JG928S4

well, the old Porsche rebuild had metal impeller, new rebuilt has plastic impeller w/Roger Inspection....Smooth sailing in the future! I just will put a Diesel powered sticker on the Butt and it will all make sense. Just kidding, aint gonna drive it w/the noise.

928Quest

I had a similar issue in February, driving on freeway when suddenly the belt tension indicator came on. I exited the freeway and pulled into a hotel parking lot, I could hear a squeaking noise under the covers and I smelled the smell of coolant. Shut it off and flat-bedded back home.

I suspect the WP bearing and the car sat in the garage until late summer when I finally got around to having it flat-bedded to Dan Warner (Exotic Motorwerxs).

The WP was shot, not much or any belt damage, everything else was OK. Replaced with new pump, new belt, and some other work.

This could have happened to me. So I guess a word to the wise is, if your belt looses tension, find out why. Don't just retention and drive on because something somewhere has failed.

H2

Frankly, when PorKen figures out a way to modify a rebuilt water pump so it's more reliable, I'll buy one. Until then, I'll be buying genuine Porsche. Price is not the issue here.

H2

worf928

BB and JG, I really sorry to this this happen!

+928

For a while now I've been telling folks up here in Yankee Land that the belt should only stretch once. If, after the post-install re-tension the belt becomes once-again loose then that means that there is a problem that must be tracked down and corrected. Randomly self-loosening belts or random belt tension warnings are not random. I'm going to, from now on, absolutely live by that.

Black Sea RD

Must it only be PorKen?

WallyP

For several years I have been scorned because I don't believe in replacing a good waterpump as a routine part of timing belt service. I think that I win...

atb

If done professonially, does anyone see any issue with welding the pulley and impeller on the shaft? In particular, woud there be any balance issues that could cause failure of the bearing catridge? Any other potential issues?

I've seen the new laso, and it is a very stout looking unit. I really want to reduce my probability of a pulley or impellor comimg off the shaft to zero on the stroker, which is going to be impossible on any mass produced unit.

Bill Ball

I'm right there with you. The maintenance schedule has no provision for routine water pump replacement.

blown 87

General automotive repair practice is to go no more than 120,000 miles on a water pump that is driven by a timing belt. (no more than every other belt change)

Failing water pumps are not just limited to the 928, some manufactures have even went as far as to design the water pump housing as a replaceable unit.

The 928, does however seem to have a VERY weak pump and if the impeller gets into the block, then you have a problem.

You have been blessed with the luck you have had with your 928 Bill.

borland

Unless you have the original factory asbestos wp gasket, I'd still recommend replacing the water pump bolts and gasket. The non-asbestos replacement gaskets from Porsche or other aftermarket suppliers tend to weep coolant into the bolt area which allows for gradual corrosion.

However as Mrmerlin has suggested coating the wp bolt threads on assembly, with a non-hardening thread sealant, can prevent such corrosion affects.

Bill Ball

120K miles or every other TB sounds reasonable, although with the quality problems lately, lord knows what interval is optimal. Perhaps once a week. Mine has been changed about every 90K miles. I try to follow the 60K TB interval but have had to shorten a couple of the change intervals for other reasons. The first pump was done at 90K miles. The factory pump looked good as new and while the bearing had less drag than a new pump, it was still very firm. I could have left it alone.

H2

PorKen is a natural born mechanical genius (in my book). Plus he accomplished something daring that no other 928 developer would have even tried...put together an auto tensioner system to help eliminate belt failures and keep steady tension. It takes ***** to mess with anything that touches the cam belt. That kind of sysle is on my 968 and should have been on the later 928s. PorKen just went and did it.

I'd put my trust in him to design a way to make sure impellers wouldn't come off....and he'd probably use better bearings too. If he weren't busy with other development work.

Maybe someone will figure this out. I hope someone does before my next WP replacement.

H2

svp928

As far as welding the pulley and impeller to the shaft- the shaft is also the inner bearing race, and is made from a special alloy used exclusively for bearings- it does NOT produce a good weld- it just cracks and comes apart. Plus, the heat would cook the grease in the bearings, and melt the rubber seals, so even if you got it to stick, the bearing would fail pretty quickly. You could EDM a hole thru both ends, and pin them together, but that would not stop the failure JG just had. The other problem, bearing migrating in the housing, can't really be fixed on the pumps as they are now. The housing does not have enough material to add a circlip or shoulder to locate the bearing cartridge..

So, for now, the best solution seems to be getting a brand-new pump- the interference fits on the components is at its best on all-new pumps. Once they have been pressed apart and back together for rebuild, that optimum fit is lost....

borland

With the impeller captivated to the shaft (either mechanically or by spot welding), the pump could be rebuilt and modified by installing a spacer(s) between the TB pulley and the pump housing so any migration of the shaft would impart severe and audible wear to the housing (or spacers) instead of the engine block. Some disk brake pads incorporate a audible wear alert design.

polecat702

If it hasn't been posted, whats the general rule of thumb on replacement times for the WP/TB? The Sensors don't come on in my 87 S4, with 113,0096 miles. PO changed the WP/TB, tension,roller,cam belt idler, v belts, ribbed belt, thermostat & o-ring, at 106248 miles. I installed the PKlamp, and new pinch bolt over the weekend I got from Roger. Thanks, Joe