Analyzing the whistling noise associated with water pump

[artronics]

Having this problem myself, I am puzzled by it and I will try to dissect it.

The water pump is a pretty simple unit: an impeller mounted on a shaft with bearings and a seal. The rest is not very significant: a pulley, a housing, a gasket and fasteners.

What could cause noise?
1. the impeller could cause noise due to cavitation, when there's air in the system
2. the bearings could be noisy due to wear, lack or lubrication or lubricant contamination with a foreign substance (dirt or water)
3. the pulley could cause noise due to friction (or lack thereof), either because of wear, contamination (like oil) or not enough tension
Did I miss anything?

OK, let me try to analyze each one:
1. cavitation noise is not a whistle in my experience: it's low frequency, more like a rumble, a vibration and definitely affected by the rpm, so the tone changes based on the speed of the impeller
2. bearings make a grinding noise when they are worn and always changing pitch with the speed
3. pulley noise is always proportional with the speed and it eventually goes away when the belt starts to grip or the load goes down

So I can't really see how the water pump can be making this whistling sound that is constant in pitch, regardless of the speed/rpm of the engine. Of course, revving it too high covers the noise, but one can still hear the steady frequency throughout the rpm range.

Now this is playing devil's advocate, as obviously VW techs and users of this forum have diagnosed and solved the issue by replacing the pump. I am merely trying to understand what's going on and where does the noise come from.

[NeedsMoreBoost]

I wish I could contribute but my Tig has thankfully gone 5k miles with no water pump issues. However I think that one of these mechanics stethoscopes could be very useful in your diagnosis. I follow these kinds of threads very closely so I'll know what's going on in case my Tig starts whistling.



http://www.amazon.com/MECHANICS-STET.../dp/B002A1IQ58

Good luck!

[chicoze]

Good point. I would go with the pulley. Maybe it never gets full grip no matter the revvs...

[CC'ed]

The waterpump pulley and belt are toothed...there is no way it can slip.

[artronics]

I wish I could contribute but my Tig has thankfully gone 5k miles with no water pump issues. However I think that one of these mechanics stethoscopes could be very useful in your diagnosis. I follow these kinds of threads very closely so I'll know what's going on in case my Tig starts whistling.

http://www.amazon.com/MECHANICS-STET.../dp/B002A1IQ58

Good luck!

Just for closure: the noise is reported to be coming from the seals. I believe they get "cooked" if air is present in the system and it must be stick-slip that makes them whistle like that.

This is what was used in my case, the one at the bottom:

[CC'ed]

My guess is that when the system pressurizes (as the engine heats-up), the plastic water pump housing distorts, causing the bearing (or the shaft seal) to bind-up a little.

[artronics]

My guess is that when the system pressurizes (as the engine heats-up), the plastic water pump housing distorts, causing the bearing (or the shaft seal) to bind-up a little.

So it's a plastic housing? Wow, I have never seen a plastic water pump before. I gotta take a look.

[jtrujillo86]

It's due to seal failure. My mom had a 2009 Tiguan SE 2WD from July 2008 to March 2012 and for 48k miles, which saw three waterpump failures. We got tired of dealing with it and she traded it in for a Passat 2.5. When the first failure happend, I was somewhat surprised; it's the same engine that is in the GTI, but there are not any posts of multiple failures in that thread

- Jeremy.

[artronics]

It's due to seal failure. My mom had a 2009 Tiguan SE 2WD from July 2008 to March 2012 and for 48k miles, which saw three waterpump failures. We got tired of dealing with it and she traded it in for a Passat 2.5. When the first failure happend, I was somewhat surprised; it's the same engine that is in the GTI, but there are not any posts of multiple failures in that thread

- Jeremy.

Thanks man. I now know it's the seals, I was just wondering how exactly do they fail. What causes them to whistle like that. Is there any way to avoid the failure?
The dealer has a new installation procedure apparently, where they submerge the new pump in boiling water to prime the seals before installation. Then they vacuum out the system before filling it.

[jtrujillo86]

Thanks man. I now know it's the seals, I was just wondering how exactly do they fail. What causes them to whistle like that. Is there any way to avoid the failure?
The dealer has a new installation procedure apparently, where they submerge the new pump in boiling water to prime the seals before installation. Then they vacuum out the system before filling it.

I'm not sure what any of the new installations procedures are or whether they work. Our three pumps failed all within about 10k miles

- Jeremy.

[artronics]

Could be because the pumps are plastic. The engine temperature must be too much for it. Talk about cost-cutting measures: the number of pumps replaced under warranty on all VW and Audi must have wiped out the savings by now.

[TIGSEL]

Could be because the pumps are plastic. The engine temperature must be too much for it. Talk about cost-cutting measures: the number of pumps replaced under warranty on all VW and Audi must have wiped out the savings by now.

The cardboard ones are in testing stage. They're still trying to workout few minor bugs such as how to make it work for the first 5 min. without falling apart

[CC'ed]

Lots of car manufacturers use plastic intake manifolds, waterpumps, radiator and heater core end-tanks, thermostat housings.....mostly without problems. VW (or rather the waterpump manufacturer) has a bum design.

[artronics]

Update: over 1000 Km later, no noise with the new pump. I hope I don't jinx it, but so far so good.