when i start my car when the car is cold there is rattling coming from what i believe is the secondary air pump. once the rpms drop to its normal idle the sound goes away. when i was in an accident a year ago this peice was replaced. what would cause this to happen? what does it the secondary air pump do? if thats not what it is can somone tell me what it is the car is a 2000 1.8tQ

Dustin

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The secondary air pump helps with emissions when you start your car up i think..

 

What you are ponting at is the combination valve for the AIR system and you are correct it is for emissions during startup. Though the rattiling noise may not be that unless it is lose. If the combination valve goes bad you will recieve a cel with code p0411. Check for loose componets such as your air pump in its metal bracket.

 

yea the secondary air pump pumps fresh air to the cat during cold starts to help it heat up faster and so it can work faster. what a worthless thing that is tossing me a CEL light and they are so damn expensive.

 

I have the same rattling noise sometimes during startup. I dont know what it is but I've also been told that its the secondary air pump.

 

The secondary air pump is under the front of the car on the passenger side, just behind the bumper. Purely an emissions device.
if you only get the rattling when the pump is on (for about 30 secs after starting the car cold) then the pump is either dying or it is loose in its housing (3 heavy bolts hold it to its bracket).

A healthy pump should barely be heard. Mine sounded like a jet turbine for a while - that lasted for nearly a year, then it started sounding like it was grinding gravel, so I figured I'd replace it before it exploded...

I just recently replaced it myself.

 

I heard that if the combination valve goes bad... it lets moisture into the SAP, which kills it, too... dealers change them simultaniously, I believe.