Long time reader and finally decied to create a account and ask a question because I am stumped and can't find this gremlin. This is probably going to be a long one and I might have two problems or they go together and not sure which yet.

A little back story Dad gave me his old 94 F-150 that he has been driving since it was brand new. Heck I remember being at the dealer with him the day he bought it when I was in 4th grade. Anyway he decied he wanted a new truck and wanted to know if I wanted his old truck first before he traded it off and I said does a bear **** in the woods?? lol So I have only offically owned the truck for maybe 6 months and to make a long story short he hasn't really manentianced the truck too well the past 10 years and I have been going though fixing things here and there on the weekends since its I consider it a play toy and not my main truck.

Ok now my problems. The motor in the truck is a 4.9L fuel injected with a 5 speed manual and there is a "whistle" sound coming from the back of the motor somewhere that I can not find for the life of me. It almost sounds like a turbo but I know there is no turbo on it. lol When you start up the truck you can't hear it and sitting just idling you still can't hear it. The only time you can hear it is while you are driving as the rpm start max out right before you need shift then it will go away when you shift. So for example the truck is ready to shift around the 10mph, 20mph and 30mph and around the 7ish, 17ish, 27ish mph you can start to hear the whistle and then you shift whistle dies down when the rpms drop. The 2nd way you can hear it is when you shut off the truck. Had my wife turn off the truck while I was standing in front of it and figured out it's coming from the back of the monitor somewhere.

Things I done are new plugins, wires, cap and rotor. Fixed a few vacuum lines and installed a new "coffee can". It was rusted out like crazy on the bottom and had a bunch of wholes in it. Figured that would have been the whistle but it was not. Changed the oil and oil filter, tranmission fluid, and put a new M5OD bushing in. I looked at the PCV valve it seem fine not sure if there is a offical way to test it and haven't replaced it yet.

I asked dad how long has that whistle sound has been going on and he just said "oh years. I figured it was a vaccum leak and didn't mess with it." Now to my 2nd problem when the EGR vaccum line is hooked up the truck runs like crap and bucks and surges and sometimes acts like it wants to die at low rpm as you are driving. So for right now I just have the EGR vaccumm unhooked and I made a EGR plate but I havn't installed it yet because I want to make sure that whistle sound is not a vaccum leak and making the EGR not want to open up.

So does any of you 4.9L owners heard of his problem or seen it and can tell me where to look next cause right now I am stumped. lol

 

Hello Zalinth, and welcome to the forums.

That's an fun time keeping something like that in the family. Every little thing you fix will help keep it around for a long time. (However, seeing I drive an '81, I always get a laugh when someone calls a mid-90's truck "old" )

My first thought on the whistling was a bad throwout bearing on the transmission. Mine made some funny noises for a long time. One quick test on that is when it makes the whistle, put the clutch in and see if it goes away.

Otherwise, it might be something like a pinhole in the EGR pipe or exhaust that a small amount of air is coming out of?

With the EGR, it simply sounds like the valve is bad. They're supposed to be closed at idle, but if they "die", they'll stay open when they're not supposed to and make your engine run rough. A new EGR valve should simply fix the issue.

Have fun!

 

Welcome to the forum, zalinth! You said you have "fixed a few vacuum lines". Keep looking for a vacuum leak as leaks of this nature can make a whistling or hissing sound. Do as AbandonedBronco recommended regarding seeing if the whistling sound goes away when pressure is placed on the clutch pedal.

The "unhooked" EGR vacuum line... is it capped off?

 

Thanks for the replies and you had me laugh on that one. Yeah you are right mid-90s is not that old yet. Dad and I just got in a bad habit of calling it old red.

I will take it for a drive later tonight when it cools off and let you know if it whistles when I push the clutch in. That's another issue saving for later day when it gets hot outside it starts kind of rough and whole truck shacks pretty good, but when it cool outside no issue.

Yes it is I put some electoral tape around the hole of the rubber vacuum attachment but did not put any tape around the EGR valve itself. The only reason I have the EGR valve unhooked is so I can drive it smoothly. If fact that's one of the vacuum tubes I fixed. I lightly bumped into the green tube and shaped it clean in two when I was changing the spark plugs. I remember thing wow that was freaking brittle. The 2nd vacuum line I found that was broke in two was the white tube that I think opened up the heater flap to let hot air into the cab of the truck.

 

The electric tape may not be completely sealing the vacuum tube. You can use a golf tee or appropriately sized screw to plug the end of the vacuum hose. It is a good practice to replace all of the "now old and brittle" plastic vacuum lines with the appropriate sized rubber tubing. Not only can the plastic tubes break in half, but they can split lengthwise which is hard to see.

 

Ok so I was a bit wrong on the whistle during driving. I thought it started whistling right before you needed to shift. I was wrong on that part it starts to whistle after you shift and lift off the clutch. I did push in the clutch again for giggles when I heard it and it did stop.

Maybe I will just do that this weekend and go vacuum line by vacuum line and replace them with rubber hoses. I found last night the hose connected to the throttle body and carbon can on the frame is all shot to **** and cracked. I wounder if that is sucking in air making that whistle sound also.

Might have to order hoses online when I figure out the OD and ID. Don't remember seeing much of a rubber hose section at advance auto parts here in Kansas.

 

"Might have to order hoses online when I figure out the OD and ID. Don't remember seeing much of a rubber hose section at advance auto parts here in Kansas."

Most auto parts houses keep the vacuum hose behind the counter on reels, so it can be sold by the foot. The rubber hose you get will be larger in diameter than the plastic line. Go to the end of one of the plastic lines and you will see a rubber fitting/adapter. You need to match the replacement line to fit where the larger end of the rubber fitting/adapter attaches.

 

Ok good I was hoping that would be the case. I didn't ask when I was there last getting a vacuum hose for the EGR when I broke it by mistake. Found a tiny maybe foot of plastic vacuum hose in one of the rows at the store and basically took that hose and fit it over the broken hose on the side of the block and connected it back up to the EGR. Wasn't proud of that of it but it seems to work for right now and then just ended up taping off the vacuum line because reading on this forum figured out it the reason it was running like crap is because of the EGR valve.

Dad been driving it like that for years and thought the fuel pumps where getting weak and said when I was your age I rebuilt that 289 in the 67 fastback mustang sitting in your moms garage when we where still married and when you where in diapers still, but I'm getting too old for this **** and usually hurt for a week when I start crawling around engine bays. Glad you are figuring it out and bring old red back to life. LOL