85euro928

I need some advice.
I've owned my 85 Euro since '08 and I'm now about to put in the fourth WP in 20k miles.
A little history; I pulled the engine in '10 to fix a broken cam shaft. I also replaced the WP with a new Lasso unit as there was play in the bearing (but no running noise) I also installed a Gates racing belt and a PKT. A few years later I blew the front main seal (my fault). I pulled the engine, rebuilt everything and replaced the WP again as there was play in the bearing again and I didn't want to chance it. 11 months ago right before Frenzy I had this happen and replaced the WP again.
(sorry for the video quality).
Driving back from the GTG at Tass's in June my car was running a little cool. I didn't think anything of it as I had just changed out my stock radiator to a new unit that I thought was maybe cooling better. I came home, put the car up on jack stands, and started to rebuild the AC system (the wife drew the line going to GTGs w/o AC). I finally finished this weekend, started the car and noticed that the top rad hose was hard and hot but the bottom hose was was soft and cool, and the 11 month old WP was making noise. Figuring that the tstat had been stuck open and was now stuck closed I changed the tstat but still have this WP noise.
From the sound of it I'd say the WP bearings are going bad. The first two I caught before I heard them but these last two are noticeably loud. I run 50/50 antifreeze and even strain the liquids with a paint filter before putting it in so I know the coolants clean. I drained the antifreeze in to a clean bucket yesterday and it looks fine. I'm going to replace the WP AGAIN but come on...

Mrmerlin

Thom put a regular belt on the engine.

GregBBRD

Interesting that all of the failures are bearing related...without coolant leaking from the seal.

Bearing failures from seal leakage are simple to understand....the hot water steam cleans the grease from the bearing and failure occurs very quickly.

Bearing failures without seal leakage are another matter, completely. You didn't specify the brand of pump in the later failures, but if Laso, that would be strange....Laso uses a high quality bearing.

Multiple bearing failures without seal leakage can come from only two possible sources: Terrible luck or excessive pressure on the water pump bearing.

It would be interesting to see how much piston travel you have from the aftermarket tensioner system when the engine is hot.....I'm betting it is close to being "bottomed out".

The Audi tensioner retracts when the engine expands to compensate for the increased belt pressure. Given that the Gates racing belt stretches less than the stock belt, the combination of these two aftermarket pieces could drive the tensioning piston back as far as physically possible, yet still require more movement to reduce belt tension.

This senario would significantly increase belt tension, "killing" water pump bearings.

At any rate, toss all that aftermarket "problem waiting to happen" stuff in the trash can. Use a factory water pump, factory cam belt (or "regular" Gates), and a stock tensioner. Replace all the worn pieces when you assemble, make sure the tensioner gets bled and doesn't leak, and you won't have any more problems. Everything will last for 45,000-60,000 miles (mileage depends mostly on the condition of all four of the gears the belt touches.)

Yes, you will need to adjust the belt initially at 2,000 miles and every 15,000 miles after this, but this is a very simple proceedure.

85euro928

Stan,
Thanks, I think this will be my first step. Unfortunately the belt is new :/

Greg,
I have the last two WPs stashed away someplace so I'll check but I'm 99% sure they were Laso pumps. Here's another video you may find interesting. This is the pump I replaced last year.
Also, I'm not positive but I think I measured the PKT last time and it was 7mm and the limit was 9mm but again I'm not sure. I know I was worried because I had the heads cut and they're now all the way to the limit but I remember that I was within tolerance with the PKT. I'll investigate when I take it apart and report back.

The other interesting thing is that these failures just appear to happen instantaneously. I have my head in the engine compartment most everyday I drive the car listening for just such things and these failures don't slowly occur, they're not there, then they are.

Lastly, in case anyone was wondering the gears and roller have about 10k on them and I rebuilt the componants of the PKT last year, probably less than 5k miles ago.

Mrmerlin

Gregs suggestions are worth consideration as well .
I was thinking replace one thing at a time,
but hey return everything to stock it will work fine.

85euro928

I was thinking one thing at a time as well starting with the belt but also carefully analysing the PKT both on removal and installation. Need to do some homework first on exactly what that means.

docmirror

If you want to do FA, then just make one change at a time, and given the low duty cycle you'll have your answer in 3-5 years. If you want to stop replacing WPs, just go back to bone stock. Presuming you don't race your 928, and don't plan a teardown after 2-3 track sessions.

Again, given the low duty cycle, your Porsche designed components should give you about 18 years of service, (20k miles in 9 years = 2200 miles per year) with minimal inspections and an adjustment after the first year or so.

ROG100

Hi Thom,
Sorry that you are having issues.
We supplied you with a new Laso with plastic impeller April 2014.
Roger

ROG100

We have had no issues what so ever with the Long Life Gates belts with over 300 sold.

ROG100

Thom,
New water pumps have lateral play in the bearings and looking at your video I think this is what you are seeing. I have no records of Laso pumps with bearing failures.
If the bearing was failing you would hear it and bearing wear would effect the seal and it would leak.
Are you sure you have an issue with the pump??
It would be interesting to know the make of the other pumps you used?
Roger

ROG100

I also agree with GB that it would be worth checking the extension on the PKT now that we know you shaved the heads. How much did you shave off the heads?

85euro928

Yes, you can hear that WP squealing away in the first video and showing how much play it has in the third video. The Laso pump with plastic impeller that I'm currently using I got from another friend.

So that I know we're speaking the same language I consider lateral to be up and down (radial) and axial to be in and out. I didn't measure each of these on the last two pumps but in the third video I posted I'm moving the shaft up and down (radial) and the noise it made while running is in the first video, however none of the pumps I've had fail leaked.
I'm 99% sure it's the WP as the noise it's currently making is the same as the last one I had fail. I chased it down with a stethoscope hoping it was the rebuilt compressor but it's not.
I will check but I'm almost certain that all the pumps I've used are Laso pumps with plastic impellers.


I will definitely measure the extension on the PKT.
As to the heads the machinist told me he had to shave them all the way as they had been shaved by the PO's mechanic and weren't level to his standards so whatever factory says is minimum is where I'm at.

Thanks for the input.

ROG100

Lateral = up and down - correct.
This is the first bearing issue on a current Laso pump I have heard of. The fact that you have had two or three would be concerning to say the least. Maybe just unlucky or something else is going on.
Prior to 2014 the Laso would probably have a metal impeller.

85euro928

If you knew me you'd know the answer was "unlucky"

PorKen

So, you are saying it would become a stock tensioner?

The stock tensioner barely retracts, if at all, and the belt is installed and tensioned (and re-tensioned) at a level much higher than necessary. If this 'theory' were true, you would have seen many more failures with the stock system.

There have been many, many installations of Racing belts with PKTs. Just like newer cars with very little tire profile require a more compliant suspension, the PKT is ideal for the Racing belt as it reacts to belt length in real time, instead of using high static tension (pre-stretching) to compensate for the shortcomings of the stock tensioner.