2.5L DOHC Head Gasket Failure *PICS*

WAWalker · #1 01-29-2007, 08:07 PM

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 · #2 01-29-2007, 11:05 PM

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 · #3 01-30-2007, 06:36 AM

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

Reveeen · #4 01-30-2007, 06:49 AM

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?

grossgary · #5 01-30-2007, 08:25 AM

Quote:

Originally Posted by WAWalker

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 · #6 01-30-2007, 09:37 AM

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

grossgary · #7 01-30-2007, 10:03 AM

Quote:

Originally Posted by RallyKeith

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 · #8 01-30-2007, 10:21 AM

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 · #9 01-30-2007, 10:24 AM

Quote:

Originally Posted by unobtainium

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 · #10 01-30-2007, 10:58 AM

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.