S4ordie

If a true 50,000 mile / 5 year WP could be manufactured that addressed the common problems of the present WPs available and if people like Greg B, Roger and others with lots of expereince with this issue were to endorse, I'd buy that WP and only that WP. I'd also be willing to pay a premium for that insurance. Same is true for other elements related to the TB.

GregBBRD

The bearings seems very adequate (except for the "Chinese" pump). I've seen very few bearings that actually failed...and when they did, the seal had been leaking for quite some time.

The main problem seems to be either the impellers coming loose, or the pulley falls off. I think the problems with the "rebuilt" pumps are that these pieces get reused over and over again.

I was thinking about this, today. Seems like the stock casting is a good casting and the bearing is plenty strong. I'm going to look into having new CNC impellers made and new pulleys made....both with higher interference press fits. It might also be possible to have the impeller and the pulley welded onto the shaft of the bearing.

S4ordie

I would think it possible to design an impeller that also increased flow with today's FEA/FEM/CAD/CAM/CNC design and manufacturing tools. A stronger, more reliable WP with greater flow = higher premium many are prepared to pay.

jon928se

I don't think the flow characteristics of the impeller are any part of the problem.

If well maintained the stock 928 cooling system seems more than capable of holding it's own whatever the environment it is operating in.

Greg Brown's recent experience aside the most frequent water pump failures would appear to be either the impeller migrating towards the block or just becoming loose so it doesn't rotate, the pulley falling off or multiple rebuilds leading to leaks and slow failure of the bearing.

There are simple fixes for the first two - pin or weld the pulley/impeller, and the third - avoid multiple rebuilds.

The 928 water pump new from Laso is not expensive by European car standards in fact it compares favourably in price I paid for a replacement wp for a GM Vauxhall Astra (1.6 litre econobox) 5 years ago.

Hypothetical solution to the problem

Persuade Laso to refine the pump design even if it costs 50% more. Put enough comment on the internet about how bad all the other pumps are and nobody will buy anything but new good Lasos. Pump problem solved.

Black Sea RD

Greg,

We recommended this welding solution on the last thread.

Why not just TIG weld the current impeller and pulley onto the shaft. No need to incur more costs as these Laso pieces are good as is. The Laso pulley and impeller are both metal at this time which will facilitate the welding fix.

Making new impellers and pulleys will make you have to remove the old ones and replace them with these new ones, in essence giving more room for problems to crop up during the rebuild.

A few simple TIG welds done by a trained welder will keep the heat soak down and not damage the seals of the bearing unit. Problem taken care of easily and without great expense.

However, all this is really conjecture until you find out what caused the Laso pump to fail on the dyno runs that has caused this whole thread to begin with. And again, how many failures have there really been of new Laso and Porsche pumps to warrant a drastic change?

By the way, IIRC the rebuilt units have new pulleys and impellers installed onto a new bearing unit, with the aluminum housing being the only thing that is re-used. However the interference fits we don't think are as tight toleranced as ones that come straight from the manufacturers brand new.

Sailmed

And then there is the third option...............

The scamwhale special...

Yes, ladies and gentlemen - you now have the chance to "save" your 928 from those "new and unproven designs"!
I have a proven used Porsche pump off a 30 year old car for sale at 1/2 the new cost!
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But wait....


If you act now we will even include a free bottle of worry wart Rum...

WallyP

If I were going to "fix" a new pump that had a metal pulley and impeller, I don't think that I would weld it. Welding makes it a throw-away.

I would consider drilling a small blind hole into the interface of the impeller and shaft, parallel to the shaft. Tap the hole and install a small Allen grub screw, using blue Loctite.

A pulley or impeller installed thusly will not come off, but can be removed if desired.

GregBBRD

Obviously, the pulley or impeller is easy to drill and tap for a set screw. The problem is that the shaft that they get pressed onto is very, very hard (bearing material). The set screw therefore has nothing to "bite" into, so it is worthless, which is why everyone doesn't do this.

Black Sea RD

Hi Wally,

Good to see you join in!

What you describe is an alternative that was also discussed.

However current thinking is that Laso water pump housings are made of a softer cast material and they shouldn't be used as rebuild cores. In essence they are throw-aways after their use. In fact any aluminum housings, unless they are designed with rebuilding in mind, should probably not be used again.

Although do-able, this method will also require a bit more finesse than just TIG welding a few spot welds.

Posted before seeing Greg's comments too.

Cheers,

WallyP

I have a drill press and a tap - I don't have a TIG welder...

GregBBRD

Rebuilts reuse the impeller and the pulley. The "fit" problem is because the pulleys and impellers have been pressed on and off, so many times. New pieces would solve this.

Hvithaien

Are the seals and bearing in the pump obtainable from seal and bearing suppliers?
Would surprise me if the bearing and seals in the pump are one offs made only for Porsche.
If they are obtainable, I would consider to rebuild the original Porsche pump I have as a DIY project.
To get the pulley and impeller to hold on to the axle should be a minor hurdle (I think.... )

Anyone tried to find the bearing and seal from other sources?

I've seen rebuild kits on Ebay, but I guess we wouldn't know the quality of those products... http://cgi.ebay.ca/1977-90-Porsche-w...3%3A2|294%3A30


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E

Black Sea RD

Hi Greg,

Understood about the TIG welding.

As far as making new impellers and pulleys, I thought you meant getting a brand new Laso pump and just changing out these two parts with your new ones. Then what you suggest goes back to rebuilding the whole unit and re-using the Laso water pump housings which are not made for rebulding in the first place. Which then comes full circle to building a whole new water pump housing, impeller, pulley and bearing unit.

As far as re-using the impeller and pulley in rebuilds, the "Porsche" rebuilt units I've seen use a plastic impeller that looks brand new. The pulley might be re-used but it is replated at least since they also look brand new. Don't know though which ones we are describing to each other, you might be describing another rebuilt pump from another vendor?

Hope all this is being taken as a problem solving discussion. I in no way am questioning anyone's experiences on this water pump matter in a debating sort of way.

Regards,

GregBBRD

Yes, excellent discussion, from my point of view.

I was actually thinking of rebuilding/having rebuilt the original Porsche pumps, not the Laso pumps. Certainly, many of these have been rebuilt more than once, but as long as the aluminum housing where the bearing gets pressed into doesn't get distorted or worn, these castings should be good. This can, of course, be measured.

I've thrown ideas around with Mark Anderson quite a bit, since his rebuilt units (he uses the same rebuilder that Porsche uses) have worked very good, for me, over the years. Like I said, I can live with the occasional leaky seal....that's going to happen with any brand of water pump. The problem with the rebuilder is that he is reluctant (not interested at all) to spend any additional effort in rebuilding these units. Simple careful measuring of the impellers, pulleys, and housings would eliminate most of the problems with "migration" of these pieces...simply throw away the pieces that are no longer tight enough to be reused. As "good" pieces become unavailable, manufacture more.

Porsche provided and sold the plastic impeller, separate, for quite some time. Not sure why...seems like you'd need the bearing, too. Perhaps they knew that the plastic impellers could get damaged and wanted people to be able to replace these on units with good bearings?

ROG100

In my discussions with Laso I broached the question of the perceived softness of the casting material.
They use a sand casting process to lower tooling costs but add "something" to the metal to establish a strength of material equal too or better than pressure casting.
I checked this out with my contacts at "Doncasters" and "Wyman Gordon" - both large Aerospace casting houses - and this is normal practice with sand castings, so apparantly correct.
So the softness of the Laso casting is a non issue.