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Old 03-31-2014, 09:19 PM   #1
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Water Pump with Metal Impeller

Busted plastic impeller in the water pump. Never did expect that.




Followed the information overload on the forums about the plastic or metal variants. Decided on the metal due to the above breakage. But there are both sides, mostly quality issues of German vs. Chinese. I bit the bullet and went with a metal impeller water pump from .. (aghast) Autozone: they had it in stock for (you kidding me?) $150, with lifetime warranty. Figured I can just pull every couple years and check if necessary.
The quality looks great in the following picture, but there are casting issues.



Detail around the metal impeller and the casting; look good.



But the casting in the German original part is much finer. Probably 10x more expensive casting mold. The pictures may not due justice, but the casting finesse around the impeller cutout in the German part is exquisite.



This image shows a casting fault in the Autozone pump within the water passage. The black silhouette inside the passage is metal that I used a dremel on to remove to smooth out. Still, I was very glad for the metal product as shown below.




Another note as well regarding the gasket. The Autozone pump came with a paper gasket. I purchased the correct metal gasket from the Porsche dealer with the embossed detent that will compress correctly. Also, the correct torque is quite minimal, so be sure to use a 1/4" torque wrench to hit correctly to prevent leaking.

After replacing, I debated if I should flush; during the week waiting for Saturday to install the new pump, I purchased the Airlift vacuum coolant system, and figured flushing will give a bit of experience, and if there is a leak, save me the $120 on the Pentafrost SF coolant. Very glad I did flush : critical step.

The black specks are all the plastic impeller remains flushed out with 4 1/2 gallons of distilled water. When I first drained the remaining the coolant during the repair, more remains flowed out. After this I was extremely glad I flushed and I got the metal impeller pump; I think it is the correct way to go.



Airlift - great tool! Checked the tightness of the new installation per instructions: Get the vacuum up to 25 psi, and check it does not go down. The instructions stated the hoses 'may collapse'. Very True! The picture is the main water hoses collapsed.



Finally, it is just incredible to me to see a car so clean with 140k+ miles. This is the coolant pipes running under the car, behind the plastic underguards. Yes, there is a shield protecting the underbelly, but still, 13 years old, a lot of miles, daily driver. Super clean! Not to mention working on a car for 12 hours without a scraped or bleeding knuckle.



Points :
Metal impeller, flush, proper gasket, Airlift.

For better or worse :
I actually enjoy working on this girl. Sigh.
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Old 04-01-2014, 02:27 AM   #2
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Metal impeller.........B I G mistake.
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Old 04-01-2014, 03:06 AM   #3
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Metal impeller.........B I G mistake.
+1. When the bearing starts to get loose and wobble, and they all do, your metal impeller with happily start machining your engine cases, doing damage that may not even be fixable. There is a reason Porsche used composite impellers...........
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Old 04-01-2014, 03:54 AM   #4
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The metal impellar may never cause a problem or it may mill your block to the point of ruin before you ever know it. Not worth the risk to me. Nor would I buy one from Autozone - could never trust the origin, and hence the quality.
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Old 04-01-2014, 04:53 AM   #5
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Mine rubbed for quite some time before I swapped it. Very loud at startup. I am sure you heard yours for some time? Waited waaay too long. If you wait that long now, big problems. The old one clearly rubbed for quite a while before it broke.

Also, Porsche parts only.
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Old 04-01-2014, 05:21 AM   #6
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Metal impeller.........B I G mistake.
#2 on this
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Old 04-01-2014, 05:48 AM   #7
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#2 on this
I've seen the results of a metal impeller milling a block.

Not sure if they ever got that block to work again (next time I see my mech I will ask).

Either way -- not pretty.



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Old 04-01-2014, 05:58 AM   #8
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Quality never costs more. Quality can, and will, save you.
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Old 04-01-2014, 06:15 AM   #9
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I see people try to "out smart" this water pump issue all the time by using the metal impeller pumps.

I know of 3 people who ruined blocks this way in 2014 alone. I have developed a product to save the blocks and to protect them from metal impeller damage, but its too expensive for the distributors to carry.
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Old 04-01-2014, 06:20 AM   #10
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Old stories.
By the time the water pump is actually wobbling enough to mill the block, it'll be making noise and probably leaking. Shame on you if you continue to drive on it.

Is it better to have the plastic impeller shred and scatter all over your cooling system? You know, block entire cylinder head cooling ports... you know, stuff like that.

Pick your poison.

OR, a third option. Change your plastic water pump every 15,000 miles.
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Old 04-01-2014, 06:35 AM   #11
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From ecstacy to agony

I have a funny feeling that seawind has some serious regrets now. The info you guys gave is very interesting, I would have never thought of plastic being better and safer than using metal for impeller blades. I learn something everyday in here. Thanks guys.
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Old 04-01-2014, 06:45 AM   #12
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I have a funny feeling that seawind has some serious regrets now.
I bet he does, too. But Seawind did say:

"Followed the information overload on the forums about the plastic or metal variants. "

I wonder what forums he searched? I've never seen a recommendation for the metal impeller here, Rennlist, nor Renntech. That just about covers the Porsche world on the internet.
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Old 04-01-2014, 07:16 AM   #13
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Take a look at the May, 2014 Tech Notes in Excellence Magazine. There is a good write up on this debate under "Anxious Pump Watcher". Here is a quote,

"Although one problem is solved with a metal impeller, it creates a worse situation, because the crankcase cannot be repaired."

They suggest replacing the pump every 50,000 miles or every 4 years, whichever comes first, and use the Porsche genuine factory pump. They go on to recommend a complete drain, flush and refill of the coolant system every two years. Too many bad things can happen when a metal impeller comes loose.
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Old 04-01-2014, 08:03 AM   #14
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Boy, seawind went through a lot of trouble for this April Fools Day joke.
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Old 04-01-2014, 08:43 AM   #15
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April fools or not....

I had a metal impeller installed and I droved about a year w/ them before I changed it out to plastic impeller pump. I paid about $250 at Oreilly's even though they had the metal impeller for about $150.

I didn't pay more because of the plastic impeller but mainly it advertised w/in specs of EO parts and has lifetime warranty.
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Old 04-01-2014, 09:09 AM   #16
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Old stories.
By the time the water pump is actually wobbling enough to mill the block, it'll be making noise and probably leaking. Shame on you if you continue to drive on it.

Is it better to have the plastic impeller shred and scatter all over your cooling system? You know, block entire cylinder head cooling ports... you know, stuff like that.

Pick your poison.

OR, a third option. Change your plastic water pump every 15,000 miles.
Don't bet on it. We have had customers come in complaining of overheating issues in heavy traffic. While the metal impeller replacement pumps had some play in them, they were not leaking or making any observable noise at the time we removed them. Along with randomly machined engine cases, the entire cooling system was full of finely disbursed aluminum filings caused by the water pump impeller wear on the cases. After spending a couple hours cleaning the metal out of the entire cooling system and installing a new water pump (composite), the car's still had heat issues, but these were now observed to be caused by the new pump's impeller now having significantly more clearance due to case wear and not being able to move coolant as effectively. Similar instances were recently written up in Excellence Magazine's technical section as well.
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Last edited by JFP in PA; 04-01-2014 at 09:12 AM.
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Old 04-01-2014, 09:33 AM   #17
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Originally Posted by Bigsmoothlee View Post
Old stories.
By the time the water pump is actually wobbling enough to mill the block, it'll be making noise and probably leaking. Shame on you if you continue to drive on it.

Is it better to have the plastic impeller shred and scatter all over your cooling system? You know, block entire cylinder head cooling ports... you know, stuff like that.

Pick your poison.

OR, a third option. Change your plastic water pump every 15,000 miles.
It will be making noise, but may not be leaking. Mine was not leaking even though it had been rubbing for a while.

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Old 04-01-2014, 12:45 PM   #18
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^is that plastic impeller?
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Old 04-01-2014, 01:08 PM   #19
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^is that plastic impeller?
Yes. Non-Porsche. 3 ounces lighter than the Porsche pump.
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Old 04-01-2014, 04:53 PM   #20
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don't use non-OEM

I few years ago I picked up a handful of non-OEM WP to save a few $$.

Installed 2 of them in family cars ---

One failed within 1K miles the other I pulled and it was already wobbling.

OEM might only last 30K miles -- but I would not trust a non-OEM one again.

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