Water Pump

[TKE878]

I have a 2001 S with 78K mile. This weekend start to pick up a knock. Its a contant steady knocking sound that doesn't seem to vary with RPM. Can someone tell me what the symptoms of a failing water pump are? I don't have any leaks, but am wondering if the bearing is going bad. Car is running great.

I'll take it in to have it looked at, just curious about possibliities. I'm hoping its something simple.

Dan

Edited September 19, 2011 by TKE878

[logray]

Usually water pumps failing make more of a bearing noise rather than a knocking. Also the water pump is driven by the crankshaft pulley belt, which does vary with RPM, and so the noise should increase or decrease accordingly.

If you open the engine bay, does the noise seem to come from the top of the engine or underneath? If you put your ear near the drivers or passenger side rear wheels is the noise more pronounced with either side?

Edited September 19, 2011 by logray

[TKE878]

I'll check on the location tonight. And get a better description.

Dan

[Rapewta]

Dan...

I have the exact same symtom with 76k on the odometer. Just started about a week ago and was wondering... did you

sort it out? What was causing the "knock"?

Don

[Rapewta]

Well.. I hope you got it fixed. I couldn't (with stethascope) locate it so I took the car to an independent Porsche shop with

a good rep.( Frank's Automotive) Diagnose and report. It was the water pump. No leaks but it was the culprit. I drove the car home. While I am at it,

I am going to replace the idler pullys. 76K miles on the car and it is expected.. $300( me and parts) vs $1000( shop charge) I will try it on my own.

[ChrisJP]

Just had a problem with upper pulley, so thought I might jump in...

Before doing any R&R on the idle pulley, just listen to the noise by putting a metal rod on the central bolt and listen to the sound from the other end while the motor is on. (I don't remember if the central nut on the tensioner pulley is rotating or not).

If you hear any "grinding" noise, then the bearing is toast and it worth the replacement.

You can also try to turn any pulley by hand as well: if it turns freely without noise, then you're OK (at 100$ a piece I would not replace the pulley as a preventive maintenance).

One more thing: the bolt on the upper pulley is quite long and you will need to slightly bend the metal housing (at the connector location) to have it out.

[TKE878]

Just to close out this thread. The knock I had was a result of a crappy Korean made serpentine belt that was replaced during the 60K service. On the smooth side it was starting to come apart and was missing a 1/2 inch chunk which was causing the knock as it went over the pullies. It disappeared at higher RPM because it moved too fast over the pullies.

All is well.