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Interesting HG info


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34 replies to this topic

#1 Ranger83

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Posted 09 July 2006 - 07:44 PM

Surfing around and found possible solution and the real reason why HG blowPosted on legacygt.com

####################


This is from the Toronto Subaru Club(TSC)

FAQ - Blown Head Gaskets on Phase I&II EJ2.5 - Toronto Subaru Club

Quote:
Originally Posted by [b
Quote[/b] ]
by mutant_dan@[EMAIL PROTECTED] Jan 14, 2005 at 09:42 AM

FYI:

From: *Gene Goldenfeld <genegold@[EMAIL PROTECTED]
Thu Jan 13, 2005 *8:06 pm
Subject: *Re: [outback] Head Gasket failure info

There is an interesting discussion about head gasket failure in 2.5L
Subaru engines over on the subaruvanagon mailing list. (This is a
mailing list for people with VW Vanagons who have swapped in a Subaru engine to replace the VW water boxer.)

Indeed. In the interest of getting the discussion over here (and
providing me a copy to archive), I've copied Al Wick's posts on head
gasket failure from the Subaruvanagon group. I let him know.

Gene
-------------

I was in unusual situation where I was able to find the head warp
"gasket fail" problem before the dealers were getting any failures.
Many years ago I adapted a new 2.5 (10k miles) to my airplane. I have
sensors galore on the plane, so when the head first started leaking, I
was able to look at the data on my laptop and see that the head leaked
pressure to coolant system 3 seconds after I hit full throttle. It then
dissipated 5 seconds later. I really learned a lot and deliberately
operated at full throttle for long periods (hour or two). All the time
logging the pressures and temps every few milliseconds.

So here's the deal. All failures are caused by air in the cooling
system. No air, no problem. If you have air bubble AND you operate
at high throttle settings, the head will warp. It takes a long time to
show up. So if there was trapped air 6 months ago, then you might
now start to see discolored coolant, overheating. Or it might only occur
climbing a hill in hot weather. Only the 2.5 has this marginal
condition. All other Subaru's bullet proof.

My flying partner makes a living replacing gaskets on 2.5's these days.
Number one repair item. *It appears that the 2.5 has an area at center
of block/head interface which doesn't have enough coolant flow. When a
bubble passes by, it boils locally. This eventually causes head to
warp, gasket to give out. Subaru has tried 3 different style gaskets,
even adding coolant conditioner to improve heat transfer. Still a
problem. But absolutely all failures caused by trapped air in system.
All models of 2.5 liter the same.

The solution is very simple. Just drill and tap your coolant crossover
pipe and add a fitting that allows air to leave engine and rise to your
swirl pot. You will never have a problem. I operate my engine full
throttle for hours at a time. Fabulous engine.

-al wick

--------------
I got a couple other private messages regarding the same. I'll try to
clarify...

The crossover tube is the aluminum coolant tube that lives under the
intake manifold. It's rectangular in shape and the main coolant hose
attaches to one end of it. It's the one everyone reverses. I'm unable
to say there is a "best place" to add a fitting to the tube. Likely it
does not matter where you place the fitting. Just somewhere in the top
of this tube. The fitting needs to be on this cross over tube because
this is the highest point in the ENGINE cooling system. Your goal is to
purge any air that happens to be in the engine. This is different than
purging air from your radiator or from your heater core. Air in the
engine causes head warp. Air in other components just reduce their
efficiency. We imagine that air flows with the moving coolant, but
actually it only does to small degree.

Drill and tap this tube. Install a fitting, and run hose from that
fitting to your swirl pot. No dips in hose, it must gradually rise to
swirl pot. As long as the swirl pot is above the engine it will
automatically purge all air from the engine. This results in a "robust"
cooling design. Robust meaning it handles unusual conditions. If your
brother in law borrows your vehicle, blows a hose, and doesn't realize
he needs to bleed air, no problem. Because your system automatically
purges all air from engine.

#2 nipper

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Posted 09 July 2006 - 07:55 PM

makes perfect sense. i just couldnt figure out the cause and effect.

nipper

#3 Olnick

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Posted 09 July 2006 - 08:57 PM

Makes perfect sense and is consistent with everything I've read about 2.5 head gasket failures.

I've often wondered why there isn't a valve at the highest point in the cooling system so air could be bled out as coolant is being added. Nissan Maxima V6 had such a feature back in 1990, iirc.

My only question here is what the heck is a swirl pot?

#4 nipper

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Posted 10 July 2006 - 12:02 AM

its an airplane thing.

nipper

#5 outback_97

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Posted 10 July 2006 - 12:03 AM

This has been discussed before:

http://www.ultimates...ead.php?t=28600

And here:
http://www.ultimates...69951#post69951

I was pretty excited to read about it because it sounded interesting and plausible... but some other pretty knowledgeable folks here were pretty skeptical of the idea. I don't know, I just keep driving my Phase 1 2.5 hoping for the best but being prepared for the worst.

Steve

#6 ericem

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Posted 10 July 2006 - 12:32 AM

Air trapped in the system. Ya that does make sense doesn't it. Maybe subaru should check up on this and fix all these HG errors.

#7 Olnick

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Posted 10 July 2006 - 01:49 AM

This has been discussed before:

http://www.ultimates...ead.php?t=28600

And here:
http://www.ultimates...69951#post69951

I was pretty excited to read about it because it sounded interesting and plausible... but some other pretty knowledgeable folks here were pretty skeptical of the idea. I don't know, I just keep driving my Phase 1 2.5 hoping for the best but being prepared for the worst.

Steve


Thanks for the links, Steve. Interesting reading--don't know how I missed the discussions when they first appeared.

I'm still convinced that, while it may not be the cause of it, there's a connection between trapped air and HG failure.

Just be super careful and very observant when you change your coolant and I sincerely hope you never face "the worst."

#8 rlsimpso

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Posted 10 July 2006 - 12:26 PM

Okay, I read all the posts listed here and still have a question: Has anyone tried this one US spec phase I ej25? Does anyone have any pictures?

I think I know what a swirl pot is now, and I don't have one.

I would assume it should be done with the pipe off the car to keep metal bits out of the engine.

I ask because I just clicked over 160,000 and think my HGs are going again:mad: . That is one set every 80 miles. I am trying to decide if it is worth replacing them, or just replace the entire car. If I do replace them, I want to do whatever else I can to ensure they don't fail again. Even if it doesn't work, at least I can say i tried.

I really would like to get a few more years out of this car.

BTW: I don't drive around a full throttle for hours at a time, although I would like to:) .

#9 BruceyWV

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Posted 10 July 2006 - 01:07 PM

I'd be on this like fly on stink if I could see it done, I cant see it harming anything since I'm already way out of warranty and I dont feel like having a HG job anyway.

#10 rlsimpso

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Posted 10 July 2006 - 03:06 PM

Along with the venting, has anyone had this o-ring procedure done?

http://wac.addr.com/...headgasket.html

Unless I missed it, there is no suggestion of what to use for the o-ring itself. One illustration suggests using .041" diameter wire. I guess that would work.


This may be overkill, but again, at least I can say I tried.

#11 blitz

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Posted 10 July 2006 - 07:23 PM

The gymnastics associated with wrestling the boxer into an airframe might result in the X-over pipe becoming the highest point in the system, but on both of my cars in their stock config - on level ground, the rad-cap is clearly the highest point.

**** ******!

#12 Legacy777

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Posted 10 July 2006 - 08:44 PM

The gymnastics associated with wrestling the boxer into an airframe might result in the X-over pipe becoming the highest point in the system, but on both of my cars in their stock config - on level ground, the rad-cap is clearly the highest point.

**** ******!


You missed one word he mentioned.....the "engine" cooling system.

He's separating the systems, radiator, engine, heater core.

As to the validity of that.....ehh....I see his point, but I question it. The reason being.....you can bleed the system by opening the cap, and letting the coolant circulate and move the air to the highest point. Granted it may take a trip or two with the system pressurized to move trapped air, but it does work.

I'm not saying what he said is incorrect, but if that were the case, I'd say it's a poorly designed cooling system as a whole. I also think the air bubbles will more move then he leads on....at least in a normal car configuration. He may be running something different on the airplane.

#13 Setright

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Posted 11 July 2006 - 12:56 AM

The reasoning might be wonky, but I would agree that the likely killer is the presence of air in the cooling system.

And the flat engine will have a tendecy to trap air. Proper purging is all that's required.


I wonder, has any EJ25 HG failed on the factory filled cooling system? Or does it happen after a service where a careless mechanic has allowed air to remain in the cooling system??

#14 Wayne Boncyk

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Posted 11 July 2006 - 11:00 AM

Interesting, and pausible, but not necessarily for the exact reason that he suggests. Here's my "analytical" take on it. The cooling system operates over a range of pressures and temperatures at any given time. Obviously the coolant immediately in the water jacket around the combustion chambers and heads is the hottest, and as coolant passes thru the radiator, it cools off (as it is supposed to do). As long as there is no trapped gas in the system and as long as the system stays under the critical temperature that would allow the coolant to boil (which should be the case for any properly designed cooling system), everything is OK. BUT once you have an air bubble trapped in the system (as happens regularly with any of these subie configurations that are not properly "burped" when filled) then you introduce a compressible element into the system. Gas compresses, liquid does not (at least not very much).

Once there is a compressible air bubble in the system, no matter where it is, it can allow expansion of coolant in a hotter part of the system - that area near the HG for example. So, a gas bubble of coolant "steam" can form more easily in the water jacket of an engine that has an air bubble somewhere else in the system, without the system pressure rising much. That gas bubble in the water jacket may be the culprit that allows the Head-Block interface to warp just enough to cause the HG to blow, since cooling in the area of the gas bubble will be much less efficient than if liquid were present.

I can believe it -- but I can't prove it without being able to fully instrument an engine cooling system. That is something that Subaru should be doing!

#15 grossgary

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Posted 11 July 2006 - 11:18 AM

what are the differences between the 2.2 and 2.5? i've yet to see a local 2.2 with a blown headgasket for sale eventhough i've seen some with 200,000 plus. see about one 2.5 every month or 2 for sale with a bad headgasket....and that's only the ones that admit it! the problem areas may lie where the 2.2 platform was changed to accept the 2.5 goodies. seems to me the coolant passages would be similar since the heads are interchangeable between the two, but i've yet to open an EJ yet either.

#16 Legacy777

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Posted 11 July 2006 - 11:35 AM

That's the thing....looking at the deck of an EJ22 & EJ25....they should look very similar if not the same. So I'm not sure why the EJ25 has so many issues.

#17 nipper

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Posted 11 July 2006 - 03:18 PM

isnt the earlier 2.5 an open deck design?

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#18 blitz

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Posted 11 July 2006 - 03:38 PM

The 2.5 is a stretched design. The 2.2 was the largest displacement in the EJ-series ..until it was gambled to squeek smore 'splacement in there. :-\

Boring out the unsupported-but-adequate EJ-22 cylinder liner from 97mm out to 99.5mm leaves it thinner and weaker.

Add to that, the extra piston side-loads associated with shoe-horning a 79mm stroke into a 75mm stroke design architecture and suddenly the tops of the bore-liners are walking around a bit, carving away at the gaskets.

The top brains on Legacy Central had this all figured out and documented years ago. I'm sure that they still have various articles archived on the site somewhere.

**** ******!

#19 nipper

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Posted 11 July 2006 - 04:06 PM

i was in the autoparts store today, and along with stop leak type products, i saw a headgasket stop leak product, "desighned especially as a last ditch repair" before sepnding 1000's of dollars. the label said it was some sort of ceramic and fiber solution. You needed to drain the cooling system and flush it. Remove the offending cylinders spark plug Pour this suff in. Run the car for 15 minutes. Let it cool. reinstall spark plug. Run Again, Let cool. Drain flush and fill with coolant.

anyone heard of this?


nipper

#20 rlsimpso

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Posted 11 July 2006 - 04:53 PM

Stop leak in the combustion chamber? That seems like it would get blown out the exhaust long before it could be forced in to the gap in the head gasket? Is there an obvious way to determine where the gasket has failed?

#21 nipper

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Posted 11 July 2006 - 05:02 PM

Stop leak in the combustion chamber? That seems like it would get blown out the exhaust long before it could be forced in to the gap in the head gasket? Is there an obvious way to determine where the gasket has failed?


you can tell by exmaing the sparkplugs. the one with the bad HG will be cleaner then the others.

this is it http://www.barsprodu...oduct.cfm?id=41

nipper

#22 rlsimpso

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Posted 11 July 2006 - 05:23 PM

Interesting. I wonder it has any effect on rings or scratches in the cylinder walls.

#23 nipper

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Posted 11 July 2006 - 05:25 PM

so i guess we need a guinni pig ....
:brow:

nipper

#24 johnceggleston

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Posted 11 July 2006 - 05:37 PM

i think the operative words are "last ditch"!!! there's no way this can work. why wouldn't subaru say "use this, it works". that would be lots cheaper than new gaskets.!!



so i guess we need a guinni pig ....
:brow:

nipper



#25 Legacy777

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Posted 11 July 2006 - 06:01 PM

i think the operative words are "last ditch"!!! there's no way this can work. why wouldn't subaru say "use this, it works". that would be lots cheaper than new gaskets.!!


One...because they're in it to make money, and by charging you to replace the headgasket....they make money.

Either way, I doubt that stuff works.




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