HELP! Knock in 4.6L F150
 

So I am new to the forum so forgive me in advance if I violate any decorum but I need help...

I recently bought a 1 owner 97 F150. 4.6, 2WD 5 speed showing 141k. I have a noise coming from (the best I can figure) the front or bottom of the motor. It drives fine (although idles loud) and seems to slightly change pitch with increased engine speed (2000- 2500 RPMs. i dont think the noise itself gets louder at speed but it drowned out when motor is reved. Previous owner states noise has been there for a year (but who nows how that goes). To me it sounds like an accessory pulley bearing- which it what I thought it was and chose to buy it. However, I took off the serpentine belt and noise is still there. I also went and took off the harmonic balancer and noise is again still there. I havent pulled the oil pan but I did change the oil with 10-30 and a qt of Lucas and STP filter. The oil was dark coffee colored but I didnt see any debris.

-on a side note- the bolt for the HB seemed out of balance so I took it in and they put the big impact on it and it ended up snapping the bolt off in the crank... so now that has to be drilled and tapped so a new one can be installed.

So with all that said, what do I do to figure out this noise? One mechanic told me timing chain guides and the other told me new motor. Hopefully yall can help.

Also, Ive never owned this motor before- it has engine code 6- so any advice on PM or trouble spots to look for would be greatly appreciated.

Didn't you see on the oil filler cap your engine needs 5-30? Sound like an exhaust leak to me. Run the engine in the dark and look for an exhaust leak. Lucas is garbage in overhead cam engine. Use the right oil. Change it often. Dont put stuff in it. Clean 5-20 or 5-30.. I've heard many exhaust leaks that sounded like a rod knock.

How often is often? Ive been a pretty loyal user of Lucas for years now but I am open minded. Why is Lucas not good for overhead cam engines? I never thought of an exhaust leak- what is the best way to look for that? Any other words of wisdom?

Modern, good quality oil has all the additives in it that you need. Adding stuff is too much of a good thing. The advice above is excellent.

I would change it somewhere between 3500 and 5000.

Sent from my iPhone using IB AutoGroup

Lucas is a viscosity index improver, which in plain English, makes the oil thicker. You compounded it by using a 10w instead of a 5w oil, which is what Ford recommends for good reason. The clearances in a Triton are tight, and thick oil will cause dry starts.

STP filters are also questionable - you should be using Motorcraft filters, they don't cost any more and you can even get them at Walmart.

Look at the engine in the dark. You'll see flashing around the leak if the leak is near the manifold.

Heres one I bet nobody has heard!!

So as stated earlier the HB bolt had been crossthreaded or otherwise improperly installed and snapped off in the crank. Once the bolt was drilled and tapped and a new one from Ford installed NO MORE NOISE! I dont know why- maybe a piece was loose in there somehow? What I do know is that repair bill with a comma in is now gone!

Thank you for this. The oil filler cap is generic and doesnt have a recommended weight on it so I went with 10-30. Ill be changing oil and filter next week to get proper stuff in there. Thank you all for your help! This truck isnt really a project truck, but I do hope to improve my shadetree mechanic skills with her as she needs a little help getting her where I nee her to be.

its a 16 year old truck. Your ether going to have to work on it or pay someone..

Hb
 

QUOTE
Hello, I am experiencing similar noise. What is the hb and hb bolts you are referring to? Sorry if I sound like a noob.

HB stands for Harmonic Balancer. That is the big pulley at the bottom of the engine.