What is this Vaacum noise I hear from my car when I start it cold in the Morning?

GAF_DESIGN

MEMBER
2003 VOLKSWAGEN JETTA
14,700 MILES

Hello,

I have a 2003 VW Jetta GLS 5 sp. Manual with the 2.0 Naturally aspirated 4 cyl engine. The car has approximately 147,000 miles. My MIL light has been on for some time now. I recently got my local mechanic to run diagnostics on it and he reported two error codes (411 and 420). To my understanding, 420 is due to the imminent failure of a catalytic converter, an issue which I have addressed by replacing Plugs, wires, distributor, and cat.

My real question is, I would like to know if a mysterious Vaacuming sound that comes from my car whenever I start it cold in the morning and persists for about 25 seconds, and then comes on and off intermittently, is related to the 411 code. My local mechanic told me that there is some kind of exhaust recirculation motor that may be going bad.

Please help. I love my VW and want to keep it running properly rather than give it up, so long as there is no seriour problem that is impractical to fix.

Thanks!

4 Replies

KHLOW2008

MECHANIC
41,814 POSTS

P0411 - secondary air injection system incorrect air flow detected.

This should be the cause of the abnormal vacuum noise durng startup and it could be a partially clogged air passage.

As to P0420, that indicates a fault with the catalytic converter and if it has not failed yet, it is most probably be going out soon. The code should be coming back sooner or later.

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Saturday, September 29th, 2012 AT 4:58 PM

GAF_DESIGN

MEMBER
2 POSTS

Thank you so much for that answer! I really appreciate it! Any suggestions on how to go about fixing the issue?

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Saturday, September 29th, 2012 AT 5:15 PM

KHLOW2008

MECHANIC
41,814 POSTS

Start by checking the Secondary Air injection Valve, it vacuum hoses, passages and its wiring circuit.

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Saturday, September 29th, 2012 AT 5:47 PM

EXOVCDS

MECHANIC
1,883 POSTS

The Secondary Air Pump is held together with small rivets... they
break over time and the pump halves start to come apart. As the
pump starts to separate, air that is blowing under pressure is blown
out between the pump halves and that is what you are hearing:

The following are clips I found on Youtube from a 1.8T engine, but
the pump & operation is the same as on your 2.0L engine.

http://www.youtube.com/watch?v=B9xXRYIgkAc

Once the rivets are replaced and the pump is a solid one piece again, the
noise will be gone.

http://www.youtube.com/watch?v=2PgAwSqrWuk

The best way to find the noise is to have someone start the engine
while you listen for the noise with the hood open and plastic
engine cover removed.

Attached is an image of the SAI System

- red - split in pump halves
- green - pump rivets
- yellow - air feed to pump from air filter housing
- blue - pressurized air from pump to "combi valve" and then to exhaust pipe.

A fault in any of the shown parts can cause a "low flow" code to be set.

Thomas

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