Engine change problem. Water pump impeller chewed up....Where's the pieces?
 

Hello all...I am in the process of installing my new/used engine after throwing the rod in August. I was thinking that I would reuse the water pump from my blown engine as it only had a couple of thousand miles on it. When I removed it, the impeller was chewed completely up. It seems that when the engine blew, metal pieces from the engine case, rods or pistons entered the water channels and destroyed the pump. Any suggestions on how to clean out the cooling system short of removing everything?

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Actually, I'd go the other way around; your water pump may have came apart (on the track, if memory serves), and the bits blocked some of the water passages to your head and more importantly, the oil cooler area, and that is probably what started the fatal chain of events leading to your rod failure. Not that uncommon, this is why Jake is suggesting changing out the water pump every three years, even if it is working fine...........

Getting all the bits out is a major pain, probably will require total disassembly unless you are very lucky.

If one of those pieces, as small as a pencil eraser gets in the right cylinder head capillary, you'll have a cracked head.

You must disassemble the entire cooling system and clean every part.. A flush won't cut it.

If it were mine I'd change the radiators and throw the old ones away.. Gotta take this seriously, if not you'll pay the price the hard way..

Yikes! Agreed that your woes are not over. Impeller grenade fragments have lodged themselves in every nook and cranny of your cooling system. Hard to say at this point whether it was chicken or egg (failed rod or failed impeller) that went first. Was your replacement water pump a factory Porsche part or aftermarket?

I may be missing something but I think he did change out his water pump, because he stated that it only has a few thousand miles on it.

Yes yes, understood.

Inquiring minds want to know if when the WP was changed, it was replaced with a Porsche factory part or an aftermarket supplier (i.e. less expensive/less reliable) part. My car is at 92k and I will be replacing my wp soon as a preventative measure. Knowing the source of potentially unreliable replacement water pumps is of keen interest to me, and probably other Boxster owners as well.

They all fail.. No matter if its OE or not.. No brand is better or worse than another in my experience.

This is why it should be changed on a regular basis.

Definitely going to clean the cooling system....
 

and have the radiators vatted. I will have to further evaluate replacing the radiators as I am out of MONEY! The water pump was 8 months old at the time of the explosion, and was an after market unit from NAPA. The car was not running hot prior to blowing up so I am pretty certain that it was engine parts that destroyed the impeller and not vice versa. Thanks all for the input.

I thought Jake knew of a specific
 

OEM water pump supplier to Porsche that was much better than the others. One he sold. I thought he said that on a forum a while back. Recent experience now says that isn't right? Or is all he is now saying that they all eventually fail?

Same recollection here. When I change mine out, I want the most robust replacement.

Afraid I cannot agree………..
 

If your engine had already “detonated”, and was in the process of stopping when shrapnel got to the pump vanes, you wouldn’t be searching for the vanes, they would still be near the pump, along with the chunk(s) of metal shrapnel that tore them loose (which also would not have have had time to been reduced to small bits and dispersed). If the vane debris totally disintegrated and made it all the way to the radiators, they had to have time to do so; the pump failed first.

quoting Mike "I thought Jake knew of a specific OEM water pump supplier to Porsche that was much better than the others. One he sold. I thought he said that on a forum a while back."

That's what I recall also. For some reason, the peeps at FSI becaome very evasive when asked which brand of pump that is, exactly. Seems to be some kind of a secret.

My car still has the original water pump - 12 years and 116K kilometres later. Because of all the dire warnings, I'm going to change it before I drive the car again in the spring. The fact remains, however, that it has been in there three times longer than recommended and has not detonated.

Hard to know what to think sometimes. :confused:

Not evasive at all.. Because we never know what pump we will be getting from Porsche, which is where we source them from.

No pump has proven to be better than any others at this point, just know that they ALL need to be changed every 3 years, no matter the mileage if you intend to prevent failures from occurring.

But you don't know that.. The pumps do not have to catastrophically fail, make noise of seize to cause engine failures.. One chip from an impeller blade is all it takes to wipe out an engine.

There is nothing dumb about preventive maintenance, if yours hasn't failed it needs to be changed so it doesn't fail. I come from an Aviation background, I take preventive procedures seriously and thats why those who have us service their vehicles never have engine failures.

Like playing Russian Roulette? Some must because they do it everyday even though they know what the repercussions could be.

Now I don't know what to do. I too was thinking of replacing my water pump in the spring, and using the Flat6 pump because, like Mark T and Mike Focke, had seen that it was a better pump.

Flat6 $314, Suncoast $234, both with gasket

At some points we have thought that one pump was better than another, but the fact is that it hasn't been..

Until we step up and have something made from billet it probably won't be.. The problem with that is that not enough people will buy it, based on the price point.. Everyone is concerned with price on the water pump, so just changing the pump every 3 years is the way more people will go..

Maybe at some point enough people will be willing to spend more money for something thats bulletproof, but it seems those people end up buying our complete engine anyway, sometimes when they haven't even had a failure~

Can just the impeller be replaced on a stock water pump? Maybe make a special FSI or LNE impeller can be produced and retrofitted onto a Porsche pump? Would be a cheaper route IF that's possible.

Quote:

Originally Posted by JFP in PA If your engine had already “detonated”, and was in the process of stopping when shrapnel got to the pump vanes, you wouldn’t be searching for the vanes, they would still be near the pump, along with the chunk(s) of metal shrapnel that tore them loose (which also would not have have had time to been reduced to small bits and dispersed). If the vane debris totally disintegrated and made it all the way to the radiators, they had to have time to do so; the pump failed first.

i completely disagree. let's say it took ten seconds from the start of the problem until the motor quit turning. at full tilt, byron was likely averaging 6,000 RPM's.

the water pump pulley is a little smaller than the crank pulley. let's say it's 15% smaller. this means the water pump would have turned 1.18 revolutions for each crank revolution.

at ten seconds, we're looking at over SEVEN HUNDRED rotations of the water pump during the failure. this is enough time to circulate the entire contents of the cooling system MANY times over. the missing debris is in the radiators.

So Jake....Have you guys ever seen a water pump that just started shedding vanes from the impeller? If the impeller was completely gone, I would be more inclined to agree with the diagnosis that the water pump impeller broke apart. Normally when we are talking about water pump failure, we are talking about bearing failure. The bearing in this water pump is perfect. The fact that just the vanes are chewed off is what led me to conclude that the engine bits from the exploding case destroyed the vanes, and not vice versa. Truth is, there is no way to be sure what really happened. It's all water under the car now!!! :D

My two concerns now are how to adequately evacuate the cooling system of debris and will it be best to go with a OEM water pump vs. after market?

Theoretically interesting, but practical experiences say otherwise. Byron is of the impression shrapnel from his grenadeing M96, complete with holes in the block, tore up the pump; but if that were the case, there is no way the engine continued to run for ten seconds after dispatching a rod through the block, or even two seconds for that matter. These engines stop pretty quickly when things are lashing around the inside. So if the shrapnel from the failure got into the pump, the engine should have already been slowing considerably. Looking at his photos of the impeller, there are no vanes at all. Small metal bits would take a lot of time to do this, so I would expect to find some fairly large metallic chunks that would be required to do that amount of damage in a very limited time in or near the pump; but none are visible in the photos, and he has not mentioned finding them. The photos also do not show the gouging in the housing, or on the impeller disc itself, which begs a question: What size and shape object(s) could have gotten into the pump and proceeded to very quickly and cleanly cut off all the vanes, and then vanish entirely (along with the vanes) without leaving any other marks? That is why I questioned the supposition in the first place, the photos do not appear to support it.

When daily drivers/street cars have the vanes break off, and then drive to my shop, and we located most if not all of the bits in or near the pump housing and thermostat housing areas, sometimes after as much as an hour’s running time…..

Quote:

Originally Posted by JFP in PA Theoretically interesting, but practical experiences say otherwise. Byron is of the impression shrapnel from his grenadeing M96, complete with holes in the block, tore up the pump; but if that were the case, there is no way the engine continued to run for ten seconds after dispatching a rod through the block, or even two seconds for that matter.

mine ran for about fifteen seconds before it stalled out. it still turned over a couple more times with the starter before it locked. byron - how long did your motor continue to turn over after you started seeing smoke? i think i remember you stating that the entire process (from the INSTANT you noticed a potential problem) took several minutes. am i correct?

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.