z driver 88t

Prepping for a timing belt service later this year (belt is about 5 years old, and cam gears are close to shot). I've done a ton of reading and searching on the forum about rebuilt water pumps and why not to use them on a 928). It looked like back in 2008 the general thought was to replace water pumps during t-belt service, but back then they were only $200-$300. Prior to that time it was pretty common to use rebuilt water pumps sold either directly from Porsche, 928 Specialists, or 928 INTL.

It was suggested that part of the problem with the water pump rebuilds is that there was no way to track how many times a pump was rebuilt and that failures were the result of too many rebuilds pressing bearing in and out of a housing too many times.

These days only new pumps are generally sold from what I can tell and at $430-$500 for a water pump is the rule of thumb to still do a replacement every service or do people replace water pump every other timing belt service.

In other cars I've rarely seen OEM qualtiy water pumps fail at less than 100K so I'm thinking every other tbelt service might be appropriate. However, the penalty for water pump bearing failure on a 928 seems to be loss of timing belt tension (why on earth did they do that?) so maybe every timing belt service is more desirable.

I'm sure there will be differing opinions on this (some conservative owners will change it every time, others won't), but is there a forum concensus of what are other owners currently doing?

James Bailey

Chris your 1984 is NOT a valve bender.....so no worries about a t-belt failure. Far different on the 32 valve cars. Your car just stops running and all it needs is a belt to be good as new !! My old very brown 1980 we at LEAST ten years before it jumped time at Willow Springs so then it got a belt and water pump. I had no idea how old the pump was.

SeanR

^^ what Jim Said.

GlenL

It's pretty simple: change the pump if it needs it and only if it needs it.

Some people like putting in all-new stuff. If you have time, remove the belt and check the feel of each pulley and the water pump. Then get those parts that felt loose or turned roughly.

ROG100

If you know the pump history and it is not a rebuild of dubious quality - take it off and check the feel of the bearing - if good new gasket and back on.

Doug_B_928

For the water cooled 911s, concerns have been raised, I believe most notably by Jake Raby (of LN Engineering among other companies) with the plastic impellers degrading over time, breaking off, and getting lodged in the engine such that these pieces of impeller are very difficult to remove from the engine. So, I recall reading that Jake recommends a fairly short time period for replacement of the water pump (I don't recall exactly, but I think it is something like every 3 years). Others have suggested to test the pH of the coolant and if it is below 9.5 to change the coolant (and the pump since the Porsche coolant used in the 911 is very expensive and the water pump is a bit less costly than that used on the 928). Since most of us are now using the Laso plastic impeller pumps, does this concern apply to the 928 as well?

928 at last

IIRC the problem Raby is referring to occurs after the shaft/impeller migrates to the point it contacts the block. No block damage, but the bits can migrate throughout the system and potentially block small ports into the heads causing hot spots and cracking. In our cars, and I may be wrong here, but I would expect to see leakage before it got to that point.

Adamant1971

The pump I just pulled out tonight was 928 108 140 0R

It seemed fine and probably could be left, but it's piece of mind.

New laso on order.

I can get rebuilt units for $200 locally. But it would drive me insane every time I drove.

GregBBRD

The impellers on the water cooled 911 vehicles are small and the actual "vanes" are thin. While I have never seen one of them missing, this might be what they are seeing happen (they certainly see a lot more of these cars than I do).

The 928 impellers are very robust...difficult to imagine these vanes breaking off.

ROG100

Doug - what is a 911??? 8>)

DougM

If you ask most people, it is a number you call in an emergency.
If you ask a stripper, **** star or hot woman, it is a sports car.

928 at last

Whatever it is, it would appear to be 17 Standard Galactic Units less than anything worth considering...
And that's without the application of Bistro Math which of course superseded the tired old Infinite Improbability Drive Theories.
Sorry,
Having a Douglas Adams moment....

Imo000

Yes the 996 pump vanes are very thin. When I was repairing my non running project, a piece of an old vane fell out of the head when I was re lapping the valves. I put a pic up on the build thread. The 928 pumps are bult like a tank when compared to the 996 and the heads feel and look much less fragile too.

Doug_B_928

It's a car that is increasingly becoming like a 928

Good to know that the 928 impeller is more sturdy.