The Stovebolt Site Forums The Shop Area Engine Shop Mysterious Chirp

Sitting at a stop light I hear a faint chirp coming from I believe the engine compartment. It occurs about every 5 seconds. I leave the light, truck rolling and revs up and the chirp is still there - every five seconds. Makes no difference if the truck is moving or stopped. Engine RPM increase and its still every few seconds. no increase in either situation. Baffling!

Sounds like a metal to metal body parts squeak. Take a rubber mallet and start tapping around where body panels meet until you hear the squeak.

could be a metal-to-metal noise as Carl sez, and maybe check the water pump pulley isn't slightly touching the pump body at a point in it's revolution

Bill

Thought of all that but it chirps whether or not the truck is moving or the engine goes from idle to higher revs. Same cadence, same chirp. It is a mystery. Will get a stethoscope on it.

Heater motor?

Almost sounds like an AC compressor cycling with a loose belt. You don't have vintage air on your '49 do you?

Take off the fan belt and see if the ''chirp'' goes away. if its not chirping anymore, you know where to look, I have seen fan blades cracked that make the chirping noise . maybe water pump.

No heater, no AC. What baffles me is the chirp does not go faster or slower no matter what the engine speed. Its constant.

does it matter if your in the truck or not?

I have not tried that. You may be thinking seat squeak but stopped at a light it still squeaks and I am sitting still. It definitely sounds like its coming from the engine compartment.

Doesn't change w/rpm or vehicle speed? That almost rules out engine/drive train mechanical. What electronic device would chirp at a steady rate? Cell phone low battery, vehicle alarm low battery, stray volts getting to the horn some how (maybe a loose horn relay ground wire?) Fancy radio?
Charging varies w/rpm but likes been said remove the fan belt and test.
I dunno....
You might have a pizzed off critter in your defrost duct

Good luck
Dave

You've got lots of ideas, you're not going to solve it without trying to diagnose it yourself, let us know what you find

I was thinking suspension

I had a sound I thought coming from the engine compartment. But every time I got out of the truck it would stop.

It was not a chirp...more of a ting
ended up being a broken upper shock mount.

Keep us posted.

do you have an self exciting Alternator?

might be in your cell phone, someone from Tx trying to reach you

Well if it still makes the sound with the engine off, and you run out of ideas, here's a temperature crickett chirping formula. May as well rule that out, unless it's around 40-45 deg F there.

Volfandt could be right about the critter, though .

Checked water pump, fan belt. Have no fancy radio or electronic gear. Cell phone is fully charged and not in truck.
The fact it happens whether it is moving or not, idling or at speed and its still there is what baffles me. Engine off it does not make a sound. Critter under hood? Nope, checked that. Its stuck in the garage behind a bunch of cedar fencing since yesterday so I should have it out again tomorrow. And I don't get calls from TX any more. Sob!

DADS50 no I have a generator. But just what I can c0mpare the sound to. The chirp you get when the battery in your smoke detector gets week. And no I don't have a smoke detector in the truck!

I had a cracked flexplate make a funny noise. Came out in three pieces. Different subject, got any pics of your g-bodies? I loves those cars

Have you tried to bang around with a rubber mallet yet? Your noise cannot be caused by any revolving mechanical part since the cadence does not change with change of speed or engine RPM. Are you positive the cadence of the chirp does not vary? You either have a metal to metal squeak brought on by a specific vibration caused by the running engine, or someone with a high degree of ingenuity and access to your vehicle has installed an elaborate electronic squeaking device which only comes on when the engine is running. I do not know you, nor live anywhere near you, so it wasn't me. Besides, it is much easier to drive someone batty by putting a zip tie on the drive shaft with the long tag end left on to smack the floor board.
Carl

Tried banging the body with my fist. Nothing. Don't forget it still chirps when the truck is stopped but the engine is running. I do have a bit of an on-going feud with the local constabulary so they could have put that electronic device on the truck but I really doubt it. The truck is locked up at night and frankly they are not bright enough. The zip tie on the torque tube ...... don't think so.
Today it will be found I hope!!

Do any of the gauges fluctuate in time with the chirp?

Are the wipers on but not functioning?

I'm just thinking of what is mechanically independent from the engine, but is receiving pressure/signal to remain at a constant position.

Brad

Just a thought, but I have heard a sound that was a definite "chirp" coming from a small leak around the base of my carb, I even think around the throttle shaft. Whatever it is, do you hear it at idle with the hood open and your ears in the engine compartment?
Karl

maybe one of the relays vibrating in the voltage regulator? That would not be affected by engine speed or moving or stopped.

Relay! That is one of the better ideas! I checked everything top and bottom with me in and out and cannot find a thing. When I stopped the engine after a 5 mile drive I did notice it was still there but stopped a few seconds later. How would I fix the relay if that is the cause?
Karl I did not check the base of the carb though. I rebuilt it 2 springs ago.

Sedgewick;

Does it chirp when the engine is cold? Could it be the thermostat cycling or the radiator cap burping/chirping?

SimS

when you first posted you did not state how long
the truck was driven before the chirp started... you stated
that when you stopped at the light, etc..

what happens at first start? and then how long before
the chirp starts... let me know.. I think I know the answer

Take the top off the voltage regulator and see if the points behind the BAT wire are opening and closing in cadence with the chirp. It's possible the regulator settings are wrong and the cutout relay is cycling, causing the belt to slip on the pulley intermittently. If that's the case, the ammeter is likely to spike up and down in the same cadence.
Jerry

SimS. It starts as soon as I drive away cold and continues until I stop even after a few miles and the temperature is at the operating level.
Joker as I replied to SimS. Starts right away and continues until I shut down. But I noticed today that after I shut the engine off it chirped a couple of more times. Chirped on my ride tonight and when I came into the garage. But when I turned off the battery cut-off it stopped.
Jerry I had seen spikes in the ammeter in the past but it only made a slight knocking noise in time with the spike. Its away now but I'll check it in the morning.

But when I turned off the battery cut-off it stopped

there you go...you found the answer

I did? Clue me in.

start it up, and then disconnect battery while running and
see if the chirp is still there...

The chirp is electrical. Try removing the BAT wire from the voltage regulator and insulating the bare terminal with a couple of wraps of electrician's tape, then do a test run or a short test drive on just battery power. Don't worry about draining the battery- - - -a well-charged battery should burn half a tank of gas or more before it gets too low to operate the ignition. Just dont run headlights, heater fan, etc. I'm going to bet the chirp goes away. It sounds like you need to adjust or replace the voltage regulator.
Jerry

Excellent tips. Will be moving the cedar lumber out of the way and getting the truck out of the garage later. Will keep you posted. Thank you!

You are describing an electrically powered device that is activated when the engine is started but is still powered when you turn the key off.

Check every hot wire that doesn't go through the ignition switch.

What comes to mind is an old diaphragm electric fuel pump. But you never know what strange thing a PO wired in with direct power.

Do you have an add-on vacuum canister? I did and mine developed a crack that had just the squeal you describe.

Cosmo made me think about the vacuum wiper motor. A bad one might continue to make a chirp a time or two after shut down.

Not the wiper and I have no electrical accessories except my radio which is not wired yet. Took her out today and strained to hear for that elusive chirp. None! I am sure it didn't really go away but is just hiding knowing that I am into some serious investigation. Took the regulator cover off and all is quiet in there. Disconnected the battery with the motor running and it was still quiet. Feel like I'm chasing ghosts.
Anyway let's say it has gone and thank you to all the great input. I have however determined it is electrical.

ha, I know the problem, at your age you are hearing things..lol

might have been just a belt that decided to get back in the groove ........glad it is better..

my age? what things? huh!

Every morning theres a redheaded woody woodpecker that wears one section of my guttering out. Sounds like a jack hammer. Later on I see him hopping vertically up the tall Maple just off my den, pecking and hopping all over that tree.
Crazy little bird.
Ummm, now what were we talking about? Oh yeah chirping, I wouldn't call what ole Woody is doing as chirping and I don't know why I'm posting this here.
Oh well, I hear crickets sometimes, toads too, they all seem to drown out the fuss'n I oft-times get so I guess they are good sounds.
Only sounds I hear in my ole 49 3100 is tickety tickety tickety of the valve train and sometimes a clicking in the speedo, otherwise I just drives and thinks
Good luck Sedgewick