hjeff1985

I just bought a 1996 ls400 w/ 144000 on it great car but when I shut it off it makes a low honking noise. What is it?

Banshee365

Loud honking noise, like a horn honk? Or like a quick discharge of air somewhere?

hjeff1985

well it sounds like a low honk, but not from the horn...it could be a air release of some kind, evry 10 sec or so for about a minute....i dont know...

Banshee365

Well I think we'll need more of an idea where it's coming from. See if you can find what general area it's coming from. I was going to guess a lose spark plug but that won't reoccur after shutdown. Does your car have air suspension? You can tell by switches near the gear selector. The air pump near the passangers side wheel well if I remember correctly, my car does not have it. My guess is that it's coming from that system. May be normal if someone with the air suspension can chime in.

cbach

I have also recently purchased a 95' LS400 that does the same thing. Having very accute hearing, it drives me nuts while driving and fades away after turning the car off. Kind of a low humming sound that seems to come from behind the dash and will come back with the ignition on, engine off.

Sounds almost like some sort of electric pump running, and I'm thinking it may have something to do with the brake accumulator.

Banshee365

Again, check if you both have air suspension........

cbach

Not on mine. Most people likely wouldn't even hear it, or think it was anything abnormal. And after reading hjeff's post again, mine is likely something different, as his is a recurring noise that comes and goes, while mine is consistent.

amcdonal86

Yes. I think I know what you're talking about! It happens on my car, too!

I think it has something to do with the HVAC. Have you ever shut the car off and just sat in there for a few minutes? The HVAC system seems to continue to adjust the vents and things even after the car is shut off. From outside (and very close to the car), it can sound sort of like a muffle duck call.

Mine is a '97. I think it's pretty normal.

(I guess the brake accumulator is a good explanation, too...)

1pinchole

Im having the same problem on my 96 ls400. Not only does it make that low honk, dying duck or whatever sound you wanna call it, itll make that noise far after Ive turned my car off. Sometimes itll still be making that noise the next day! I timed it yesterday and it was every 5 seconds. (not to say that its always every 5 seconds since ive had this problem for months and never addressed it till now) Not sure where its coming from or whats causing it. Please any suggestions? Also sometimes it doesnt make the noise at all which is just as confusing.

FloridaCam

This sound also happens to my car. I think it is from the radiator but don't want to do anything with it since it does not affect the driving whatsoever.

UNDaaron

My 96 makes the exact same noise. One day it did it after the sun came up and the temperature of the air rose up to around 80 degrees...I hadn't even driven the car that day! I think it's in the fuel evap system at the front driver side of the car?

Kdfwagen

My 1996 ls400 has always done this. Could never figure it out. But seems like it would have to do with the evap.