Knocking Sound Coming from 5.4L
 

Hi guys a friend of mines has a Expy with a 5.4L and it has a knocking sound coming from the engine. The sound seems to be louder towards the bottom of the motor, and im trying to help her decide if she should sell the thing immediately, or if its something that may not be too expensive. The knock doesnt seem to have any effect on the power or performance of the truck, but its kind of annoying and takes away from the overall beauty of the beast! Where should I start? Is this common on these engines? Any and all help will be appreciated!

How is the oil level? Does the CEL come on? Is the knocking just occur when you first start the engine? Does the knocking increase when the rpm's increase? Can you pin point the location of the knocking? What type of oil filter are you using? Is it a knocking or a ticking?

Please provide as much information as you can. Oh, by the way, welcome to the fourm.

Thanks for the welcome. She just got the truck two weeks ago. This past weekend I changed the oil to Mobil 1 5w-30 full synthetic with a Mobil 1 oil filter. The oil level and pressure is fine, check engine lights is not lit, and the knocking happens at startup and doesnt go away. The knocking also gets faster with increased acceleration. And the sound is definetely a knock not a tick. Thanks for the help.

This vehicle has only been owned for 2 weeks and now it has a knock? That's pretty suspicous. What it thoroughly checked out before it was purchased? Did you pop the hood and listen to the motor BEFORE you put your money down? Was it bought AS IS? The knock is due to a spun bearing on crank or rod because it was run low on oil. Very bad news. This means a teardown. You won't know whether it's a rod or main until you pull the pan. You must examine the journal where the spun bearing is located for damage. If you have scoring or gauling the crank has to come out to be turned. You can tell a spun bearing because the locator tab will be snapped off. You should plasti-gage all the mains and install new shells. You have to do the big ends too. Good luck! You should do what the previous owner did to you and look for a buyer that doesn't pop the hood before buying a vehicle.

Considering that they're the type of people discussing passing the truck off on some other unsuspecting soul, I'd call it poetic justice. I see someone with a future as a used car salesman.

Is there any warranty on the vehicle?

Lol no I wasnt present when she brought the truck, I do know how to shop for a vechicle and besides internal engine work im pretty knowledgable about automobiles. The truck wasnt knocking when she brought it, or she would have never told me about it she would have just thought that was the way the truck was supposed to sound. The truck was brought from a private owner so theres no warranty. I think I'll take it to my mechanic on her next day off and see what they say. Thanks

Don't you find it curious that only after 2 weeks the truck develops an engine knock which wasn't there when it was purchased a few days ago. That's a red flag for sure. It's too late now. You can either run it until it fails or bite the bullet and pull the pan. This is a major tear down.

You sure it wasn't knocking when she was looking at it? Maybe she didn't notice it until she bought it a drove it more. Man, if not what a heck of a thing to happen after only two weeks. Spun bearings don't typically happen overnight. It definitely sounds like that and like others said, engine rebuild time.

Well good news I was able to squeeze it in at the Ford Stealership today, and come to find out its just a exhaust leak coming from both manifolds. I went and picked up both manifolds and gaskets from NAPA today and I will replace them both tommorrow morning.

I thought a bad gasket or crack on the exhaust manifold would cause more of a "ticking" than a "knocking".

Yeah me too but they had the truck for about 5-6hrs and they ran a compression test, pulled the pan, and did a couple other things and found nothing wrong with the motor itself. I have had exhaust leaks on a couple of my old schools (85 monte, 77 cutlass) and they sounded terrible but this sound was a little different. I will post again tomorrow and let you guys know how it sounds after I replace the mani's.

Wow, heck of a knocking sound from an exhaust. Glad to hear it wasn't anything major.

While your at it, you should replace the studs with stainless steel. Coat them with anti-seize compound. Also, when installing the gaskets, use a dab of rtv or other adhesive to hold them in place while you fit the manifold on. Spray down the EGR tube and all the studs the night before with WD-40 or some other penetrating oil of choice.