# Engine knock & whistle under car



## slhaas (May 1, 2005)

I just brought home my '04 sentra and have noticed 2 noises. Fist is a knock/ping from the engine & exhaust after I shut off the car. Is this just cheap fuel from the dealer? Second is a slight whistle from under the car while running. Perhaps an exhaust leak?


----------



## Jarek (Mar 29, 2005)

slhaas said:


> I just brought home my '04 sentra and have noticed 2 noises. Fist is a knock/ping from the engine & exhaust after I shut off the car. Is this just cheap fuel from the dealer? Second is a slight whistle from under the car while running. Perhaps an exhaust leak?


cant be engine knock... cars brand new isnt it? plus its tuned for cheap gas (87 octane) says so in the user manual

The whistle you hear... is im not sure what, because i have a 1.8s (auto) bought it new off the lot... ive always heard it while driving.. not sure what it really is..but it has never caused a drivablitlity problem.. more than likely its the sucking action from the intake. you hear the whistle under hard acceleration? correct?


----------



## slhaas (May 1, 2005)

Jarek said:


> cant be engine knock... cars brand new isnt it? plus its tuned for cheap gas (87 octane) says so in the user manual
> 
> The whistle you hear... is im not sure what, because i have a 1.8s (auto) bought it new off the lot... ive always heard it while driving.. not sure what it really is..but it has never caused a drivablitlity problem.. more than likely its the sucking action from the intake. you hear the whistle under hard acceleration? correct?



Yes and no... the whislte is also evident when I am at idle, but more faint. The engine knocking sounds like the clicking of my older cars when I shut them off till they cool down. I went with the used '04 with 17,000 miles, so no, it's not brand new.


----------



## Zac (Mar 10, 2004)

The pinging is the heat shields retracting from the heat produced specefically from the cats as they get very hot, causing metal to expand and contract. It is noisy but harmless. Almost all Sentras have this.

The whistling sound is just the car; I would imagine it has to do with simple aerodynamics. If the whistle is while simply idling, I have also noticed this. Why? I could not tell you but I do not believe it has to do with an exhaust leak. If it is a leak, it is easy to tell by starting the car and placing your hand over the areas where the exhaust is connected. If you do this, 1) be sure the car is in park/ebrake jacked and preferably have someone in the car holding the brake and 2) do this when you are just starting the car to avoid the likelyhood of a burn.


----------



## slhaas (May 1, 2005)

Scroto Baggins said:


> The pinging is the heat shields retracting from the heat produced specefically from the cats as they get very hot, causing metal to expand and contract. It is noisy but harmless. Almost all Sentras have this.
> 
> The whistling sound is just the car; I would imagine it has to do with simple aerodynamics. If the whistle is while simply idling, I have also noticed this. Why? I could not tell you but I do not believe it has to do with an exhaust leak. If it is a leak, it is easy to tell by starting the car and placing your hand over the areas where the exhaust is connected. If you do this, 1) be sure the car is in park/ebrake jacked and preferably have someone in the car holding the brake and 2) do this when you are just starting the car to avoid the likelyhood of a burn.



Thanks... will try. I just want to get all of the possible issues addressed while it's still under B2B warranty.


----------



## slhaas (May 1, 2005)

I checked it out and couldn't find any exhaust leak to explain the noise. I did seem to think it came from the rear of the car though. I also noticed, while parked with the engine running, that the noise did NOT change with RPM. It did, however, change when I rolled my window down (power windows) and kept the button depressed after the window was all the way down. If I would turn on headlights or something electrical, the noise would change slightly for just a moment, and then go back to the normal whistle.

On another note, I noticed that the transmission will not shift out of first as fast as I'd expect. The RPMs get high and then it kicks into 2nd... not hard, but not smooth. Is this just how the Sentra is? I have never had an auto before, so maybe I'm just not used to it yet. I also noticed that putting it into gear from park, especially the 1st time after it's been sitting, is a little hard. Not hard to do, but not really smooth either. Also normal?


----------



## crunchie (Apr 29, 2005)

The "whistling" might actually be high pitched "whinning". From your description, it looks like it's might be electrical noise. See if anything changes if you turn off all non-essential components (headlights, cabin light, radio, cigarrette lighter, etc...).


----------



## Zac (Mar 10, 2004)

There is truth to the auto being relatively rough shifting in our cars.


----------



## slhaas (May 1, 2005)

crunchie said:


> The "whistling" might actually be high pitched "whinning". From your description, it looks like it's might be electrical noise. See if anything changes if you turn off all non-essential components (headlights, cabin light, radio, cigarrette lighter, etc...).


That's what I'm gathering, but I hear it outside of the car, and it's louder under the car and to the rear. It isn't audible at all when I'm in the car unless I roll down the window and listen for it, but it does change when different electrical components are used... if only momentarily before going back to the otherwise standard pitch.


----------



## Jarek (Mar 29, 2005)

slhaas said:


> On another note, I noticed that the transmission will not shift out of first as fast as I'd expect. The RPMs get high and then it kicks into 2nd... not hard, but not smooth. Is this just how the Sentra is? I have never had an auto before, so maybe I'm just not used to it yet. I also noticed that putting it into gear from park, especially the 1st time after it's been sitting, is a little hard. Not hard to do, but not really smooth either. Also normal?





Scroto Baggins said:


> There is truth to the auto being relatively rough shifting in our cars.



I have a 04 1.8s Automatic... it is pretty rough... especially when the damn thing is cold... good grief! It gets better the more you drive... but yeah under hard acceleration especially going towards red line, not only is there a noticible kick back.. but some torque steer as well... it almost feels like manual with a some funky clutch feathering lol...


----------

