John's Chirping Noise

What could possible make a Dodge Caravan chirp… exactly every 11 sections?

A very good question, indeed.

This week on Car Talk, John from Maryland had Tom and Ray stumped. His Dodge Caravan is making a chirping sound every 11 seconds. It only happens when he’s moving. Ray’s 100% sure it’s the AC compressor, but John’s 100% sure it happens even when the AC is off, so that’s one answer that’s down the drain. Tommy’s thinking of a loose heat shield, but the 11 second interval sends that answer to the scrap heap. So, our humble hosts say, “Uncle!”, and that’s where you come in. We want your diagnosis. You can hear Tom and Ray’s chat with John right here, and then share your suggestions.

And, on behalf from Tom, Ray – and John in Maryland – thanks!

guys! can’t belive you on this one - I have tried to call in with the same stinking problem!!! I have a chirping, sometime timed and other times only at shift points… it was driving me nutty- ier. but after the clutch pulley melted off the altenator, and $180 later I found the new alt. making the same racket… I looked at the belt while it was running (not a great idea for the novice) but seen some crazy belt movement, and replaced the tensioner ($36) and no more chirping! My van had 170K miles when this part finally burned out… and it works like a Ninja and kills off everything else before you even suspect anything is wrong! atleast I will never have to replace the altenator again - lifetime warr-n-tee care of Oriely auto parts - lol - this should fix John’s van right up and then he can get back to selling coats out the back of it! lol - great show - Barry Farmer

I am going with a brake component. Possibly related to the warning sensor. Could it heat up chirp and cool periodically? Or, does John have an old house smoke detector in the back of the van that slid under the seat and needs the battery replaced?

I have a 97 gmc pickup. sometimes the compressor will run even when I have the climate control off! It happens when the AC button is left pushed in and everything else is turned off. So it’s possible that Ray’s theory may be right…nah

I have had personal experience with Chrysler tensioners going bad, but fbodiescatfish’s solution appears to be “rotational”, which you guys ruled out. If that solution doesn’t work, John might have a look at the fuel pump. I never owned a Caravan, but I once had a Dodge Dynasty from the same vintage, and the fuel pump was inside the gas tank (which seems like a questionable piece of design, but it checks with John’s impression that the noise is coming from the rear.) I recall once that it made some strange noise, and had to be replaced. Being an electrical problem, it probably was at regular intervals unrelated to speed.

I can never get my toughts together at one time!

even though Tom and Ray “ruled out” rotational noise, the tensionor is a tricky peice of trash. when the engine is not moving the tensionor applies enough pressure to hold the belt tight enough, and when the engine is running the tensioner tries to apply the correct pressure to the belt but “bounces” back too slow, and in turn every “11 seconds” the belt grabs traction on the pulley, thus creating the mating call of the Mopar song bird! its a real head scratcher, and can sometimes sound like its from the rear, while you drive, or sit. I was almost ready to use my cash for clunker deal, when I fixed mine.

Did someone lose a battery-operated smoke detector behind a seat that is telling John it needs a new battery? Also possible: John is running his climate system in some mode (such as defrost) that turns on the AC compressor even though the AC switch appears to be off.

I like the AC - so what’s to say that the AC switch is not working correctly & the AC is actually on. Or is the heater set to defrost which would activate the AC. AC all the way.

Test - remove the belt that drives the compressor & get your stopwatch out!

Tom missed by not asking if it was set to defrost mode; that would vilify his most glorious notorious nefarious indeiferous suggestion and probably proper diagnosisis of AC.

great test Johneh!
but if John is not a highly skilled mechanic he might let it run too long with out water pumpimg through the engine.

actually I am sure he would know to watch quick and shut it down after a few minutes (max) before the engine really starts to make any real heat. I just wanted to put that out there… water is very important to most engines… minus those crazy air cooled rides - like my Ford Ranger sometimes is! hahaha! of course you could just let it run for a bout an hour with out the belt, and then you won’t hear the chirp any more!.. B/C you will be driving a new car!

Well, I don’t have an answer about John’s chirping noise, but I think I know what’s causing the thumping noise in the ceiling of Ray’s house whenever the water in the kitchen sink is turned off. I used to design commercial plumbing systems in a former life. It’s called a water hammer effect. It happens when you get the water moving inside the household pipes by turning on a valve, such as in the kitchen or when a toilet flushes. Normally, a turn-type valve doesn’t result in a water hammer effect because water is turned on and off slowly. But in a lever-type of valve, such as a kitchen sink, you can start and stop all that water moving suddenly. When all that water in the pipes comes to a sudden stop, it transfers the kinetic energy to the pipes which causes them to rattle. We used to specify water hammer arrestors that prevent all that water banging around in the pipes. It’s common in older houses. Hope it helps.

Ray is heading in the right direction. It is probably the AC compressor. You have to remember, in most cars the compressor is activated at times other than when in the AC mode. The AC system works when the climate control is in the heat and defrost mode so that condensate does not build up inside the car and/or windows fog up. Some foreign cars do not have this function and are uncomfortable to be in and, somewhat, dangerous to drive when the windows are not clear.

I’d guess either a belt tensioner or, it is possible that the odometer is skipping. I had that happen to me on an older VW


I may have heard it wrong, but I think he was saying that the thumping noise in the ceiling wasn’t just a couple of loud, rattling “bangs”, but more of a succession of thumps in more regular intervals. When that’s the case, doesn’t it have to do instead with the expansion of hot water pipes that were cold and now have hot water running through them? The only thing that I know to do in that case is to tighten up a loose pipe-hanger or two. I guess if it’s in the ceiling, though, it’s best to just leave it alone, right?
Help me out on this one, please. I’m certainly not an expert and would love some clarification on this point (mainly because it’s happening in an inconvenient spot in my house, too!)
Thanks! :slight_smile:

You may be right. If you throw a valve and the thump or thumps immediately follow, then it’s water hammer. It may also cause the pipes to rattle a bit for a few seconds as the pipes swing back and forth like a pendulum. The effect is that, after time, joints weaken in the same manner a paper clip will eventually break if you bend it back and forth several times. That’s why we spec’ed water hammers for commercial applications, but not so much for residential. A public toilet in a shopping mall is flushed dozens of times a day. A household toilet, not so much. I once worked in an old, old building in Oakland, California where the water hammer effect actually caused the windows in half the building to rattle with an accompanying “BAM! BAM, BAM, BAM, boing, boing, boyoyoyoyoying” sound. You can eliminate the effect by replacing lever valves with twist valves, or just be mindful and slowly open and close lever valves. If you’re correct and the cause is expansion and contraction, then the pipes will probably outlive the house. It may be annoying, or it could be a benefit. Just tell the kids to do their homework or eat their vegetables or the ghosts in the ceiling will get them.

Absolutely the expansion and contraction of pipes, hot / cold copper has to move when introduced to the different temperature extremes.

My first thought was the A/C trying to cycle on and moving a squeaky belt. Could there be an electrical problem in the A/C switch that tries to turn on the A/C whether it should be on or is already on? If the A/C off the start could cause the noise; if it’s already on, then there might be a surge that speeds up the belt. Otherwise I got nothin’

So…I’ll take this away from the AC theory to a completely different one.
My family owned a vintage 1993 Dodge Caravan and for about 5 years (until I totaled it) it made a kind of “chirp” sound on a regular basis. All of my male relatives (all engineers) debated the cause of this over the course of many a family meal. It was the computer engineer who deduced that the cause of this “chirp” was our family cell phone. I am not aware why, but it was explained to me that cell phones interfere with speakers and cause feedback. The theory goes that since our van had speakers positioned throughout it, the feedback caused at the tape deck/radio control to broadcast that feedback throughout the van. Perhaps that is all this is.
Of course, I got my degree in French so they could have been pulling my leg all the time.
– Ex-Minivan Driver