2.5L DOHC Head Gasket Failure *PICS*

[WAWalker]

As can be clearly seen at the bottom on the cylinder, this is were the cumbustion is leaking into the coolant passages. Every 2.5 DOHC engine with leaking head gaskets leak in this same spot.

 

 

 

Should have cleaned the block up a little more for this pic, but you can still see at the bottom of the cylinder were the combustion leak is.

 

Any of the "Updated" OE head gaskets that I have seen fail...........Same Same.

 

This is a 160K mile engine. No piston slap on start up when driven into shop. Definetly hydrocarbons in the cooling system. Very little to no residue in coolant recovery bottle. These hadn't been leaking for very long. I have seen coolant recovery bottles as black a coal inside from head gaskets that had been leaking for a long time.

 

What can't be seen in the pics, and I can't get a picture to show it is..........Were the leak is, the origanal milling marks on the head and the block are worn away. They can be seen all around the rest of the matting surfaces. So, there has to have been movement between the cylinder and gasket and the head and gasket were this wear is occuring. Correct?

 

Question for those smarter than me. (1) What could be the cause of this movement? (2) How can any head gasket be designed to stop this movement.

 

Now the updated gasket.............rather than the origanal designe of one thick layer between to thin layers with a solid fire ring, they are one thick layer with two thin layer on one side one on the other, with out a solid fire ring, and the area that seats to the cylinder is graphite coated.

 

Correct me if I'm wrong......................Multi layers without a solid fire ring would allow for the layers to move aginst each other and maybe not brake the seal at the cylinder and cylinder head. Then wouldn't the movement between the layers allow for wear, then add in the fact that there is not a solid fire ring couldn't a leak develop between these layers? But then there is the graphite coating on the mating surfaces. Woould this be to allow movement at those surfaces without the wear?

 

Engineers?

[unobtainium]

Useful, good pics, thanks.

 

The milling marks can disappear because there's motion or because the hot gases from the cylinder erode them. There was a time when you'd find "gas cutting" on Alfa cylinder heads from an endemic HG problem (2L engines, long stroke, open deck + wet liners). The problem surfaced on the 2L engines because of the increased stroke over the 1750s, making for a longer block. Changing the HG every 60 k miles was just considered preventive maintenance.

 

What year car was this from? There is a vaunted fix for the '03 and later EJ25s and I'm wondering if the problem's going to surface on my '05 LGT in spite of that fix.

[weddes05]

wow, on 2 cylinders! that was a good one. mm mm mm mm mm....toasty

[Reveeen]

I hate to say this but, I don't see stopping cylinder movement with a "special" head gasket, maybe welding the block, or pinning the cylinder to the head, but gaskets alone can't be designed to stop movement.

It's the "hot" side too, pinning wouldn't be a good idea, maybe increase the cooling in that area? or make the cool side run hotter?

[idosubaru]

What can't be seen in the pics, and I can't get a picture to show it is..........Were the leak is, the origanal milling marks on the head and the block are worn away. They can be seen all around the rest of the matting surfaces. So, there has to have been movement between the cylinder and gasket and the head and gasket were this wear is occuring. Correct?

i'm almost positive that is not correct. most head gasket failures i've seen show this type of wear. even non-EJ25 engines show this. and in the ones that have been driven awhile i have seen significant amounts of material missing, like a crevice where the head is not re-usable....well it could be if you want to risk it and it could be welded/machined but i wouldn't do it. but the point is, for 1/8" of material to be missing, it is absolutely impossible for movement to cause this kind of wear. it is the leak, the heating, the gases, something else, but not movement. the ones with very little damage, just the maching marks missing, are the very beginnings of this process. like you just said and documented - this engine was at the very beginning stages and shows just very minor wear.

 

if you could circle or indicate the leakage area, that would help some people. edit in a circle or something maybe to help everyone see it?

[RallyKeith]

Is it coincidental that the failures occured on the exhaust side of the head?

 

I'm wondering if the is an inherent design flaw that is causing extremely uneven heating of the head which is causing greater expansion and contraction of only that side of the head leading to the failures. The eninge I tore apart looked bad everywhere, and the overflow tank was "black as coal." I never took the time to examine it closely like this.

 

Keith

[idosubaru]

Is it coincidental that the failures occured on the exhaust side of the head?

good point. the one completely blown head gasket i've seen, it was an XT6 not an EJ25, it was driven while overheating, it blew at the exhaust side. the exhaust side of the head would probably heat up the most?

[WAWalker]

This is a '99. But ALL DOHC '97-'99 have the SAME failure.

 

As I said the leakage is at the bottom of the cylinder. Were the dicoloration is. It is most obvious on the cylinder head. I didn't wipe the block off before taking the pic, so some of what you see there is the coating from the old gasket.

 

Gas erosion came to mind last night after posting. That makes perfect sense.

 

It is not just two cylinders it is all four. I just took pictures of the worst side.

 

One other note: This is the left bank. The right bank has more (thicker) support at the tops of the cylinders.

 

Failure on the exhaust side of the head is probably not coincidence.

 

What I am trying to get at here is the root of the problem. This does not happen to just a few of these engines. It will IMO happen to all of them.

Why is it happening? Without know this, how can we be sure that a different head gasket will prevent it from happening again?

[WAWalker]

What year car was this from? There is a vaunted fix for the '03 and later EJ25s and I'm wondering if the problem's going to surface on my '05 LGT in spite of that fix.

 

The '00 on EJ25's are SOHC engines. Different animal. I would like to get to the bottom of that problem also.

 

What is the fix you speek of for the '03 and later?

[robm]

I think WAWalker is correct about it moving. The erosion isn't due to the motion, but I bet the expansion of the unsupported cylinder is what breaks the seal. That whole side of the cylinder is unsupported, and gets hot, as it is closest to the exhaust port.

 

If someone wants to live really dangerously, and has an engine that is otherwise scrap anyway, would it be possible to jam a slab of aluminum down between the cylinder and the block to support the cylinder wall? The block would probably have to be rehoned, at the least, and lord knows what the cylinder shape would be when it warmed up. Not round is a good guess.

 

Probably not practical, but it might be interesting to try. A different way to cause a catastophic engine failure, if blowing head gaskets isn't enough fun.

 

Having seen these photos, I think I will stick to closed deck blocks. That thing looks like a problem waiting to happen.

[ccrinc]

As I have said before, I'm no expert on the actual engine rebuild process. BUT, we use a proprietary torque procedure that seems to work well. (It's a bit different than what SOA uses.)

 

I believe that procedure may be what keeps the movement you mention from happening (or at least to an absolute minimum.)

 

Just my .02 worth

 

Emily

http://www.ccrengines.com

[idosubaru]

be interesting to see similar EJ22 pic's since they don't blow headgaskets.

[idosubaru]

emily - do you have any insight on the failure of a replaced gasket? have you seen any?

 

gah, silly we didn't think to request a response from emily. they would surely know more than anyone, and be able to talk about it, about failures of a replaced EJ25 headgasket.

[cookie]

There are some guys on the west coast that use these engines in sand buggies all hopped up. They fill in the block gaps with machined alloy and weld them. Expensive as heck.

The intake charge cools the intake side so the exhaust side suffers, and yes blowby removes the material. The cheapest way for Subaru to fix this is to have a gasket material tough enough to tolerate movement and that's what they have done. O ringing would also fix it but that costs a bomb.

[WAWalker]

The cheapest way for Subaru to fix this is to have a gasket material tough enough to tolerate movement and that's what they have done.

 

So you feel that the "updated" gasket is a sure fix and under normal operating conditions it should not fail again?

[cookie]

I think it will probably go at least as long as the OE gasket if properly installed. It is always tougher to get a second gasket to work well.

In most cases that will see one of these engines to the end of the rod bearings and rings.

In MHO most engines are pretty knackered at 200,000 or so and take a bit of looking after if you nurse one to 300,000, at least in normal use. If you do the high mileage on a longer commute it is much easier on the engine.

At over 130,000 my Forester is still going fine but you have to watch the oil. By being fiddly about it I expect to see 200,000 before I sell it to some kid who will probably blow it up.

In most cases I think the last fix gaskets will last the remaining life of the engine. If somebody did not get the block and head clean and flat, or there is stuff in the headbolt holes all bets are off.

[WAWalker]

I think it will probably go at least as long as the OE gasket if properly installed.

 

My thoughts exactly. Without many on the road that are not at the aproximate miles of original failure, you can't expect anything more.

 

In most cases that will see one of these engines to the end of the rod bearings and rings.

In MHO most engines are pretty knackered at 200,000 or so and take a bit of looking after if you nurse one to 300,000, at least in normal use.

 

This maybe true. But.............................

2.2L Subrau engines have been know to go 300k still running strong. There is not that much difference between the lower ends, so why can't a 2.5L do it.

I think the demise of most 2.5L DOHC's is over heating due to head gasket failure. Repeat and/or severe over heating takes a toll on the entire engine.

My veiw on this is......................If people would just accept the fact that the head gasket failure is a real problem and will most likely happen to their DOHC 2.5. Then maintanance can be approched is such a way that the head gasket failure can be taken care of before it leads to over heating, in turn avoiding unessasary engine wear. And likely provide a longer engine life.

I have replaced head gaskets on these engine with as little as 88k and as much as 189k. Is it prudent to replace head gaskets on a 189k mile engine? If it's not using oil, doesn't have pistion slap, compression is good, and the owner doesn't want to buy a new car?

Now if the replacement gaskets start failing on these engines at the same aproxament milage as the origanals did...............the engine that would be pushing the 300k mile mark wouldn't be a canadit for another repair, but the one that would be pushing the 200k mark, if everything eles checked out, why not.

[cookie]

Some of the high mileage ones have had rod bearing failure after replacement. I'm sure the overheating does an engine no good and for me preemptive replacment would be in order. I put my money where my mouth was after all and had my head gaskets replaced on my Phase 2 at about 89,000. All I had was a tiny weep mark.

The 2.5 is going to put a bit more strain on an engine for the few ccs more and who knows what too much is.

If I had a 2.5 that was otherwise perfect and had high mileage I'd probably risk a gasket change. If it was already burning a bit of oil I think I'd call Emily.

No arguement the 2.2 could hit 300,000 while the car falls apart around it.

[RallyKeith]

Some of the high mileage ones have had rod bearing failure after replacement. I'm sure the overheating does an engine no good and for me preemptive replacment would be in order.

 

The higher mileage ones that show rod bearing failures is not due to the over heating. The big problem is that when these gaskets fail, they don't fail big. They go a little bit, and go un-noticed by the driver for many miles. During that time some coolant is sucked into the oil. That coolant in the oil eats away at the bearings and is what truely causes that failure. The longer you drive it with the blown head gasket, the shorter the bottom end will live.

[WAWalker]

Some of the high mileage ones have had rod bearing failure after replacement.

 

I assume you are refuring to the SOHC 2.5L. Yes, I have seen this with the SOHC engine before and after head gasket replacement, due to oil comtamination from the coolant leak.

 

Rod bearing failure in the DOHC is fairly uncommon due to oil comtamination. I don't see antifreeze contamination as a problem in the DOHC engine, but have seen MANY that have had the oil hot enough to melt the sickers off oil filters, and bubble the grippy stuff on the FRAM oil filters. Have seen them hot enough to seize the pistons in the cylinders (they usually run after cooled down). That kind of heat and expantion of parts ain't doing the bearings, rings, or pistions any good, and they ain't going to last after that.

The DOHC head gasket leak is a funny thing. Try to diagnoise it on a cold engine, probably not going to find it. This is a big reason why so many of these cars get t-stats, water pumps, and radiator thrown at them before anyone decides to fix the head gaskets, by that time they have probably over heated enough times that they are questionable for repair. It dosen't leak all the time. Normally the leak will only occure when the engine is at full opperating temp. and under load. Idleing, and in town driving, more often than not will not cause leakage. When driven at highway speeds there is enough combustion chamber pressure to push past the gasket. There isn't enough cooling system pressure to push coolant into the combustion chamber. There for no antifreeze contamination of the oil.

 

But as I keep saying. The SOHC head gasket failure is a different animal. And one I would like to discuss. Mixing the two in the same thread only causes confusion though.

[cookie]

I should not have mentioned my engine then. No I meant the DOHCs when I said rod bearing failure and I suspect the cause is very much as Rallykeith postulates, plus a bit more load.

I merely used my phase 2 as an example to prove I would change any head gasket that was suspect.

They did manage to contain the cylinder gasses with the same wimpy sealing surface on the phase 2, so it can be done. Now if they can just keep the coolant in the engine at the same time....

[WAWalker]

I should not have mentioned my engine then. No I meant the DOHCs when I said rod bearing failure and I suspect the cause is very much as Rallykeith postulates, plus a bit more load.

 

Well, I've done 30+ DOHC head gasket replacements with not one comeback for rod bearing failure or anything eles. I see a lot of first timers come though the shop with new head gaskets that have been installed eleswere still running strong. I don't hear from other shops about rod bearing failure after head gasket jobs. So just have not seen this as a problem on the DOHC engines. SOHC, different story. Have seen more rod bearing failure in the last year with them, than DOHC's in the last 5 years. Maybe I'm just not looking in the right place.

[RallyKeith]

Something that I feel should be mentioned is the replacement of the head bolts. WAWalker, do you install new head bolts when you do the gaskets? I spent some time discussing this before both on the USMB, and with the head mechanic at my local subaru dealer. The Torqueing procedure for the head bolts stretches the bolts. The bolts are then further stretched once the engine gets hot, and of course further once over heated. My local dealer said that they were originally not replacing the bolts when doing the headgaskets. They also were having cars come back a second time needing new head gaskets. They said that about 2 years ago now, they starting replacing the head bolts, and ther were getting fewer cars back for repeat headgaskets. If I were doing the job, and I have, I would spend the $100 and replace the head bolts right away.

 

Keith

[cookie]

I'm sure you are seeing your area's problems. I have not heard about rod bearing failures yet on phase 2s. I've only heard of a few phase 1 rod bearing failures after repair and I always wondered just how bad they were in the first place. Come to think of it the failures do have something in common, Donner pass in the mountains. This was also where a revered board member bit the dust (with original head gaskets).

Now I have to worry about my rod bearings on the way home. The phase 2s are just getting old enough to have the big problems now.

[WAWalker]

Something that I feel should be mentioned is the replacement of the head bolts. WAWalker, do you install new head bolts when you do the gaskets? I spent some time discussing this before both on the USMB, and with the head mechanic at my local subaru dealer. The Torqueing procedure for the head bolts stretches the bolts. The bolts are then further stretched once the engine gets hot, and of course further once over heated. My local dealer said that they were originally not replacing the bolts when doing the headgaskets. They also were having cars come back a second time needing new head gaskets. They said that about 2 years ago now, they starting replacing the head bolts, and ther were getting fewer cars back for repeat headgaskets. If I were doing the job, and I have, I would spend the $100 and replace the head bolts right away.

 

Keith

 

No I do not replace head bolts. Don't know of to many people who do. Dealers will do most anything and spend as much of your money as they feel the need to in order to limit their liability.

The last I heard, and I hope Emily will correct me if I'm wrong, CCR doesn't install new head bolts. They say to go ahead and reuse them. Emily?