98 4.0 ohv engine knock

[johnny dangerous]

Hi all. Today I bought a 98 Explorer (4.0 OHV 250,000 km/150,000 miles) for $550 with brand new tires and a decent body. My 99 Explorer (4.0 OHV, 350,000km/210,000 miles) has a power steering fluid leak from the rack and pinion and a number of other problems.

The engine in the '98 I bought has a loud tapping sound at all RPM's that increases and decreases in frequency with engine speed. Thoughts? Maybe a pushrod or lifter? I haven't got my manual around so I'm not sure about the engine, I never had it apart before.

My '99 has a pretty quiet engine. I'm considering a swap. Or could I just replace the head(s) if it was a valve problem?

Thanks for any replies.

 

[deweyville65]

You need to define "knock". An engine knock is usually used to describe a heavy sound, like a main bearing. If it is the valve train sound, usually defined as a clatter or rattle. The OHV in my 96 has a clatter, needs pushrods and rocker arms on the right bank. Left bank has been replaced. No need to replace heads if only valve train clatter.

 

[johnny dangerous]

Thanks for the feedback deweyville65, I would describe it as a heavy/loud tapping sound.

 

[deweyville65]

Thanks for the feedback deweyville65, I would describe it as a heavy/loud tapping sound.

Another help is the frequency of the sound. Either with the engine RPM or half the Rpm. Try taking a long screwdriver or piece of garden hose, hold one end to your ear, check around the valve covers for the sound. My guess is rocker arms and push rods. I suppose you have adequate oil pressure for the gauge to register?