Marine Blue

Technically the bushing OD does have increased surface area in immediate contact with the impeller but the ID of the bushing remains the same since the shaft diameter hasn't changed. The question is "when these pumps failed was it due to the impeller material failing or was it due to the shaft material failing?" If the impeller is the failure point they may be on to something with this change.

GregBBRD

Sure, although your (and Mark's) rebuilder claims that they do the rebuilding for Porsche.

GregBBRD

There are actually many differences between all the pumps, which I did not go into, for reasons of space.

The "factory" pump's impeller appears to be forged....and it is balanced. The Laso pump's impeller appears to be cast and is not balanced..or it was so perfect that it did not need to be balanced.

The pulleys, on the factory pump and the Laso, appear to be very close to the same. Destructive testing would be needed to determine materials used.

Clearly, since the rebuilder uses factory impellers and pulleys, these are of factory materials.

Rebuilding these pumps is very easy, for the rebuilder. Press them apart, clean the parts. Surface (sand) the housing flat. Throw on a coat of paint, and press in new bearing. Very high profit, when done in any kind of volume. He should be able to have all of the impellers and pulleys measured, very accurately and reject those that are worn or oversize. Of course, that would mean that he would need to give a crap, which is very questionable. I have copies of Mark's communications (back and forth) with the rebuilder. He seems to be only interested in not being responsible for any failures.

DR

Yep, I'm here :-)

My experiences (so far) with the rebuilt water pumps have luckily been a little different then some.

In the last 10+ years of selling them I am only aware of 4 failures from our customers. I am sure there are some we haven't heard of, but can't say for sure. While 4 failures are still 4 too many, it is pretty good considering the amount we have sold.

Of those 4 failures one happened in 1998 and was found to be "noisy" upon installation and immediately removed, obvious defective bearing assembly. The next one was sold in 2003 and customer noticed an increase in temps after approx 12k miles and approx 2 years. Impellor or pulley was evidently slipping. The 3rd was sold sometime in 2006 and put into service later in 2007?, this was a catastrophic failure of the pulley. The last one was sold earlier this year and started leaking after only 2k miles.

Up until Porsche basically stopped selling rebuilt units all of our rebuilt pumps were Genuine Porsche rebuilds. When they stopped selling them in late 2004 we started getting them directly from the rebuilder Porsche used. When we contacted them we were told there were 3 different "rebuild levels". We were told that the highest (and most expensive) version was the one they did for Porsche and we instructed them that this was what we wanted to sell and have been ever since. I can't say what the difference is between their different rebuild levels is, but was told the versions with the plastic impellors were the "Porsche Version". FWIW, if you look at the years of the 4 failures we had 2 were Genuine Porsche and 2 were the "Porsche Version rebuilds"

Even thou the cost of using the "Porsche version" was basically a wash or slight loss for us when we sold them at the market price of $115, I felt it was important to use the highest quality rebuild offered on such a critical item. I have no knowledge of what "verion" was used by others so I can't say if using this version helped give us a better track record than some, or if it was just good luck.

However, after watching this thread (and others) and after some discussions with Mark (regarding some of the issues Greg mentioned) I too have become very concerned about the future of rebuilt water pumps for our beloved 928s. IMHO, the hand writing is on the wall.

If only we had all come up with some sort of a universal secret marking system so we could track how many times a core had been rebuilt, we as vendors could have better monitored this and culled out some of the cores rebuilt "X" number of times. I would guess it is way too late for that now, although it might help a little.

In the past year I have been in contact with a manufacturer about making a new robust user rebuildable waterpump, but that will not happen quickly and may not happen at all.

Like Mark and others I am starting to get more leary of the rebuilds and am watching them closely as they arrive.

In the interim we will also be offering the Laso water pumps for those that don't trust the rebuilds. Current pricing is $225 for the 87-95 version and $285 for the 78-86 version.

Hope this info helps the cause!

Happy "almost" New Year to everyone.

fst951

Hi there.

There is no need to do destructive testing Greg. You gave me a hard time before when I suggested how to cut some tough materials awhile ago, but this time maybe you would like to hear me out. Send me both pulleys or as many as you want and I can scan them with a special metal testing gun and tell you the composition and density of the items. It will tell you if they are forgeds, cast, vacuum cast, die cast, investment cast etc. We have a friend with one of these guns. They cost about 20k, but they are well worth it.

I won't charge anything to test the pieces if you guys really want to know.

Thanks.

GregBBRD

I was just going to smack them with a hammer, while clamped in the vise and see how they broke...there's another way?

That sounds like a great offer. I'll pack them up and send them. Forward me an address by PM and I'll get Mary to ship them up to you.

Thanx!

RyanPerrella

OHHH COOL

Thats some nifty laser beam! I had no idea such thing even existed.

sounds like that could come in real handy, especially when trying to compare the quality of all these different pumps.

ew928

Testing both pulleys and impellers?
Or just the pulleys.

Or does the hardness of the impellers not matter.

GregBBRD

I'd say we test both. More knowledge has to be better.

Damn. Now I need to find something else to hit with my hammer. Anyone need their engine tuned?

Bill Ball

Thanks for clarifying, Mark.

Rick Carter

Great offer, thank you.

John Veninger

Who would have thought getting a quality rebuilt water pump would be this difficult.....

What are the 944 guys doing, or are their pumps "better"?
You would think the volume of those pumps being re-built over and over would be much greater.

jon928se

It probably is much greater but there's only about 50 people reading this thread

gauntlet thrown down - let's make 2009 the 928 year of the water pump.

ROG100

Hi DR,
Thanks for the very imformative post.

You say that Porsche stopped doing rebuilds back in 2004 - before my time I know - however I have been supplying Porsche rebuilds (not many) for the last 2 years. Just ordered another one for Greg to test. They are available.

Greg,
Would you be kind enough to let me have your shipping address by email or PM and I will get the pump to you.
Roger

Black Sea RD

From all that's been posted so far, it would seem that rebuilding aluminum water pump housings that were not really designed for rebuilding is not a good thing. From my limited knowledge this makes a lot of sense since the rebuilder and his/her selected rebuilding parts and methods become very important to the end result.

Since a 928 water pump failure can have catastrophic results for the 928 engine, it would seem prudent to put in brand new water pumps in your 928. From what Greg B. has found so far the two leading contenders are the OE Porsche water pump made by GPM and the Laso water pump.

The Laso pump has taken a lot of abuse on this list because of it's rougher looking casting and that these housings were not being accepted for rebuilds. Not because of a verified higher failure rate. A fact somewhat verified by DR in his post.

The price for a new Laso pump at between $200-$300 depending upon model year seems very fair. Rebuilt water pumps initially look like great price deals until you are not given back your core charge or when they fail. That 928 Intl. will no longer be offering rebuilt water pumps based on what Greg B. has found should be a good clue for most 928 owners on what not to buy.

I personally believe this whole water pump deal has become a bit too hysterical. There are viable options currently available for the 928 owner without getting involved with a totally redesigned and expensive water pump that, although might be attractive to a select few, will not be able to able to break even on the R&D costs to develop one.

Just my humble opinions,
Constantine
P.S. One option for those that want extra security would be to spot TIG weld the impeller and pulley to the bearing shaft of a Laso water pump. A good welder can get this done with no heat soak damage to the internal water pumps seals. Why a Laso pump? Because these are not readily accepted for rebuilds, are cost effective to purchase and well made.