melted piston!!
25 October 2004, 08:37 PM
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melted piston!!
I purchased an impreza turbo (my99) back in August. It had done 56k miles, had full service history and appeared to have been really well looked after with just uprated brakes (black diamond discs, mintex pads and braided hoses all round) and a pro drive back box.
I was completely devastated and very concerned for my wallet when a run on the motorway the other week ended with a complete loss of power and loads of smoke pouring from the exhaust and an engine which appeared to be only running on 3 cylinders. My local Subaru dealer confirmed a piston had melted but couldnt say if the bore had taken any damage.
The car is now off to Scooby clinic but Im not sure how far I should go with tuning and replacing other worn parts like the clutch and turbo etc which will probably go in the not to distant future.
Any ideas?
I was completely devastated and very concerned for my wallet when a run on the motorway the other week ended with a complete loss of power and loads of smoke pouring from the exhaust and an engine which appeared to be only running on 3 cylinders. My local Subaru dealer confirmed a piston had melted but couldnt say if the bore had taken any damage.
The car is now off to Scooby clinic but Im not sure how far I should go with tuning and replacing other worn parts like the clutch and turbo etc which will probably go in the not to distant future.
Any ideas?
25 October 2004, 08:48 PM
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Originally Posted by jjones
how fast were you going before this happened? and for how long?
I had been going for about 20 0dd miles from home. i always let everything heat up properly before going over 3000rpm. Once everything was up to temperature i sat at 90 for a short while before stopping in some services for a coffee. i opened it up going back up the slip road to rejoin the motorway and was doing just about a tonne when i lost power all of a sudden and made the decision that this was serious and stopped immediatly
25 October 2004, 08:51 PM
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I had the same thing the weekend lol on the motorway and lost all power (no boost) and when i looked in the mirror i had filled the road with smoke... good head turner tho 
) drove it back not out of choice but made it home done a compression check and i have 165 on 3 and bugger all on the other sent the turbo off before i did a compression check and found someting had left the engine and mad its way through the turbo 
so its turbo and engine strip down....
what i want to know is it a linered engine...can they be removed or are they pressed in plus whats the cost of i.e. pistons, rings, and liner if its is ofcourse linered....
and does the lump come out from the top as easy as it looks i resheld mine but sat the car on the engine and running gear so i dont know....
) drove it back not out of choice but made it home done a compression check and i have 165 on 3 and bugger all on the other sent the turbo off before i did a compression check and found someting had left the engine and mad its way through the turbo so its turbo and engine strip down....what i want to know is it a linered engine...can they be removed or are they pressed in plus whats the cost of i.e. pistons, rings, and liner if its is ofcourse linered....
and does the lump come out from the top as easy as it looks i resheld mine but sat the car on the engine and running gear so i dont know....
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25 October 2004, 08:52 PM
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Originally Posted by Flat 4x4
Tom
I'm afraid it does happen to Imprezas. My 99MY with FSSH went pop at identical mileage. £2100 + vat and I decided to do the clutch at the same time (extra).
I'm afraid it does happen to Imprezas. My 99MY with FSSH went pop at identical mileage. £2100 + vat and I decided to do the clutch at the same time (extra).
Cheers for he info.
25 October 2004, 09:58 PM
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And my MY93 import with no history whatsoever (could be 25 cars made into one and hammered to death in japan) is still going strong with 120k on her now and still does nearly double the speed limit!
just show that FSH is not everything.
just show that FSH is not everything.
25 October 2004, 10:12 PM
#14
if a piston has melted that suggests running hot. there is a common theory that above 100 ish mph (on the classic shape - i.e. yours) the air is deflected from the bonnet over the air scoob. this means that the intake temperatures rise. this could be the cause of the problem.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
25 October 2004, 10:12 PM
#15
Is this a UK or JDM?
Melted pistons is not caused by oil problems - big ends on the otherhand are.
Lean fuel mixture, incorrect fuel (for JDM or PPP'd, 22b's p1's etc), or duff knock control are your causes.
what oil where you guys using and what petrol station did you use?
Lean fuel mixture, incorrect fuel (for JDM or PPP'd, 22b's p1's etc), or duff knock control are your causes.
25 October 2004, 10:16 PM
#16
Could it be intercooler heat soak, after sitting at the services?. Would probably cause det when being opened up. Why the limp home mode didnt come on though is beyond me!!.
25 October 2004, 10:36 PM
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Tom, sorry about your engine.
I have an MY99. This is now fitted an equal length header/manifold. Apart from the torque gains achieved with this, I was advised at the time, that with the original un-equal length header, the piston with the shortest distance to the turbo on the offside can can suffer these meltdown problems.
Was this the one that melted on yours? If so it might be a good idea/insurance to fit one, once the engine repairs have been carried out.
Graham.
P.S. Mine came from Power Engineering if interested.
I have an MY99. This is now fitted an equal length header/manifold. Apart from the torque gains achieved with this, I was advised at the time, that with the original un-equal length header, the piston with the shortest distance to the turbo on the offside can can suffer these meltdown problems.
Was this the one that melted on yours? If so it might be a good idea/insurance to fit one, once the engine repairs have been carried out.
Graham.
P.S. Mine came from Power Engineering if interested.
26 October 2004, 02:45 AM
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No its the n/s rear cylinder thats lost compression on mine. I thinking i know why this might of happened is because i lost a lot of oil when from what i could see is hit a speed hump in the road and destorted the filter after that it started smoking thats why i sent the turbo off. i had something like this happen before on a turbo car and it ended up the spindle snapped so i was thinking turbo with all the smoke and no boost, then i thought i best do a compression test..gutted or what so its £380+ and what eva the engine is to repair....just a reminder if anyone knows if its linered
26 October 2004, 10:18 AM
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Originally Posted by jjones
if a piston has melted that suggests running hot. there is a common theory that above 100 ish mph (on the classic shape - i.e. yours) the air is deflected from the bonnet over the air scoob. this means that the intake temperatures rise. this could be the cause of the problem.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
So whats the best way to watch out for this? Intake sensors? EGT sensor?
26 October 2004, 12:56 PM
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AFR gauge.
i think the best thing to do is sort out the fueling on the car when you get it back.
fit a new MAF sensor, uprated pump, and a good FPR.
melted pistons are usually caused by det due to running lean, the fuel is what keeps the piston crowns cool, if you don't have enough fuel then the crown overheats and melts the ally.
an under reading MAF sensor is the usual suspect on the MY99 cars.
i would get all these done after the re-build as the problem may still be there, last thing you need is another re-build!
a knocklink is also a good idea as it gives you peace of mind when giving it some
i think the best thing to do is sort out the fueling on the car when you get it back.
fit a new MAF sensor, uprated pump, and a good FPR.
melted pistons are usually caused by det due to running lean, the fuel is what keeps the piston crowns cool, if you don't have enough fuel then the crown overheats and melts the ally.
an under reading MAF sensor is the usual suspect on the MY99 cars.
i would get all these done after the re-build as the problem may still be there, last thing you need is another re-build!
a knocklink is also a good idea as it gives you peace of mind when giving it some
26 October 2004, 01:02 PM
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Originally Posted by jjones
if a piston has melted that suggests running hot. there is a common theory that above 100 ish mph (on the classic shape - i.e. yours) the air is deflected from the bonnet over the air scoob. this means that the intake temperatures rise. this could be the cause of the problem.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
26 October 2004, 01:39 PM
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Originally Posted by turbo tom
Hi J Jones,
I had been going for about 20 0dd miles from home. i always let everything heat up properly before going over 3000rpm. Once everything was up to temperature i sat at 90 for a short while before stopping in some services for a coffee. i opened it up going back up the slip road to rejoin the motorway and was doing just about a tonne when i lost power all of a sudden and made the decision that this was serious and stopped immediatly
I had been going for about 20 0dd miles from home. i always let everything heat up properly before going over 3000rpm. Once everything was up to temperature i sat at 90 for a short while before stopping in some services for a coffee. i opened it up going back up the slip road to rejoin the motorway and was doing just about a tonne when i lost power all of a sudden and made the decision that this was serious and stopped immediatly
26 October 2004, 08:28 PM
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Originally Posted by jjones
if a piston has melted that suggests running hot. there is a common theory that above 100 ish mph (on the classic shape - i.e. yours) the air is deflected from the bonnet over the air scoob. this means that the intake temperatures rise. this could be the cause of the problem.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
you car is also a 99 model. these models had the dodgy maf sensor. if this was under reading (which is what they do when they start to fail) then the engine would have been running lean. this will cause the high temps that on motorway run will kill the engine.
JJ,This exactly what i was informed,By a fellow scoobie engineer,He said "QUOTE"The imports were designed to run at max 112mph..After which,The under bonnet cooling temps get messed about with and the ???????Gets a diffrent reading = running weak,So perhaps ...The guy,And yourself are correct...????? Kev.
26 October 2004, 09:09 PM
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That same happened to me about a month, a month a half ago. cilynder number 3 decided it was time to go, so off the car went to API. I took the opportunity and changed the clutch, flywheel and turbo.Grand total cost was 3.5k.
27 October 2004, 08:54 AM
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Originally Posted by WRX STI Type RA.
JJ,This exactly what i was informed,By a fellow scoobie engineer,He said "QUOTE"The imports were designed to run at max 112mph..After which,The under bonnet cooling temps get messed about with and the ???????Gets a diffrent reading = running weak,So perhaps ...The guy,And yourself are correct...????? Kev.
But im guessing it could happen to UK cars as well though, how come they're de-restricted? Interesting
27 October 2004, 01:45 PM
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MAF on 99 MY
My MAF sensor was taking the Pi$$ on my MY 99 scoob, luckily (so far) I was able to change it with out any apparent damage. It was really annoying me as it was hesitating all the time up hills on part throttle. I got it changed (there were NO ECU error stored) and it ran fine afterwards. Notably when you reset the ECU (remove battery for a while) if there is a problem with the MAF you will more easily notice it can't remember why but it happen to me. After an ECU reset the car kept stalling all the time and hunting like crazy (0 RPM- 1000 RPM).
Regarding the 100mph theory, I mostly drive at about 100mph on the motorway and have been known to run at full throttle for at least half a tank. It seems to me the with so much air I cannot see how it could get too hot unless there is some kind of vacuum? Just leave it running for a few minutes when pulling into the petrol station, or slow down before you get there.
Regarding the 100mph theory, I mostly drive at about 100mph on the motorway and have been known to run at full throttle for at least half a tank. It seems to me the with so much air I cannot see how it could get too hot unless there is some kind of vacuum? Just leave it running for a few minutes when pulling into the petrol station, or slow down before you get there.
27 October 2004, 02:02 PM
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running lean can cause det, but det doesnt melt pistons, it hammers them and destroys bearings.
Running lean will cause egts and incylinder temps to increase, this excess heat is what melts pistons.
I don't see how an equal length tubular manifold will help with that.
what you need is proper mapping on a chosen fuel with ignition and fuelling to suit.
You can keep an eye on the fuelling with a wide band lambda sensor which is a row of leds which light up accordinging to how lean or rich you are running. You need to get a feel for where it should eb and when, but this is easy and can be picked up in about 2 mins.
A knock sensor is also useful, this detects det and lights up more leds on your dash to tell you something is amiss.
The theory about the scoop is a valid one.
If you are concerned then by mapping the car at 110mph plus the mapper will see the intake temps mean it will start over fuelling, as hot air can't support as much oxygen which is needed to burn the fuel, this will leave you with unburnt fuel in the cylinder.
Again, am ot sure how this would leave you running lean enough to melt a piston.
MAF sensor is a good theory.
Running lean will cause egts and incylinder temps to increase, this excess heat is what melts pistons.
I don't see how an equal length tubular manifold will help with that.
what you need is proper mapping on a chosen fuel with ignition and fuelling to suit.
You can keep an eye on the fuelling with a wide band lambda sensor which is a row of leds which light up accordinging to how lean or rich you are running. You need to get a feel for where it should eb and when, but this is easy and can be picked up in about 2 mins.
A knock sensor is also useful, this detects det and lights up more leds on your dash to tell you something is amiss.
The theory about the scoop is a valid one.
If you are concerned then by mapping the car at 110mph plus the mapper will see the intake temps mean it will start over fuelling, as hot air can't support as much oxygen which is needed to burn the fuel, this will leave you with unburnt fuel in the cylinder.
Again, am ot sure how this would leave you running lean enough to melt a piston.
MAF sensor is a good theory.
27 October 2004, 07:41 PM
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Originally Posted by THOMO
what oil where you guys using and what petrol station did you use?
27 October 2004, 07:48 PM
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Originally Posted by DarkStar66
Did you let the turbo cool down when you got to the services? I'm not sure if this had anything to do with your problem but apparently you can fry the oil in the turbo if you've used it a lot and then just switch off. You should let it idle for a few minutes before switching off.