I think I must have bought myself one of the rarest OBWs out there. I thought it had a blown head gasket because the compression read 28psi in one hole, which would make it very common. But this one's special. I tore the heads off today and the gaskets, factory original at that, looked great. It was only when I looked closer that I realized what the problem was.

 

See anything wrong here?

 

 

 

No? What about here?

 

 

 

Busted exhaust valve. The gasket looked perfect. How's that for freaky?

But since I'm in here already, the other head is coming off, both are going in for a quicky valve job. Should have this bad boy back on the road by next weekend, all for less than $1500 including the purchase price. Yeeeeeehaw!:cool:

Nice photos. I am wondering what would cause the valve to be damaged like that. Not seating correctly?

Well, it could have just been one of those parts that didn't come off the assembly line quite up to the standard. Hard to say, really.

which cylinder? Mine was # 3 in 99 forester

Well, it could have just been one of those parts that didn't come off the assembly line quite up to the standard. Hard to say, really.

My guess? Something (pick a reason) caused the valve/seat to "burn", and it just devolved from there. Once the valve head can't make proper contact with a spot on it seat, that part of the valve head will start to overheat and erode.

 

Saw something similar in a motorcycle engine...

 

Beautiful pics!!!

Great pics, and interesting story. Thanks.

would noone be concerned about where those pieces went? through the oil supply, stuck in a crank bearing somewhere? i'm not saying that would happen, just that i don't know. but if pieces are missing that is strange.

would noone be concerned about where those pieces went? through the oil supply, stuck in a crank bearing somewhere? i'm not saying that would happen, just that i don't know. but if pieces are missing that is strange.

No (practical) connection between combustion chamber and oil supply. Even if it got down into the pan either the pickup screen, the oil pump gears, or the filter would have trapped them.

 

The usual scenario for foreign objects entering the combustion chamber is they may rattle around and ding the piston crown and combustion chamber and then exit out of the exhaust valve and on downstream to pipe (or turbo...). There is no obvious combustion chamber damage (though there is some odd looking stuff in the picture to the left of the valve), and the exhaust valve itself does not appear to have "broken" inwards anyways.

 

I still hold with a badly burned valve.

cool, just curious since i'm unfamiliar with this kind of internal block stuff, not trying to scare anyone or make a problem out of nothing.

which cylinder? Mine was # 3 in 99 forester

Ladies and gentlemen, we have a winner! And a pattern, perhaps! #3 it was.

 

This car was religiously serviced at Jiffy Lube. They lost one of the two clips that holds the air cleaner halves together and, rather than letting the mechanically ignorant former owner know, they just mooshed the two halves together and used the one clip. When I bought the car it was running like hell and the air cleaner housing was up on one corner. There was evidence that unfiltered air had made its way into the engine (more dust than you would expect on the clean side of the filter and in the intake). There's a screen near the MAF that would stop stones from getting through, but it wouldn't surprise me if some grit made its way in and got stuck between the valve and seat.

 

Just a thought, mostly because I hate Jiffy Lube and try to blame them for every single problem I encounter in life.

... Just a thought, mostly because I hate Jiffy Lube and try to blame them for every single problem I encounter in life.

...Like JL telling me that all tires on a tow vehicle were properly inflated prior to a certain LONG trip. Left rear was around 17PSI...

Busted exhaust valve... burnt.. unless the pieces burned so hotly that they disentegrated(sp?) into exhaust.. they are probably trapped in the exhaust system... most likely in the catalytic converter... I had something similar to this happen on a Yamaha Blaster... the top of the piston started coming apart like that.. and a pretty decent pebble size chunk made it into the "big" part of the exhaust and wont come out either direction.. so it's just in there rattling.. dont feel like cutting and welding

I think I must have bought myself one of the rarest OBWs out there. I thought it had a blown head gasket because the compression read 28psi in one hole, which would make it very common. But this one's special. I tore the heads off today and the gaskets, factory original at that, looked great. It was only when I looked closer that I realized what the problem was.

 

See anything wrong here?

 

 

 

No? What about here?

 

 

 

Busted exhaust valve. The gasket looked perfect. How's that for freaky?

But since I'm in here already, the other head is coming off, both are going in for a quicky valve job. Should have this bad boy back on the road by next weekend, all for less than $1500 including the purchase price. Yeeeeeehaw!:cool:

 

Just a tought : that's exactly where the piston would contact the edge of the valve in an interference episode.

The valve was probably burnt due to lack of periodic adjustment.

The valve was probably burnt due to lack of periodic adjustment.

 

Probably. But why there and at no other place on the valve outer perimeter? I was just offering a possible answer to that question.

The valve was probably burnt due to lack of periodic adjustment.

Well, that's a thought... But there's no sign of valve contact with the piston.

 

This is just one of those great, unsolvable mysteries.

A burnt valve in an EJ25 engine is common. It's one of the weaker points...that's why we always use new exhaust valves. Cause? Probably running too lean. And once the damage is started, it continues even after the problem is fixed.

 

Emily

http://www.ccrengines.com

Thanks for the input Emily. You folks should know.

...but valves that fall out of adjustment tend to have greater lash than those in adjustment. Which means the valve would have been noisy, which they weren't. And there's no sign of valve contact with the piston.

 

That's not always true. Valves with too much lash generally don't get burnt. My observation has been that exhaust valves in this engine burn due to too little lash. For this to happen only requres more valve seat wear than lifter/cam wear. Things get to a point when the valve in question isn't fully closing, then heat isn't transferred properly from the valve to the head, and the valve overheats and fails.

As far as contact between the piston and the valve...

 

Last I knew, valves rotate during operation. The postion of the burnt / busted spot in the picture has no relevance AFAIK.

 

Commuter

As far as contact between the piston and the valve...

 

Last I knew, valves rotate during operation. The postion of the burnt / busted spot in the picture has no relevance AFAIK.

 

Commuter

 

I was making myself the same objection when I wrote my post. But I never was sure that is what is really happening (valve rotation). How do we know this? Not that I'm holding up the opinion that the cause of the break was a contact between valve and piston since q240z did'nt see any sign of a contact on the piston top and 99obw explanation is quite satisfactory.

That's not always true. Valves with too much lash generally don't get burnt. My observation has been that exhaust valves in this engine burn due to too little lash. For this to happen only requres more valve seat wear than lifter/cam wear. Things get to a point when the valve in question isn't fully closing, then heat isn't transferred properly from the valve to the head, and the valve overheats and fails.

AVAST YE!! You posted this four minutes after I edited that brainfart out of my post! You must have quoted me before I snuck the edit in.

 

Good call, btw.:-p

FRESH UPDATE

 

I just got an email from www.1stsubaruparts.com telling me that their Overhaul Gasket Set doesn't include valve cover gaskets, spark plug gaskets, or the half-moons on top of the head. I wish they'd advertize it as an Incomplete Overhaul Gasket Set...