4.2 Engine Noise - Can anyone identify from audio clip?

[verreaul]

My son took the jeep out for a spin and this noise just started all of a sudden.

There is a constant tickety sound now and there is a clunking noise every once and a while that occurs on acceleration.

Thanks for any assistance

John

 

[Torxhead]

Hows the oil pressure? Sounds like either low on oil or a clogged lifter. A clogged lifter sometimes requires a few oil changes with a good quality oil.

 

[Lumpy Grits]

Are all of you manifold bolts tight?
Was the engine warm, or was that a cold start??
Look for an exhaust leak(you have one).
What weight oil are you running?
How many miles on the engine?
Pull the valve cover, start the engine and watch the travel of EACH rocker arm.
LG

 

[verreaul]

Hows the oil pressure? Sounds like either low on oil or a clogged lifter. A clogged lifter sometimes requires a few oil changes with a good quality oil.

Oil pressure is 50PSI cold. Oil level is full. I am almost due for an oil change (every 3000 miles 10w30 and I always add 1/2 qt Lucas Stabilizer).

 

[verreaul]

Are all of you manifold bolts tight?
Was the engine warm, or was that a cold start??
Look for an exhaust leak(you have one).
What weight oil are you running?
How many miles on the engine?
Pull the valve cover, start the engine and watch the travel of EACH rocker arm.
LG

Problem seems to be there hot or cold, engine was warm started when problem began, It's 75 here today. Oil 10w30 with 1/2 qt Lucas stabilizer. Mileage 95,000.
Compression on engine in May varied between 138 and 148 on all cylinders.

Engine has an almost consistent thumping which you can feel (and hear) every few seconds. I'll check the manifold bolts, look for an exhaust leak, and pull the valve cover in the next couple of days.

Since I can feel the thumping i'm assuming it will not be related to exhaust or manifold bolts.

Thanks
John

 

[Lumpy Grits]

What is important, is warm OP. Cold means nut'n....... What is hot engine OP at idle and 2500rpm steady.
If this is the OEM ele, gauge. DON'T TRUST IT!
Go with blue bottle of STP over Lucas. Far more ZDDP(Zinc)which is a lube.
That 'thump' could be a rod knock.
LG

 

[mtnwhlr]

The AMC 258 i6 / 4.2l has a problem with spinning the #6 rod bearing and it will cause a knock.

 

[Lumpy Grits]

The 258 has a problem with spinning the #6 rod bearing and it will cause a knock.

Isn't that from being at the end of the 'oil-line'?
LG

 

[mtnwhlr]

Isn't that from being at the end of the 'oil-line'?
LG

I have always thought so. I think as one gets old the #6 gets starved of oil.

 

[verreaul]

What is important, is warm OP. Cold means nut'n....... What is hot engine OP at idle and 2500rpm steady.
If this is the OEM ele, gauge. DON'T TRUST IT!
Go with blue bottle of STP over Lucas. Far more ZDDP(Zinc)which is a lube.
That 'thump' could be a rod knock.
LG

I have an aftermarket oil gauge.
Hot OP (175deg) is ~20PSI at idle and a little less than 50PSI at 2500rpm
Thumping noise is constant at idle about 1 every second. You can hear and feel it.
I'll pull the valve cover tomorrow for further investigation.

 

[verreaul]

Are all of you manifold bolts tight?
Was the engine warm, or was that a cold start??
Look for an exhaust leak(you have one).
What weight oil are you running?
How many miles on the engine?
Pull the valve cover, start the engine and watch the travel of EACH rocker arm.
LG

Just pulled the valve cover and saw that the pushrods from cylinder # 3 were not seated in the rocker arm. One is very very slightly bent and the other one has a nice bend in it. I'm not a mechanic so I don't know if you can just replace the pushrods and call it a day. What should be my next steps. Thanks. John

 

[Lumpy Grits]

Replace all of the PR's.
LG

 

[verreaul]

Replace all of the PR's.
LG

All as in all 12 PRs I assume.
Also I have an 1981 engine. There is supposedly a service bulletin that says to replace the PRs with 9.7" length. The ones I have currently are 9.62" Original Part No. is 3227329 and new Part No. is 3242395.
Noticed the bridge is also bent so I'll be replacing that as well.
John

 

[Lumpy Grits]

YUP-All 12 with the longer ones. Just make sure you blow the oil passages out and wet'em down with oil
Good luck and keep us posted.
LG

 

[verreaul]

YUP-All 12 with the longer ones. Just make sure you blow the oil passages out and wet'em down with oil
Good luck and keep us posted.
LG

I replaced the bent pushrods with new ones of the same length (9.622"). I also bought new rocker arms but ended up not using them because one of them wobbled side to side. I reinstalled the old rockers with a new bridge and all is back to normal. Thanks for the help LG.

 

[mtnwhlr]

Glad to hear it wasn't anything major.

 

[verreaul]

Glad to hear it wasn't anything major.

Forgot to mention. The 2 new pushrods are rotating at a much slower rate than all the other ones. They are rotating so they will wear evenly. I hope I don't need to be concerned.

 

[Lutheros]

Glad you found the problem. Just wanted to ease your mind about the PR rotation. the old rods spin faster due to minor wear reducing their length slightly. As long as the new ones are rotating there should not be any problems.