44 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHWater pump: plastic impeller or metal?
Reported or suspected cause
clearance face
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause
My thinking / understanding was it was the clearance face on the engine block (LH) which gets chewed as the impeller is able to move around.
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Suggestion
The chewed up face would need to be at least cleaned (removing material) or replaced since the surface is part of the block this would require a new half block or a shimmed face for the pump either way it would probably require the breaking down of the engine and hence a rebuild.
Leading evidence: 'clearance face' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'clearance face' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Clean (removing material) or' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
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Reported cause
The issue is consistency between crankcases in this region, which is all over the place.
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Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
We already fitted ceramic hybrid bearings to water pumps..
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Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed
We've installed a couple hundred of them over time.
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Performed · outcome unconfirmed
I installed an oem pump and have already put 5000km on it with no issues
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Clean (removing material) or
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1
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Suggestion
The chewed up face would need to be at least cleaned (removing material) or replaced since the surface is part of the block this would require a new half block or a shimmed face for the pump either way it would probably require the breaking down of the engine and hence a rebuild.
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Suggestion
Jake, Greg Brown on the 928 forum (been building and modifying 928 for decades) built a system to repair scored 928 blocks that had impellers dig into them.
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Suspected cause · Original poster
Also seems to me that the risk of plastic bits breaking off and finding there way into the recesses of the cooling passages is likely a bigger problem than scoring from a metal impeller (especially if I were to notice the problem rather quickly).
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
44 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T130754Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I recently purchased a 2000 Carrera with 82K miles. The seller had the clutch and IMS bearing replaced just prior to sale. I do not have records on prior service, so I plan to replace spark plugs, associated tubes, serpentine belt, water pump, and thermostat in the near future (maybe some other goodies as well).
Over the past year or so I have read (in Excellence among other places) about the potential hazards posed by water pumps with plastic impellers. That is, plastic bits can break away, find their ways into nooks and crannies of the cooling system, and impede flow of coolant. So, the deal was to get a water pump with a metal impeller.
Last summer I replaced the original water pump in my former '99 Boxster at 51K miles. The new water pump I got from Paragon came with a metal impeller, and the stock pump that I pulled out of the Boxster looked perfectly fine. When the buyer of the Boxster had a PPI done, I mentioned the new water pump with the metal impeller, and the mechanic said the metal impeller is bad. Apparently there is concern that if the bearing goes bad, the impeller can wobble and score whatever part of the motor the impeller resides in.
So, what's a DIY mechanic like me supposed to do???
I think that if I change the water pump, say, at 50K miles, then I should go with plastic or metal and not worry about it. Seems to me that I pay enough attention to my car that I would pick up some sign of a problem before a failure. But maybe not. Also seems to me that the risk of plastic bits breaking off and finding there way into the recesses of the cooling passages is likely a bigger problem than scoring from a metal impeller (especially if I were to notice the problem rather quickly).
So, forced to make a choice, at this point I think I would go with metal.
Opinions?
It seems the best solution would be a water pump with a metal impeller and either a ceramic hybrid or journal bearing! (or maybe just an oil line to extend bearing life, or maybe a roller bearing)
FWIW, I replaced my 996's original water pump at 67K miles as a preventive mntce. measure. I chose to install an OEM pump.
The old pump's plastic impellers still look new and the bearing feels fine. It makes a nice paper weight/conversation starter now.
relinuca
Stick with oem porsche parts. Don't bother with oem supplier pumps like Laso. I tried that before and it lasted about 5000km. I installed an oem pump and have already put 5000km on it with no issues
I'd go with the oem plastic, there's no point in a stronger impeller as Jake said if the bearings fail your going to tear up the block. Its the bearing that fails the blades only break when the failed bearing allows excessive movement and therefore contact with the block.
I've recently had to replace a failed water pump at 130,000 miles (original pump). Since we were busy I had the dealer do it and there was a couple of missing pieces. The dealers opinion was they've seen plenty of failed pumps and never had a issue cooling failure or hot spots following. If it had been a metal impeller I'd be looking at a new block / engine. I have 5k miles on it since and no issues so far. Bearings fail sometimes at the predicted life sometime a lot less.
I just did a porsche oem from sunset. I know a couple guys running around with metal impellers with no problems. I think it's up to you and your risk tolerance.
I started writing that as a joke, then realized it might not be a terrible idea. I've never taken apart a wp bearing, but I assume it's a sealed greased ball bearing. Do you use OEM pumps on your engine builds?
Jake, Greg Brown on the 928 forum (been building and modifying 928 for decades) built a system to repair scored 928 blocks that had impellers dig into them. Its a very clever system where there is a custom mill and then different size spacers that brings back the block to factory clearance. It's a portable system run off a hand drill. Very simple to use and is most importantly accurate. Thought might interest you. Could be easily tranfered over to M96 engines.
The issue is consistency between crankcases in this region, which is all over the place.
But the key is a wear surface that's installed when the water pump is.. That wear surface is disposable should the impeller take it out... This isn't something worth patenting so I may as well spill the beans.. It'll just get copied faster now, that's all.
We've installed a couple hundred of them over time. I've had one of them leak within 3 months, buts thats all. One more lost a bearing within 6 months.
Quality goes up and down between all the different choices with each batch. Whats good today isn't in 6 months. The only thing that stays the same is that everything constantly changes.
makes sense, and making the impeller a bit smaller diameter won't impart a significant change to coolant flow rate. Must mean a new pump head casting, or machining a groove in an old casting?
2003 Carrera 4S Speed Yellow / 1955 356 Continental 1500 Rust Red
The particular pump will not move enough volume. I have been working with John Benson, Director of Davies Craig, the company that makes the EWP 115. The 115 has proven to only be adequate to act as a post cooling pump after the engine is shut down, or to boost volume when used in conjunction with the stock pump.
We are developing the EWP150 version of the pump now, to see if it is adequate as a sole unit, or not.
I understand the joke, but....
Hot oil with a modern detergent package is pretty good at washing away grease. Hot water and antifreeze not so good.
A water pump bearing will start to leak coolant early on...and will be easily seen by a careful owner. The IMS bearing is hidden away inside the engine and won't exhibit easily observed signs of incipient failure.
May be I'm missing a point here but do the plastic impellers ever fail with out a bearing failure? If they don't the only advantage of a metal impeller is that it may not fracture and send small pieces into your water ways. However it will chew up the mating face on your block and require a engine rebuild to ensure the correct coolant flow.
It's not the mating surface that gets chewed up by the impeller and I'm not sure how an engine rebuild will fix this. It would have to be repair for the waterpump cavity.
My thinking / understanding was it was the clearance face on the engine block (LH) which gets chewed as the impeller is able to move around. The chewed up face would need to be at least cleaned (removing material) or replaced since the surface is part of the block this would require a new half block or a shimmed face for the pump either way it would probably require the breaking down of the engine and hence a rebuild.
Guys on the 928 board already figured out how to fix a dug in water pumped block. There is no reason the method couldn't be duplicated on our engines too. After all the 928 is an all aluminium block too. Their technique doesn't require anything more than removal of the water pump.
We've had a product for this for a while now. The inconsistencies in the blocks keeps us from distributing it. We can even apply it proactively with a new pump with a metal impeller. It can require machining to fit, but that machining can be done in-car with a fixture, cutter and a big enough drill.
I'd hate trying to support people on this one so it hasn't made it outside the Flat 6 facility.
That's similar to what we've done for the M96, but with some changes. It's the only way to solve the issue. One distributor wants to take the product we created and couple it with a metal impeller water pump. If they'll deal with the headaches of support I'll consider it.
Replaced my water pump in an emergency situation with one from O'Reilly's (gasp). Intended to swap it with the Pierburg asap, but it failed before I could even do that. 1000 miles exactly. Thanks O'Reilly's!
Have you found any issue with the OEM pump moving volume when you add a 3rd radiator (specifically the cup rad)? Would you recommend changing the pump more frequently if adding more cooling capacity?
Two times warnimg oberheated engine. Tsb for the coolant canister checked. Third time overheated engine waterpump thermostat failure. Repaired under warrsnty but engine had to come out so one week repair😡
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