Piston damage or head gasket?
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I've had two different mechanics look at my V7 JDM STI and they both suspect different faults. One thinks I've fried a piston and the other thinks it's probably only a head gasket.
The fault occured whilst driving hard in 6th gear. For some reason I lost Power and when I pulled over it was only running on what sounded like three cyliners. It didn't cut out at all or make any loud engine type noises and still managed too get me 2 miles home(slowly). It still starts and idles (on three cylinders) and hasn't lost any water or oil to speak of. The only patch of oil I can see is by the turbo.
If anyone could shed any light or input any opinions as to what might be or is most probable to be wrong, I'd really appreciate it.
Thanks for any replies.
The fault occured whilst driving hard in 6th gear. For some reason I lost Power and when I pulled over it was only running on what sounded like three cyliners. It didn't cut out at all or make any loud engine type noises and still managed too get me 2 miles home(slowly). It still starts and idles (on three cylinders) and hasn't lost any water or oil to speak of. The only patch of oil I can see is by the turbo.
If anyone could shed any light or input any opinions as to what might be or is most probable to be wrong, I'd really appreciate it.
Thanks for any replies.
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It has lost compression on cylinder 4 and a bit on 3 I've been told.
But would it run at all if the piston has gone? Or should I have clouds of smoke coming out the exhaust?
But would it run at all if the piston has gone? Or should I have clouds of smoke coming out the exhaust?
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I'm doubtfull the piston will have fried, the STi7 has forged pistons as standard, unless your runnig silly boost without mapping, pistons should be fine. Number three normally goes on other engines.
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons
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I'm doubtfull the piston will have fried, the STi7 has forged pistons as standard, unless your runnig silly boost without mapping, pistons should be fine. Number three normally goes on other engines.
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons![Lol1](https://www.scoobynet.com/images/smilies/lol1.gif)
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons
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Either way, its engine out time for a proper inspection, rather than speculation.
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I'm doubtfull the piston will have fried, the STi7 has forged pistons as standard, unless your runnig silly boost without mapping, pistons should be fine. Number three normally goes on other engines.
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons![Lol1](https://www.scoobynet.com/images/smilies/lol1.gif)
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons
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I'm holding on to that glimmer of hope that my £1k budget can save the scoob!
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Forged pistons are not indestructable. They melt almost as easily as cast ones. Any piston can melt....just because one cylinder may be more common that others, doesnt mean it doesnt happen to others.
Either way, its engine out time for a proper inspection, rather than speculation.
Either way, its engine out time for a proper inspection, rather than speculation.
Forged pistons do melt but not a readily as normal cast piston otherwise you would fit forged pistons when building a bullet proof engine, you'd just stick standard pot cast jobbies in.
Diagnostics of the engine will decide whether he will sell, or repair. I'm only trying to help, cheap first is the obvious thing to start with imo, not, "ah just pull the engine and wrip it apart, thats the only way to see what wrong with it"
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I'm doubtfull the piston will have fried, the STi7 has forged pistons as standard, unless your runnig silly boost without mapping, pistons should be fine. Number three normally goes on other engines.
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons![Lol1](https://www.scoobynet.com/images/smilies/lol1.gif)
I'd say head gasket, when you say you've lost no water or oil, have you actually checked the water & oil levels? It normally goes between water way/oil way/bore & bore, not normally visable externally unless the car has been hydraulic'd.
Pressurise the coolant system, if it looses pressure, that would confirm my thoughts.
STi7's dont fry pistons
![Lol1](https://www.scoobynet.com/images/smilies/lol1.gif)
that'll be why there are quite a few "warranty" blocks doing the rounds with piston/bore damage??
we see quite a few failures of the STi hyperpeutic (spelling??) pistons - n0.3 not generally being the most common
best advice is as above and get it checked correctly before starting to pull it to bits
alyn
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The EJ207 had forged pistons up through v7. Since that time Subaru switched over to hypereutectic, version 8 onwards meaning version 7 had proper forged piston fitted from what I know.
Last edited by Northern Nick; 30 April 2008 at 12:30 PM.
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there is another thread discussing this and Zen confirmed that the STi8 uk has forged pistons.
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Head gasket, Piston damage, or valve/seat damage.
Any mechanic with half a wit, should be able to make a proper diagnosis fairly quickly after hearing it running ( or cranking over if it wont start ), and doing a compression/leakdown test, as well as a quick look at the plugs.
If they cant, take it elsewhere.
Any mechanic with half a wit, should be able to make a proper diagnosis fairly quickly after hearing it running ( or cranking over if it wont start ), and doing a compression/leakdown test, as well as a quick look at the plugs.
If they cant, take it elsewhere.
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I've got to say I'm glad I posted this. I thought the scoob was doomed and you've all given me plenty to get checked out. Any more suggestions are welcomed. Thanks all.
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P.S my car was not using oil or water and comprision tesk 100% ok
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Thanks m8. There might be some hope left then. However, mine idles but won't rev past 3.5k really. I gotta grand in reserve to sort it. If that doesn't just about cover the problem then it's gonna have to go. I hope mine is a head gasket!
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regardless of factroy "forged" or later hyperpeutic pistons they fail just the same (albeit maybe slightly higher) as std ones, we re-build quite a few of these
alyn
alyn
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https://www.scoobynet.com/general-te...lp-my-wrx.html
take a look at that, tried many things, sounds like same issues youre having, sorry mate![Frown](https://www.scoobynet.com/images/smilies/frown.gif)
I got a new engine in the post
take a look at that, tried many things, sounds like same issues youre having, sorry mate
![Frown](https://www.scoobynet.com/images/smilies/frown.gif)
I got a new engine in the post
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https://www.scoobynet.com/general-te...lp-my-wrx.html
take a look at that, tried many things, sounds like same issues youre having, sorry mate![Frown](https://www.scoobynet.com/images/smilies/frown.gif)
I got a new engine in the post![Wink](https://www.scoobynet.com/images/smilies/wink.gif)
take a look at that, tried many things, sounds like same issues youre having, sorry mate
![Frown](https://www.scoobynet.com/images/smilies/frown.gif)
I got a new engine in the post
![Wink](https://www.scoobynet.com/images/smilies/wink.gif)
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