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2003 v70 buzz buzzing intermittant car off left side engine compartment under hood V70-XC70

posted by  analyzer on  Mon Dec 30 23:14 CST 2013
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last visit: Wed Jan 1 17:41 CST 2014
[RELATED]

Hello Brickboarders,

This is an informational post to help those looking for an answer to a
buzzing sound that occurs under the hood after you shut off the engine. It may alternate 10 seconds on 2 seconds off...or advance to long runs with short breaks if you've ignored it for some time.
It comes from a cylinder shaped item buried below the air box on the left front of the engine compartment.
It is from the Brake Vacuum Pump.
http://www.fcpeuro.com/products/volvo-brake-vacuum-pump-s60-s80-v70-xc70-xc90-hella-31317445?gclid=CPm3tOfT2bsCFbFxOgod7DQAyQ
I also replaced the Booster Vacuum Switch.
http://www.fcpeuro.com/products/volvo-booster-vacuum-switch-s60-v70-xc70-s80-genuine-volvo-31265825?gclid=CNuVi5LU2bsCFag7Ogodg20A5g

I had let this go a long time (> 1yr) and the runs of buzzing pump grew longer and would last 30-60 seconds...I stopped counting. Several with short breaks.
I changed out the Booster Vacuum Switch because it was easily accessible and that changed the buzz to rapid short bursts that ended after a minute.
Then I spent the time to work my way down to the Brake Vacuum Pump and replaced it. No growling buzz. I bought it used for $40 on ebay and took a chance.
If you have a growling buzz then change out the pump. I can't say whether I wasted $60 on the Booster Vacuum Switch but I'm not going to bother swapping the old one back in. After all it gave me 200K service and the new one totally changed the demand on the growling pump.

If you let it go indefinitely I suspect that one day the pump will fail and you might not have Brake Vacuum at spec before the engine has a chance to produce it. I've seen other forums where people have referred to the system as over-engineered. I would disagree.

Analyzer
2003 V70 220K
1997 850R 139K
Retired/Sold/Totaled; 244, 245, 744T, 965, V90








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    2003 v70 buzz buzzing intermittant car off left side engine compartment under hood V70-XC70

    posted by  afm on  Mon Feb 8 08:34 CST 2016
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    last visit: Sun Oct 19 04:58 CST 2014
    [RELATED]

    I found this earlier post very helpful... but have a question.

    The car is a 2003 XC about 120K miles. The brakes work fine, no apparent change from normal.
    Yesterday for the first time I heard the noise after driving the car a short distance. It lasts a couple of minutes and then stops with key in OFF position. I started and stopped several times ..... always the noise for a minute or so.
    Since it's cold and snowy here....finding the problem quickly is on my mind:

    I will follow the Mathews repair procedure link.

    Normal braking would indicate it's not the little booster pump ???
    Fuse 33 operates the Vac. switch... does the fuse also feed the Pump motor??
    or is that a separate fuse...??
    The fact that the noise/pump runs after shutting off the engine would indicate something (like Vac. switch is hung up.) But why would it open in a minute or so shutting off the pump??? Vacuum bleed down... it would make sense if
    the Vac switch senses engine Vac and not boost pump Vac.???
    You can see I am trying to make this a simple Vac. Valve replace.... by
    understanding what's happening......
    Thanks








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    2003 v70 buzz buzzing intermittant car off left side engine compartment under hood V70-XC70

    posted by  analyzer on  Wed Jan 1 17:43 CST 2014
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    last visit: Wed Jan 1 17:41 CST 2014
    [RELATED]

    http://www.matthewsvolvosite.com/forums/viewtopic.php?f=9&t=43817

    See the above link for a superb write up on this job.

    Analyzer







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