geekapalooza

Well some day I’ll laugh about this hopefully, but not today.

Just finished up the Timing Belt job with new PCNA rebuilt water pump, new rollers, and tensioner rebuild. I also replaced the noisy power steering pump while in there.

My Shark started and runs perfect, no drips, no errors, just perfect.

EXCEPT – After idling a couple of minutes, now there is a bad moaning sound. I double checked to make sure the accessory belts are not too tight, they’re perfect. Then I put a long screwdriver (improvised mechanics stethoscope) on the water pump, and low and behold the moan can be clearly heard through the makeshift stethoscope (picture lots of four-letter words being muttered at this point!).

Then I watched the TB through the cam cover breather holes, it looks like it is moving fore and aft on the gears as it turns. Is this another sign that the issue is the water pump, or a bad new tensioner roller maybe?

As can be imagined, I’m a tad bit pi$$ed about this, since I went the extra mile to locate a genuine new Porsche Rebuilt Water Pump. They are tough to locate lately.

Ok – Looks like I have to go right back in and replace something again. Any suggestions on other things to check before I dive back in?

Feeling Shark Bit,
Rob

Warren928

Did you manually check the turning of the water pump shaft, pulley rollers and tensioner rollers for play? Did any of them feel loose or have any wear signs or resistance upon turning them? Did you notice any bolts that went back into the car that couldnt be torqued or seemed somewhat stripped? Among others, these things seem to be part of the TB problems after a R+R.

geekapalooza

Nope - No stripped bolts at all, rollers turned nicely without any free play.

BUT - I did notice when turning the new water pump by hand, that it required more resistance to turn (about twice as much), than the old one coming off the Shark. At the time I just figured it would loosen up after installation and usage, and certainly the rebuilders wouldn't let such an obvious thing go if there was indeed an issue?

Is the added resistance to turn the new WP another telltale sign?

Also the new waterpump shows a decal that says "Remanufactured by Auto-Pac". Is this indeed the rebuilder for PCNA?

Old & New

Rob,

I don't mean to rub salt into the wound, but I think it is worth reiterating that it might not always be a good idea to replace a perfectly good water pump during a TB job. I get a lot of flack on the board whenever I present this opinion, but I have heard enough horror stories to validate it.

SharkSkin

O&N, I agree with you, but I don't know how to definitively tell the difference. I don't want to hijack this thread with a huge debate, I'm just curious... how do you know that the old WP is going to hold on 5 yrs or 50K? I swapped mine because it was an unknown. Good thing I planned for the WP, because things turned out to be a mess in there. I will probably do so again at TB time, just because I can't be sure that I can really outguess the WP. Bearings are easy enough to check, but the seals are very hard to evaluate IMHO. When you do your own maintenance it's your call. For a shop owner, I can see why it's in their best interests to insist on doing both. IIRC it's recommended by Porshce, isn't it?

Some stiffness in the new pump is to be expected. The new bearings(if sealed) and the new seal on the shaft will always start out with some noticeable resistance due to the new seals and the shaft not yet polished by the seal. It's a matter of degrees though... it should have been no harder to turn than any other water pump. Go to any auto parts store and spin a few water pumps if you need a reference. All automotive water pumps in common cars are basically the same, with regard to this issue.

There are at least two possibilities aside from a buggered bearing, which CAN happen during rebuilding. If pressed with too much force a bearing race or ball can be deformed... dimpled or flattened, respectively. Either can be overlooked by someone not paying enough attention. Mostly I'm talking about the guy who put it in the box if it left the rebuilder's that way. Being dropped could account for it too. Either way this can set up a vibration. Or the Impeller could be pressed town to where it rubs the WP body.

The two other possibilities I see aside from some issue with the bearings or assembly of the pump itself are:

1) Impeller rubbing block

2) Belt slipping on pump

Safest thing to do is tear it down and check it out. See how the WP feels while it's still on the block. If it feels different than when you spun it before, pull it off and find out where it's rubbing.

There are some things you can do to check it out, but they are less safe:

a) Listen again, but with the motor off. Have someone slowly turn the crank a few degrees. If you hear nothing, keep turning. IIRC the crank gear is close enough to the size of the WP pulley that you will have to turn at least a revolution to make the WP turn one rev. If you hear grinding, especially when you listen at the WP pulley, it's (1) above.

b) ONLY if you hear nothing in test (a) start the engine again, only this time spray a small shot of clean water into the air hole in the top of the left (Driver side US) cam cover. Or, if you have the cover off, spray the top run of the belt. Use a sprayer that squirts a mist. You want to get a section of the smooth side of the belt nice and wet as it goes by. If the moan changes at all, then your problem is most likely (2) above.

If it's not (1) or (2), maybe you left the old pump in there and they are trying to make little pumps.

Seriously though, there may be other possibilities... someone with far more experience in this area is bound to chime in soom.

HTH

Bill Ball

I agree that they new WP bearings are stiffer than a used pump. That is probably not the issue, but you need to find out why the belt is moving fore and aft. Yes, it could be the tensioner roller if really loose. There was a thread on an identical complaint on the 928 email list. It appears to have been play in the roller due to incorrect bushings. Join the Rennlist 928 email list if you haven't already and search "walking". Did you replace the plastic bushings? Also, there were a number of MY changes to the tensioner arm and WP. Hope you got the correct WP.

Weissach

The timing belt might be to tight, that's what happed to me. Loosen it up a little and see if the noise goes away.

Garth S

Agree that the first thing to check is the belt tension - then bleed the tensioner again: it can be difficult to chase all the air out initially, and this will influence the operating tension ( not the static tension!)
When doing this, you've had the opportunity to check the backside of the belt for any scuffing when going through rotations to TDC.
As to the belt 'walking', Bill's call on the bushings is the most common cause: did you ckeck and/or replace?
BTW, using the wrong pump is a very difficult thing to do, although nothing is impossible. Rob had to transfer the 12mm pivot stud from the old pump to the new one: the pre-S4 pumps have a ~ 3/4" tall machined boss that accepts a 12mm pivot bolt - and the idler roller is pressed onto that boss.

Old & New

Yes, that is the bottom line. Are you feeling lucky today with that "new" pump?

In this case, (assuming for arguement) we are looking at an original pump with 48K miles on it. If the shaft bearing felt (very) good and there was no sign of seepage at the shaft, I wouldn't have touched it. But again, that's just one man's opinion; YMMV.

GlenL

O&N,
Count me in as another heretic. I've had two chances to replace the water pump and have not done so. This includes an engine rebuild where it was off the car. Why? Because the pump didn't leak and the bearings felt smooth. In that case putting in a rebuilt offers no immediate improvement, just risk and the hope that the rebuilt will last longer than the old one. I did consider putting in a brand new one, but at the price, I figure if it fails I'll fix it then.

To the thread topic, here's an outside idea:

Did you put on the wrong belt? The two types are the same except for tooth shape. Putting a square toothed belt on your car would create a hum, I'd recon.

geekapalooza

Thanks for all the great info guys, definitely very much appreciated!

Well well well.... Looks like maybe I got lucky and (hopefully) stumbled upon the culprit.

Penny for your thoughts everyone, on the picture attached....

Thanks,
Rob

SharkSkin

So what exactly are we looking at? It looks to me like the backside of that belt has been rubbing awfully hard against something. That pattern in the pic looks like it may have rested against a very hot roller. Someone with more TB experience will probably recognize which one.

ErnestSw

Dave,
Your observation about the hot roller making that mark on the belt explains the part I couldn't figure out.
The only roller in contact with the back of the belt is the tensioner. Looks like the tensioner seized.

Paul D

Doesn' t the tensioner pulley have a split down the middle that could make that kind of depression?

geekapalooza

I agree - Tensioner roller apparently overheated and cooked the belt where it rested on the roller.

Looks like I prematurely "tried and convicted" the water pump in my original post. Oops...

The belt was not overtightened, and the bushings were also replaced.

Maybe just a defective tensioner roller from the factory? Maybe as a result from installation? Who knows....

Questions:
1. When I replace the bad roller and the cooked belt again, should I also consider replacing the tensioner arm? I wonder if it got too hot.

2. Judging from the tracks (pic in above post), is the roller too "off center" of the belt?

Here's a pic during the swap-out. I also subsequently de-rusted that arm also before reinstallation (apparently caused from a coolant leak that I recently fixed at the intake crossover coolant pipe, that the P.O. let leak for a long time).