Hey, My 1999 Ford F150 5.4 V8 has a low knocking noise. It starts when I start the truck, goes away when I start going a little but if I rev it the knocking gets worse. The oil pressure stays fine, so I thought it might be a crack in the flex plate. It could be a rod bearing as well, but I really don't know. I took it out on the freeway and it sounded like it was gonna explode when I got up to around 75 mph. Any suggestions, theories, or remedies to make my engine last a little longer would help.

 

Some of my mechanic friends told me to put some lucas oil addative in the engine, so I did, and it sounds worse honestly.

 

I would drain the oil out and check for metal filling and that type of material . i have had this noise before and it turned out to be the connecting rods bearing. it gets louder at higher speeds because oil clearance open up and the oil just fly through and doesn't stay long enough to lube it .

 

Take an oil sample and send it away to have it tested. I use Blackstone Labs. They will send u the sample kit for free. Fill out the info along with a check or credit card and u are good to go. They will let u know all about what is going on inside your engine.

 

Well i'm almost 99 percent sure it's the rod bearings, so now i'll see if I can fix those or get a whole other engine put it, which will cost a pretty penny if that's the case. What did you do Darin?

 

when i ran into my problem we lucked out and caught it in time that the crank journals never got scorded at all so just changed out the bearings and we were good to go but depends if your crank is damaged that could mean more money.

 

if you're crank is not damaged, spend the $203 on new rod cap bolts and new bearings. that should fix you're problum. look under https://www.f150forum.com/f11/early-...k-death-40031/ for step by step directions on how to perform this surgery. hope this helps

 

i pulled mine apart because it was knocking
turns out i had a bent rod
the rod was hitting the cylinder and the piston was hitting the crank

 

NVM re read your post

 

Well My buddy and I pulled the thing apart, and not only were my rod bearings hashed, but my crankshaft was pretty much done for. I was surprised that my truck was still running. So now comes the decision to rebuild the d*mn thing or buy a used engine.