Slow Thud from underneath the car

Whole new coupe....whole new faults some only just coming to light
Post Reply
roscozx
Searching in the dark
Posts: 4
Joined: Sun Oct 22, 2017 1:51 pm
Real Name:
Coupe: Gen3
Engine: 2.7(v6)
Has thanked: 0
Been thanked: 0

Slow Thud from underneath the car

#1

Post by roscozx »

Hi all,

Just joined and just purchased an 2.7 04 plate.

Just wondered if anyone has experienced this. When first starting the car a noise which I can only describe as a continuous knocking sound ( about a second delay in-between knocks) starts from underneath the car near the rear.
Seems to go away when driving but after stopping and turning the engine off it comes back for about a minute. I've taken it to a mechanic who has never heard it before and seems to think its coming from the petrol tank.
I found this video on YouTube, this is the identical noise to what mine is making. https://www.youtube.com/watch?v=GxxcPHvUUg8


User avatar
robbo
Club Supervisor
Posts: 3423
Joined: Fri Sep 06, 2013 9:10 pm
Real Name:
Coupe: Gen1 (1996 -1999)
Engine: 2.0
+_number: 0026
Has thanked: 18 times
Been thanked: 92 times
Contact:

Re: Slow Thud from underneath the car

#2

Post by robbo »

Could be fuel pump, do you get a ticking noise from rear when you turn car off?


Sent from my iPhone using Tapatalk
My F2 Evo build
Member #0026: Never knowingly under polished
roscozx
Searching in the dark
Posts: 4
Joined: Sun Oct 22, 2017 1:51 pm
Real Name:
Coupe: Gen3
Engine: 2.7(v6)
Has thanked: 0
Been thanked: 0

Re: Slow Thud from underneath the car

#3

Post by roscozx »

no ticking noise just the thudding noise for about 40 seconds
User avatar
Rod Panhard
Regular contributor
Posts: 1346
Joined: Mon Jul 07, 2014 1:51 am
Real Name:
Coupe: Siii / TSiii
Engine: 2.0
Has thanked: 2 times
Been thanked: 7 times

Re: Slow Thud from underneath the car

#4

Post by Rod Panhard »

Is there ventilation to the petrol tank?, if it's a vented tank and that venting is blocked the petrol tank which is plastic could be expanding and contracting in "thumps" due to the constriction.
User avatar
Rod Panhard
Regular contributor
Posts: 1346
Joined: Mon Jul 07, 2014 1:51 am
Real Name:
Coupe: Siii / TSiii
Engine: 2.0
Has thanked: 2 times
Been thanked: 7 times

Re: Slow Thud from underneath the car

#5

Post by Rod Panhard »

Been checking and apparently there is a fuel tank vent valve so it might be worth checking out.
roscozx
Searching in the dark
Posts: 4
Joined: Sun Oct 22, 2017 1:51 pm
Real Name:
Coupe: Gen3
Engine: 2.7(v6)
Has thanked: 0
Been thanked: 0

Re: Slow Thud from underneath the car

#6

Post by roscozx »

Thanks, I'll definitely check this out
nissan300zx
Has thanked: 0
Been thanked: 0

Re: Slow Thud from underneath the car

#7

Post by nissan300zx »

could be the exhaust hitting the underside.
Post Reply