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More insight on the Chirping Explorer

Everyone,

I apologize in advance for the length of the post that follows. This is a puzzling problem that I have been chasing for almost 2 years and I could use the collective experience of the group to help me solve it. There are several others with similar problems, so I hope this will benefit others.

Almost a year ago I began posting messages to the group regarding an intermitent chirping or squeaking noise that both my 94 and 95 XLTs make. The noise increases in frequency and volume with the engine RPM. It does it occassionally in idle, but most often when the RPM are above 2K. It does it VERY often but it comes and goes during driving and is extremely unpredictable (except in the fact that it seems to stop...without fail...ever time I take it to the shop). I had many respond and suggest a cracked flexplate and many other respond with belt pulleys or belt driven devices as the possible culprit. After many months of detective work, I am narrowing the field of options and need some help narrowing it further. Here is what I know to date:

I have replaced the scerpentine belt, tensioner (which was broken) and idler pulley (which had a worn bearing). These did not solve the problem. I have taken the truck by the transmission shop and they have driven it (without being able to reproduce the noise) and concluded that based on empirical evidence, the transmission appears to operate within normal limits. I invested a few bucks in a stethoscope in hopes of narrowing the origin of the noise. I have been somewhat successful in my efforts. I checked the alternator and AC pulleys and they are not the culprit. The noise eminates from the rear of the engine compartment and I can hear it quite clearly when I touch the steth. to the engine block right at the firewall.

Tonight I had a break in the storm. The noise was very pronounced when I left the office so I took the truck to the tranny shop. The owner (who has been helping me try to locate the source) listened to the noise and poked his head around underneath the car and said "That noise is not coming from your transmission. It is coming out of your exhaust system." True to form, I left the tranny shop and drove 25 yards across the parking lot to the MIDAS shop to let them hear it, and it stopped when I pulled up to the store.

I talked to one of the mechanics who suggested a few options: 1) cracked exhaust manifold 2) catalytic converter malfunction [as a side note I have a check engine light on that throws a catalytic converter inefficiency code] or 3) leaky exhuast manifold gasket.

My questions are these: 1) Is this type noise consistent with one or more of the problems I just mentioned? 2) How much am I looking at to fix these problems?

I had the MIDAS shop check the cat. converter when I started getting the Cat. Converter Code and they said that they banged around on the CC and did not hear any rattle that suggested worn or loose parts. They claim the CC code can be indicative of an O2 sensor that is about to go bad, but in light of my problems, I wonder if the CC is the source of my problem.

Whew...that is a lot of info. What do you guys think...assuming you did not fall asleep reading this post?

Reply to
Bradford C. Hatchett
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Brad,

We've corresponded once or twice on this as well. Thought I'd also follow-up to confirm that I also suspected it might have been something like a squeaky manifold connection or something similar along the exhaust system. The squeaking we both hear is definitely a metallic chirp, like two pieces of metal touching but cyclically rubbing in time with the engine RPM. In my observations, my chirping has been half crankshaft speed. I also got one of those mechanic's stethoscopes. If you touch it to any of the fuel injectors while the engine is runnning, you will hear the clicking of the injectors, which also is half RPM speed. In other words, if the engine is running

1000RPM the clicking will be 500 times a minute. That's of course because on a 4 cycle engine the engine fires each cylinder once every two revolutions of the crank. So anyway, that's where my detective work ends - the fact that the chirping is exactly half speed, and in lock-step to the clicking of the fuel injectors, makes me think that the chirping is somehow mechanically linked to the engine. I would have also thought it was the flexplate, except the flexplate turns at crank speed, not half crank speed. About the only other thing I can think is that maybe it's some internal squeak from like a camshaft bearing that's in need of oil, or perhaps a squeaky valve lifter (the V6 is a pushrod engine), or something along those lines. I think that only cuz the camshaft & valves are the only other things in the engine (aside from the injectors and spark plug) that move/rotate at half crank speed.

Perhaps, and this is only a light hunch, the only connection I've been able to make so far is that if I top off the oil, then the chirp seems less prevalent. I will also say that the Ford tech I showed this to, examined the engine while it was squeaking, and came away with the general diagnosis that the squeaking was coming from the upper part of the engine (where it was not getting all the oil??) and not from the transmission.

Some on the NG have also suggested a squeaky fan clutch, which does make some sense because the squeaking goes away after the engine warms up. Same with fan clutch - it engages when the engine warms up (and you presume any squeaking would cease, which it does). The only hole in that theory is that a squeaking fan clutch would not always be 100% lockstep with 1/2 crankshaft speed. I say that cuz the fan blade itself kinda just drifts around at it's own speed anyway, until the clutch warms up and it engages fully. In other words, at a given engine RPM, a squeaking fan clutch would vary in it's frequency based on engine temp, and not always be at half crank speed. Also, I did disconnect the serp belt once and ran the engine for a couple seconds, and the squeak was still there. So, anything driven by the serp belt was instantly eliminated.

In all, and like you, I have not really narrowed it down yet. Other than that, the engine seems to run fine. Go figure!

Mike

Reply to
Mike Mayer

Timing chain, perhaps?? Dave

In my

Reply to
Dave Brower

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