2006 Hyundai Sonata Engine buzzes on cold start

Tiny
KENTRD
  • MEMBER
  • 2006 HYUNDAI SONATA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 172,000 MILES
I recently purchased this car. It runs well, but when cold starting, there is a rather pronounced buzzing/clattering sound from the engine compartment. Lasts for about 3 seconds, and then stops abruptly. Does not recur unless car is turned off for a few hours. My guess is fuel pump or ABS self-test, but seems unusually loud. Should I be concerned?
Sunday, June 6th, 2010 AT 11:18 PM

3 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Could you desrcibe it as a fast ticking sound? Is the oil level full and has it been changed recently? Could possibly be a little slow to oil the lifters, this will cause what you describe time wise, but it is more of a fast click. If the oil is fairly dirty or due for achange, be sure to use the fatory recommended weight of oil and the correct high quality oil filter
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Monday, June 7th, 2010 AT 11:36 PM
Tiny
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Yes, it is a fast buzzing sound. I've only had the car a few days, so I haven't changed the oil yet (but the oil looks new on the dipstick). I'll give that a try though.

But it doesn't really sound like lifters to me, for two reasons:

1. While the buzzing seems to be coming from the engine compartment, it doesn't appear to be coming from the engine itself. The buzzing has a clattering characteristic that makes it seem to be coming from some other component.

2. Also, the buzzing ceases very suddenly (it doesn't taper off). In my (limited) experience, lifter noise tapers off as the lifters pressurize.

However, since the noise only occurs when the engine has been shutoff for several hours, it does seem to be related to a system that slowly depressurizes (which is why I suspected a fuel pump). But that's probably in the tank (in the back), I'm guessing.
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Tuesday, June 8th, 2010 AT 3:54 PM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Yes, the pump is in the tank. Check to see if the vehicle has air injection on it. If it does there should be a big check valve on the pipe that goes to the exhaust.I have heard the check valves rattle before, and the air injection usually only comes on when it is a cold start. Thisis definitly one thta you will have to listen around for to get a general area of where the noise is coming from
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Wednesday, June 9th, 2010 AT 8:07 AM

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