. Drove it around for a couple months when I noticed a rough idle.

In March, car began idling roughly when out of gear, RPMs jumped between 500-1500, occasionally so low that the car stalled. Noticed this when the car was both hot and cold and was not temperature dependent- this only happened at low speeds (under 20 mph). A misfire later developed, noticed more when idling or accelerating quickly. Recently started overheating as well.

Brought it to a mechanic for a leak down test but ultimately decided against it due to coil and spark plug on cylinder 4. Recently ran an engine code, bank 1 too lean. Suspect a vacuum leak at bank 1 but have not done diagnostics.

Considering an engine/turbo rebuild but I want to look at my options. Is there anything else that could be causing these symptoms?
 

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Outback 2011 3.6R Premium
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You have a whole lot of issues going on with that engine.

It is not common for the Turbo engines to have head gasket failures as they use a (MLS) multi layer steel gasket.

The misfire could be caused by numerous things including the number 4 spark plug that is of unknown serviceability due to the coil being “glued on” or the “lean” code that has been set in the ECU.

Running lean can also cause an overheating problem although I would expect there to be more frequent error codes if this was the cause of the overheating.

Before spending $5,000 to $8,000 on an engine and turbo rebuild I suggest you get the actual cause of the multiple problems diagnosed by a known good Subaru workshop as this could save you some dollars.

Seagrass
 

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2001 VDC/SC One of a Kind
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This is a lot, so get a coffee.

When the ECM sets a lean code for bank 1, it's the both banks. There is only one AF sensor and it's reference is Bank 1.

Idling up and down is the computer trying to find the idle rpm and it's is moving the throttle plate in vain, hunting. Generally this is a large leak in the system aft of the MAF sensor. It could be an air pipe/hose is disconnected somewhere between the MAF and throttle, a vacuum hose is off, or a gasket on the intake. Easy way to find a leak is either with smoke or use compressed air. The smoke is pushed in to the system at low pressure and it will come out where the leak is. Using compressed air you pressurize the system to about 15 psi and the air will escape where the leak is.

The overheating could be due to a low coolant level. Seems to me that if the HGs were replaced, then the water pump, someone may have botched the HG work and was trying to keep it from overheating by keeping the coolant pressure low by having continuous flow through the radiator. By your not knowing about the thermostat condition, the HG may have been breeched the whole time and when the level dropped in conjunction with high temps, the engine got hot.

With the "glued" coil, I highly suspect that either the shop or the person who did the work is a dumbass and instead of fixing it right took a shortcut. If someone took a shortcut on the coil, there were probably shortcuts on the engine work. Thermostat condition is another indication.

It's now your problem to deal with.

My suggestion is take the engine out and tear it down. Check everything as you go. Turbo condition, oil lines, coolant hoses, timing components, Japanese water pump in place, (AISIN), condition of the throttle body and intake, pressure test the intercooler, etc. When you get the heads off, check the valve seals and seats, springs, adjustment and repair accordingly. Check the pistons for signs of an impact. If one is cracked it has bad rings you'll have an excess of carbon in that cylinder due to excessive oil intrusion. Have the plane of the heads checked, or do it yourself with a flat bar and feeler gauge. Check the block deck.

After it's disassembled and checked/repaired, clean everything and put it back together correctly. Make sure the banjo bolt has the screen removed and any other modifications you want done, do it with the engine out where it's easier to work with.

Parts suggestions: Mitsuboshi belt, AISIN water pump, (you can find these together in a timing kit with the pulleys and tensioner), Mahle, Beck Arnley or "Subaru" thermostat, OEM head gaskets, Mahle engine gaskets, (valve cover and tube seals, Intake and exhaust). Use NGK or Denso spark plugs. You can go with platinum plugs and you'll be changing them at 60k miles interval with the timing belt. Get a new PCV valve and replace old PCV hoses.

Before you put the engine in, flush out the radiator and heater core. Replace any coolant hose that are suspect. The inside of the hoses will be breaking down after a lot if years use. If you put your finger in a hose and it comes out blackened, it's past time for a hose replacement. Reseal the AC joints while the engine is out. Cheap and easier to deal with while the engine is out. May as well clean out the engine bay, optional, so if a leak develops it'll be easier to track.

Make sure all the air piping is sealed tight when you put it all together in the car. Have new gaskets for everything and check all the rubber and plastics for cracks.

Done correctly, once the engine is in all you'll need to do is oil changes and other scheduled maintenance on the car. I've got a few customers with WRXs and STIs that have high mileage and never had major problems with these cars because they kept up with everything and did not ignore issues. I'm talking HIGH mileage, close to and one over 200k. One has an 04 STI that's been in the fam since new and it's at 180k miles as of last month.

Keep us posted.
 

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This might be a long shot, but any advice is appreciated.

I bought this 2005 Subaru Outback XT last April, not having owned a Subaru before. This car drove great until I took it on a road trip the following August. The engine overheated while going 80 mph in 100 degree weather. No coolant leaks, fan still working. Assumed that the problem could be related to bad head gasket, water pump or thermostat- as car did not cool down when out of gear, only when in gear and driving slowly/low RPMs.

Decided to test my luck and tackle the cheapest option. Replaced the thermostat on the side of the road and found that the thermostat had been open- pried open so that it was stuck permanently 'open'. I assume that this had been done by the previous owner and not a malfunction.

Got back home and decided to do a compression test (to check the head gasket). First 3 cylinders were all at 125 psi. Unable to get the fourth spark plug off, found that it had been glued to a cracked coil. Was told by a friend (that has worked on cars for several years) that the car may only be running on 3 cylinders. Did not look into this.

Reached out to the previous owner and was told that the car overheated in 2018 and the head gaskets were replaced. The water pump was replaced shortly after. I do not have the paperwork, but the Carfax records seem to line up with this timeline. I did not drive this car for a few months, but found no problems with the engine or overheating when I started it in January. Drove it around for a couple months when I noticed a rough idle.

In March, car began idling roughly when out of gear, RPMs jumped between 500-1500, occasionally so low that the car stalled. Noticed this when the car was both hot and cold and was not temperature dependent- this only happened at low speeds (under 20 mph). A misfire later developed, noticed more when idling or accelerating quickly. Recently started overheating as well.

Brought it to a mechanic for a leak down test but ultimately decided against it due to coil and spark plug on cylinder 4. Recently ran an engine code, bank 1 too lean. Suspect a vacuum leak at bank 1 but have not done diagnostics.

Considering an engine/turbo rebuild but I want to look at my options. Is there anything else that could be causing these symptoms?
 

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I have seen this alot! First get MAF cleaner ,clean your Mass Air Flow,sensor,change coil GET OEM, then plugs wires,and the little curprit that a lot of MECHS.Forget is coolant temp sensor .install these and disconnect - for 20 mins and preform the IDLE RELEARN PROCEDURE ,,MR. SUBIE @ YOUTUBE I THINK SHOWS THIS! IF you still have problems it's you UPSTREAM OX2 FUEL AIR SENSORS,IF YOU STILL HAD A MISS ,,TIME TO CHANGE TIMMING BELT ,ITS JUMPED A KNOTCH OR TWO,getting worn!
 

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"Souparu" 05 OB XT
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Discussion Starter #6
This is a lot, so get a coffee.

When the ECM sets a lean code for bank 1, it's the both banks. There is only one AF sensor and it's reference is Bank 1.

Idling up and down is the computer trying to find the idle rpm and it's is moving the throttle plate in vain, hunting. Generally this is a large leak in the system aft of the MAF sensor. It could be an air pipe/hose is disconnected somewhere between the MAF and throttle, a vacuum hose is off, or a gasket on the intake. Easy way to find a leak is either with smoke or use compressed air. The smoke is pushed in to the system at low pressure and it will come out where the leak is. Using compressed air you pressurize the system to about 15 psi and the air will escape where the leak is.

The overheating could be due to a low coolant level. Seems to me that if the HGs were replaced, then the water pump, someone may have botched the HG work and was trying to keep it from overheating by keeping the coolant pressure low by having continuous flow through the radiator. By your not knowing about the thermostat condition, the HG may have been breeched the whole time and when the level dropped in conjunction with high temps, the engine got hot.

With the "glued" coil, I highly suspect that either the shop or the person who did the work is a dumbass and instead of fixing it right took a shortcut. If someone took a shortcut on the coil, there were probably shortcuts on the engine work. Thermostat condition is another indication.

It's now your problem to deal with.

My suggestion is take the engine out and tear it down. Check everything as you go. Turbo condition, oil lines, coolant hoses, timing components, Japanese water pump in place, (AISIN), condition of the throttle body and intake, pressure test the intercooler, etc. When you get the heads off, check the valve seals and seats, springs, adjustment and repair accordingly. Check the pistons for signs of an impact. If one is cracked it has bad rings you'll have an excess of carbon in that cylinder due to excessive oil intrusion. Have the plane of the heads checked, or do it yourself with a flat bar and feeler gauge. Check the block deck.

After it's disassembled and checked/repaired, clean everything and put it back together correctly. Make sure the banjo bolt has the screen removed and any other modifications you want done, do it with the engine out where it's easier to work with.

Parts suggestions: Mitsuboshi belt, AISIN water pump, (you can find these together in a timing kit with the pulleys and tensioner), Mahle, Beck Arnley or "Subaru" thermostat, OEM head gaskets, Mahle engine gaskets, (valve cover and tube seals, Intake and exhaust). Use NGK or Denso spark plugs. You can go with platinum plugs and you'll be changing them at 60k miles interval with the timing belt. Get a new PCV valve and replace old PCV hoses.

Before you put the engine in, flush out the radiator and heater core. Replace any coolant hose that are suspect. The inside of the hoses will be breaking down after a lot if years use. If you put your finger in a hose and it comes out blackened, it's past time for a hose replacement. Reseal the AC joints while the engine is out. Cheap and easier to deal with while the engine is out. May as well clean out the engine bay, optional, so if a leak develops it'll be easier to track.

Make sure all the air piping is sealed tight when you put it all together in the car. Have new gaskets for everything and check all the rubber and plastics for cracks.

Done correctly, once the engine is in all you'll need to do is oil changes and other scheduled maintenance on the car. I've got a few customers with WRXs and STIs that have high mileage and never had major problems with these cars because they kept up with everything and did not ignore issues. I'm talking HIGH mileage, close to and one over 200k. One has an 04 STI that's been in the fam since new and it's at 180k miles as of last month.

Keep us posted.
This is incredibly helpful. I will be ordering the spark plugs and ignition coils this afternoon, then running a compression and leak-down test. For reference, this car’s seen some better days. Just hit 220 k miles, so it’s surprising the engine has made it this far.
Any other recommendations for maintenance or prevention while I have it up on the lift?
I’ll keep you updated as I go forward with diagnostics and the rebuild. Thank you!!
 

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"Souparu" 05 OB XT
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Discussion Starter #7
I have seen this alot! First get MAF cleaner ,clean your Mass Air Flow,sensor,change coil GET OEM, then plugs wires,and the little curprit that a lot of MECHS.Forget is coolant temp sensor .install these and disconnect - for 20 mins and preform the IDLE RELEARN PROCEDURE ,,MR. SUBIE @ YOUTUBE I THINK SHOWS THIS! IF you still have problems it's you UPSTREAM OX2 FUEL AIR SENSORS,IF YOU STILL HAD A MISS ,,TIME TO CHANGE TIMMING BELT ,ITS JUMPED A KNOTCH OR TWO,getting worn!
Thanks for the recommendation! Timing belt was done with the water pump 10k miles ago and the MAF looks clean, but I’ll look into it a little more while the car is on the lift! It’d be nice if this were a simple fix, but in all honesty, I think this car is going to need a lot of love.
 

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"Souparu" 05 OB XT
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Discussion Starter #8
You have a whole lot of issues going on with that engine.

It is not common for the Turbo engines to have head gasket failures as they use a (MLS) multi layer steel gasket.

The misfire could be caused by numerous things including the number 4 spark plug that is of unknown serviceability due to the coil being “glued on” or the “lean” code that has been set in the ECU.

Running lean can also cause an overheating problem although I would expect there to be more frequent error codes if this was the cause of the overheating.

Before spending $5,000 to $8,000 on an engine and turbo rebuild I suggest you get the actual cause of the multiple problems diagnosed by a known good Subaru workshop as this could save you some dollars.

Seagrass
Appreciate the advice. New to the Subaru world and haven’t done any major work on cars to date, so I’m still learning! My next step is to replace spark plugs and run the compression test and leak-down, but I’m fully expecting some extensive work.
 

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2001 VDC/SC One of a Kind
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Subarus are easy to work on once you get used to how it's laid out. and you have to pay attention to all the details of the little stuff like grounding, the battery, connections, corrosion, etc.
 

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Discussion Starter #10
Feel like I've taken my whole car apart just to remove the spark plugs! I was able to get them all out and all seem to be in good condition but have some oil on them, which I'll clean. I was able to run a compression test on the fourth cylinder, which read at 90 psi (other three cylinders ~125 when I tested last fall).

It was recommended that I retest all cylinder compression- both wet and dry (using motor oil for the wet test to check piston seals?), then running the car until it heats up before pulling the spark plugs to check if they've heated (still not sure on the purpose of this last one). I was told that there was no reason to run a leak-down test if the cylinder was the source of the rough idling. Thoughts? Any other recommended tests?
 

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The purpose for heating up the engine is because of metal expansion with heat. The downside with a boosted boxer is all the parts you have to take out to get to the spark plugs allow the engine to cool off a bit by the time you install the tester. Plus it makes for a hot working environment. So it's a moot point with the XT. Compression test cold would suffice. If you get low compression on a single cylinder, drop the exhaust manifold and look up at the valves to see if one has a dropped seal.
 

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Discussion Starter #12
The purpose for heating up the engine is because of metal expansion with heat. The downside with a boosted boxer is all the parts you have to take out to get to the spark plugs allow the engine to cool off a bit by the time you install the tester. Plus it makes for a hot working environment. So it's a moot point with the XT. Compression test cold would suffice. If you get low compression on a single cylinder, drop the exhaust manifold and look up at the valves to see if one has a dropped seal.
Makes sense. I had my concerns about getting the spark plugs out fast enough for a heat test to even make a difference, so I'm glad your experience is the same. Just finished with the wet/dry compression tests, still trying to make sense of the results.

For cylinder 1, I read 80 psi dry and 85 psi wet (added ~5 mL motor oil to socket).
Cylinder 2: 90 psi dry and 90 psi wet
Cylinder 3: 85 psi dry and 90 psi wet
Cylinder 4: 85 psi dry and 85 psi wet

These seemed really low, but I used the same gauge that I did last fall, which gave me ~125 psi for cylinders 1-3. I rented a different gauge from AutoZone to check and read ~100 psi wet for cylinder 3, so there is a small difference between gauges.

I'm thinking that the low compression suggests cylinder head problems. Thoughts?
 

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The real lack of difference between wet and dry would rule-out ring or cylinder wall sealing issues (the liquid "seals" imperfections in those gaps).

I'd wager the throttle body wasn't open during the test as Subaru says 110 psi is the limit, 90 is pushing it for combustion success. But the evenness is a good thing.

You can confirm/deny the results with a leak-down as well.
 

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Have you checked the timing belt and timing marks? If the timing is off, you can get lean codes, rich codes, misfires and rough idle.

On a side, the mileage doesn't really matter unless the engine has been abused or neglected. I have customers with high mileage WRX and STIs and have only performed scheduled maintenance on them. No HG issues, no valve problems, no turbo problems. It comes down to how the car was treated. Apparently yours has seen some neglect and maybe the HGs work was done correctly.
 

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"Souparu" 05 OB XT
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Discussion Starter #15
The real lack of difference between wet and dry would rule-out ring or cylinder wall sealing issues (the liquid "seals" imperfections in those gaps).

I'd wager the throttle body wasn't open during the test as Subaru says 110 psi is the limit, 90 is pushing it for combustion success. But the evenness is a good thing.

You can confirm/deny the results with a leak-down as well.
This is good to know. How can I check if the throttle body is open? What would I be looking for/to confirm with a leak-down test?
 

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Discussion Starter #16
Have you checked the timing belt and timing marks? If the timing is off, you can get lean codes, rich codes, misfires and rough idle.

On a side, the mileage doesn't really matter unless the engine has been abused or neglected. I have customers with high mileage WRX and STIs and have only performed scheduled maintenance on them. No HG issues, no valve problems, no turbo problems. It comes down to how the car was treated. Apparently yours has seen some neglect and maybe the HGs work was done correctly.
I will look to check the timing today. Thanks for your ideas!!
 
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