Jaeger

i agree with that. i also see oem grade water pumps made by reputable makers for various German cars priced at $30 all the time, i've checked their reputation, customer reviews and most of the bigger companies make a good product, found nothing that would indicate people are having problems. But i also always ask or research each company and their product carefully before deciding, and if possible try to use parts from companies i've already tested successfully.

I ordered a $55 one for my 928 off ebay and it looks every bit as good as any of them i've seen, advertised as made to meet / exceed oem standards.

Jerry Feather

Perhaps this is one for the Myth Busters. Cheap versus expensive means poor quality? Actually Cheap versus Expensive simply means only a difference in the price. The quality of two different items depends wholy on criteria other than price. After all, "cheap versus expensive means poor quality" translates to the proposition that there is no meaning to the word "bargain." "You get what you pay for" is easy to say, but actually has very little real meaning. If it had any it would mean the the half off sale currently going on at 928 Int'l means that suddenly all of their used goods are only 50% of their previous quality.

"Any 928 water pump for less than $150 is crap?" Show the data.

"Don't ever use a rebuilt 928 water pump?" Show the data. In fact, The guardian pump is simply a rebuilt pump with a neat coupler design incorporated in it, and it even needs to be "run in" (worn out a bit) before it will work successfully, according the knowledgable authority in this thread. And, it costs much less than some of the other pumps for sale. Does that mean it is that much lesser quality?

I will bet that there is a plethora of $50 eBay pumps in service in 928s owned by members and users of this Forum, but so far there is almost no data to support the proposition that they are unworthy to be used. By "almost" I simply mean that they are not likely failing at any greater rate than the $1400 ones or any in between.

James Bailey

That is the beauty of an open market....you each get to choose what suits you best. And for the record many engines do NOT use the timing belt to drive the water pump our situation makes the water pump a much more important part of the equation....

ROG100

We already did by sending them to GB and having them dissected - search is your friend.

Again masses of failed rebuilt WP data here on Renn - maybe you do not know how to use the search button!!

Well know fact that rebuilt WP's failed because they became rebuilds of rebuilds and that is why any reputable 928 parts supplier will not supply a rebuilt water pump. Once the interference fit is compromised it is a crap shoot. There is a big difference between a competent 928 savvy engineer like Ed and some "fly by night" eBay seller.

As Jim B says it is an open market and YOU can buy what ever you want to buy and all I have to say is good luck with that. That is why 928 owners come to Renn to get advice. Up to them if they use it or not.
Your car so you get to use what you like on it.

mark kibort

I put a new factory water pump in the holbert car from Day ONE! it failed at the track after a year. the plastic impeller came off the shaft that was knurled.
looked like a poor design.

ive used the metal impellers from laso after that and haven had any fail yet that wasnt reallly old. failure mode for me has been water leaking out the front of the pump bearing that becomes loose with time.

Now that i have 3 pumps in possesion that are bad.(well 1 is bad, the others are old) what should i do with them.... anyone want the cores?? can i sell them. can i rebuild them??

Speedtoys

What is so different about a 928 pump, that they seem to fail at 10000x the rate of everybody else's pumps?

Wisconsin Joe

It's not the failure rate, it's the consequences of a failure.

I've had WPs go in small block Chevys. Driven by either the fan belt or the serp belt (depends on how old the car is).It makes some noise & leaks from the shaft seal. If you let it go long enough the motor heats up. No big deal.

The PO of my Cayenne had the WP replaced when it failed. Driven by the serp belt. Again, no big deal (not cheap at the dealer though).

If the WP in a 928 fails, the TB will likely fail. Typical scenario - WP fails & seizes. Car overheats, driver stops. Belt had been sliding over the WP pulley and is on the edge of failure. When the motor stops, the heat on the pulley cooks the nearly failed belt onto the pulley. IF the driver is smart and has the overheated car towed to a shop, then he is most likely fine.

BUT... If he lets the motor cool and tries to fire it up to limp home (which a lot of us would probably do)...

The belt snaps and valves crash and the bill becomes...

Big.

Speedtoys

I get the consequences of the failure..but still, the failure RATE is way way higher than the rest of the world.

If WPs failed elsewhere at the 928 rate AND manner, Auto Zone would have nothing but water pumps in stock.

Impellers dont fall off other cars, that I -ever- read about, anywhere. But on 928s...

What is the 928 design issue that causes the RATE of failure -and- failure mode that is also unique.

WPs rarely seize in other cars..they leak and you replace them. I just dont see the "seize and impeller" issues anywhere else. Why?



I believe that the evidence here, is that when we get a new known GOOD global supplier online with metal impellers, and we question them and they balk at it with annoyance...maybe it's been -a- problem with -a- vendor bad design in the past, but not a pump design issue that actually exists in the water pump world.

Mark Thornton

check his feedback?

Imo000

Impellers come of other engines too. Common with plastic impellers pumps.

mark kibort

exactly. my experience is the plastic impeller coming loose.. also, most failures are a leaky pump and it makes noise. I think the HUGE failures are when folks fail to listen to the engines. any issues and the pump starts to make noise.. except the slipping impeller on the shaft. (ask me how I know that). Scot had a moving impeller to the rear, and it did graze his block, but there was no problem with cooling afterwards . replaced with Laso pump

lousy designs.. I don't know what they could do, but a roll pin is all that thing needs to keep in place!

outbackgeorgia

Wow, better than an oil thread!
Bearing design, quality, and seal design and quality are things not discussed. Casting precision is also a factor.
A ball bearing is a precision part, and quality varies greatly. I believe Porsche quality control of their vendors on this low volume part is the primary reason for their high price. Millions are not made, so the unit cost is high.
Even if a single example of a non Porsche pump turns out to be a bargain high quality part, what assurance exists that the next batch will be equal?
Dave

Cosmo Kramer

Porsche has had the castings for decades. If someone can duplicate and sell for a profit at $150, charging what Porsche does is pure gouging. You can't tell me stricter quality control and a high quality bearing costs $800 more per pump. Ed hand builds his pumps, tests each one and sells low volume for $450. Porsche should not be charging more than this.

Some people wonder why high end German used car values tank so badly? This is why. Cost of maintenance becomes prohibitive.

James Bailey

Exactly the point. They need only make a pump which LOOKS like a 928 pump. No doubt sourcing bearings from other low cost sources. And as noted no understanding of the original design beyond it is JUST A WATERPUMP..... and they took one apart once , when they copied it

kos_007

Even reputable automakers like Porsche make bed design decisions from time to time. 928 water pump design is one of the examples. Another example is IMS bearing design in 996 and others.
In case of 928 the water pump was designed as a part of the timing belt system. The 8 food long timing belt itself transmits significant forces both static and dynamic to propel 4 camshafts and 32 valves. In addition to static forces there is significant vibration of the timing belt at higher RPMs - these dynamic, harmonic frequency forces are transmitted to the water pump shaft, bearings and seal. In case of 928 water pump the radial load is controlled by a roller bearing and axial movement is controlled by a ball bearing. Some cheap water pumps have 2 ball bearing design which cannot cope with significant radial forces.
The nature of this design makes 928 water pumps more likely to fail then in almost any other car.
Another consequence of this design is that if the water pump fails it frequently leads to timing belt failure which in turn scrambles the valves.
Water pump failure is in fact the most common cause of timing belt failure in 928. For many cars it is the end of the road and many of them end up being parted. I believe that combination of bed design and outrageous price of a new Porsche water pump is a leading cause of demise of our cars.
Having said that I would still use only a new original Porsche water pump and I am in full agreement with Greg Brown.