I bought this truck 2002 ford f-150 4wd supercab 5.4 a couple weeks ago. I brought it to a local repair shop and told them to do a full inspection and diagnostic. They cleaned fuel injectors, replaced the fuel filter, replaced spark plugs and boots, transmission service. Still I noticed that the engine is making a sound that I don't think is normal. it does it when it is in drive or reverse mostly. I cannot hear it when the truck is in park and it is idling or if i press accelerator pedal down. But it sounds like a hiss-hiss-hiss-hiss sort of chugging type sound but more high pitched like it is either not hitting on all cylinders or there is an exhaust leak or ? At any rate it is not smooth sounding like it should be. Does anyone recognize this sound and or know what it is? I posted video to YouTube


it's almost like a light helicopter sound

 

Here is the link:

 

hmmmm im guessing you arent getting any codes either? with it in your garage can you isolate what side of the engine is making the noise?

 

I can't really tell what side the noise is coming from but if it helps it kind of has the pattern of a sprinkler chick chick chick chick chick chick chick chick chick

 

That sounds like an exhaust leak to me but i would also be checking all of my plugs to be sure they were torqued down correctly. Take some soapy water while your engine is cold and pour it over your exhaust manifolds directly after you crank your truck. If the leak is there it will blow bubbles.

 

Yea, manifold leak maybe. A shop vac will reveal every leak in the exhaust and manifolds. Since your testing manifolds, a shop vac is the tool to use. That way you don't have the clutch fan spinning and engine running while checking for leaks. Check all that jprevat has suggested but use a shop vac for leaks, you'll see everything lol.

 

I hear a exhaust leak. When I got my truck there was cracks on the exhaust around the the first bank or the second Bank of catalytic converters and where the two exhaust pipes couple into one. I heard a knock too. Like a carbon build up on a piston. I might just be projecting but i hear a slight knocking sound that I've heard in my truck before it use to drive me crazy and no one wanted to try to figure out. Then one day when i was doing the spark plugs i fished my inspection camera into the cylinder and found two of the pistons had huge amounts of carbon build up.

 

OK guys I think you are onto something, it sounds like it's coming from under the truck not the engine, which makes me think that it is an exhaust leak also. How can I pinpoint where the exhaust leak is?

 

Yours is loud enough you should just be able to hop under there and look at it and just look for cracks mark them with a chalk or a grease pen and take the truck down to the mulffer shop to get welded up. Its like 20 to 30 bucks a weld.

 

jprevat and I just told you. Soapy water and a shop vac, it works every time and work well. You just connect your shop vac up in blower mode, shove the hose into your tail pipe turn it on. Most shop vac hoses are sized perfectly to fit your tail-pipe. If you only own a little shop vac, or vac with a hose, home depot sells an adapter for 5 bucks that fits your tailpipe. This will pinpoint all exhaust leaks in seconds.