Strange engine noises

[kyle_in_rure]

Hello all,

Have recently noticed two unfamiliar noises coming from the engine. When it is cold, I hear what I could best describe as a "tapping" sound. It's present at idle and increases with acceleration but goes away totally once it warms up. It's not incredibly loud but I can hear it in the cab.

The second sound also is somewhat like a tapping or clicking. This happens between 2000-3500 RPMs and it reminds me of a Diesel engine. It only happens maybe twice a week or so. Any suggestions on what may be causing this?

It's a 97 EB 4.6. With 220K miles. I use valvoline maxlife 5w20 synthetic. It leaks a about a quart every 1000 miles but I keep it topped off.

Some history:
I was throwing an O2 sensor code over the summer but I cleaned out the throttle body and it never threw another code. The engine also overheated back in August after blowing a heater hose. But there's no head gasket leak.

New plugs and wires at 170K

Thanks all.

 

[stamp11127]

The tapping you hear is from metal to metal contact inside the engine. This occurs when there isn't any oil between the parts and/or the clearance between them is excessive.
The cams rotate at half the speed of the crank so the frequency of tapping can help locate the area that it is coming from.
You may also have an exhaust leak that will vanish when the exhaust system is hot. I woild rule that out first.
If you could post a video that would help the members to determine the cause. Escpecially the diesel sound you mentionedm

 

[kyle_in_rure]

Ok. I will do that shortly when I can get a friend to help me so can video from under the hood.

I forgot to mention the firs "tapping" sound occurs at idle speed but only when the truck is in gear. I can't hear it in park or neutral

 

[Snag]

Stamp is correct. At a glance it sounds like insufficient oil or exhaust manifold, both common problems on these engines. The exhaust manifold is not life threatening but the oil tap certainly is. I would dig into the tick sooner then later as the oiling problem will likely kill your engine, or at least create some very expensive repairs.
Your engine is the first gen so arguably a better engine then the next series but some problems are common to both. You might also want to listen to the front of the engine as well because the timing chain tensioner is also a known failure problem creating ticking. At 220k miles the tensioners are certainly a possibility and should be replaced with the rest of the timing components. And at 220k replace the oil pump with a Melling unit, its right under the lower timing chain crank gear.

Good luck

 

[kyle_in_rure]

I'm probably an idiot but is there an easy way to upload a video file here ?

 

[stamp11127]

Put it on a hosting site such as youtube then link to it.

 

[docraymund]

Most likely the noise you hear when the engine is cold is piston slap. Not much of a concern. The second noise would be coming from a loose piston pin or worn connecting rod bearings.

 

[kyle_in_rure]

Here is the first sound it's making. Now that I've poked around a bit it sounds like it's coming from the bottom of the engine....maybe the transmission?

Sorry it cut off early. I ran out of memory. When I get someone else who can keep the brake on while I poke around I may post another video. It increases with acceleration and only makes that sound when it's in gear.

 

[stamp11127]

Sounds like a rod knock to me.

 

[kyle_in_rure]

Hmm. What is strange to me is that it goes away totally once warmed up.

Would a knocking rod keep making noise ?