blown 87

There are a lot of what ifs in your question, does it have all new gears? is it a Porsche belt or a Conti? does it have new idlers, what kind of tensioner?

I think the lowest mileage for a failure with factory parts was in the low 30,000 mile range.

I can tell you what I am going to do, and I am sure others will not agree, but mine got all new gears, idlers, pump, PK tensioner, Porsche belt and I am going to change it at 30,000 miles, but it should go at least 50,000.

To me it is just not worth the small amount it costs to remove the belt, check every thing and put a new belt on it at 30,000.

That being said, I doubt I will make it to 30,000 with out having it apart again, it has all ready been apart at about 5,000 miles.

polecat702

Blown87, I don't know what type of belt or other parts were used in the WP/TB service, I do know that the pump cost $209.00. I'am going to assume that would be for a rebuilt pump at that price. I think that doing this job over myself would be the smart thing to do for my own peace of mind.

blown 87

That is up to you, some here will say that there is no difference in the belts, some say there is.
The water pumps are a gamble, new or not, if it feels good and is not leaking I would be tempted to leave it alone with that few miles on it.
At $209 it could be a rebuilt or a new Lasso, so that is hard to tell.

worf928

I've been thinking about this question a lot lately. I'm leaning towards not replacing water pumps as frequently. But, in the cases where there is high-confidence of a metal impeller rebuild installed, I will lean towards replacing it with a plastic impeller pump or at least removing the pump and checking the pulley and impeller clearances.

F451

Me too. I've been collecting the parts for a timing belt/wp job and am concerned about putting a replacement wp in there. I like the idea of taking the old one off and inspecting it. Would be good to know if it has the metal impeller.

If so, that would be a deciding factor right there.

And I've been kind of hanging on for a new engineered wp from one of our many talented listers here, but so far haven't heard of anything on the near horizon so may be forced to go with one of the current options, which doesn't thrill me.

fraggle

Is there some nice inspection guide out there for those who want to just inspect the pump and flop it back in? Can someone write one? I'm going to leave mine in until it leaks. Of course I just rebuilt everything (!!!) 2500 miles ago...

heraclitus

It looks like it may be time for someone to redesign this system and mount an external water pump feeding the engine and replace the internal pump with an idler bearing....Sounds like a good future engineering project.

ew928

Roger or someone here can probably scavenge up a new/good pump and measure backface of waterpump to tip of impeller distance so those wishing to recheck their WP impeller for movement will know if what they have in hand is good for re-use.

brianrheffron

Besides the 928 my other fun car is a Triumph Dolomite Sprint
modified to period race car spec.
This has a quite highly tuned 2 litre OHC 16 valve engine with
a water pump driven off a spiral gear on a jackshaft in the block.
The water pump output is marginal for the state of tune plus
the drive from the jackshaft is prone to failure.
The latest cure for this problem is to remove the drive from
the jack shaft, blank off the water pump housing in the block
and install an electric pump. I'm not very knowledgeable
about the Porsche water pump problem but could a solution
not be found along these lines. The pump could be inserted into
one of the main water hoses and the old pump replaced with
a machined housing taking a much bigger/ better bearing for
the "water pump" pulley.

Lizard928

Brian,

Replacing the WP with an electric unit is doable. But it is NOT for the faint of heart.

You will need to either modify the factory WP housing or make your own with a spot to attach the rollers for the belt onto it.
You will then need to weld or somehow seal off the thermostat housing in the water bridge. You will then need to put the WP into one of the coolant pipes, and either add a controller to base the waterpumps speed off of temps, or add a remote thermostat and tap into the other hose.

blown 87

From what I have seen, that measurement can and does change from different pumps.

sidehatch

Another penus pump thread,we have got to get these pumps rite fellas,well see ya later.

Landseer

Thanks for posting Sidehatch. Always a pleasure.


Back to the subject, what an interesting idea. In inline pump mounted inside or in the place of one of the radiator hoses. Did I hear that right?

SharkSkin

The problem with that approach is that normally water circulates in the block during warm-up and flow through the hoses is blocked. Any external pump will have to have a way to provide this initial warm-up circulation AND move water through the hoses when needed.

Charley B

Like a thermostatic switch?