Loud when cold

[jacksheadache]

The motor is pretty loud before it warms up. Is this normal?

It's almost like a really light ping or knocking sound. It does go away after the truck warms up.

It's a 98, with 70,xxx on the clock.


Thanks!

[Wicked_Sludge]

could this perhaps be described as a "ticking" sound? if so its probably the 4.0's infamous pushrod rattle (or lifter tick if you like).

it would help if you could pinpoint the noise. with the engine running (stay clear of fans, belts, pulleys, blah blah), use a long screw driver with the handle held to the ear...place the pointed end on valve covers, belt tensioner pulley, each injector, the engine block, the oil pan....ect.

[MAKG]

A regular tapping sound at crank RPM that goes away with warm-up suggests piston slap. Has the truck been overheated?

[jacksheadache]

I would say you can call it ticking..

No idea if the truck has overheated in the past.. it has 70,000 something on it and I just picked it up last week from a dealership so no info from previous owner.

If it is piston slap.. that would be irreversible damage right?

[MAKG]

It's reversible by replacing the pistons and probably boring the block.

Not impossible, but expensive.

It's important to determine whether the tap is at cam or crank speed. Compare it to a timing light. Note that 4.0Ls have waste spark ignition, so a timing light fires at crank speed, not cam speed like on engines with distributors. Valvetrain taps -- which are quite common and much more easily repairable -- operate at cam speed.

The usual reasons for valvetrain tap on 4.0Ls are spalled rocker arms. Those can be replaced with minimal tear-down. But spalling is the same at all engine temperatures.

[jacksheadache]

Well I bought the truck for a reliable daily driver.. so I hope nothing on the bottom half needs to be fixed or replaced.

How can I determine whether the tap is at cam or crank speed? I'm a little bit confused with using the timing light to do so..

thanks again

[jacksheadache]

http://www.therangerstation.com/tech_library/40Problems.htm

should I give all of this a try also?