Need Help FX going back into shop again.

K

Kimbereley

Member
Location
Florida
Name
Kimber
Hello please just call me Kimber. OK enough about me & more about my baby

Infiniti FX35 2008 with 52,000 miles

It seems I am joining the Thumping noise club now, I started to hear a thumping noise from the rear end of my FX about 3 months ago.
The sound only happens in this sequence
The car has to be driven for about 30 minutes, then shut it off for about five minutes.
Start the FX & then the thumping starts while parked. This is the only time you can hear the thumping noise, never while driving.

I have taken it to Infiniti & I was able to duplicate the problem. They found the sound coming from the area of the spare tire, on further investigation they felt the thumping when they put their hand on the fuel pump/intake under the back seat, so they replaced it claiming this was the problem. Well, that lasted all of 3 days & now the noise is back. Like I said this only happens when parked, air on or off, brake on or off, I've put it in reverse/drive/neutral & it makes this thumping noise but stops as soon as I drive. A small part of me also thinks it's louder when it's warmer outside.

I've been reading lots of post about the thumping noise from all kinds of forums but no one seems to have the same sequence or it's from their front end or while they are driving. I hope someone out there can help or have more ideas as to what it could be. I'm putting her back in the shop on Wed morning & have a bad feeling she will be coming home with a thump so any help would be greatly appreciated.

I will not be able to respond to reply's until later as I am working the night shift

Thanks in-advance

-Kimber
 
So it makes the noise whether you are in P, R, or D? But only while stationary and stops as soon as you move? That's strange, as if you're in P there is no load on the driveshaft or rear differential which is what I would have guessed based on your symptoms. But if it does it in P, that's not it.
 
Thanks for the response.
Yes, it only makes this noise while the car is stationary in P,R,N,D after the 5 minute restart. Also you can only hear the thumping while in the vehicle, I tried to do a walk around to locate the sound but could not hear any odd noises.

Thanks
-Kimber
 
Since they already replaced the fuel pump/intake, I would have them look at the vent tubes. I would hope that the filter was checked/replaced when they did the pump.

If they are certain that it is not anything to do with the fuel system, have them take a look at the exhaust. Sounds weird, but certain vibrations you'll only be able to notice/hear from within the car. And with the weather getting warmer, there would be less "thumps" because the metal would expand faster decreasing any gaps in the metal

(btw...I've been the victim of both of these issues in the past on two different vehicles)
 
Could it not be gasolin pressure in the fuel tank, gasses expanding(increasing when temperature is rising) there must be something like gaspressure overflow from the tank to the outside so that it can escape while pressure is to high. Maybe there is an obstruction.
Case
 
Check the fuel damper hose by bank1. Next to cylinder#1 on the passenger side(left side) while the noise is there. Feel the hose to see if the thumping is the same rithm as inside the car. If it is replace it! Heres a picture of it.
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