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"Chirring" sound from top of engine?

6K views 12 replies 5 participants last post by  JohnSawyer 
#1 · (Edited)
My 1994 GL with 3.8 engine is making what I'd call a high-pitched "chirring" or fluttering chirping noise in the area behind the alternator, somewhere on top of the engine, even when the car isn't moving. It starts as soon as the car is started up. It doesn't seem to be coming from the belt or any of the pulleys it runs. From what I've been able to gather from reading the thread here about the infamous Dorman camshaft synchronizer, my model doesn't have a camshaft synchronizer/positioning sensor assembly since it has a distributor, so presumably the sound I'm hearing isn't due to that, and it doesn't sound the same anyway. Any educated guesses? If it helps, I can try to post a YouTube video with the sound.
 
Discussion starter · #4 · (Edited)
How do you know?
I've moved my head back and forth to try to locate it, and it does seem to come from further back than the belt and pulleys. But true, I'm prepared to find it may be from the belt and/or pulleys--I've been fooled before when trying to locate a sound under the hood. My power steering fluid pump makes an annoying buzz (but it works fine, and I understand the PS pumps Ford used can be noisy), and for a while I was convinced the buzz was coming from the alternator right next to it, then I changed my mind and thought it might be from the A/C compressor below it, until I removed the cap on the PS pump reservoir to check its fluid while the engine was running, and found the buzz got a little louder.

So, I'll do like JW657 suggests, and take off the belt to be sure.
 
Discussion starter · #5 ·
Thanks WJC and JW657--I removed the belt, and the sound DID turn out to be from one of the accessories or pulleys. It may be the idler pulley to the right of the water pump. It looks like my normally good skills at stereo-locating sounds, needs some training for work under a car's hood. This time, I used a cardboard tube from a used-up roll of paper towels as a cheap stethoscope (I know, I should just buy a cheap stethoscope), and when I got it close to this idler, the squeaking was loudest, and when I rested the tube on the alternator (actually my first suspicion), I heard no squeaking through the tube. I guess the squeaking might instead be from the water pump, but I'll deal with the idler first of course.

This might be the origin of the squeaking: A few weeks ago, I replaced the belt (it had snapped due to a frozen A/C compressor clutch/pulley). While doing that work, I rotated the apparently squeaky pulley I found today, and found that though it rotated pretty freely, it still seemed a little sticky to me, so I removed it and used some kind of spray lubricant (something better than WD-40, but I don't remember now) to flush out any grit from its bearing, and then I decided to put it back in place, instead of getting some grease into the bearing (though I don't remember if that idler's bearing allows you to get grease into it). Maybe my putting too thin a lubricant into that bearing is causing it to squeak, but I thought it was squeaking before I did this--maybe not. I normally take notes when I discover something on my car, but I can't find a note telling me when the squeaking started. I'll be removing the idler later today and seeing if I can get some grease into its bearing, and if not, I'll replace the idler.
 
Discussion starter · #9 ·
A good bearing will have slight resistance, no noise, no play, no binding or grinding of any kind. Did you pull the orange dust cap off the bearing or something? It likely got contaminated either way. I would also check the alternator and a/c compressor very closely, the tensioner pulley too. Is it possible that the noise is a belt slipping? How much does the tensioner flex as the engine runs? Does the A/C still work in the car?
The idler bearing rotates too freely for there to be much actual grease left in it. The bearing doesn't have a removable cover on either side--instead, the idler has a non-removable bolt that holds a couple plates in place on both sides of the idler, that cover the bearing. But the plate on the engine side of the bearing does have four small openings around the non-removable bolt, into which I'd previously squirted the thin lubricant, but these openings are too small to get grease into, so a couple days ago I squeezed into them a lubricant called "SuperLube", which has a little body (thinner than grease, but thicker than liquid lubricant), and which contains Teflon, that comes in a small plastic tube. The loudness of the squeak reduced a little, which seems to be more proof that it's coming from this idler. I'll just replace the idler after I've gotten some more critical/annoying problems fixed.

There's no undue noise coming from the alternator, and about a month ago I replaced the tensioner pulley with a new one, and the A/C compressor with a new bypass pulley, since my compressor was shot and I'm not ready to go through the process of refurbishing the A/C system yet (though this summer I'm sure I will be--the temperature here gets into the high 90s and low 100s for weeks). The tensioner flexes/wiggles a tiny bit as the engine is running, but it doesn't seem excessive to me. The belt is also about a month old.
 
Discussion starter · #10 · (Edited)
if teh idler pullyey is suspect, just replace it. I had one lock up on me, snapped the belt and left me 90 miles from home. Serpentine belt drives everything, once that goes you're SOL.
The belt in my Taurus snapped at the end of December 2010, when the A/C compressor pulley bearing froze up (thoroughly rusted out, missing ball bearings, etc.). But before the belt snapped, its rubbing against the seized pulley caused rubber to be melted and stripped from the belt, which got deposited around the pulleys for the tensioner, alternator, and power steering pump, filling the gaps between the ribs around each pulley. I had to replace all three because the melted rubber had hardened so much that it was nearly impossible to scrape it off.

Luckily, it happened only about half a mile from home, and it happened while my brother was driving the car (big puff of black smoke from the rubbing belt, then a big bang). He lost power steering, but he managed to get it home anyway (I tried steering it this way, but couldn't, so he must have had to put some real force into it). And luckily the engine was still relatively cool, so lack of coolant circulation wasn't a problem for the short drive back home.
 
Discussion starter · #11 · (Edited)
My 3.8 has 230,000 miles and it has had the idler pulley replaced at least three times.
Three times? I'll have to keep a better eye on the pulleys! I got my Taurus in 2007 (it was my parents' car originally), with 134,000 miles on it, and I know only a little about its prior service record, so I don't know if the idler has been replaced before.

It also seems that the camshaft synchro/distributor gear isn't nearly as prone to failure as the one on the Vulcan engine.
In 2008, I had a mechanic do some work on my car, during which he found that the gear on the engine end of the distributor shaft (which is what you're describing?) had several broken teeth. But somehow what was left, had been enough to keep things going without noticeable symptoms. Of course, I had him replace the distributor shaft to be safe.
 
Discussion starter · #12 · (Edited)
I'm finally getting back to this task (replacing the squeaking idler pulley), after taking care of some more important issues with the car, like fixing its gas and exhaust fumes problems.

I bought a new Gates idler pulley (38006) because it seemed like a good one, but after I got it home, I realized that since it doesn't come with a mounting bolt or a big washer on the backside of its bearing to prevent the bearing from pressing against the mounting point on the engine, and to keep the pulley centered around the bolt, that I'll need to remove and reuse the bolt and washer from the backside of the old idler pulley.

Problem is, the old pulley's big rear washer is a type that locks onto the bolt, and I don't know how to remove it. Any ideas? I spent some time searching the threads here but didn't find any info on doing this.

Here's the front (top picture) and backside (bottom picture) of both the old and new idlers--on the old idler, notice the locking points on its backside washer, on either side of the bolt:

Auto part Grommet Tire Automotive wheel system Automotive tire


I'll also have to return the Gates pulley and get a different manufacturer's (maybe the Duralast 231016), since the inner diameter of the well in the front of the Gates pulley isn't large enough to hold the big black metal "washer" that I'll be removing from the frontside of the old pulley. I'm guessing that one function of the big washer on the frontside is to protect the bearing from dust?

EDIT:

Fifteen minutes after I posted this, I figured out how to do it: I grabbed the sides of the backside washer with a pair of pliers (it wasn't easy at first because the washer was so close to the bearing), and rotated the bolt head from the frontside using a box wrench. There was some resistance at first, and some slipping of the pliers until there was enough distance between the backside washer and the bearing to get a better grip on the washer, but the bolt came out of the washer after several turns. I hadn't tried it before because I thought it was going to be tougher than this, and I thought I might do some damage. Now all I have to do is return the Gates pulley and get one that will take the frontside washer.
 
Discussion starter · #13 ·
I replaced the suspect idler, and the squeaking is gone. First I went back to O'Reilly/Kragen and exchanged the Gates 38006 idler for a Gates 38023 (the original label on the new idler's box said Goodyear 49017, but O'Reilly had put a sticker over part of this label, marked "38023 Gates 49017" (and to make things even more confusing, someone had written 4946182, whatever that means, to the left of this sticker)). The Gates 38023/Goodyear 49017 looked exactly like the old idler I'd removed, including some numbers on the bearing cover, so it's possible my Dad, the former owner of the car, replaced the idler at least five years ago (before he passed away) using the same part number (maybe even from the same store). I'll see how long this one lasts.
 
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