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Discussion Starter · #1 ·
I fear that I may have blown the head gaskets on my 2002 LL Bean H6 with 160K miles. I committed the cardinal sin of any Subaru owner by not checking the temperature gauge after I started the engine, and I was about 4 Interstate miles from home when I glanced at the temperature gauge and saw it above the H reading. After freaking out in a panic, I decided to limp at 55 mph to my exit, and my home is about 1/2 mile from there. Speaking of limping, I'm recovering from foot surgery and didn't want to stand around on the side of the Interstate waiting for AAA in my temporarily disabled state.

I'd not noticed any high temperature gauge readings prior to this incident, and I'd just had all the seals replaced on the engine a month ago to stop an oil leak and so it was running well. There was some coolant loss, and so this morning I refilled the radiator with the remainder of a container of coolant I had and started the engine. Temperature gauge stayed on the C mark until finally rising slightly after 5-10 minutes of idle. I heard no bubbling from the radiator or overflow tank. There was the right amount of fluid still in the overflow tank.

However, when I turned on the heat and cranked it up to 80 degrees, I got nothing. I turned on the A/C and cold air came out.

There was some whitish smoke coming from the exhaust, but it was also a cool and wet day, so it was hard to evaluate if that was coolant or water vapor.

My questions are:
1) Is there perhaps an issue with the heater core?
2) Is driving for about 5 minutes with the temp gauge above "H" enough to ruin the head gaskets?
3) If the HGs are blown, should I have them replaced, or should I have a JDM engine installed?
4) Or....should I sell this piece for parts, cut my losses and go find a Toyota?

Thanks for your help!
 

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2021 Subaru Outback Premium, 2015 Toyota Sienna LE AWD
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90% chance you blew the head gasket. Only way to know is to visually inspect the heads and if nothing there do a compression test. Not the end of the world, but I would make sure you take it to a competent Subraru mechanic.
 

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You may need to do a 'burp' routine of some kind to get any big air bubbles out.

check the rad cap, check that fans are operating, clean any debris from between the a/c condenser and the radiator.
 

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Outback 2011 3.6R Premium
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Running an engine in the H zone does not necessarily result in blown head gaskets.

If you run the engine multiple times with the engine coolant boiling, this may result in blown head gaskets.

I suspect your cooling system may have a slow coolant leak which you are not aware of and the loss of coolant has caused the engine to run hotter than normal. I also suspect that the heater core does not yet have any coolant flowing through it, which is a common problem with the H6 engine after coolant loss. This would also mean that you still have a large air bubble in the system that needs to be bled/burped out.

To try and fix the problem park the car on a slope, with the front of the car higher than the back as this will help the air bubble to be burped out.

While the car is parked with the front higher than the back (and the engine is cold) remove the radiator cap and top up the coolant in the radiator. Start the engine and turn the heater on high. Keep the engine running until you feel hot air coming from the heater (this will confirm that coolant is flowing through the heater core). You may need to rev the engine to around 4,500 RPM a few times to help push the coolant into the heater core. This is not always necessary but some members have advised it is helpful.

Make sure (when the engine is cold) that you check your coolant level in the radiator and overflow bottle every day for at least a week and top up as needed. If the level keeps dropping each day you have a coolant leak which you will need to find and fix.

As your car is nearly 20 years old you should be checking coolant and oil levels at least once a month and topping up as required to prevent any major engine damage.

Seagrass
 

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I certainly wasn’t implying that driving on H would cause the gaskets to blow. But, given the motor, the age and the symptoms my guess is it has been leaking for awhile.

Running an engine in the H zone does not necessarily result in blown head gaskets.

If you run the engine multiple times with the engine coolant boiling, this may result in blown head gaskets.

I suspect your cooling system may have a slow coolant leak which you are not aware of and the loss of coolant has caused the engine to run hotter than normal. I also suspect that the heater core does not yet have any coolant flowing through it, which is a common problem with the H6 engine after coolant loss. This would also mean that you still have a large air bubble in the system that needs to be bled/burped out.

To try and fix the problem park the car on a slope, with the front of the car higher than the back as this will help the air bubble to be burped out.

While the car is parked with the front higher than the back (and the engine is cold) remove the radiator cap and top up the coolant in the radiator. Start the engine and turn the heater on high. Keep the engine running until you feel hot air coming from the heater (this will confirm that coolant is flowing through the heater core). You may need to rev the engine to around 4,500 RPM a few times to help push the coolant into the heater core. This is not always necessary but some members have advised it is helpful.

Make sure (when the engine is cold) that you check your coolant level in the radiator and overflow bottle every day for at least a week and top up as needed. If the level keeps dropping each day you have a coolant leak which you will need to find and fix.

As your car is nearly 20 years old you should be checking coolant and oil levels at least once a month and topping up as required to prevent any major engine damage.

Seagrass
 

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Running an engine in the H zone does not necessarily result in blown head gaskets.

If you run the engine multiple times with the engine coolant boiling, this may result in blown head gaskets.

I suspect your cooling system may have a slow coolant leak which you are not aware of and the loss of coolant has caused the engine to run hotter than normal. I also suspect that the heater core does not yet have any coolant flowing through it, which is a common problem with the H6 engine after coolant loss. This would also mean that you still have a large air bubble in the system that needs to be bled/burped out.

To try and fix the problem park the car on a slope, with the front of the car higher than the back as this will help the air bubble to be burped out.

While the car is parked with the front higher than the back (and the engine is cold) remove the radiator cap and top up the coolant in the radiator. Start the engine and turn the heater on high. Keep the engine running until you feel hot air coming from the heater (this will confirm that coolant is flowing through the heater core). You may need to rev the engine to around 4,500 RPM a few times to help push the coolant into the heater core. This is not always necessary but some members have advised it is helpful.

Make sure (when the engine is cold) that you check your coolant level in the radiator and overflow bottle every day for at least a week and top up as needed. If the level keeps dropping each day you have a coolant leak which you will need to find and fix.

As your car is nearly 20 years old you should be checking coolant and oil levels at least once a month and topping up as required to prevent any major engine damage.

Seagrass
I figured an overflow bottle that shows lost fluid (for example, used to be on FULL MARK but now it's lower than that) would be sufficient enough that a radiator fluid check wouldn't be necessary.

Sent from my SM-N986U1 using Tapatalk
 

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I figured an overflow bottle that shows lost fluid (for example, used to be on FULL MARK but now it's lower than that) would be sufficient enough that a radiator fluid check wouldn't be necessary.

Sent from my SM-N986U1 using Tapatalk
This is not correct AND has seen many members having overheating problems.

When coolant loss is happening, often the radiator can be a half quart or more low and the overflow bottle still has coolant in it. If the radiator level is low the vehicle engine is likely to overheat.

You need to check the radiator AND overflow bottle when the engine is cold and top up as needed.

Seagrass
 

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This is not correct AND has seen many members having overheating problems.

When coolant loss is happening, often the radiator can be a half quart or more low and the overflow bottle still has coolant in it. If the radiator level is low the vehicle engine is likely to overheat.

You need to check the radiator AND overflow bottle when the engine is cold and top up as needed.

Seagrass
Noted. Thanks.

Sent from my SM-N986U1 using Tapatalk
 

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Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
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If you're near me, I vote you sell it for scrap value (don't look up what scrap value is these days, though) to me.


Pegging the gauge and only loosing a bit of coolant likely means it only got to 220-230, and only briefly. Not likely enough to do any serious damage.

Letting it run for a few minutes and not having any heat isn't a death sentence by itself. Drive it a few times, you may still have air in the system. Get it up to temperature, and see what it does. Might be a good idea to plug in a code reader and read live temperature readings.
 
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I would suggest you do the burp procedure suggested by @seagrass, followed by careful monitoring daily for a while. If there's a slow leak, find and fix it if easy to get at (i.e. not head gaskets).

And then just monitor regularly.

No need to discuss pre-emptive, invasive engine procedures on a 20 year old, 160k mile Outback. You either did damage, or you didn't. Wait and see what happens, stop worrying, learn to live with it as-is, and don't start out on a cross-country trip with it for now.
 

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check that the overflow tube's end is not sitting in debris on the bottom of its tank - I cut mine at a 45* angle. I also used 2 small zipties to clamp the tube to its nipple on the rad. neck. Just in case air was getting pulled back in. DO NOT trust a Motorad or other typical parts store (often rebranded motorad) rad. cap for other than temporary use. I had one fall apart and it led to low coolant. Get OEM or other Japanese maybe Stant.
 

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2002 Subaru Legacy Outback.. EJ20 swap. Base or L. 4S3BH665527xxxxxx
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Definitely do a quick burp!!

I did on mine two or three times (I've also driven it for hours) and I believe it has purged the air.

Systems usually purge themselves, unless they maybe occasionally get a funky air pocket that doesn't want to dislodge.. burps are a good way to get rid of those, again, I did mine two or three times.. apparently, some engines have their "spots" where they can form an air pocket.
 

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Might be blown, might not.

My 2002 H6 has had 2 significant overheating events. Had a radiator hose burst and dump most of the coolant. Later had a hose clamp break, blow off a radiator hose, and dump most of the coolant. Both times Mal got over 240F per my ScanGauge2 limping to safety. The second time cracked an end tank on the radiator.

Replaced lots of cooling system parts, burped the system a bazillion times (you really do need one of those cooling system funnels), and he's still running along. No oil/coolant mixing on the dipstick, no bubbles in the radiator.

Did I get lucky? Probably. Did I likely take 50K+ miles of life off his engine? Almost certainly. But he seems to be powered by spite some days.

If you did turn out to pop your HG, it is cheaper and easier to drop in a used JDM H6 engine unless you already have all the tools to do the entire job yourself and don't put a $$$ value on your time if the vehicle is worth repairing to you.
 

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Might be blown, might not.

My 2002 H6 has had 2 significant overheating events. Had a radiator hose burst and dump most of the coolant. Later had a hose clamp break, blow off a radiator hose, and dump most of the coolant. Both times Mal got over 240F per my ScanGauge2 limping to safety. The second time cracked an end tank on the radiator.

Replaced lots of cooling system parts, burped the system a bazillion times (you really do need one of those cooling system funnels), and he's still running along. No oil/coolant mixing on the dipstick, no bubbles in the radiator.

Did I get lucky? Probably. Did I likely take 50K+ miles of life off his engine? Almost certainly. But he seems to be powered by spite some days.

If you did turn out to pop your HG, it is cheaper and easier to drop in a used JDM H6 engine unless you already have all the tools to do the entire job yourself and don't put a $$$ value on your time if the vehicle is worth repairing to you.
I am not an expert, BUT, I have ALWAYS felt, that..

If your Overheating/drive carefully home because the side of the highway is NOT where you want to be event results in a blown hose, cracked radiator, etc...

Then you are in a good place, because there is a greater chance your head gasket survived, and the excess pressure blew something else.

If it didn't pop anything "external" (hose, radiator.. had a BMW blow a hose off once..) then you have a greater chance of blown HG, or blown/warped head/block.

If you are brave, tet replacing head gaskets and you will soon find out if anything else was damaged.

Most will recommend a new engine, not even bothering with head gaskets, but I'd probably try head gasket first.. unless they get the engine apart and find that the head gaskets were not blown.

If that is the case, just take the engine out and get a new one because it's either one or both heads and or block that has the issue, and if it's the block then.. that's the engine..

Alllll different schools of though on this.

Just burped my H4 system again today. It's almost gone, that slosh. Had the super minorest recurrence but again, burping is good.
 

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Discussion Starter · #15 ·
UPDATE: I had to add almost 2.5 gallons of coolant to the system. Burped and purged air twice. I drove it 50-60 miles over the past few days with the temp gauge staying in its usual position. This included highway driving, idling at lights, etc. Seemed like the HGs were probably fine, but the question still remains why I needed to add 2.5 gallons of coolant to the system, so perhaps there is a leak or breech in the system somewhere.

Tonight, however, I drove to the pharmacy. It started with a 5 mile drive on the Interstate at 75 mph. Temp gauge stayed in its usual position. Then, while idling in the pharmacy drive through, the temp gauge started to rise to about 3/4 position. I turned off the engine as I waited. After I picked up, I drove off with the heater going full blast. The gauge stayed in its usual spot. Eventually, however, the gauge rose to about 3/4 position again, then would drop and slowly rise again. By the time I got home, it was at that 3/4 position (but not pegged on H).

When I turned the engine off, there was no bubbling sound. As I got out of the car I smelled the faintest whiff of coolant, but it wasn't overpowering. I didn't check the level, but will in the morning after everything has cooled. Oil on the dipstick still looks fine.

Is it possible I still have some air bubbles in the system that I need to purge again? Or do I need to consider that the HGs are now compromised? Next up is one of those chemical tests for blown HGs.
 

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UPDATE: I had to add almost 2.5 gallons of coolant to the system. Burped and purged air twice. I drove it 50-60 miles over the past few days with the temp gauge staying in its usual position. This included highway driving, idling at lights, etc. Seemed like the HGs were probably fine, but the question still remains why I needed to add 2.5 gallons of coolant to the system, so perhaps there is a leak or breech in the system somewhere.

Tonight, however, I drove to the pharmacy. It started with a 5 mile drive on the Interstate at 75 mph. Temp gauge stayed in its usual position. Then, while idling in the pharmacy drive through, the temp gauge started to rise to about 3/4 position. I turned off the engine as I waited. After I picked up, I drove off with the heater going full blast. The gauge stayed in its usual spot. Eventually, however, the gauge rose to about 3/4 position again, then would drop and slowly rise again. By the time I got home, it was at that 3/4 position (but not pegged on H).

When I turned the engine off, there was no bubbling sound. As I got out of the car I smelled the faintest whiff of coolant, but it wasn't overpowering. I didn't check the level, but will in the morning after everything has cooled. Oil on the dipstick still looks fine.

Is it possible I still have some air bubbles in the system that I need to purge again? Or do I need to consider that the HGs are now compromised? Next up is one of those chemical tests for blown HGs.
I didn't know an H6 even held 2.5 gallons of coolant!!!

Hmmm... I would start the car (when cold) with the radiator cap off. Do you see bubbles?
 

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UPDATE: I had to add almost 2.5 gallons of coolant to the system. Burped and purged air twice. I drove it 50-60 miles over the past few days with the temp gauge staying in its usual position. This included highway driving, idling at lights, etc. Seemed like the HGs were probably fine, but the question still remains why I needed to add 2.5 gallons of coolant to the system, so perhaps there is a leak or breech in the system somewhere.

Tonight, however, I drove to the pharmacy. It started with a 5 mile drive on the Interstate at 75 mph. Temp gauge stayed in its usual position. Then, while idling in the pharmacy drive through, the temp gauge started to rise to about 3/4 position. I turned off the engine as I waited. After I picked up, I drove off with the heater going full blast. The gauge stayed in its usual spot. Eventually, however, the gauge rose to about 3/4 position again, then would drop and slowly rise again. By the time I got home, it was at that 3/4 position (but not pegged on H).

When I turned the engine off, there was no bubbling sound. As I got out of the car I smelled the faintest whiff of coolant, but it wasn't overpowering. I didn't check the level, but will in the morning after everything has cooled. Oil on the dipstick still looks fine.

Is it possible I still have some air bubbles in the system that I need to purge again? Or do I need to consider that the HGs are now compromised? Next up is one of those chemical tests for blown HGs.
The total coolant capacity is only 8.1 quarts. So if you added 10 quarts of coolant it is definitely going somewhere and fast.

It could be it is spraying out of a hose once the system is heated and pressurized. It could also be going out the overflow.

Cooling issues at idle but while moving point towards the fans no being operational, make sure they come on and at full speed.
 

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Discussion Starter · #19 ·
So I see a touch of white smoke upon initial start-up. Again, it might just be water vapor, and it doesn't last long. No distinctive smell, but there is a faint odor of coolant coming from the engine bay.

I think I determined that the HGs are bad today though. It was down 2 more quarts today and when burping the system with a funnel, I saw a faint stream of exhaust coming into the funnel. No boil over and characteristic bubbles though. Perhaps it's a small breach at one the HGs, but then where is all that coolant going?

I'm not up to repairing the HGs myself, nor putting in a new engine, especially in my injured state. I've heard that the HG job can take a shop about 20 hours to do correctly. How long would it take for them to put in a JDM engine? That may be the better option at this point, and not necessarily any more expensive.
 
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