2.5L DOHC Head Gasket Failure *PICS*

[WAWalker]

Closing the deck or O ringing would fix it but be more expensive. They seem to have been going the cheapest way which would be a gasket capable of taking movement.

This also explains why engines often fail on a long trip. You get into another whole level of heat soak then and my thoughts are that the liner moves then.

 

The point of this thread was to try and help people to understand the nature of the beast.

 

Yes, there are very expensive ways to "fix" the problem, but not realistic for the every day driver.

 

I think the best that the every day driver can do is to understand and accept the "problem" and make their decisions as to how to minimize unwanted break downs and engine failures based on the nature of the problem. Rather than based on statements like "The updated gasket fixes the problem". Subaru never told anyone what the CAUSE of the problem is, or that the updated gasket was designed to FIX the problem. They just gave us the "updated gasket" and stoped making the engine. Just seems fishy to me. There has been enough dissapointment over this engine as it is. If it turns out the problem is engine design that a gasket can't fix, there is sure to be a lot more dissapointment.

 

Make informed decisions. If you like the car your driving and want to keep it..............................

 

I say put the "updated" gaskets in, your engine, or a rebuilt, hope for the best, but don't rule out another failure.

This is the approach I take, and everything that has come up in this thread so far tells me that it has been a very good decision.

[nipper]

The point of this thread was to try and help people to understand the nature of the beast.

 

Yes, there are very expensive ways to "fix" the problem, but not realistic for the every day driver.

 

I think the best that the every day driver can do is to understand and accept the "problem" and make their decisions as to how to minimize unwanted break downs and engine failures based on the nature of the problem. Rather than based on statements like "The updated gasket fixes the problem". Subaru never told anyone what the CAUSE of the problem is, or that the updated gasket was designed to FIX the problem. They just gave us the "updated gasket" and stoped making the engine. Just seems fishy to me. There has been enough dissapointment over this engine as it is. If it turns out the problem is engine design that a gasket can't fix, there is sure to be a lot more dissapointment.

 

Make informed decisions. If you like the car your driving and want to keep it..............................

 

I say put the "updated" gaskets in, your engine, or a rebuilt, hope for the best, but don't rule out another failure.

This is the approach I take, and everything that has come up in this thread so far tells me that it has been a very good decision.

 

There is some solice in the fact that subaru isnt the only one with this issue.

 

nipper

[WAWalker]

There is some solice in the fact that subaru isnt the only one with this issue.

 

nipper

 

I understand this. And It is a good point. I am aware of a lot of these other issues, not all, but a lot.

Subarus are my bread and butter. I do my best to educate my customers about their cars and problems associated with. I also tell them that every car maker has its problems, so just because they are upset with their Subaru, going to another make isn't nessasarly going to give them a lifetime of trouble free driveing. They will just have to learn about a different car, and find a different mechanic.

[nipper]

I understand this. And It is a good point. I am aware of a lot of these other issues, not all, but a lot.

Subarus are my bread and butter. I do my best to educate my customers about their cars and problems associated with. I also tell them that every car maker has its problems, so just because they are upset with their Subaru, going to another make isn't nessasarly going to give them a lifetime of trouble free driveing. They will just have to learn about a different car, and find a different mechanic.

 

i wasnt picking on you.

 

Just to give everyone an idea how a gasket works. I was designing and making gaskets by hand for a long time (fuel cell company). I learned a lot. Almost all the selaing a gasket does is on the edge of the gasket. Once this edge is compromised, gasket failure will soon follow.

A head GAsket is one of the hardest gaskets (if not the hardest)

to design. On one side it has 18,000 psi gasses at a ludicrous tempertiur it has to seal against an open chamber with much cooler liquids on the other side. Then you need something that will survive Antifreeze, deionized water, and engine oil. You also need something that will deal with the expnasion and contraction of aluminum, while being helod in place with steel bolts. Since the steel bolts do not expand and contract as quickly as the aluminum, you have additional varrying compression forces.

With a closed deck, you had the assitance of the metal deck to help counter some of these forces. With an open or "hybrid" deck, this assitance is removed.

Now add in steel piston sleeves. This makes for a very very very complicated system. A open or hybrid deck does not fully support the piston sleeves as well as a closed deck. I think someplace in here is the key to the problem.

I dont know if the 6cyl and H6 is a hybrid or closed deck design. I feel that they dont fail because you have a much more even application of clamping forces (3 Cylinders as opposed to two and the applicable bolts)

All the forces are more spread out. In the past 10 years HG development and design have grown leaps and bounds. IS the pronblem solved, most likely. Will it ever appear again in another design (generically speaking - other mfgs) probably, as emission laws change, so do the design requirements of this gasket.

 

nipper

 

PS if you over heat don't forget to get an oil change, as the oil gets hot too.

[WAWalker]

I know you weren't picking on me. (this time:grin: ).

I was just explaining my position on the subject. Some would have me tared and feather for my suggegstions of "Head gasket maintainence". Or if I told them that if they buy a VW 1.8L Turbo, to replace the timeing belt and water pump @ 60k miles, when the owners booklet cleary states 100 and some k for t-belt replacement.

[Setright]

Pardon me for being tardy:

 

 

I'd stick with a Subaru Genuine rad cap to replace the old one.

 

Over here at least, the factory fitted caps read "1.1 Bar" and the replacements read "108Kpa". The same rating, yes, but the new text indicates a revised part.

[The Dude]

I have driven a lot of cars, and Subaru is the only one I have driven with the "mystery" temp gauge. You know, as soon as the car reaches operating temperature, the needle just stays there in the middle of the gauge. No mater how heavy the load, or how high the ambient temperature, there is absolutely no movement in the gauge needle. Why? What benefit does the driver get from NOT being able to see the heat loading of his engine? What would we see if a Subaru had a "normal" analogue temp gauge? Maybe wild and extreme swings in engine temperature, with even higher transient heat spikes. So, why does Subaru have that strange "three stage", no in between coolant temp gauge?

[johnceggleston]

not much different than a red warning light, only harder to notice.

 

I have driven a lot of cars, and Subaru is the only one I have driven with the "mystery" temp gauge. You know, as soon as the car reaches operating temperature, the needle just stays there in the middle of the gauge. No mater how heavy the load, or how high the ambient temperature, there is absolutely no movement in the gauge needle. Why? What benefit does the driver get from NOT being able to see the heat loading of his engine? What would we see if a Subaru had a "normal" analogue temp gauge? Maybe wild and extreme swings in engine temperature, with even higher transient heat spikes. So, why does Subaru have that strange "three stage", no in between coolant temp gauge?

[The Dude]

Ok, South Carolina isn't exactly the South Pole. But we do need our car heaters in the winter. I have never driven a car that reaches operating temperature as rapidly as the Subaru Forester. It's uncanny. Even with ambient temps in the high twenties, the temp guage is showing fully heated and heat is pouring out of the heater after only one mile of operation. Is this normal? Why does the Subaru heat up so quickly?

[WAWalker]

Ok, South Carolina isn't exactly the South Pole. But we do need our car heaters in the winter. I have never driven a car that reaches operating temperature as rapidly as the Subaru Forester. It's uncanny. Even with ambient temps in the high twenties, the temp guage is showing fully heated and heat is pouring out of the heater after only one mile of operation. Is this normal? Why does the Subaru heat up so quickly?

 

The entire cooling system only holds like 6.3 quarts of antifreeze. Only what is in the engine and heater core has to warm up in order to have heat, maybe like a gallon of antifreeze.

[Tech1967]

Anyone else notice the "coolant conditioner" goops up the rad cap and prevents it from sealing?

[WAWalker]

Pardon me for being tardy:

 

 

I'd stick with a Subaru Genuine rad cap to replace the old one.

 

Over here at least, the factory fitted caps read "1.1 Bar" and the replacements read "108Kpa". The same rating, yes, but the new text indicates a revised part.

 

Yes, having a good radiator cap is part of good cooling system maintenance. Yes, they go "bad" fairly offten. Most bad ones still hold some pressure.

I've seen you post this in another thread.

Loss of coolant through the recovery bottle due to a bad cap is going to be minimal. The coolant in the system can only expand so much under normal conditions. In order for excess amounts of coolant to be pushed out there has to be somthing creating more pressure than the expanssion of the coolant itself, i.e. combustion gases, or of course boiling of the coolant=vapor. And yes, the coolant will boil at a lower temp if not under pressure. But most if not all 2.5L DOHC engines with failed head gaskets have obvious signs of hydro carbons in the cooling system.

[WAWalker]

Anyone else notice the "coolant conditioner" goops up the rad cap and prevents it from sealing?

 

Shouldn't be an issue on the DOHC engines. The "coolant conditioner" should not be added to these engines.

 

That being said................Yes. On the 2.5L SOHC engines that have had the magic stop leak added, it goops up the radiator cap, and the bottom of the coolant recovery bottle. Having the valve in the radiator cap and the hose in the recovery bottle plugged will cause coolant to not be drawn back into the cooling system as the engine cools. The recovery bottle becomes over filled and radiator level gets low.

[jon38iowa]

Ok, South Carolina isn't exactly the South Pole. But we do need our car heaters in the winter. I have never driven a car that reaches operating temperature as rapidly as the Subaru Forester. It's uncanny. Even with ambient temps in the high twenties, the temp guage is showing fully heated and heat is pouring out of the heater after only one mile of operation. Is this normal? Why does the Subaru heat up so quickly?

My Forester takes forever (at least five minutes) even in the summer, for the gauge to slowly creep up to the near center mark. It has been this way since day one and even after two rebuilds.

[cookie]

My Forester is also no rocket on the temp. My BMW with much larger engine and cooling system warms up quicker. The little alloy engine in the Forester also cools down quickly. Of course I only notice at all on cool days.

[nipper]

After owning a GL with a 1.8L engine, and various cars with less then 2L capacity, i think my 2.5L kicks but in the heat department. those other engines once it got below 25 had no heat.

 

Now look at the subaru engine. it is essentially two 2 cylinder engines opposing each other. you have twice as much surface area and water jacket area exposed to air. So they will be a little slow to warm up.

 

nipper

[Tech1967]

Shouldn't be an issue on the DOHC engines. The "coolant conditioner" should not be added to these engines.

 

That being said................Yes. On the 2.5L SOHC engines that have had the magic stop leak added, it goops up the radiator cap, and the bottom of the coolant recovery bottle. Having the valve in the radiator cap and the hose in the recovery bottle plugged will cause coolant to not be drawn back into the cooling system as the engine cools. The recovery bottle becomes over filled and radiator level gets low.

 

 

What about localized hotspots causing a layer of insulating vapor between the cylinder and the coolant. This was one of those 5min discussions at school years ago. I was interested but havent found anything on it since. Would not lack of pressure in the system make this possible or worse if already there? If so this would contribute to uneven expansion.

 

This will tie in to what I've learned about the cooling system when I can figure out how to get my pictures to work. Seems like a good spot for an engineer to pipe up too.

[nipper]

What about localized hotspots causing a layer of insulating vapor between the cylinder and the coolant. This was one of those 5min discussions at school years ago. I was interested but havent found anything on it since. Would not lack of pressure in the system make this possible or worse if already there? If so this would contribute to uneven expansion.

 

This will tie in to what I've learned about the cooling system when I can figure out how to get my pictures to work. Seems like a good spot for an engineer to pipe up too.

 

you rang?

 

nipper

[hankosolder2]

Just to inject another possibility into this thread- does anyone think that the position of the thermostat might have something to do with HG failures? Putting the thermostat on the coolant intake of the engine is common practice nowadays for a variety of manufacturers...supposedly it promotes quicker warm-up, but it also seems like there would be a greater lag in the T-stat responding to a sharp increase in engine temperature, like when a cold engine is flogged hard. Almost all older cars had the T-stat on the outlet TO the radiator.

I know that thermostat location has been indentified as a source of HG failure in the Rover K-series engine (aftermarket companies have come out with thermostat relocation kits!) and wonder if the same possibility could apply to the EJ25. (I'm not asserting that it DOES, I'm just suggesting that it might be possible in my somewhat uninformed opinion.) Any thoughts, gang?

 

Nathan

[nipper]

Just to inject another possibility into this thread- does anyone think that the position of the thermostat might have something to do with HG failures? Putting the thermostat on the coolant intake of the engine is common practice nowadays for a variety of manufacturers...supposedly it promotes quicker warm-up, but it also seems like there would be a greater lag in the T-stat responding to a sharp increase in engine temperature, like when a cold engine is flogged hard. Almost all older cars had the T-stat on the outlet TO the radiator.

I know that thermostat location has been indentified as a source of HG failure in the Rover K-series engine (aftermarket companies have come out with thermostat relocation kits!) and wonder if the same possibility could apply to the EJ25. (I'm not asserting that it DOES, I'm just suggesting that it might be possible in my somewhat uninformed opinion.) Any thoughts, gang?

 

Nathan

 

 

nope then every subaru engine would have this issue, including the 2.2.

The problem is the HG design, not anything else (in conjunction with the open deck and higher combustion conditions).

 

nipper

[Tech1967]

That's funny. The guy in the next building has been trying to get a Land Rover and an Olds Aurora to seal for a few months. I'll pass that on to him.

 

Maybe we've just passed beyond the conditions that the t-stat design is effective in. Hell maybe the whole cooling system needs some tweaking. I don't think that makes the whole engine design a write off though.

 

When you have one apart take a look at the coolant flow path around the cylinders. Intake above the block heater, approx 5/8" hole at 7:30 to bore two as you look at it on the stand. Exhaust side of the jacket separated from the intake by the siamesed cyls and where the bores meet the rest of the block front and rear, forcing the coolant flow from bottom to top through the head. Exits through approx 5/8" vertical hole to the transfer pipe at about 10:30 to bore four. Looks like the bottom right corner where the first oil and coolant appear is last in line for pressure and off to the side from a direct line between coolant in and coolant out. There is a distinct difference between the amount of deposits to the rear of the exit and the rest of the jacket. Deposits that aparently impede the transfer of heat from cylinder to coolant (I think it's in one of my propane books). It's like an avalanche of little problems pushed over the edge by one too many displacement increases.

 

If I could afford a test mule I'd consider popping 6 or 8 cheap single wire sensors in the block, an extra coolant pipe in the bottom rear corners of the block with a valve or orifice pipe, and flog 'er with a multimeter and a chart if I had to.

[hankosolder2]

nope then every subaru engine would have this issue, including the 2.2.

The problem is the HG design, not anything else (in conjunction with the open deck and higher combustion conditions).

 

nipper

 

Nipper,

I see your logic here, but I think you're failing to consider that factors can "stack." The 2.2 has more sealing area around the bores, so perhaps it tolerates thermostat location induced temperature spikes better than the 2.5. A design which is closer to the limit will be more sensitive to any one of a number of factors...the more temp variations the engine sees, the more movement will occur between the liners and head....notice that most of the high mile ej25s without HG failure are driven on the highway (in a 'steady state' condition, as opposed to many warm up/cool down cycles.) That's just my theory, and once again, I'm not saying that T-stat location is the magic bullet, just possibly one of a number of factors in the situation.

 

Nathan

[hankosolder2]

That's funny. The guy in the next building has been trying to get a Land Rover and an Olds Aurora to seal for a few months. I'll pass that on to him.

 

The Rover K-series engine is a 4 cyl <= 1.8 liters and was only (IMHO) used in cars sold in the UK and Europe... I think it was only used in the Lotus Elise sold in the states. So I don't think thermostat relocation applies to any of the US Land Rover engines- I didn't want to make a misleading comment!

 

Nathan

[Tech1967]

That's funny. The guy in the next building has been trying to get a Land Rover and an Olds Aurora to seal for a few months. I'll pass that on to him.

 

The Rover K-series engine is a 4 cyl <= 1.8 liters and was only (IMHO) used in cars sold in the UK and Europe... I think it was only used in the Lotus Elise sold in the states. So I don't think thermostat relocation applies to any of the US Land Rover engines- I didn't want to make a misleading comment!

 

Nathan

 

Ah. I think this one may be an 8. Didn't even look though, just laughed and teased on the way by.

[Tech1967]

you rang?

 

nipper

 

You've had plenty of time to consult your library, any facts on this?