A few days ago my 1996 Ford Explorer with 70K miles started to squeal. It is often loud enough to be heard 50 feet away. The problem is intermittent; While idling or at travel speed, transmission in Park or Drive, it can be quiet for several minutes, then scream/squeal very loudly for several minutes. It appears at random times.

The noise seems to come from the back of the engine compartment. It is a very penetrating noise and it has had me on a wild goose chase. My stethoscope sometimes suggest it is from the torque converter area. But, other times it suggest other places (even the EGR plumbing). Frankly, it is hard to nail down and I'm find myself chasing my tail.

The noise sounds like a bad bearing or bushing. Sort of like a pig that is being jabbed with a sharp stick. Or, like a water pump that has a bushing going south (wish that were the case).

Anyone have a Explorer 4.0L V-6 expert in the family? Or perhaps have a friend that works at the dealership that can offer some useful insight? It would be ideal if there was a TSB on this (I've Google and not found anything that was obvious).

I've got a technician's stethoscope, good mechanical knowledge (do all my own auto repairs), and a desire to fix this before it becomes a real problem. All I need is someone to offer miracle advice.

You probably have but just in case. Have you totally ruled out the alt belt and pully?

It's not the serpentine drive belt. I completely removed it {which idles the alt, pwr steering pump, water pump, idler tension wheels, etc.} and the noise remains. It would have been an easy repair if it was related to the belt's path.

The noise is definitely not from the front of the engine. The angry pig squeal is at the back. I suspect it is somewhere deep, where my stethoscope has not yet successfully probed. It is tricky, and I have gone in circles trying to narrow down the source. It doesn't help that the noise comes and goes all by itself (takes patience waiting for it to come back).

tensioner pully bearing, water pump bearing, alternator bearing, air pump, power steering pump, air conditioner compressor?

tensioner pulley bearing, water pump bearing, alternator bearing, air pump, power steering pump, air conditioner compressor?

The big serpentine drive belt interfaces with all these goodies. Even with the belt removed, the noise remains.

More info:
The noise will appear with the engine stone cold or at temperature. It is not related to the electric radiator fan or transmission use. It does not involve the heater, A/C, or recirc air fan. It is not the disk brakes; It occurs with the Explorer in park or in drive.

The noise is VERY loud. My mind's eye envisions a bad bushing or bearing somewhere.

I'm not a Ford guy but some 3.4L Toyotas have flywheel(flexplate)cracking issues.
This may be putting the torque convertor (bushing in the crankshaft????) in a binding(squealing, grinding) situation.
Remove the inspection plate between the engine and trans and check for rust or metal shavings. Usually it will change pitch when shifting between D or R if it's cracked.
Good luck, Chris

Try cleaning or replacing the idle air control valve.

http://www.explorerforum.com/forums/...&highlight=IAC

Try cleaning or replacing the idle air control valve.

That's the kind of tip I was hoping for. Sadly, it is not the noise source.

Good news/bad news: Using the mechanic's stethoscope, I finally found the location of the noise. It is a cruel place. It's coming from a tight area deep in the narrow space between the manifold/block and the firewall. I get very good audio pickup when I touch the area that is just behind either valve cover. My factory manual shows the oil pump and rear camshaft bearing in that general area. Not sure, but perhaps the timing chain is back there too?

This is starting too look like a ugly repair. I sure wish I knew the exact item that is squealing so that I can determine how urgent the problem is.

Try searching that Explorer forum, they seem to have lots of problems squealing like yours, I have seen a few posts that describe their squeal exactly like yours.

Originally Posted by Mr.RC-CAM

Using the mechanic's stethoscope, I finally found the location of the noise. It is a cruel place. It's coming from a tight area deep in the narrow space between the manifold/block and the firewall. I get very good audio pickup when I touch the area that is just behind either valve cover. My factory manual shows the oil pump and rear camshaft bearing in that general area. Not sure, but perhaps the timing chain is back there too?

A high pitched squeal from there would cause me to suspect the converter cover. Like an edge bent up or something. Even a small piece of gravel rubbing the torque converter could do it. The area your describing is just above the converter(bell housing).

The noise does not come from the bell housing area (I carefully probed that area). It seems to be strongest at bit higher up, mostly at the manifold/block juncture. I believe the CID sensor (includes oil pump drive) is nearby, but the area is too tight to see/probe it.

I have a feeling that unless this is a common problem on this model, the fix will involve a blind tear down. I'm getting a very bad feeling about this one.

Try searching that Explorer forum

Other than their simple google search link, I can't find a useful searching function on that site. Do I have to register in order to search there?

Getting closer: I found that the noise source is coming from the CID sensor. This part is located in an area that cannot be seen. It is at the rear of the block under the intake manifold. I had to feel for it with my fingers to navigate the stethoscope on it.

I called the local ford dealer and they mentioned that the drive shaft to the CID sensor is prone to failure, which they claim often harms the sensor. Parts for both is over $300. If they install it, add another $300-400 for labor.

Here is a picture the sensor (see page 6, round black part under "RTV"): http://www.ford-trucks.com/lc/lc.php...eplacement.pdf

Replacing it looks interesting. Has anyone here done this on the 4.0L engine? Just looking for tips in case I decide to do it myself.

Yes you have to log in to use the search, it works just like the one here and they have lots of usefull info on there.
According to the posts there is the CID sensor is bad you should get a CEL with code 214?

Yes you have to log in to use the search, it works just like the one here and they have lots of useful info on there.

Ok, I'll sign up.

EDIT: Yup, search works only if registered. I found a few folks with my CID sensor assy noise problem. No luck in getting tips on how to replace it.

According to the posts there is the CID sensor is bad you should get a CEL with code 214?

At this point I envision that it's just the bushing on the synchro drive assy (connects to the CID (Camshaft ID) sensor at the top, and runs the oil pump at the bottom). For sure, the electrical sensor itself is still working (runs fine). But, there is an angry pig in there that is being stuck with a sharp stick and is really pizzed off!

After doing some searching, I think the dealer guessed wrong on their over-the-phone repair estimate. Aftermarket pricing for the assy is ~$350 and dealer cost is ~$550. I think they were thinking of the 3.0L engine, which would be a breeze to work on. On the 4.0L, the part is in a nasty place. I probably won't tackle this myself unless I can find someone that has done it and can offer some advice on doing a DiY repair. The factory manual has some details, but real world experience would be nice.

Im not sure why they would think it was a 3.0 as there isnt a 3.0 in any explorers? Anywhere would be cheaper than the dealer though

Good luck.