Water cooled

JackDidley · JackDidley's Garage

Question for the guys with water cooled Porsches. Ever used a water pump with a metal impeller ? OE has a plastic impeller. Most aftermarket pumps are metal. Internet Chickenlittles say that will destroy your block if the pump goes out. My '08 3.4 puked its pump today and it seems absurd to pay $300 for a pump with a plastic impeller when the metal ones are $75. Soooo has anyone seen a metal impeller chew a hole in the block ??

masraum · 05:53 PM

Interesting question. I'm watching with interest.

This does seem like one of those things where a weak spot has been engineered into the system to keep from making a failure more expensive and catastrophic. It's kind of like the convertible top tie-rods that have plastic tie-rod ends. If something happens, the plastic cap breaks. A lot of folks on the Internet are selling metal tie-rod ends. I think I read an article by Wayne where he replaced the motor and several other pieces of the top mechanism that were bent and bad. Maybe a plastic part in the middle isn't such a bad thing.

HardDrive · 12-25-2017, 06:07 PM

Yeah, no data here, but I can see the argument that it's better to have to have a piece of plastic getting chewed up as opposed to a metal fragment.

JackDidley · JackDidley's Garage

Quote:

Originally Posted by HardDrive

Yeah, no data here, but I can see the argument that it's better to have to have a piece of plastic getting chewed up as opposed to a metal fragment.

Argument can go both ways. I read somewhere, the plastic pump fragments and gets lodged in places that cause problems. I also feel that one would notice the metal one making noise or leaking before it did too much damage.

sc_rufctr · 12-25-2017, 06:20 PM

Metal impeller water pumps have been used as OEM replacements on many different cars for a long time.

I've never heard of a metal impeller going bad and wrecking the block! And we all know the most common failure is the seal.

TimT · 06:27 PM

So refreshing that there is a dedicated

Boxster & Cayman Forum

drkshdw · 12-25-2017, 06:27 PM

944's have always had metal impellers. I don't think I've ever heard of one breaking. Then again waterpumps on 944's are changed every other belt change (60K miles) for peace of mind sake. But they are expensive. $150-400 each. And they are an all day affair to replace for most people. Because they are such an important part of the 944 engine, I'm not sure many people would risk using a water pump with a plastic impeller on their cars.

Then again my Camry has a plastic impeller-ed WP and they break all the fricken time. But they are cheap (about $20) and are a 30 minute job to replace.

JackDidley · JackDidley's Garage

I just searched ebay. Prices ranged from $37.74 to $577.

For $577 there needs to be some sex involved.

JackDidley · JackDidley's Garage

Quote:

Originally Posted by TimT

So refreshing that there is a dedicated

Boxster & Cayman Forum

Many 911s have the same pump and many water cooled guys are here. Also, there is way more traffic and experience here. Look at the Boxter forum. Maybe one or 2 posts daily.

legion · 12-25-2017, 06:45 PM

Quote:

Originally Posted by JackDidley

For $577 there needs to be some sex involved.

There is.....the purchaser is on the receiving end.

Nickshu · Nickshu's Garage

Metal impeller pumps are generally not a great idea. At least on the M96/97 (and probably others) engines the other side of the pump housing is part of the engine block. So if the bearing go bad on your metal impeller pump you are chewing a hole in the aluminum block. That's why the factory used plastic impellers...to protect the block in the event of a failure.

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masraum · 12-25-2017, 06:58 PM

Quote:

Originally Posted by TimT

So refreshing that there is a dedicated

Boxster & Cayman Forum

Yeah, it's great, if you want an answer a year or two later, or maybe never.

masraum · 12-25-2017, 06:59 PM

Quote:

Originally Posted by drkshdw

944's have always had metal impellers. I don't think I've ever heard of one breaking. Then again waterpumps on 944's are changed every other belt change (60K miles) for peace of mind sake. But they are expensive. $150-400 each. And they are an all day affair to replace for most people. Because they are such an important part of the 944 engine, I'm not sure many people would risk using a water pump with a plastic impeller on their cars.

Then again my Camry has a plastic impeller-ed WP and they break all the fricken time. But they are cheap (about $20) and are a 30 minute job to replace.

Yeah, I think the proactive replacement seems like the way to go with the water pumper cars too.

JackDidley · JackDidley's Garage

Quote:

Originally Posted by Nickshu

Metal impeller pumps are generally not a great idea. At least on the M96/97 (and probably others) engines the other side of the pump housing is part of the engine block. So if the bearing go bad on your metal impeller pump you are chewing a hole in the aluminum block. That's why the factory used plastic impellers...to protect the block in the event of a failure.

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I understand the theory but Ive never seen a post where the pump actually hurt the block. I am sure it has happened but what are the odds ?

osidak · 12-25-2017, 07:22 PM

never seen it on a Porsche but I have seen two case of a water pump with a metal impeller on a VW TDI loose it's bearing and chew up the block a little bit.

Nickshu · Nickshu's Garage

Quote:

Originally Posted by JackDidley

I understand the theory but Ive never seen a post where the pump actually hurt the block. I am sure it has happened but what are the odds ?

So in the end your choices are use a metal pump and replace it preventively to avoid block damage or use a plastic pump and replace it preventively to avoid the impellers breaking off.

Same same I guess. The metal pump failure being higher risk than the plastic pump failure as far as expensive damage. But you are right neither happen often really. All M96/97 gurus recommend preventive water pump replacement so it's pretty much the standard for maintenance on these engines either way.

I replaced mine last summer on my 996. After considering both options I went with a plastic pump. The first pump made it 14 years and 22k miles... Looked fine when it was removed.

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JackDidley · JackDidley's Garage

For the record my car has around 81k miles. When I bought it in '15 it had 61k. The bolts have no wrench marks so I am thinking it is original. Maybe I can tell more when I get it out. Leaning toward a $100 dollar pump. Definitely not going with a $577 pump.

Nickshu · Nickshu's Garage

Quote:

Originally Posted by JackDidley

For the record my car has around 81k miles. When I bought it in '15 it had 61k. The bolts have no wrench marks so I am thinking it is original. Maybe I can tell more when I get it out. Leaning toward a $100 dollar pump. Definitely not going with a $577 pump.

Pierberg (OEM supplier to Porsche) original equivalent pump is $267 right here on Pelican for your 2008 Cayman S.

https://www.pelicanparts.com/More_Info/99710601106.htm?pn=997-106-011-06-M244&SVSVSI=4296

911boost · 911boost's Garage

I haven’t replaced mine, but I will be going with the factory type when I do. They are better engineers than I am...

JackDidley · JackDidley's Garage

Quote:

Originally Posted by Nickshu

Pierberg (OEM supplier to Porsche) original equivalent pump is $267 right here on Pelican for your 2008 Cayman S.

https://www.pelicanparts.com/More_Info/99710601106.htm?pn=997-106-011-06-M244&SVSVSI=4296

Way better than $577. They also list a Graf with a brass impeller. Not making the call until I do some more reading. May search some threads on Rennlist. Not registered there but their forums do get some traffic.. Probably do the belt and stat while I am at it. When I make the call I will buy it all from pelican. Great service here in the past.