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Author Topic: Boom sound like drum once on warm up  (Read 1966 times)

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TestOmega

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Boom sound like drum once on warm up
« on: 13 September 2010, 18:32:10 »
Once I start my car after about 4-5 minutes of idling, I hear reasonable loud boom sound (just like you will hit a marching band drum once) as though it coincides with the secondary air injection system turning off at around 600-800 RPM.  The car starts normally cold right now around 1200 RPM.

The noise happens only once and never again while driving or restarting when it is already warmed up.

The noise comes from the left side or N/s for UK.  I have checked the clamps, etc., on all the Secondary injection joints.

Thank you.
« Last Edit: 13 September 2010, 19:17:50 by TestOmega »
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Simon72

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Re: Boom sound like drum once on warm up
« Reply #1 on: 13 September 2010, 20:57:20 »
I have that as well.

But I have discovered by getting wife to listen out for it, that is is a FLAP slamming shut under the dash.

It has something to do with the Emmisions Detection system on the air con recurculating system.

I drive to work through the country side and the outside air is nice and clean, once I get into town and get held up in traffic the system must detect the fumes from other cars and the BANG happens again and the air that is blowing into the car increases, also the smell of fumes disappears ;-)

Hope that helps
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Tonka.

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Re: Boom sound like drum once on warm up
« Reply #2 on: 13 September 2010, 21:43:18 »
Me also. It happens on the left of the dash.

Can't be normal to shut/open so violently  :-/
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Andy H

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Re: Boom sound like drum once on warm up
« Reply #3 on: 13 September 2010, 21:56:10 »
When was your pollen filter last replaced?

An old dirty filter can really reduce the quantity of fresh air coming into the cabin.

Maybe the flap has to fight a big pressure difference before it can start to move. :-/

Fitting a new carbon filter should improve the air flow and reduce the need for the flap to operate in the first place.

HTH
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Tonka.

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Re: Boom sound like drum once on warm up
« Reply #4 on: 13 September 2010, 21:58:26 »
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When was your pollen filter last replaced?

Jan 2009  ;D ;D
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TestOmega

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Re: Boom sound like drum once on warm up
« Reply #5 on: 13 September 2010, 22:30:48 »
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When was your pollen filter last replaced?

An old dirty filter can really reduce the quantity of fresh air coming into the cabin.

Maybe the flap has to fight a big pressure difference before it can start to move. :-/

Fitting a new carbon filter should improve the air flow and reduce the need for the flap to operate in the first place.

HTH
Andy H thanks I will check the Cabin Filter.

However, I am going to do a test later by turning all AC and fan off and let it idle and see if the sound is still there.  It uncanningly seems to be related to some valve shutting ( I conjecture Secodary Air Injection system) and creating a vacuum impulse all around.

Regards.
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TestOmega

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Re: Boom sound like drum once on warm up
« Reply #6 on: 14 September 2010, 19:59:42 »
Boom continues once on start with or without filter or ventilation on or off.

Any help and suggestions for a fix or cause.

Thanks.
« Last Edit: 14 September 2010, 20:13:27 by TestOmega »
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Marks DTM Calib

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Re: Boom sound like drum once on warm up
« Reply #7 on: 15 September 2010, 09:54:18 »
From what area is it coming from?
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mathewst

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Re: Boom sound like drum once on warm up
« Reply #8 on: 15 September 2010, 10:56:44 »
I have exactly the same problem.
Two possible causes were suggested to me by a mechanic , EGR  and Catalysator
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Kneepad

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Re: Boom sound like drum once on warm up
« Reply #9 on: 15 September 2010, 13:25:32 »
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From what area is it coming from?


See OP first post.  :y
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Marks DTM Calib

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Re: Boom sound like drum once on warm up
« Reply #10 on: 15 September 2010, 13:37:09 »
Quote
Quote
From what area is it coming from?


See OP first post.  :y

He says near side....front, rear, middle, engine bay, bumper, interior.....a bit more precise is needed  :y
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Kneepad

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Re: Boom sound like drum once on warm up
« Reply #11 on: 15 September 2010, 15:01:34 »
Quote
Quote
Quote
From what area is it coming from?


See OP first post.  :y

He says near side....front, rear, middle, engine bay, bumper, interior.....a bit more precise is needed  :y


Hmm see what you mean. It is a bit vague. 
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TestOmega

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Re: Boom sound like drum once on warm up
« Reply #12 on: 15 September 2010, 17:54:47 »
Quote
Quote
Quote
From what area is it coming from?


See OP first post.  :y

He says near side....front, rear, middle, engine bay, bumper, interior.....a bit more precise is needed  :y
Sorry Marks DTM Calibration I will try to clarify below,

It is a boom type sound Left Front and happens almost like a clock after 4-5 minutes in idle as though some system is switching out

Since the sound is little boomy it is hard to exactly know the location and it happens only once

I was thinking it may be related to SAI switching modes and have checked all the clamps and pipes.  I also thought that it may be related to SAI as well as plenum ram changes as RPMs drop from about 1200 on start to 500 and it happens towards and near 500 RPM.

I have checked that it is not related to AC or blower.

If I can clarify further I will be happy to.

Thanks.
« Last Edit: 15 September 2010, 17:55:34 by TestOmega »
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Marks DTM Calib

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Re: Boom sound like drum once on warm up
« Reply #13 on: 15 September 2010, 17:58:06 »
Ok, so it sounds external to the car, sort of front drivers side (as in wrong hand drive US style :y) around the wheel area?

Can you disconnect the vac feed to the secondary air injection valve and unplug the blower motor as a test?
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TestOmega

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Re: Boom sound like drum once on warm up
« Reply #14 on: 15 September 2010, 21:19:28 »
Quote
Ok, so it sounds external to the car, sort of front drivers side (as in wrong hand drive US style :y) around the wheel area?

Can you disconnect the vac feed to the secondary air injection valve and unplug the blower motor as a test?
I checked it and the following,

  -  It start to have a continuous howl (whooooooooooolwhoo...)
  -  there was no boom

I just reconnected and reseated the pipes around the SAI valve and let it cool down.

Just came from a re-start and no boom and no howl tone.  May be it has not been allowed to cool enough but I will report back later.

I think these cars have a sixth sense and they are scared of your intervention.  :D ;D ;)

Thanks.
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