FredR

OK- so we all know water pumps fail from time to time. Porsche know this and modified the specification- not sure when but they changed to a plastic impeller- and they fail- I know this because the impeller came off on my late S4 water pump shortly after I purchased it in Dec 1998.

I seem to remember replacing it with a rebuilt unit from Devek that gave me no problems for the [approx] 5 years it was fitted. I took it off when I changed the timing belt because everyone said "change the pump when you change the belt".

I followed this line and fitted a factory pump with a new factory belt becuas eof immediate availability at the time. A few months later wipeout- I lose my much loved and immaculate S4 because of some tosser from the Indian sub continent on a mobile phone.

When I purchased my GTS [with known TBF failure] we found that my S4 engine had suffered some damage- the timing belt had lost a few teeth due to minor impact damage as it ran down and as a consequence a couple of inlet valves on cyl 7 were damaged. Dilemma - do I put a new water pump to match the new belt? Well I did not. Some 5 years later my WP is still running fine but for all I know it could fail tomorrow of course.

Those of us who have used the list for a long time generally know who knows their stuff and generally I tend to accept whatever these fine gents say as fact.

My postulations:

1. If we fit a new belt for time related reasons [when there is a low mileage pump fitted] should we automatically change the pump?
2. Given that the most expensive part of the pump is the casing and generally it is not a wear item- why should a remanufactured pump not work? Is can only be a quality issue? Has anyone actually seen cpmsistent evidence of rebuilt units failing or is it one of those urban myths thatr we are all too willing to accept?
3. Is it just that whoever made quality rebuilds previously has gone out of business or was I lucky when I used one? Indeed I still have this item and one from the original GTS engine that was relatively new as well [I think]
3. Why should a used pump fail just because we put a new belt on it? We tension the belt to a specific level of tension. We all "know" that new belts reputedly are "stiffer" but is that fact or fiction? Has anyone ever seen credible evidence to support this notion or are we all guilty of passing on the info? If they are stiffer is that a viable reason why a "used" but otherwise good pump should then fail?
4. Given impellers can fall off Porsche supplied pumps should we abandon them?
5. The Laso pump seems to be universally accepted to be the "king of water pumps" fair enough it may well be- what makes it better? Is there hard evidence or just a set of opinions with nothing to support them other than perhaps gut feel?
6. Are there any other options in the far corners of the world?
7. We generally tend to accept that a good reason to replace the pump is to avoid ripping the belt to pieces if/when the bearing fails. Fact or fiction- does a bearing failure actually cause a belt to shred and valves to clatter or is it urban legend? If a bearing were to fail, doe sit fail suddenly and spectacularly?

New OEM pumps are now some $800 over here I believe and I have no intention of paying that in a year or so when I need to pre-emptively change the belt.

I believe the Laso runs in the region of $400, still expensive a lot but better than a stock pump.

What should we believe here? I have no real position on this but I am interested to hear opinions.

I would probably change a pump if it had high mileage [i.e. greater than 60k miles] but I intend to change only the belt if the pump still has significantly less than 60k miles on it.

Over to you guys-what is fact and what is fiction here?

Regards

Fred

Bertrand Daoust

Interesting, very interesting.



No real fact here exept that my last (rebuilt) pump starts leaking after four years and about 10k kms.
Found few once of coolant on the ground after storage.
Is it the cold up here that make it leaks? Maybe.

Now I have Ed's pump and plan to keep it for a longer period for sure.
Maybe a quick inspection at my next belt change et voilà!

ROG100

Laso new pump with plastic impeller $285
Porsche new pump with Plastic impeller $1000.
Fact

928sRus will NOT sell rebuilt water pumps because of their high failure rate.

New Laso with plastic impeller - one know possible failure (not proven) out of hundreds sold in the last two years.

When asked I recomend taking the pump off and trying to determine if it is a new build or rebult.
If known pedigree check the pulley for bearing noise or movement and if good reuse. New gasket of course.

borland

Assume all pumps (rebuilt or new) are junk and that any replacements have a plastic impeller.

Bill Ball

This topic is at least as flammable as oil choice, HP vs. torque, and whether it's OK to chrome plate alloy wheels.

1. I don't anymore, but that's just me personally. I don't have "customers."
2. Reusing the shaft and re-pressing on the impeller has been one issue with rebuilds.
3. In the US there is one rebuilder, APC, that Porsche and others use. The pumps have a sticker on the inside of the housing that identifies them.
http://www.auto-pac-apc-water-smog-pump.com/home
3. I don't buy that.
4. That has been an issue. I think the new Laso contruction was intended to address this.
5. Hard to say. Not much experience yet.
6. Ed's modified pump, not that it is perfect. https://rennlist.com/forums/928-foru...ics-added.html
7. Fact. Seen spectacular failures, including several, such as this one, where there was no valve damage:
https://rennlist.com/forums/928-foru...p-failure.html
but many more where there was, such as:
https://rennlist.com/forums/928-foru...p-failure.html

the flyin' scotsman

I fitted a new Laso pump when I did my last belt change.

Its getting time to replace the belt again and Im going with all new gears and water pump, new Laso w/plastic impeller

chrly924s

Just replaced the pump on the 81 with a Laso plastic pump from Roger. The pump on the car had been replaced ( lots of red RTV squeezed out around it) but I wasn't sure when & I thought I felt some movement. Pumps are cheap when you only have to do it once.

Lizard928

I will no longer reuse "good" pumps on customer cars.

I have had a number of them where the pump was good at time of service, 2 years later and less than 5k km pump was bad.

SeanR

I will with the strict understanding that if I have to go back in there it's not on my dime. I've only had two that opted to keep the old pump, I did give a good twice over though.


I have had a few pump failures and they were all leaking, not installed by me either. One was a factory pump that was a few years old and the rest were rebuilds. I won't even give the option of a rebuilt pump, only Laso or Porsche pumps.

Bilal928S4

I had a pump (rebuilt) from DEVEK that ran for 10+ years and 30k+ miles. Changed the belt and new Laso pumps just because. No leaks, vibration or belt breakage. Just tensioned belt after 1k and 15k.
Bilal

worf928

I lost count a while ago of the number of 'new', 'low-mileage', or 'just-replaced' water pumps I have pulled from 928s where the impeller was either a) in the case of a metal impeller, eating the block or b) in the case of a plastic impeller getting eaten by the block.

I've replaced (for free or almost free) half-a-dozen or more rebuilt pumps I myself have put in since 2005. The 'oldest' pump had about 8k miles on it and the youngest had barely 1k miles. I've replaced half-a-dozen or more 'new', 'low-mileage', or 'just-replaced' water pumps that were installed by someone else. I have a box of pulled rebuilt pumps with migrating impellers.

It is not a myth. I've posted pictures in various threads when this topic has come up.

It is my firm belief that every 928 with a water pump that has been rebuilt more than once is, right now, getting its block eaten by a metal impeller or its plastic impeller getting eaten by the block.

There are, no doubt, exceptions. But, there's no way to determine how many times a pump has been rebuilt.

It is simple enough to check: remove the left-side belt cover and look straight at the water pump pulley. There is a weep hole in the casting between the base of the casting and the pulley. If the rear edge (lip) of the pulley occludes the weep hole then the impeller is migrating. If the belt is up against the forward lip of the pulley then the impeller is migrating (or there's a problem with other bits that touch the belt.) If the belt is migrating towards the rear of the left-side cam sprocket and you see a "bright spot" wear pattern on the sprocket teeth then the impeller is migrating (or there's a problem with other bits that touch the belt.)

That's my story and I'm sticking to it.

namasgt

I fitted a brand new Laso with the extra bushing on my S4 during the engine rebuilt in 2010. These were the last steel impeller pumps sold before the plastic Lasos became available. The pump failed after 20,000 miles. The impeller and pulley assembly was moving toward the front of the engine. The pulley scraped against the front plastic cover and the steel impeller had machined trough the pump body, 2 mm deep. Why did this happened? I don't know, coolant was leaking from behind the pulley and timing belt warning light did come on. I think this is the only extra bushing steel impeller pump that has failed.
Back in 09 I reinstalled a rebuilt Porsche pump on Rogers GTS. It looked pretty damn good, so he decided to reuse it. I think the pump had 30 to 40,000 miles on it. So far so good, Knock on wood.
I find it interesting that its being said that pump needs to be replaced every time you put a new belt on !!!

T_MaX

I have been ponder this issue myself. My pump is a Porsche factory new, not sure how many miles exactly (<10k, >15k,), age is the biggest factor (<5yrs). Got everything torn apart and everything inside the belt cover looks like new.

Roger, please amend my list of parts to include a water pump gasket. I guess I should at least take a look at it

jpitman2

I have a 10 yr old 928intl rebuild on mine, but its only done 13k miles on it. No leaks so far. Its staying on with the next belt too.
jp 83 Euro S AT 54k

Adamant1971

I sleep better knowing my pump is new and has a plastic impeller.