A Passat 1.8T 2002 noise when started

[Tassap]

Since about a year ago, the Passat makes a whirring sound when it's starts. I’ve been told by several dealers that the sound is coming from a pump that builds pressure on the catalytic converter(cc) when there’s low pressure in the exhaust system (or when the exhaust system is cold) to allow for proper functioning of the cc.

This noise didn’t come when I first bought the car (even during the winter of ‘02). At first I accepted the dealers’ analysis. But I continued to experience the noise even during the summer months. It happens every day regardless of the temperature. I know the ambient temperature is nowhere near the normal running temperature of the car, but is it normal to hear this noise?

Although the noise goes away in 30 sec. (even on the coldest days), sometimes it reappears a block or two away from my apt. when I slow down as a approach a stop sign. In this case, the noise will disappear within seconds of pressing on the gas.

Your analysis and guidance are much appreciated. Thank you.

Passat 1.8T 2002 w/ 47,000 miles (+80% highways miles between Boston and NYC). No other mechanical troubles experienced.

[boschmann]

Did they mention it was the secondary air injection pump?

[Stevo555]

My '02 Passat 1.8T makes the exact same noise - a sort of farting sound when you first start it. I took it to the dealer 3 times, on one occasion they replaced the EGR valve, but it didn't make any difference.

Reading other forums since I had my problem has shown that this is a common "issue" with the VW/Audi 1.8t engine - not just in the Passat. I've grown to live with it, because all other aspects of the engine are fine.

The only pain is when passengers say "I didn't realise you had a diesel" when I start it up...

[Tassap]

Originally Posted by boschmann

Did they mention it was the secondary air injection pump?

Yes, the secondary air injection pump was cited by the dealers as the cause of the noise.

If that is the case, can please explain (or direct me to an explanation on the web) regarding how that system works. I was told that the pump will activate in cold weather conditions. But it turns on in the summer which is unexpected. As expected, it doesn't click on when the engine is warmed up. Now here's what really throws me... For the last couple of days it has been well bellow freezing in the Northeast. The pump has not always turned on in the last several days. While, in the summer and fall, it would turn on without fail. I don't understand these inconsistencies. It leads me to suspect it isn't working properly. But I could be wrong. Thank you in advance for helping me understand this issue.
Regards

[boschmann]

It's not uncommon for the pumps to fail. It can come on cold or hot and should only make a quiet hum, not a whine which is a sign the bearings are going bad.

Stevo555: It sounds like your chain tensioner between the two cams is bad. See if the noise is at the top rear of the cylinder head.

[Tassap]

Boschmann,

Thanks for your help! Is it easy for the dealer to check the bearings?

[boschmann]

If they whine when the pump runs, they're bad.