When I start my 2004 Disco every morning I hear what seounds like a Vacuum Cleaner turn on and then after about a minute it shuts off. It happens everyday when first starting and then I never hear it again but maybe once a week in the middle of the day while drving through downtown.

 

It might be your secondary air... I think, don't know for sure.

 

"YUP" secondary air.

 

What is the purpose of this? how do you know if it is going bad?

 

It goes bad when it makes noise . At least I think, I don't know too much about it cause I don't think my rover has it. I don't think it necessarily hurts anything if its malfunctioning, its there to assist the vehicle when starting on a cold morning.

 

its called a fan clutch, look it up

 

It is your secondary air injection.
Yours is making noise because the filter to it needs to be replaced.
Its purpose is to force fresh air into the raw exhaust to aid in the heating up of the catalytic converters.
Think of it as a black smiths bellows, you know when he uses the bellows to force air onto his fire and then it gets big and hot?
The SAI does the same thing.
A engine pollutes the most when it is cold, over half of your emissions is in the first 5 miles of driving, thats why frequent shorts trips are so hard on a car and the environment.
SO if you are going to make a quick trip to the corner store for a gallon of ice cream take the car that was driven last, either yours or your wifes because it will reach temp faster and pollute less.
Your cats work best when hot, the forced air gets them to temp in a min or two, thats why it shuts back off, the cats are at temp.
Your MPG is also cut in half when you drive with a cold engine, thats why your MPG drops in the winter time, if you live where it gets cold that is.

 

Where is this filter located? Easy to change?

 

It is ontop of it, you remove a couple of screws and it will come out, then replace it with another filter type material.
you can use the foam air filter from a push mower, or the foam filter from a window a/c unit.

 

Here you go, compliments of jycsalas

https://landroverforums.com/forum/sh...t=23245&page=3