I have a 99 F150 5.4 4x4 with 173K.

I just bought the truck on Monday, and well I thrashed the hell out of it during my test drive, nothing out of the ordinary. No oil leak, shifts fine, drove fine, abs light on but other than needing a good cleaning it seemed fine; certainly no engine noise no loud knocks or anything out of the ordinary.

Drove the truck about 500 miles and then there was a severe knock that started on the way home on the highway, I don't know how it could have just showed up but as I said I flippin thrashed the mo fo during the test drive in attempt to find any problems such as this.

I understand without hearing the knock it is hard to identify, but it is audible at idle, gets louder around 1800 - 2600 rpm and becomes inaudible above 3000 rpm. The engine idles smoothly and still seems to have the same power. There is no smoke from the exhaust, but there appears to be a bit of metal in the oil, but I was inspecting at night and I could not do anything this morning.

I am assuming catastrophic failure is eminent and I am going to have to replace the engine, I am going to take it to a mechanic because this is a bit out of my shade tree mechanic realm.

I bought this assuming that this is a pretty reliable engine...well I have had this engine before and lots of miles without a problem. I know these engines can pile on the miles and usually the overhead cam becomes an issue but not a connecting rod, but I swear the noise sounds like a connecting rod.

Any insight or ideas would be greatly appreciated.

Today sucks but at least it is not my only vehicle, but it is the one I need in the winter.

 

I bought my 97 5.4L with a slight knock similiar to yours after over 10,000 miles truck still runs and sounds like it did when i bought it. I have 18x,000 on my truck. My knock is noticable on cold starts and is still audible when driving in lower rpms until the truck warms up. I cant hear it at hwy speeds or when going wide open throttle.
From what iv read it could be.

Wrist pin
Catalytic converters
piston slap
possibly other??

Your best bet would be to get a mechanics stethoscope. Listen to the heads, valve covers, sides of the block, and oil pan. Try to pin point where the noise is coming from.

Despite some controversy. I run synthetic 10w40 oil with some lucas oil stabilizer makes the knock less noticeable.

Also make sure the correct oil filter is installed. I always run motocraft oil filters because they have an anti drain valve (or something like that) using the incorrect oil filter can cause issues such as a knock.

 

Are you sure its not just an exhaust leak? A slight ticking sound at a "beat frequency" under load or throttle is an exhaust leak, which can come and go as the truck goes through thermal cycles and load levels.

I've seen reports indicating 97-03 5.4L can have exhaust leaks between the manifold and block due to failed studs. Check around the manifolds for carbon marks on the block and manifold.

Check for rod knock by cutting spark to one cylinder at a time and see if it stops.

How loud is the noise? My mustang had a rod knock once, it was real loud at idle and got faster and louder with increasing RPM. Sounded like a midget with a ball peen hammer in the motor. Never, ever went away once it started.

My truck has a exhaust leak, comes and goes as a gentle tick at a "beat frequency."

It its coming and going, I think it is an exhaust leak.

 

Sound is much more like a rod knock, not much like an exhaust leak...definitely sounds like a midget tapping with a hammer ...I will try cutting the spark like you suggested.

 

I think I will get to leave out a bit early, up to this point all of my detective work has been in the dark. Daylight might help me a bit.

 

This is a vid from a year ago or so of my engine before i switched to synthetic 10w40.

When i took this video, i could hear the knock better while in the truck, but the camera and video seemed to pick up the knock when i went under the hood.

 

Well it is headed off to the mechanic today...at this point I am thinking rod bearing...but we will see soon enough...I will post up the results.

 

Good day!!

I picked up my 5.4L 4x4 with just about 120K on the ticker... I came back from overseas and found the oil was a little low... I did this the hard way tho... Needless to say, the needle dropping to zero was not the sensor failing... It took less than a second for my number 8 rod bearing to seize to the crank... I dropped the axle, pulled the pan and replaced the number 8 rod bearing... Ran cheap oil thru it with a new filter for 30 minutes... Pulled the pan and replaced the number 8 rod bearing again, but this time I put 10w40 Mobil 1 in it and a new filter... All good again... Now has 167K on the ticker, and not one tick from the motor... Your mechanic should be able to replace the bearings with the motor in the truck... If he can't, bring it to Augusta and I will do it... If that fixes your tick, your good again!! If not, time to pull the front timing chain cover and check the chain guides... OR you could just find out where it's coming from and go from there...

Oh, I also had the exhaust stud failure issue... I used pass side exhaust bolts from a 94/95 Mark VIII... For some reason, the assembly line wanted bolts on the pass side, and studs on the driver side... The bolt don't fail like the studs do...

Good luck!!

Cheers!!

 

Good advice, right here.

Here is a little video, to help you understand.

If the noise goes away, as shown, it is a wrist pin and not a rod knock.

The engine will live, for awhile, with a wrist pin knock, but not too long, with a rod knock.

 

Well the mechanic said that it needs a new motor.

I don't have much into it. I am looking into other options, right now looking like either Ford reman engine with 3yr warranty Unlimited mileage or a Jasper reman with 3yr 100K warranty..either is fine I won't be driving the truck that much. The mechanic shop that I took it to is supposed to be the best shop in town, I have had them work on other vehicles of mine and several of my racing buddies recommend them also...one of which owns all the NAPA stores in the area.

I know that the rod bearing could be replaced but is it worth it to just replace the rod bearing in a 173K engine....I don't know what to do because this is all beyond my abilities at this point. Sure I can change out the alternator on my wife's Jeep...it was nice enough to die on me today, but rebuilding parts of the engine are things that I have not done. So at this point I don't know what exactly to do, I have to rely on the mechanic's opinion....I have second opinion set up so I guess we will see.

$3500 for engine and $2000 for labor.....damn ***** sucks!!!!! There goes money for lift, wheels and tires!