Has anyone experienced this before? At 30mph and up I hear a shrill, hollow, high pitched sound almost like a jet engine when driving my 92' Ford Ranger XLT. It sounds like it's coming from underneath the truck but I can't tell from where. Is it possibly U-joints or something else. Thanks

 

If it happens when you have a high manifold pressure (lot of power) and it's a high pitch almost whistle sound it could be a leak somewhere in the intake plenum. Look for loose connections or a cracked hose, generally between the air filter and the engine.

 

I checked for vacuum leaks and didn't find any yet. Do you mean upper intake? Could the problem be anywhere along the intake system beginning with the intake hose leading to the air cleaner housing, or even where the exhaust manifold attaches to the engine?

You also used the word 'whistle.' Yes, you are correct. It almost sounds like a whistling sound too.

 

Have someone follow you and see if its not in the exhaust. Havent seen it in a while but pipes can collapse,or get crushed. Long shot but easy to check.

 

I was talking about the air intake path(not the vacuum system). All the hoses and plastic plenum pieces between the air filter and engine. Under high power the engine is sucking in pretty hard and will draw air in through any cracks or holes and can be surprisingly good at making a high pitch whistling sound.

Unfortunately you cannot generate high enough manifold pressure to cause the problem without a load on the engine so revving it while parked usually does not make it happen. Take the vehicle out and see if you can produce the sound by accelerating hard without downshifting or accelerating up a hill again without downshifting. You want a condition where the engine is lugging and breathing hard. If you can make the sound at will I'd start going through the intake path checking for loose clamps or cracked plenum housings. If you take it apart the leak location often has a stream of dust on the inside where it's been sucking air that has not passed through the filter.

 

I understand. I don't even have to try to replicate the sound. It happens when I drive 25 mph in the neighborhood.

I notice the intake hose for the air cleaner housing is very old and it doesn't look like it it solidy clamped on to the housing. Actually, I have been meaning to check or replace this hose for awhile. I know this is not really the area that you targeted. But could the problem originate here?

 

Dane, it almost sounds as if it is a turbo spooling up on a Cummins. All the other suggestions are great. I have one off the wall question. You don't by chance have an open rung type ladder in the bed, do you. The open rungs if positioned exactly at 90 degrees to the passing wind will make a whistling sound as you describe. Just an out of the box question.

 

It also sounds like a plugged catalytic convertor.

Does your vehicle operate normally at high speeds. Usually with a plugged cat the engine will eventually start to slow down on its own.

 

In the '70's, I would have bet on a disconnected air pump with a bad plug job, man some of those were hacked, but, being a '92, the first thing that I would look at is the loose ladder theory, including mud flaps and side mouldings, which have been known to whistle pretty good, and, if that didn't pan out, would definitely lean toward a bad cat. Based on what I have witnessed on newer vehicles, you're not going to have that kind of a vaccuum leak without some other significant drivability issues.

 

There is a bucket of things that could cause noises as the vehicle accelerates. First thing I would do is see if the cooling fan spins freely when the engine is off. I have seen many that freeze up so when the engine speed increases and the fan is designed to freewheel and doesn't it sounds like a tornado.......

 

I have an odd whistling noise coming from my Ford van one time. Within a week the alternator failed. After the repair, noise was gone.

 

That was likely a front bearing but who knows.

 

Let me respond to some of your input. It's true what Tijoe said. There could be several causes of this.

I recently had my front bearings repacked.

There was some noise from the alternator for a long time after I washed engine compartment. But noise almost completely gone.

I have dual catalytic converters. One had to be clamped years ago because one of the heat shield welds broke. As I recall, there was another similar sound from this. I have been told one of the cats is bad but truck always passes emissions

My fan rotates freely and the clutch has been engaging all summer in the brutal Arizona heat.

I don't have an open rung ladder in the bed. But I have heard of this whistling phenomena from ladders in the bed

I don't know where the air pump would be for my make/model.

Some interesting theories here. For those who have experienced this sound, isn't it irritating?

I don't have any performance issues.

I'll have to check all these possibilities and more. Then I'll respond to this thread next week

 

I looked all around in the engine compartment this weekend. And I checked under the truck also. I couldn't find anything definitive. Even though it is a jet like, whistling high pitched sound. It is also shrill, hollow, and metallic in origin too. I am leaning towards catalytic converter. But I just don't know.

 

Catalytic converters are known to have issues when the monolith breaks apart and pieces will actually turn sideways. That is uaually accompanied with a loss in performance as it restricts the free flow of exhaust gas. I believe you said you had issues with one cat. Perhaps that's the one.

 

Could be. It's such an old truck. I don't have any performance issues yet. I replaced 8 parts in two months. I think I broke my own personal record for vehicle repairs. Someday I'll donate the thing to the Museum of American History. They can put it next to Archie Bunker's chair

I have to get a couple more things repaired. At that time, I'll ask the mechanic to test drive it.