Use gt3 water pump with metal impeller?
 

Okay indie says they typically replace Boxster water pumps with the metal impeller ones found on the gt3. I've seen some threads indicating that might not be advised due to possible block milling if the impeller gets a little loose. Thoughts?

My opinion is that you need a new mechanic. You should never put a metal impeller water pump on the M96.

Agree. It's for a good reason.

NO NO NO NO NO!!!!
do not use a metal impeller. Should the bearing start to fail it will grind your engine block

Get a Pierburg water pump who makes them for Porsche
They are under $200 from warehouse 33 auto . com. (Remove spaces) If you enter RENNLIST at the checkout you get a 10% discount as well.

While you are changing the wp, replace the thermostat with a low temp one

Get a new mechanic, one that actually knows about Porsche cars

They are just buying a cheaper water pump

I agree 100% with all of the above comments. This mechanic obviously has very little experience with the M96, because no knowledgeable Porsche mechanic would recommend a metal impeller.

As stated above Pierburg is the same as Porsche OEM. You can save a few bucks by not buying the Pierburg pump in a Porsche box, but you don't want to skimp on the water pump.

There are a lot of after market water pumps out there that use reinforced plastic impellers. The GT3 engine block is different. Use a high quality one with a plastic impeller. Pierburg is a good choice - for example PIERBURG 7.31081.02.0. Or Laso 7520 0106. But there are also other good quality water pumps available. And do yourself a favour and don't buy the cheapest. ;)

Regards, Markus

Very interesting. They are very respected in the area and pretty much only work on Porsches and have for over 50 years. I'm surprised he would recommend an approach that seems so obviously wrong based on the feedback from this board. Thanks for the great feedback. I'll run the concerns by him and get his thoughts. Should be interesting.

Ask the shop if the metal impellar water pump they install fails and digs into the block if they will cover the damage. That should be an interesting discussion. :rolleyes:

I saved my old pump. It was scraping the block. You can see the marks on the impeller if they don't believe you.

That is why I work on my 99 Boxster. When I pay someone to do something I expect them to know more than me and do a better job. Not usually the case.

This subject comes up often but seldom are there detailed explanations of why metal/plastic is the best choice.The threads deteriorate just like the oil chioice threads.Not helpful. I have the curse of an inquiring mind so here are a few details that others may add to/correct.
1.The aluminum blades will only score/abrade the w/p housing if you neglect a worn bearing.
2.The plastic blades will also mark the housing if a wobbly bearing is neglected. More serious - the plastic blades can disintegrate (but why-age/heat??). You will need to dismantle the entire engine to retrieve all the little pieces .Why? Because they block the coolant passages & then......Just done that job!
So pick your poison.
Best suggestion whichever you choose - is watch for coolant leaks from the w/p or noises and replace the pump immediately or 60k miles ?

Great info. And the first post to suggest using the metal impeller pump might not be a horrible idea... I agree with the overall idea of keeping an eye on it and not letting it get to be an issue either way...

Actually, it is a horrible idea. A metal impeller pump can do serious and permanent damage to the engine cases, filling the entire cooling system with fine metal that is difficult to remove without taking the engine apart, and even then will result in reduced cooling capabilities because the space between the pump impeller and the cases is now too large to facilitate proper coolant circulation. Bad idea all around.

I always defer to experienced advice. Plastic it is !

A failing water pump will most likely make contact with the engine case, not just the WP housing. Just look at a picture of the WP, it's a giant spinning blade directly facing the engine casing.

Here are the basics of the metal vs plastic impeller argument:
-With a plastic impeller, if it fails, the plastic makes contact with the engine case and tends to break off in chucks, which normally get trapped in the radiators or oil cooler (not ideal). Since it is plastic vs metal, their is essentially no damage to the engine casing.
-With a metal impeller, you get fine metal particles that circulate through the system freely, and hole bored into the side of the engine.

If a failing water pump with metal impeller grinds into the case house, you'll have metal in your water system - means water cooler and hoses.

Not in the engine oil system or inside any moving parts or bearings! It's just in the water channels or cooling lines or water coolers.

Same to plastic parts.

The question is: are fine metal parts better or not so fine plastic parts.

After some thinking i would prefer fine metal parts.

Regards, Markus

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I think I saw one that had a brass impellor - is brass softer than aluminum? I don't want to be the one to find out - I went with the Pierburg when I did mine.

They both can block critical small passages, leading to hot spots. The major difference between the two is the permanent case damage metal impellers can do, which leads to cooling problems even after everything is cleaned out. Clean out the plastic, install a new pump, and it is as though nothing happened.

Considered this aspect.

Problem is that the plastic parts in general are much bigger than the metal parts. OK, thin metal parts could affect the bearings of a new water pump. Big plastic parts can block thin water lines. And as we all know there is not only clear fluid in this lines. Over the years we get some corrosion and other dirt - even it's an aluminium block (and there is also aluminium corrosion).

Still on the metal impeller side. ;)

Regards, Markus

You are overlooking the fact that even very small metal bits can agglomerate into passage blocking as well. We have seen it happen. And the case damage from the pump hitting is also permanent, which reduces the overall coolant flow in even completely rebuilt engines, so you have a fresh engine starting off with one hand tied behind its back.

Hi,

understand. But there are still some downsides on plastic impellers. And if you check the pump and play regularly i see more downsides for the plastic impeller, because you can't see inside if the impeller is deoriantating - which doesn't mean that the bearing has to be gone bad.

For a normal guy who doesn't check anything on his car or isn't willing to replace the pump preventively every 10 years or 100 TKm a plastic impeller pump will be the better choice.

For those who are interested in a metal impeller pump. GEBA is an after market manufacturer who is / was also OEM fpr Porsche. They offer a water pump with a metal molding impeller (not a cheap sheet metal impeller) for 986 / 996 cars. Part number is GEBA 15007. This pump is Made in Germany (not Turkey, Czech, Poland or elswhere in Europe) and uses high quality bearings from a well known german manufacturer.

Regards
Markus

If you are dealing with a replacement of a water pump that looks like post #21 above - you need to find every broken part. Here is a little practical experience to go on but others may have more to contribute.
Remove the heat exchanger/oil cooler. Examine the coolant lines and passages there.Some pieces will lodge there.
My M96 engine had a new water pump fitted just before I bought it. When I dismantled the engine(another story) I eventually retrieved all the broken pieces from the previous pump(engine has 89,000 miles). I would guess that coolant circulation was reduced by at least 50% with the broken pieces.
If you can't find all the broken pieces from the old impeller -you are taking a big risk if you just slap in a new pump - regardless of the impeller material.

Great point.

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Oh Gawd, this topic is starting to get as bad as the IMS debate.

Other than mileage, what technique can I use to determine the health of a water pump? My temps are fine. I don't hear a noise from the engine. I have 56k miles.

Is this purely proactive maintenance or can you determine when to replace?

I think it is a proactive maintenance item. If your car has its original water pump and antifreeze, I would change the pump and the antifreeze. The antifreeze is supposed to last forever but 13-14+ years is a long time. And the composite impellers eventually may start throwing off chunks of blade due to failure from repeated heating and cooling cycles.

Never ever put a metal impeller pump in an engine block no matter what engine it is. If that bearing fails then you have thousand of metal bits now making your way round your coolant system as well as reshaped ports around the pump.

As for when to replace a good rule of thumb is every 40000 miles or 4 years. That's what VW recommends on their pumps and i reckon that's not a bad shout.

I've done a lot of research the last few days on this as I'm in the middle of replacing mine.. And apparently it's a subjective opinion really. Pros and cons of both. Metal impeller versions are less likely to fail but if they do you'll chew up ur block. And plastic impeller pumps can break and block water ways causing hot-spots. I opted for a composite one

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Well, I just replaced mine because it started leaking (appeared to be the original, and impellers looked really gnarly). But if you make it a proactive maintenance every couple years, you probably don't have to worry much about this debate.

I always recommend and use factory (Pierburg) plastic impeller pumps and replace every 10 years or 60K miles. Jeff (as usual) is correct on the why. I only add, don't wait for it to go bad, just put on a schedule and replace proactively.