When my truck is runing it has a very annoying high pitch squeal/whistle and it is not coming from the back tires.

 

So is it coming from the engine compartment? If so, I'd look at your belts first. One of them could be loose.

 

yes its comeing from the engine compartment. i tightened the belts and it is still there.

its a 1978 ford f150 351m

 

Might not be the same but when our 93 Plymouth Grand Voyager Van was doing the same thing, we kept going and on out way back from a long trip, our water pump to a big stinky crap on us. That could be it.

 

I think its just the nature of the beast. Mine does it too and I know everything is right, tight and adjusted properly. Seems to be most prevalent from 50 to 60 mph, guess theres too much wind/road noise to hear anything else!! I know another guy that has a 78 F150 with the stock intake (I have Edelbrock), and his does it too.

 

I tracked a squeal like that on my 81 F-150 with a 300-6 in it...replaced the water pump, altenator, power steering pump, all the belts, the fan, the rad, and the thermostat housing......turned out the thermostat housin was the culprit it had a light leak at running temps........it was spraying the coolant down onto the belts and making them squeal...lol hope you can find it

RYan

 

I had the same noise and it turned out to be the water pump.

 

mine did it right after i rebuilt the engine, turned out the carb gasket didn't seal right and the little leak made one annoing noise.

 

possible vacuum leak that only shows up at highway speed? Low-load condition, lots of air rushing by, that or a small leak at the base of the windshield, it wouldn't leak much water but sure will stir up a racket at speed...

 

I remember mine doing that years ago and it turned out that it was the carb to manifold gasket on it. You can take a little windex and spray around the base of the carb while it is running to see if it stops doing it, if so just replace the gasket and your done

 

You can open hood with truck running and whistle is still there, right?
Get a piece of 3/8" or so rubber tubing, or a wood dowel, or a mechanics stethescope.
Carefully place one end of your choice of the above next to your ear, move the engine end around to various locations in engine compartment until you can pinpoint noise.
The farther from the noise the more faint it will be through the 'tool'. when you find 'the' spot, you'll think it's inside your ear.

 

i've tried everything and its still there so im going to have to live with it till i get my new motor running thanx anyway

 

Hi, I have a squeal or whistle at hwy speed...seems to come from draft tube...which is the rudimentary PVC system comes from back of drivers side block....would it squeal....sounds can be hard to point out...thanks

 

Do you have AC? maybe the idler pulley

 

This might be out in left field but while the belts are turning take a bar of soap and put some on the inside of belts. I hate when you can't find anything like that. Good Luck.