Rebuilt Water Pumps
08-10-2016, 07:56 PM
#31
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The shaft is part of the bearing cartridge, so it is made to very specific and very tightly controlled tolerances. (Doubtfully, no one here has the tools or a contolled environment test room to accurately measure the differences.)
Because the shaft is an integral part of the bearing, it is always replaced in a "rebuild".
Because the shaft is an integral part of the bearing, it is always replaced in a "rebuild".
08-10-2016, 09:28 PM
#32
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This help doc?
08-10-2016, 11:14 PM
#33
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Not quite as many as for which oil to use. But close. And a much more serious topic.
The first threads on wide-spread rebuilt pump suckage start ~2008 IIRC and are quickly followed by threads on block vollute surface machining due to migration of metal impellers. The first machined block I found was 2005.
08-11-2016, 01:10 AM
#34
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08-11-2016, 01:31 AM
#35
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I just removed a rebuilt pump that the impeller and pulley stayed on but the bearing cartridge was migrating forward. The impeller had eaten into the pump body a fair bit and was barely turn able by hand....
I will not install rebuilds at this time.
I will not install rebuilds at this time.
08-11-2016, 08:59 AM
#36
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Miles and where did you buy the rebuild, please.
08-11-2016, 12:06 PM
#38
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I stopped selling rebuilds a number of years ago. I would be surprised if any 928 parts supplier does anymore.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
08-11-2016, 12:33 PM
#39
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I installed rebuilt waterpumps on both the Stepson and the 89 back when I got the cars (2004 & 2005). At the time, the rebuilds were a known commodity, they were sold through ALL the major 928 suppliers, and it was a good alternative to paying Porsche prices.
I basically got 10 good years from both waterpumps.(hard to be unhappy with that)
Strangely, they both began to fail within a month of each other. New pumps this time for both cars.
I basically got 10 good years from both waterpumps.(hard to be unhappy with that)
Strangely, they both began to fail within a month of each other. New pumps this time for both cars.
08-11-2016, 12:50 PM
#40
Nordschleife Master
I installed rebuilt waterpumps on both the Stepson and the 89 back when I got the cars (2004 & 2005). At the time, the rebuilds were a known commodity, they were sold through ALL the major 928 suppliers, and it was a good alternative to paying Porsche prices.
I basically got 10 good years from both waterpumps.(hard to be unhappy with that)
Strangely, they both began to fail within a month of each other. New pumps this time for both cars.
I basically got 10 good years from both waterpumps.(hard to be unhappy with that)
Strangely, they both began to fail within a month of each other. New pumps this time for both cars.
I think a lot of people are forgetting that belt tension is important to the longevity of a water pump. I have seen some 928 belts way OVER tighten, which puts undo stress on the water pump pulley/bearing assembly. Some DIY'ers and mechanics don't take the time or bother with getting the tool to set the belt tension properly. To me belt tension is the most important aspect of the job.
Last edited by Dan87951; 08-11-2016 at 03:46 PM.
08-12-2016, 09:01 AM
#42
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The bearing on the lower right is a roller/ball bearing type which is the style Porsche uses in 928 pumps because the roller side handles the load of the timing belt.
The other two are ball/ball bearings and are used in applications where the load is light and speed is more important.
Unfortunately the cheap E-bay copy cats who sell $100 water pumps and careless re-builders use the cheaper and weaker ball/ball bearings which cannot handle the load and associated vibrations that are present in the 928 system. So you get leaking seals and impellers that contact the pump face and work there way off or the shaft moves and grinds the impeller into the block etc.
08-12-2016, 10:59 AM
#43
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The bearing on the lower right is a roller/ball bearing type which is the style Porsche uses in 928 pumps because the roller side handles the load of the timing belt.
The other two are ball/ball bearings and are used in applications where the load is light and speed is more important.
Unfortunately the cheap E-bay copy cats who sell $100 water pumps and careless re-builders use the cheaper and weaker ball/ball bearings which cannot handle the load and associated vibrations that are present in the 928 system. So you get leaking seals and impellers that contact the pump face and work there way off or the shaft moves and grinds the impeller into the block etc.
The other two are ball/ball bearings and are used in applications where the load is light and speed is more important.
Unfortunately the cheap E-bay copy cats who sell $100 water pumps and careless re-builders use the cheaper and weaker ball/ball bearings which cannot handle the load and associated vibrations that are present in the 928 system. So you get leaking seals and impellers that contact the pump face and work there way off or the shaft moves and grinds the impeller into the block etc.
So, this leads to new questions.
A) Can we source the good shaft and bearing/seal cartridge from any vendor?
B) Can we get impellers with a brass or steel bushing made?
If so, we can press the stuff together and be more sure of our WP in the future. If we can't get the impellers, maybe we can take existing impellers from the pump, remove it, and press in a knurled brass bushing then press that onto the shaft.
I've had good luck with my Ferrari rebuilds as I only use *** bearings and seals. So far, zero failures. Of course, they are under a lot less belt stress than the 928, and likely lower run cycles as well.
08-12-2016, 12:00 PM
#44
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Yes, I had a catastrophic pump failure at 85MPH on the way to 3rd coast two years ago. It was just as you described except my impeller didn't migrate, the whole thing just stopped. I didn't take it apart, but the car sat for about 2 years and I suspect the seal failed a bit and I got water into the cartridge. That's the typical failure mode. I think in Seans case, the cartridge is still good, but the impeller broke free of the shaft.
So, this leads to new questions.
A) Can we source the good shaft and bearing/seal cartridge from any vendor?
B) Can we get impellers with a brass or steel bushing made?
If so, we can press the stuff together and be more sure of our WP in the future. If we can't get the impellers, maybe we can take existing impellers from the pump, remove it, and press in a knurled brass bushing then press that onto the shaft.
I've had good luck with my Ferrari rebuilds as I only use *** bearings and seals. So far, zero failures. Of course, they are under a lot less belt stress than the 928, and likely lower run cycles as well.
So, this leads to new questions.
A) Can we source the good shaft and bearing/seal cartridge from any vendor?
B) Can we get impellers with a brass or steel bushing made?
If so, we can press the stuff together and be more sure of our WP in the future. If we can't get the impellers, maybe we can take existing impellers from the pump, remove it, and press in a knurled brass bushing then press that onto the shaft.
I've had good luck with my Ferrari rebuilds as I only use *** bearings and seals. So far, zero failures. Of course, they are under a lot less belt stress than the 928, and likely lower run cycles as well.
Yes to all.
I use Porsche impellers which have the bushing and so far I have had no issues with them other than they take forever to come from Germany at times.
Cartridge bearings and seals are readily available. I use a specially made bearing because of my shaft requirements for the drive hub but anything can be had with money.
Ed
08-12-2016, 12:46 PM
#45
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Great discussion guys. Thank you.