A buddy's got a 5.4 98 half-ton that's knocking some; I havent heard it. He said a mechanic told him that a rocker arm is loose.
Is this a tough/expensive fix? I've done this on a '53 Chevy 6 cylinder before.......but not a 98 5.4
It's got 145,000 on it and he claims that it runs perfect, just knocks a little. He took it on a 100 mile trip last weekend and did fine.

 

First thing is to isolate the knock.. you can use a mechanics stethascope (spelling), a heater hose or whatever is convenient..

That knock could also be piston slap or a floating cam shft or worse yet, a rod or spun crank bearing..

Anytime an engine is showing signs of knocking, it's not good.. Failure is usually immenant.

 

He claims the knock is very slight; he said he cannot hear it while sitting inside the truck. It has recently started in the last 2 weeks.
He claimed a mechanic located the tick and the mechanic's guess is its a loose rocker arm in the passenger side head. If it's not the rocker arm, what else could it be? There's only so much in the cyl head to go wrong and it doesnt seem that it would be a hard fix, (unless of course the head has to come off)

I've never worked on a 5.4 in a half ton.
How tough is it to get into the cylinder head? I know the 4.6 is a bit of a b!tch to get to.

 

Yea, you need to isolate that one first. - Definitely. I've never heard a 5four knock from the internals. I'd have to hear it of coarse, but if he's hearing it from inside the cab, I'd look at converters and PCV valve first.

PCV valve: - A restrictive valve (specially those "Fram" replacements), can mimic a Engine Knock. I've heard a 5 dollar PCV valve make them sound like there about ready to come undone. These engines need to breath, that's why the Motorcraft replacement valves have 4 times the Margins than any other I've seen. Also, that little 5 dollar plastic part can take an engine to a early, if neglected to much.


Converter Brick: - Yea , they can sound just like a Knock as well. That might be what's going on , - since there's Two converters in the proximity of where you sit in the cab. Ones at your feet and the others further back , about at the front /under the seat.
They can crack inside , - clean thru , then sort of section itself.
The Heat shields can make noise as well, - since their only spot welded and not very good.

Just some things to check out first.

 

Man, this guy sent me more pictures of this truck and it looks solid. A few dents, a crunch in the front bumper, and a missing turn signal. He said it rides down the highway just fine. He just spent $1,000 on routine maint on it.
He's asking $1,000 for it.

Also: he said he can't hear the tick from inside the truck, only when the hood is up. This would be a sweet deal if the motor is good and its a PCV valve...

Hmm...