blown engine
07-09-2015, 03:06 PM
#212
BTW, the pitting is interesting because you would expect if it's done by bearing debris being dragged around by the piston/rings, there should straight scratch marks like scoring in mid-stroke but instead, it looks more like the face of the moon with NO scratch marks. Looks like some form of corrosion or cavitation. Could this be the original source of the debris?
07-09-2015, 03:10 PM
#213
Rennlist Member
BTW, the pitting is interesting because you would expect if it's done by bearing debris being dragged around by the piston/rings, there should straight scratch marks like scoring in mid-stroke but instead, it looks more like the face of the moon with NO scratch marks. Looks like some form of corrosion or cavitation. Could this be the original source of the debris?
07-09-2015, 03:35 PM
#215
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BTW, the pitting is interesting because you would expect if it's done by bearing debris being dragged around by the piston/rings, there should straight scratch marks like scoring in mid-stroke but instead, it looks more like the face of the moon with NO scratch marks. Looks like some form of corrosion or cavitation. Could this be the original source of the debris?
07-09-2015, 03:52 PM
#216
Rennlist Member
Maybe it is from detonation? When it happens to the top of a piston it looks like someone has been at it with an ice pick and hammer.
That pitting looks like the top of pistons that have been subject to detonation. Perhaps a Lean mixture, Low octane (CA?) fuel + failed knock sensor could cause that?
That pitting looks like the top of pistons that have been subject to detonation. Perhaps a Lean mixture, Low octane (CA?) fuel + failed knock sensor could cause that?
07-09-2015, 04:02 PM
#217
@Rubik: yes as Jake had explained and that's what I'm suspecting now. Note the pitted part of the cylinder is at the very top where the piston rings normally don't travel to so the pitting cannot be caused by other debris such as IMSB debris.
@p.van: not sure but I would expect that to show up way earlier than 100k miles/13yrs?
@DBJoe: the coolant was very clean and there's no coolant in the oil per the UOA so definitely no intermix. I did observe there's trace amount of engine oil sucked into the cylinders (trace on the intake manifold risers).
@Frank: I don't observe the same pitting on the top of any pistons. Lots of carbon but no pitting. The engine didn't burn any oil per crinigely and it's confirmed by the very clean and healthy gray tailpipes (not black).
@p.van: not sure but I would expect that to show up way earlier than 100k miles/13yrs?
@DBJoe: the coolant was very clean and there's no coolant in the oil per the UOA so definitely no intermix. I did observe there's trace amount of engine oil sucked into the cylinders (trace on the intake manifold risers).
@Frank: I don't observe the same pitting on the top of any pistons. Lots of carbon but no pitting. The engine didn't burn any oil per crinigely and it's confirmed by the very clean and healthy gray tailpipes (not black).
07-17-2015, 10:01 PM
#221
The photo is tame compared to the carnage posted. It's a good thing JR desensitized a lot of us before with his pics first.
Sorry but I'm able to wait for updates. "Good things come to those that wait."
The question is now that the motor is gone, what's your future plan? Used motor, rebuilt one, 3.2 boxster, etc?
Sorry but I'm able to wait for updates. "Good things come to those that wait."
The question is now that the motor is gone, what's your future plan? Used motor, rebuilt one, 3.2 boxster, etc?
07-17-2015, 10:14 PM
#222
Still plan on rebuilding the engine if the crank and cams are ok. Will need a new IMS for sure. Should have some time to take off the heads soon.
If it can't be rebuilt, I may just sell the shell and keep the engine as a specimen
If it can't be rebuilt, I may just sell the shell and keep the engine as a specimen
The photo is tame compared to the carnage posted. It's a good thing JR desensitized a lot of us before with his pics first.
Sorry but I'm able to wait for updates. "Good things come to those that wait."
The question is now that the motor is gone, what's your future plan? Used motor, rebuilt one, 3.2 boxster, etc?
Sorry but I'm able to wait for updates. "Good things come to those that wait."
The question is now that the motor is gone, what's your future plan? Used motor, rebuilt one, 3.2 boxster, etc?
07-28-2015, 03:46 PM
#225
Updates:
- Bank 2 looks original (no excessive sealant) and it's in excellent condition
- I took off both heads and found that all cylinders are scored on both the upper and lower sides of the cylinders. It turns out the pitting in the borescope photos before was actually dirty residual oil/carbon. Once wiped down, you can see the light scoring but you can't feel them with your finger tips
- No debris in bank 2 cam cover scavenge pump pickup area (the lowest part of the head + cam cover)
From the above, it's looking more like the IMSB broke down and its debris got flung around by the bank 1 timing chain. Some debris landed on the bank 1 cam cover bottom and got picked up by the bank 1 scavenge pump, destroying it in the process.
No debris got into the main oil feed that feeds all the bearings. The oil pump picks up the oil and pushes it through the oil filter, then to the oil/coolant heat exchanger, then to the bearings. I flushed the heat exchanger and didn't find any debris. All the debris were caught in the filter. The larger pieces actually settle at the bottom of the sump and not even picked up. If any significant debris have got through (e.g., filter valve bypassed), I would expect all the bearings (cam, crank) damaged.
Damn, a new IMS is $1,300+ and the cylinders will need to be re-sleeved too. A rebuild is gonna be like $10k just for the parts...
The heads got reassembled for storage.
- Bank 2 looks original (no excessive sealant) and it's in excellent condition
- I took off both heads and found that all cylinders are scored on both the upper and lower sides of the cylinders. It turns out the pitting in the borescope photos before was actually dirty residual oil/carbon. Once wiped down, you can see the light scoring but you can't feel them with your finger tips
- No debris in bank 2 cam cover scavenge pump pickup area (the lowest part of the head + cam cover)
From the above, it's looking more like the IMSB broke down and its debris got flung around by the bank 1 timing chain. Some debris landed on the bank 1 cam cover bottom and got picked up by the bank 1 scavenge pump, destroying it in the process.
No debris got into the main oil feed that feeds all the bearings. The oil pump picks up the oil and pushes it through the oil filter, then to the oil/coolant heat exchanger, then to the bearings. I flushed the heat exchanger and didn't find any debris. All the debris were caught in the filter. The larger pieces actually settle at the bottom of the sump and not even picked up. If any significant debris have got through (e.g., filter valve bypassed), I would expect all the bearings (cam, crank) damaged.
Damn, a new IMS is $1,300+ and the cylinders will need to be re-sleeved too. A rebuild is gonna be like $10k just for the parts...
The heads got reassembled for storage.