I have a 99 F150 with a 5.4L engine in it. Here’s my problem; I have a knock that seems to come and go. If the engine is cold it almost always knocks, however letting it idle a few minutes the knock will go away, most of the time. Some times though it will continue to knock as long as you drive it. When it first started I suspected a lifter but as time has gone by it has gotten deeper and sounds as if it is coming from the lower back part of the engine or possibly the bell housing. I have used an automotive stethoscope and can not pin point the noise. Oil pressure is unaffected by temperature or length of time running and remains normal at all times regardless of RPM. I also haven’t noticed any loss of power.

The engine has an oil leak on the passenger side due to a leaking head gasket and the truck has been run low enough on oil, at least twice (that I know of), to lose oil pressure. Onetime it was ran long enough that I had to replace the timing chains and bottom gear. The cams show obvious signs of oil starvation.

For what it’s worth, never loan your truck out… you guessed it, both times the truck had been loaned out. Not a good idea!

Any ideas?

Thanks!

 

I would hook up a real oil pressure gauge and see what actual pressure that you have. The factory gauge is a dummy gauge and will read around 1/2 or so as long as you have enough pressure to keep the light out. (about 7psi)
Sounds like it could be a cam follower or a connecting rod.

 

I had actually picked up a mechanical gauge and wound up putting it in a 94 F150 that I have, but I know I need to do that to get a more accurate reading.

The cam follower is a good possibility as is the rod. Since it was oil starved it could also be a main, I just hate saying it!

I guess I just need to pull the engine and check it out. It’s really a shame that Ford didn’t issue a recall on the head gaskets. There is little doubt in my mind that if it hadn’t been leaking oil and therefore ran out that the engine would still be in good condition.

Thanks for your reply!

 

I have had the symptoms you describe in my '98 Expedition 4.6 4X4. The truck ran great. oil pressure looked fine, just an occaisional knocking sound, much like a weak lifter. I got to checking with a stethescope and the noise was loudest at the rear of the engine pan area. Pulled the pan and found #8 rod had spun the bearing and ate the crank about .060 deep (junk), I was hoping to replace the rod bearings and get it up and running quickly (not). I had an engine from a '98 Mark VIII qwith less than 1,000 miles on it sitting in my garage and am currently in the process of changing it over to a 4.6 DOHC. It might be done someday.

 

Thanks for the reply Moto Mel!

I have heard several stories about spun rod bearings just like yours. Since the noise is so low and to the rear I really believe that’s what it is, even though I can’t seem to wrap my mind around the fact that I have had no loss in power, a hole in the side of the block, no apparent (sill haven’t checked it with a mech gauge) loss of oil pressure and the fact that the knocking does stop. Oh well, a tear down will tell all.

A 4.6l DOHC… that’ll wake the expedition up! Those are some pretty awesome engines… my dad had one in a Mark VIII, it was a fun car to drive. Turn the traction control off and go Camaro hunting… lol!

 

There is enough room to remove the oil pan without pulling the engine. It will be tight in a 4X4 and a little more work . If you drop the pan just go to the last 2 rods on the crank and push up and then pull down, if there is any movement, that is where the problem is. While down there you should check the rest of the rods the same way, especially if you don't locate the problem at the first rods you check.
Good luck with it and keep us posted.

 

I hadn't thought of dropping the pan, not a bad thought.

I guess my thinking was that since the head gasket has been keeping OPEC profitable for a while now , and I was going to pull the heads that I might as well pull the engine.

I might drop the pan though, you've got me rethinking this thing! Thanks again!

 

For what it’s worth, never loan your truck out… you guessed it, both times the truck had been loaned out. Not a good idea!

In motorcycling we have a saying;"It's better to loan out your wife or girl friend than your bike, at least you will know how she's been used". The same goes for your car or truck.

Let us know what you find in the pan.

 

Lol! I'm not sure the wife would go along with that!

I would have a hard time loaning my bike out. Of course not many people would want to borrow it for to long at the time anyway... the seat has the ability to do permenant damage.

What kind of bike do you have?

 

The seats on early Viragos and all Sportsters are horrible.

Right now I'm down to 2 1/2, an older Virago and 2 mid '90s Sportsters. Looking for another Goldwing. I've logged over a million miles on bikes during my lifetime and hope to make a few hundred thousand more before it's over.

 

The knock you hear at cold start sounds like piston slap. It would make sense especially since it goes away once the engine warms up, but that doesn't explain it coming back.

My truck had a similar noise as well when I purchased it and it turned out to be an exhaust manifold gasket. When the engine got to temp it would get quieter, and after a period of time it actually got worse. When I swapped it, it quieted right down.