Water pump: plastic impeller or metal?
 

I recently purchased a 2000 Carrera with 82K miles. The seller had the clutch and IMS bearing replaced just prior to sale. I do not have records on prior service, so I plan to replace spark plugs, associated tubes, serpentine belt, water pump, and thermostat in the near future (maybe some other goodies as well).

Over the past year or so I have read (in Excellence among other places) about the potential hazards posed by water pumps with plastic impellers. That is, plastic bits can break away, find their ways into nooks and crannies of the cooling system, and impede flow of coolant. So, the deal was to get a water pump with a metal impeller.

Last summer I replaced the original water pump in my former '99 Boxster at 51K miles. The new water pump I got from Paragon came with a metal impeller, and the stock pump that I pulled out of the Boxster looked perfectly fine. When the buyer of the Boxster had a PPI done, I mentioned the new water pump with the metal impeller, and the mechanic said the metal impeller is bad. Apparently there is concern that if the bearing goes bad, the impeller can wobble and score whatever part of the motor the impeller resides in.

So, what's a DIY mechanic like me supposed to do???

I think that if I change the water pump, say, at 50K miles, then I should go with plastic or metal and not worry about it. Seems to me that I pay enough attention to my car that I would pick up some sign of a problem before a failure. But maybe not. Also seems to me that the risk of plastic bits breaking off and finding there way into the recesses of the cooling passages is likely a bigger problem than scoring from a metal impeller (especially if I were to notice the problem rather quickly).

So, forced to make a choice, at this point I think I would go with metal.

Opinions?

Buy Porsche OEM water pumps with plastic impellers from Sunset and replace about every 4 years.

+996 (or every 60K miles, or whichever comes first) :cheers:

That scoring renders the entire crankcase worthless… You'll never build cooling system pressure with a damaged counter surface.

It seems the best solution would be a water pump with a metal impeller and either a ceramic hybrid or journal bearing! (or maybe just an oil line to extend bearing life, or maybe a roller bearing)

We already fitted ceramic hybrid bearings to water pumps.. But people wouldn't buy them.

H2O pumps
 

FWIW, I replaced my 996's original water pump at 67K miles as a preventive mntce. measure. I chose to install an OEM pump.

The old pump's plastic impellers still look new and the bearing feels fine. It makes a nice paper weight/conversation starter now.

relinuca

Thanks for all the input. Looks like I'll go with OEM!

Stick with oem porsche parts. Don't bother with oem supplier pumps like Laso. I tried that before and it lasted about 5000km. I installed an oem pump and have already put 5000km on it with no issues

We have the OE and Laso water pumps available. For more information Click Here.

http://c1552172.r72.cf0.rackcdn.com/394852_x600.jpg

I was told that the 997 water pumps had larger, stronger fins and bolt right up. Worth exploring if true....

I'd go with the oem plastic, there's no point in a stronger impeller as Jake said if the bearings fail your going to tear up the block. Its the bearing that fails the blades only break when the failed bearing allows excessive movement and therefore contact with the block.
I've recently had to replace a failed water pump at 130,000 miles (original pump). Since we were busy I had the dealer do it and there was a couple of missing pieces. The dealers opinion was they've seen plenty of failed pumps and never had a issue cooling failure or hot spots following. If it had been a metal impeller I'd be looking at a new block / engine. I have 5k miles on it since and no issues so far. Bearings fail sometimes at the predicted life sometime a lot less.

I just did a porsche oem from sunset. I know a couple guys running around with metal impellers with no problems. I think it's up to you and your risk tolerance.

I started writing that as a joke, then realized it might not be a terrible idea. I've never taken apart a wp bearing, but I assume it's a sealed greased ball bearing. Do you use OEM pumps on your engine builds?

Yes he (Raby) does.