byron -

with most water pumps, the issue is the bearing. with the plastic pumps, there is the ADDED concern that the impeller can shear off at the hub, leaving it just uselessly sitting there. if you are missing vanes, IMO that occured as a result of foreign object damage.

as for cleaning the cooling system? there are the radiators, the heater core, the overflow tank, and all of the connective tubes. i believe the boxster's heater core ALWAYS has coolant circulating & that heat is actuated with air flaps rather than water flaps. this means your heater core could be mucked up, too......

Here's the video....
 

http://www.youtube.com/watch?v=lPBjaIOwERU

I first heard the clatter at 45 sec, it quit running at 59 sec. Suffice it to say that it was running poorly those 14 seconds. I mainly coasted down the esses, and only gave it gas again to try and power up to the exit road. When I gave it that little bit of fuel is when the big puff of smoke happened.

14 sec = PLENTY of time to circulate metal bits. have you drained the oil from the old motor yet? i think it would be worth a look. my guess is that it's got some froth in it. you said the coolant was oil-free, though?

i think i'd pull the radiators & take them to get reconditioned. ditto for the heater core.

No water in oil or vice versa
 

No water in oil or vice versa

"Quod Erat Demonstrandum". If there was no intermixing of oil and water, how did engine metal shrapnel get into and destroy the pump? Short answer: It didn’t, the pump failed.

The pump can fail in at least 3 ways, two of which aren't catastrophic for the pump.

1- Bearing failure: this is audible and generally is noted before the engine is driven further

2-Complete impeller failure: this can lead to a compromised engine, but usually makes enough noise and the temps climb high enough that the car is shut down and towed home safely. In this scenario the cooling system is filled with foreign object debris that can block a capillary in a cylinder head and lead to a crack.

3-Partial Impeller failure: This is the scariest of all because there are no sounds, no noises and nothing out of the ordinary. In this type of failure a small chip off an impeller blade detaches and ends up floating around in the coolant until it finds a capillary to block. When this happens the engine gains a cracked head and then gets intermix out of the blue.

Then people start misdiagnosing the issue as a heat exchanger, bad head gasket, etc and they will sometimes repair the cracked head and never even pull the damn water pump which caused the issue to begin with!!

If not caught in time the intermix contaminates the oil and kills the cylinders, then the engine is dead, like the 4 I have downstairs right now that are all here and all dead because of the damn waterpump.

What you guys need to remember is that a component doesn't have to grenade to create collateral damage that will kill the engine.

If an engine has lost an impeller, or has a chipped impeller that broken piece must be found, even if that means complete disassembly of the cooling system. If you can't find it, its probably already jammed inside a cylinder head~

We learned this while repairing heads and milling the cracks open... When finding pieces of impeller blades inside the cylinder head cooling passages one can feel pretty confident as to what the issue is and why its occurring.. We had 13 of those instances in 2010.

let's think this out from a failure mode standpoint. let's say you are correct and that, somehow, every one of the impeller blades sheared off and entered the cooling system. let's also consider that, somehow, even though we lost EVERY impeller blade, the water temp did not rise prior to engine failure. in the motor, there are four general places the coolant will go:

1. left head
2. right head
3. water jacket (bottom end)
4. oil cooler

if the debris enters either head, it can plug up one or more of the SMALL passages designed to cool the head. if this occurs, water will continue to circulate in the system and the dash will read normal temperatures. this, incidentally, is why this type of failure is so dangerous. at any rate, once a small passage is plugged up, a LOCAL hot spot will occur. this causes uneven expansion of the metal and a crack in the head forms. this failure allows intermix of oil and coolant & loss of compression. engine is dead.

if the debris enters the water jacket, it will probably exit back out. this area is comparatively large. if it DOES happen to plug up a portion of the water jacket, we will again see a localized temperature rise in the metal matrix composite (MMC) cylinder wall material. if this occurs, we would expect to see a crack / failure in the MMC itself. this would be the D-chunk type failure. engine is dead.

if debris were to enter the radiators & restrict flow, we would expect to see elevated water temperatures. eventually, if left unchecked, oil temperatures would also rise. this would lead to a collapse of the viscous layer between metal parts (like rod bearings & crankshaft journals), allowing metal to metal contact and eventual failure.

finally, we get to the ONLY viable failure mode i can think of where we'd lose the BOTTOM end of the motor as the result of debris in the cooling system: debris enteres the oil cooler. were this to occur, i think it is possible for coolant temps to remain stable while oil temps are allowed to rise. in this situation, it would be possible for the oil to lose viscosity & allow contact between the rod bearings & crank journals. i have to admit, i am unsure as to the exact passage the coolant follows leading into the oil cooler & am not 100% sure that the debris wouldn't get filtered out by this point.

so, theoritically, were the impeller to disintegrate, it MAY be possible to kill the bottom end of the motor without seeing higher coolant temps and without intermix.




now, let's look at byron's actual case. he had EXTREME detonation of the bottom end. rod caps were hurled through the case. this was VIOLENT. even if it was not the cause of the failure, i would be shocked if the MMC of one or more cylinders wasn't cracked, if not outright compromised. further, the chances of shedding EVERY impeller blade simultaneously with no debris contact is, well, almost zero. it simply doesn't happen.

finally, let's look at what we know of the M96's shortfalls and what we know of WHERE byron was on the track. the M96 is known to suffer oil starvation issues that are caused by cavitating the scavenge pumps in the cylinder heads. byron's failure occured shortly after the infamous turn 12. this is a sustained, high-g, right hand corner. the boxster has known issues with sustained high-g right hand corners: the oil pools toward the back of the driver's side cylinder head, AWAY from the scavenge pump. this allows cavitation of the sump & a drop of oil pressure. the result is metal to metal contact in the motor's bottom end, resulting in catastrophic failure similar to what byron experienced.




byron - can we take this thing apart this summer?

Debris generally doesn't accumulate in water jackets.. What kills the bottom end is intermix.

Most debris ends up in the heat exchanger, internal passages and the 4-6 cylinder head.

The year of the engine has a huge impact on what the capillaries in the heads accumulate.

The pieces that cause the most damage are smaller than a pencil eraser, the big chunks can't make it into the cylinder heads at all.. The smaller the pieces the deeper they can go.