Odd 'buzzing/hissing' noise from rear of car
08-05-2018, 03:24 PM
#1
Teching In
Thread Starter
Join Date: Jan 2009
Location: midwest
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Odd 'buzzing/hissing' noise from rear of car Hi everyone, I've searched the forums while I’ve found some threads about a ‘hissing noise’ from the rear, they are about 9-10 years old, don’t seem to be quite the same issue, and have very few responses. Hopefully this one will fare better. My apologies in advance for the long explanation, but I just want to give a decent description of the issue...
I've owned a 1998 Trans Am (A4) for about two years. Recently, the car developed a noise in the back that I can best describe as a combination of 'buzzing and hissing'. I first thought it was the fuel pump, but it actually seems to be a noise in addition to the fuel pump - when the ignition is turned on (without starting the car), I can hear the fuel pump start/prime, and this new noise begins a fraction of a second after the fuel pump. The noise does stop soon after the fuel pump is primed, but when the car is then started, the new noise slowly builds up and rises to a steady level - loud enough to be heard over the exhaust and from several feet away. It doesn't change pitch/tone or get any louder when the engine is revved up, and the engine itself runs just fine while the noise is present (no indication that it isn't getting enough fuel).
Here's the part that I find interesting - this isn't a constant issue, it only seems to occur after a substantial amount of driving time. I recently made a trip of about 5 hours. On the way to my destination, the last stop I made was about 4 hours into the trip, and I had not yet noticed the noise. However, when I arrived at my friend's place, I stopped and put the car in park, but got out of the car with the engine still running - I immediately noticed the noise (and this is the first time I had ever heard it). So it seems as if the noise didn't occur until at least a bit over four hours into the trip. My friend and I put the car in his garage and jacked it up to try to pinpoint the noise, but we were not able to find its source/location - it seems to be a bit louder on the driver side, but it can also be heard very easily on the passenger side. Additionally, once the car cooled down, the noise stopped, and we were unable to replicate it again.
My trip had a very quick turnaround (arriving Friday night, leaving Sunday morning), so I was not able to get the car to a mechanic. On Sunday, the car seemed start, idle, and run okay, and the noise was not present, so I decided to take my chances and see if the car could make the return 5 hour trip. No issues at all with the engine during the drive, and I stopped fairly frequently to listen for the noise. It wasn't until about 4.5 hours into the trip that I noticed that the noise had returned. I made it home without issue, and as before, once the car cooled down, the noise disappeared.
I've driven the car around town several times since then, and have even made a 1 hour trip to a neighboring town (2 hour round trip), and I have not heard the noise at all. I wouldn't be so worried about it, but I do have to make another multi-hour trip in a few weeks and I'm guessing the issue will arise again.
The car is not throwing a code and since it takes so long for the noise to present itself, I can't simply run it by a mechanic for a quick listen and diagnosis. The car runs just fine, but there is obviously something amiss. I was hoping someone on this forum could provide some guidance due to perhaps dealing with a similar issue at some point. Any thoughts or suggestions?
Thanks in advance.
I've owned a 1998 Trans Am (A4) for about two years. Recently, the car developed a noise in the back that I can best describe as a combination of 'buzzing and hissing'. I first thought it was the fuel pump, but it actually seems to be a noise in addition to the fuel pump - when the ignition is turned on (without starting the car), I can hear the fuel pump start/prime, and this new noise begins a fraction of a second after the fuel pump. The noise does stop soon after the fuel pump is primed, but when the car is then started, the new noise slowly builds up and rises to a steady level - loud enough to be heard over the exhaust and from several feet away. It doesn't change pitch/tone or get any louder when the engine is revved up, and the engine itself runs just fine while the noise is present (no indication that it isn't getting enough fuel).
Here's the part that I find interesting - this isn't a constant issue, it only seems to occur after a substantial amount of driving time. I recently made a trip of about 5 hours. On the way to my destination, the last stop I made was about 4 hours into the trip, and I had not yet noticed the noise. However, when I arrived at my friend's place, I stopped and put the car in park, but got out of the car with the engine still running - I immediately noticed the noise (and this is the first time I had ever heard it). So it seems as if the noise didn't occur until at least a bit over four hours into the trip. My friend and I put the car in his garage and jacked it up to try to pinpoint the noise, but we were not able to find its source/location - it seems to be a bit louder on the driver side, but it can also be heard very easily on the passenger side. Additionally, once the car cooled down, the noise stopped, and we were unable to replicate it again.
My trip had a very quick turnaround (arriving Friday night, leaving Sunday morning), so I was not able to get the car to a mechanic. On Sunday, the car seemed start, idle, and run okay, and the noise was not present, so I decided to take my chances and see if the car could make the return 5 hour trip. No issues at all with the engine during the drive, and I stopped fairly frequently to listen for the noise. It wasn't until about 4.5 hours into the trip that I noticed that the noise had returned. I made it home without issue, and as before, once the car cooled down, the noise disappeared.
I've driven the car around town several times since then, and have even made a 1 hour trip to a neighboring town (2 hour round trip), and I have not heard the noise at all. I wouldn't be so worried about it, but I do have to make another multi-hour trip in a few weeks and I'm guessing the issue will arise again.
The car is not throwing a code and since it takes so long for the noise to present itself, I can't simply run it by a mechanic for a quick listen and diagnosis. The car runs just fine, but there is obviously something amiss. I was hoping someone on this forum could provide some guidance due to perhaps dealing with a similar issue at some point. Any thoughts or suggestions?
Thanks in advance.
08-22-2018, 12:56 PM
#3
Teching In
Thread Starter
Join Date: Jan 2009
Location: midwest
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Hi Biketopia - thank you for the reply. No, I have never done anything to the car. But I've only owned it about 2 years and it had over 145,000 miles on it when I bought it, so hard to say what might have been done by the previous owners. I will check out your suggestions. Thanks again!