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Used Subaru- Is EJ25 SOHC or H6 more reliable?


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Will be looking for another used Subaru at some point (maybe an older Outback) with an automatic so everyone can drive it. Looking for something that shouldn't need major repairs (assuming it was properly maintained). 

 

I know the early to mid- 2000's EJ251/ EJ253 engines had few head gasket failures than the previous EJ25D, but they still occur with some regularity.

 

Throwing around the idea that maybe the H6 would make a more reliable engine. Not in need of the extra power, but like the idea of a timing chain and reportedly fewer headgasket problems. My question is are there still a greater likelihood that headgaskets may go and how long should the timing chain, guides, etc... last?

 

Also I know the H6 likes premium, but at 50 cents more a gallon than regular, I would likely want to run regular. Wondering how badly gas mileage would suffer if that were the case.

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My wife and I have both been driving H6 powered cars for a number of years.  They are a much more reliable and powerful engine than the 2.5 in any configuration.  A turbo may make a 2.5 more powerful but certainly not more reliable.  I just lost an H6 to the failure of the metal bypass pipe it rusted thru resulting in a total loss of coolant in a short time.  The bubbles in the expansion tank tell the story.  This is a weakness of the H6 and needs to be replaced if it looks questionable. The motor had 215,000. miles and didn't burn a drop of oil.  It got a consistent 24 mpg as did all 3 of the H6's we had/have. 

 

I replaced it with another H6 powered car with 115,000. That I hope will see 3 times that much.  When I first got the car it was giving me 22.5 mpg.  I replaced the air filter the mpg stayed at 22.5.  Then I cleaned the PCV valve now it's giving me 24.0 mpg.   My wife replaced her 2003 H6 sedan; that she ran into a tree, with a 2006 H6 3.0L R in a outback sedan we both love it; and I now have a good replacement H6.

 

We use the mid-grade gasoline it's a dime more per gallon and only falls short by 1octane 89 instead of 90.  When I just top of the tank < half a tank I'll use the premium grade hoping it will boost the overall octane of the gas.   Changing plugs can be a bear but it's only every 100,000. miles.  I take off the motor mount nuts one side at a time and lift the motor on that side one side at a time.  This way the motor doesn't move front to back and drops right back in place.  I remove and install the plugs from under the car.

 

If you decide on an H6 I don't think you'll be disappointed!  Good luck in your quest.

Edited by screwbaru2
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Check that metal by pass pipe at the gooseneck; it is in a bad spot and is prone to rusting from the outside in.  If it looks bad try to get them to replace it, it looks like one of those small jobs on an engine stand but a nightmare in the car.  I was going to take one out of a 2003 sedan I have.  After a couple of attempts at removal it seemed to me that if the Y- pipe and steering knuckle weren't in the way it would be a lot easier job!  The bolt on the rear hanger is almost invisible. That's a good price!

Edited by screwbaru2
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Look for every sign of head gasket you can. H6's do have head gasket failures and they are prone to:

 

1. Overheating, sometimes in hard to reproduce situations.

 

2. Also prone to being sold with existing head gasket issues for that reason. I've seen in inordinate percentage of H6 for sale with HG issues. No doubt because they're crazy expensive to repair and easy to trade in or sell at auction or sell outright due to their ability to hide symptoms.

 

H6's are great and i prefer them as well but walk the head gasket line cautiously.

 

The single best tip is to assess the seller. If they just got the car or it was sold atvsuction recently or they know nothing about it or don't/can't answer any questions then that's suspect and you need to read my list of checks below.

 

If it's a single owner professional selling the car after 10 years with maintenance records and no major repairs and has a family and kids and meets you in front of his house and just need the car gone, that's Much better and worth a premium.

 

If you have limited info then go into it with the idea you'd likevto rule out the head gasket as the reason it has changed hands recently:

 

Look for any prior cooling system work - new rad cap, new coolant, new radiator, hoses.

 

Look for dried coolant residue around rad cap battery and anything in that vicinity.

 

Look at drivers side headlight and fender for any cloudiness from hot coolant spraying on it.

 

Let it idle awhile with AC on high.

 

Drive car extensively with a/c on and off highway speeds.

 

ideally check radiator and overflow tank coolant level before and after test drive to look for comsumption. This is annoying since you'd have to wait for car to cool down.

 

Look for bubbles in overflow tank at idle and after a highway stint.

 

I've seen and bought all of these issues before including by dealers and people flipping auction cars. They are no doubt hitting auctions for this reason. Used sellers are clueless and just flipping them

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The H4 head gaskets are much easier to diagnose usually as they leak externally.

 

Get a good h6 and they're awesome. No timing belt very limited maintenance.

 

Replace the two serpentine bearings as soon as you gret one and replace them every 60k - 100k. They fail regularly but are only $10 and less than 30 minutes to replace. Real simple maintenance.

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Didn't some of the H6s have chain guide problems?

 

yes, but it's largely benign for a few reasons.

 

it's rare, i think only early models (maybe only 2001's or both 01-02), can be driven 100,000 miles even if they're making noise, and you can test drive and listen for it.  so while it's an "issue" it's nothing catastrophic, negligible risk, low concern, presents itself on a test drive, making it really low priority for most 15+ year old inexpensive subaru purchases.

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Engines that require higher octane fuel, do so because of static compression ratio or due to being forced induction. Wiki states the EZ30 is 10.7:1 which is rather high for a street engine. Most performance builds for V8's 10:1 is often the watermark as pump gas only goes so high in the US.

 

If you don't run premium, it'll ping and pull timing back making it less responsive, and detonation can be very destructive on an engine. So while it might "run", it's not running at peak efficiency. Remember, octane is the ability to resist detonation, and with an engine at 10.7:1, it'll be more sensitive to this than a 9.5:1 compression ratio. 

 

Run what's it's supposed have. Read this: http://www.contactmagazine.com/Issue54/EngineBasics.html  for some basics.

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Don't forget, Subaru open deck aluminum block engines are a world apart from a closed deck cast iron block as far as hotspots and cooling, and then with EFI and electronic timing adjust. The ej25 has been 10:1 since about 1999-2000... I thought the 6cyls were tuned for 89

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Agree as previously mentioned:

 

The EJ251 / EJ253 is a  good engine apart from the the external head gasket issue and cam belts etc to replace at the required intervals  but its

 

much easier  / cheaper  to repair than the H6 3.0 which is actually a better engine because it has  less of these  issues and no cam belts etc to

 

replace  (chain driven)

 

 

Also if both engines are serviced regularly and cooling systems flushed 2 yearly and the correct fuel used ie premium in the H6 (as

 

recommended by Subaru)

 

all these issues will be reduced  / minimised.

 

https://allwheeldriveauto.com/subaru-head-gasket-problems-explained/

 

https://allwheeldriveauto.com/subaru-head-gaskets-problems-explained-part-ii/

Edited by subnz
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i prefer the H6, but i can see it sort of bein a toss up depending how you look at it: the H6 has fewer (like 1) but a more ominious issue and is more expensive generally (up front and gas mileage)

 

the H6 has one big issue - headgaskets.  it can strand you, is costly / pig of a job and replacement engines are less common/a bit more pricey (particularly 2005+ models). 

 

the H4's have a bit more issues and maintenance.  but they're cheaper up front (usually), cheaper gas, good engines, and OEM headgaskets usually give years and 50,000 miles to plan a repair.

 

i've never had a problem running regular gas in H6 Subaru's - EZ30 or the newer tribeca EZ engine. 

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  • 3 weeks later...

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