Strange ongoing humming tone from 94 Accord

Hello,

I recently bought a 1994 Honda Accord LX, with 195,000 miles. As I was
walking out to my car this morning, I heard a strange ongoing
high-pitched tone, which could best be described as a more faint
version of the horn. I panicked, thinking that the horn switch somehow
froze in place (I'm in Boston) and drained the battery overnight, and
sounded faint because it was on its last legs.

However, I got in the car, and it wasn't the horn - in fact, the car
had plenty of juice to crank and turn over. I got to work (with the
strange tone still blaring) and identified it as coming somewhere from
the engine bay. It almost sounded similar to a door buzzer (though I
don't recall what the door-ajar sounds like since I've only had the car
about a week) but it was loud enough to hear from about 10 feet away
from the car.

The beeeeep sound continued but started to go off and on, and finally
shut out right as I was about to disconnect my battery.

Any ideas on what this could be / have been?? I'm so completely
baffled.

Thanks,
Pravin

 

I have a similar sound that sometimes will eminate from the gas tank
area-- a kind of whirring that is constant, then goes to a cycle on off
mode, then stops. I'm guessing the fuel pump is doing something. The car
runs great, so I haven't looked further. I'm curious what your inquiry
will yield, because they sound like similar things, only different
places on the car. BTW, mines' an Inifiniti G20T I4 engine.

wrote:

Hello,
I recently bought a 1994 Honda Accord LX, with 195,000 miles. As I was
walking out to my car this morning, I heard a strange ongoing
high-pitched tone, which could best be described as a more faint version
of the horn. I panicked, thinking that the horn switch somehow froze in
place (I'm in Boston) and drained the battery overnight, and sounded
faint because it was on its last legs.
However, I got in the car, and it wasn't the horn - in fact, the car had
plenty of juice to crank and turn over. I got to work (with the strange
tone still blaring) and identified it as coming somewhere from the
engine bay. It almost sounded similar to a door buzzer (though I don't
recall what the door-ajar sounds like since I've only had the car about
a week) but it was loud enough to hear from about 10 feet away from the
car.
The beeeeep sound continued but started to go off and on, and finally
shut out right as I was about to disconnect my battery.
Any ideas on what this could be / have been?? I'm so completely baffled.
Thanks,
Pravin

 

You mean your car had been parked overnight and when you went to your
car in the morning with the engine off it was emitting a tone? Could
it be something aftermarket? Never heard anything like that from my
1994 Accord and I've had it since day one. The only sounds the car
emits with the engine off are the <ding-dong> when the headlights are
left on and the <buzz> leaving the keys in the ignition with the door
open.

 

Exactly, in other words, the tone was there whether the engine was on
or off. This is why I am ruling out a fuel pump. I can't think of any
other buzzers or beepers that the car has. The lead to the positive
battery terminal did look as if something aftermarket had been
installed (an alarm system perhaps?) so I'm going to further
investigate to see if I can find anything. I'm still baffled though,
because the tone was way too faint to be an alarm, yet too loud to be a
keys-in-ignition buzz.

 

It was the fuel tank breathing in and the pressure (vacuum) relief
thingy caused the sound. Hint - almost completely close the back
of your throat and now breathe in with effort - you'll get a similar
noise!

 

In my post in this thread, I failed to mention that my sound only occurs
after I've shut the vehicle off. It's constant for about 30 seconds,
then starts cycling on and off for a couple of minutes.

 

Sounds like a plausible explanation for the sound I'm getting. Do you
know if this is something that's considered 'normal' and nothing to
worry about?
Thanks for the response!

 

The problem with this explanation is that the tone occurs regardless of
the key being in or not - i.e. regardless of the fuel pump being on.
Also, the noise is too consistent (as in, it's a tone of a particular
pitch) - think "Meep meep" horn being held down, but not as loud as a
regular horn. Also, the regular horn itself is unrelated to this noise,
and functions properly. The tone started blowing again on the way to
work - currently the battery is disconnected.

Any ideas, folks?

 

It is a pure pneumatic effect and doesn't require the pump to be running.

After a journey of a mile or two, the tank stores the partial
vacuum until the temperature falls causing even more vacuum and the
relief valve gives in as described above. You may not get it to do it if
you remove the battery since that will dissuade you from using the car
which is a pre-requirement. This effect can occur hours after the car
was run. As to the constancy of the tone, have you noticed that most
farts sound the same even from different people? 8¬)

HTH

 

Correcting my error, the sound it makes if you leave the key in the
ignition and open the door with the motor off is a repeating
<beep-beep-beep-beep> sound and not a <buzz>. Getting up there in
years.

 

My vote is for a very light short in the horn that's causing it to hum
under very low current. Try pulling the horn fuse and see. How did you
decide that it wasn't the horn?

 

Abeness,

That's something I'll look into. The only reason I decided it wasn't
the horn was because the horn seems to blow perfectly well, and it's an
entirely different pitch. (Higher pitched). I'm may just take it into a
shop tomorrow, my patience and time are at a premium, especially in
this weather.

Pravin

 

I'm starting to think pravinkpant has bought himself a car that's had
abysmally poor care and maintenance in its life...

 

Tegger,

With all due respect, how do you figure that it's been poorly
maintained, because of what could be a horn short?

FWIW, the rest of the car works great - super smooth engine, 5-speed
tranny shifts beautifully with a smooth clutch, steering feels tight,
brakes have plenty of pad left, and timing belt was just done. Just
curious.

Pravin

 

HAHA -- I guess the flatulence-phenomena may hold true, but the tone is
definitely electrical, as it can be turned off and on by
disconnecting/connecting the battery.

Pravin

 

Well, that is the first mention you have of that fact!

 

My apologies for not having been clearer. Yeah, it's definitely
electrical.

 

id try to find out what, if any, servo motors are under the hood, and
take a stethoscope to each one. is there a cruise control servo?

 

I'd understand that! It's pretty damned cold here too (if you mean that
it's cold, that is).

 

Hm, interesting coincidence: my '94 Accord LX also has 195 K miles in
it. however I experienced no such problems as you described. Is yours
assembled in Japan or here in the US?

Rudy