Sounds like a jet plane

When I first start my car it sounds like a jet plane! Then after say 2 minutes the noise goes. I have been told its my vacuum or something like that. Is there a way of sorting this noise out? Or is it a normal noise for these cars? It's done it since day one of be buying it but I have noticed lately it's staying on doing that noise that bit longer

That would be the secondary air pump, it's normal.

Yup, the sap. It heats up the o2 sensors

It might be normal, might be a sign that your hose is corroding internally and clogging the valve. Squeeze the hose and if it feels soft and squishy, replace hose...and check inlet to the valve (if you have one) and see if it's clogged. If so, remove gunk...with dental pick, vacuum, whatever.

Also, just read that someone here rebuilt his pump...I assume that means replacing bearings on it. Something I might need to do someday, but doubt you do.

Originally Posted by dmax

It might be normal, might be a sign that your hose is corroding internally and clogging the valve. Squeeze the hose and if it feels soft and squishy, replace hose...and check inlet to the valve (if you have one) and see if it's clogged. If so, remove gunk...with dental pick, vacuum, whatever.

Also, just read that someone here rebuilt his pump...I assume that means replacing bearings on it. Something I might need to do someday, but doubt you do.

Ok thanks mate, I'll check all the hoses going to it today after work and I'll order some new ones from BMW.
When you say inlet to the valve, where would I be looking or looking for?

Follow the hose from sap out...it goes to the valve...silver thing on exhaust side of engine, with vac hose leaving out the back...assuming, in the UK, you have this pump. The clue, so you know, is that you said the sound disappeared after two minutes...that's how long the SAP runs on cold start, plus or minus a bit.

Remove SAP.

/problem

It is right behind the windshield wash tank, which is right behind the clear corner that you probably learned about instead of the proper care and maintenance process that you should have learned about first.

sounds more like a vacuum cleaner. jets are much MUCH louder.

Originally Posted by Stickbuilder

It is right behind the windshield wash tank, which is right behind the clear corner that you probably learned about instead of the proper care and maintenance process that you should have learned about first.

So just hearing this sound now equals me not knowing about the car?! :-/
I take good care and maintain all my cars to a very good standard. I just wasn't too sure on which pipes to check, I know there is 2 of them coming out of the SAP but wasn't sure if I was to check the one coming out of the top of it towards the engine head, or the one closer to the front of the car at the bottom of the SAP.

Originally Posted by dmax

Follow the hose from sap out...it goes to the valve...silver thing on exhaust side of engine, with vac hose leaving out the back...assuming, in the UK, you have this pump. The clue, so you know, is that you said the sound disappeared after two minutes...that's how long the SAP runs on cold start, plus or minus a bit.

I have checked both pipes that are coming from the SAP and one seems a little more easier to squeeze than the other, but there really isn't much difference in the two. What do you suggest? I am able to push either side of the pipe in and they touch each other, but just barely.

That's the inside of the valve, I have just put a cloth in and wiped around and it's come out with a little bit of dirt on, nothing major

Also just opened up the SAP lid and it's clean too

I am not getting what you asking for.
you said it sounded like jet engine so we told you its the sap working.
its supposed to sound like a vacuum cleaner.
if anything, the motor could go bad and you end up with a very loud motor.

Originally Posted by Solidjake

Yup, the sap. It heats up the o2 sensors

+1, sorta.

The noise is the SAP, but it does not heat up the O2 Sensors.

The CAT uses air and heat to convert fuel into clean air. When the CATs are cold they do not work very well so air is introduced into the exhaust stream. The exhaust stream already has air in it, and there is fuel, but there is no heat to speak of. The absence of heat is countered with more air molecules so the fuel molecules have more to bond to. When the heat arrives, the fresh air can be shut off.

The O2 Sensors heat up because they have internal heaters in them that are turned on. After the exhaust system heats up, the heaters in the sensors are switched off. I'm not sure of the timing of the heaters, but logic says the timing should mirror (more or less) the same timing as the SAP.

OHHH ok. So it's ment to sound as it does when the car starts up from cold.

Sorry my mistake on what I have read

Originally Posted by M4RKY N

OHHH ok. So it's ment to sound as it does when the car starts up from cold.

Sorry my mistake on what I have read

yes, to heat up the cat.

Originally Posted by M4RKY N

Also just opened up the SAP lid and it's clean too

I'm confused. You have been told tht the noise is the SAP, and that it is normal. What are you looking for? Why are you trying so hard to fix something that is working right?

No I was just wondering why it's making such a noise, and from comparing it my friends e46 and his doesn't make the sound at all... So I was just wondering. Also someone above in the thread has said to check certain things so I have done and was just writing back to say what I have found.

Originally Posted by M4RKY N

No I was just wondering why it's making such a noise, and from comparing it my friends e46 and his doesn't make the sound at all... So I was just wondering. Also someone above in the thread has said to check certain things so I have done and was just writing back to say what I have found.

You ONLY get the Secondary Air Pump on the initial start when the engine is stone cold. If you drive somewhwere and park, then start again before the engine turns to a frozen chunk of steel, the SAP will not come on. If you drive to work and park all day then come out at 4:30, the SAP will start for about 2 minutes.

Some of them make a whine that sounds like a vacuum cleaner, and some make far less noise. The noise is not indicitave of a problem.