Loud when cold

[jacksheadache]

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[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]

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[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]

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[jacksheadache]

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