Greetings,

I recently purchased a 96 4WD Aerostar off of eBay, from the USPS. It runs good, has no codes stored, gas mileage is what I expected, However, it makes and intermittant howling noise. Not usually around town, but almost always after a ride on the interstate. It seems to be coming from the air intake snorkle. My brother, a goodyear tech, listened to it last Sunday, but he has no idea the cause. This week he called a Ford tech he knows, who suggested it might be the "hooter hose" or the Idle Air Control. I've never heard of a "hooter hose" and can't find it on google. Can anyone tell me what's going on and steps to diagnose and correct this problem?

 

I have never heard of that before either? You might want to ask your brother what he means by "Hooter Hose".

I doubt that it is in the IAC (Idle Air Control Valve) otherwise you would be having problems manifesting in poor idling and accelerating from a stop. I am not sure, but someone might have removed the silencer causing the intake to be louder, or you have a slight vacuum leak.

 

It sounds like you clutch fan and it is operating as it should. It is RPM controled and thermistatically controlled. The clutch fan locks up when the under hood temperature gets to a certain degree. It will unlock at higher (Interstate) speeds or when the teperture is lower than the preset degree is. In your case you are cusing down the free way with all that nice air flow coming through the radiator and and pushing the air past the engine and out under the van. When you stop all of a sudden there is not all of that air flow the under hood temp rises as well as your water temp and the thermistat locks up the clutch so the fan can pull more air through the radiator past the engine and out under neeth the van so you do not over heat. Its a good thing.

 

Though heat has something to do with the problem, I'm pretty sure this howl is air intake related. Once it begins to howl it usually doesn't stop, even if the driving conditions are varied. I've opened the air filter box and the howling is much louder, coming from the intake snorkle. It only happens at idle, the noise goes away with the slightest touch of the accelerator, even turning on the a/c diminishes the howl.

The silencer might be a lead. When I picked up the vehicle last month, I was able to peruse the maintenance record, though it is gov't property, so I couldn't have it. (I guess I could have stuffed it in my pants) The record was unremarkable, except for the head gasket job in the past year. Could the silencer have been left off at that point? How would I know? How accessable is the silencer.

 

if it sound like a vacuum cleaner then do this.

remove IAC and clean it thoroughly and recheck it. if it solved then you got 2 choice...let it go or replace it.

 

Dracoscott,

My '97 A* makes the "hoot" sound, my '93 did not. I was told by my local Ford tech that it was the "MAF sensor", the mass air flow sensor. The MAF sensor is located between the air cleaner housing and the air intake intake duct. I was also told the sound didn't indicate failure and that it was expensive to replace... so I didn't. That was 100K miles ago. It hoots during the summer months, particularly at idle, but doesn't hoot during the winter. I live with it, 'sup to you what you do.

DadVan

 

This is the exact reason I came to this board, to see if anyone solved the howl problem. I have a 96 4l bought used with 30k miles. Now has 105k miles. Started howling at 40k miles. Only does it during the summer months and only at idle. Took it to the shop, said it was MAF and $500 would solve the problem! Didn't take them up on that. I removed the air intake filter hose, effectively bypassing the MAF. (Only briefly though!) Still made the noise. Took a stethoscope and it seemed to be most pronounced at the EGR valve. My guess is that the EGR is opening up and creating gas recirc flow noise that is causing this howl. Maybe the pipe that leads to the exhaust manifold is partly plugged helping cause the noise. If there is a way to temp disable the EGR, so that it stays closed, and the noise goes away, then maybe that is one way to diagnose the problem. I have also replaced the IAC due to a code I had. It did not affect the howling. I have the maint record on my van and they did change the EGR early on. Don't know why though. I do not have the problem during winter. I guess the EGR does not have to recycle exhaust gas until the ambient temp is hot. I had it in my mind to pull the EGR and clean it and the pipe. Never got to it!

 

These posts have given me some clues to check out. I'm going to meet my brother this weekend to go camping. He says that cleaning the IAC is easy so we'll try that first and see if it solves the problem. If not, we'll look at EGR and MAF, although I don't see anything in the MAF that would make any noise. Anyway, I'll keep you posted.

 

Another thread started by wxboy (dated 6/29/03) in Ranger B series forum discusses the same loud howling noise. Thread is titled Idle Air Control Valve. Several responses noted that they either cleaned or replaced the IAC valve and the problem disappeared. They had a photo of the valve and after seeing it, I believe that what I had the stethoscope on (see earlier post) was actually the IAC. I am going to pull mine and clean it tomorrow. But one note--several folks said they tried cleaning and it didn't work. They replaced it and the howl went away. Also said that aftermarket will have much,much,much better prices than the dealer. Good luck and let me know how you do. I'll do the same.

Sound familiar........
...."Ok guys...lately as you know my truck has been making a LOUD humming noise at idle when the engine is warm. Over at The Ranger Station, some other guys say their 4.0L does the same thing. It is VERY loud, and today when it happened I popped the hood, took the air box apart, and the noise got even louder. So it has something to do with the air flow into the engine.
It was suggested to me to try a new IAC. That is the Idle Air Control valve, right? Because I checked four different auto parts stores, and none of them have an IAC listed for my truck. Only Autozone has something they call an "Idle Air Bypass" for my truck, and it's $132.00!! Can somebody help me? All I have is the Haynes manual, and it's worthless of course."

 

Pulled the IAC. It wasn't as dirty as I was hoping but it did have some carbon/crud/gunk in it. Cleaned it with carb cleaner, then wd 40, then rubbing alcohol. Then repeated the same process about 5 times. Then blew it out with compressed air. I also popped the plastic breather cap off the top and cleaned it and the port hole thouroughly. It (the port hole---must be some kind of equalizing port, or something) is so small it could get plugged really easily. I finally think I got it clean. I also energized it with 12v. The solenoid is very weak. Does not move the valve seat almost at all. Maybe it is just designed to keep constant pull in one direction while vacuum in the intake pulls in the other direction. I don't know, but I took it for a spin and NO HOWLING. I popped the hood and you could hear a similar sound but extremely reduced compared to HOWLING. Wouldn't really recognize it if you never heard the real problem. I'll feel better if I am "howl free" after 1 or 2 more weeks. My thought as I was energizing and watching the solenoid is either I have a weak solenoid, or it needs to be very, very clean to operate properly. Pulling the IAC is 10 minutes. Cleaning it is as long as it takes. If the howl returns soon I am going to replace it with new. Called a few places---OEM dealer is $125, aftermarket varied from $40 to $70 to $230. Looked it up online AdvancedAutoParts and it was about $70. So shop and good luck!!!!

 

Problem Solved! This turned out to be an easy job. After cleaning the IAC valve, the howling continued, all the way to the Autozone store, where I picked up a replacment for $50.00. Put 300+ Howl free miles on the car over the weekend. Thanks for all the help!

 

Still howl free after 3 days and counting. I didn't replace, just cleaned the daylights out of the old. Congrats to the both of us. I've been after this problem for 60,000 miles!!!!!!

 

Ahhhhhhhhh!!! So the fix is a new IAC? Thanks a lot folks!!!

 

DOHC.....,
You can clean it also. That is what I did. But it has to be very well cleaned to stop that obnoxious hum. New IAC approx $60. Mine is still hum free one yer after cleaning it........really cleaning it!

 

Cool, I'll try that first. Thanks!