Is my 258 knock-knock-knockin on heavens door? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-02-2002, 03:38 PM Thread Starter
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Is my 258 knock-knock-knockin on heavens door?

My 84 CJ7's 258 recently started a knocking sound that appears to be coming from under the valve cover or that vicinity. The engine has 89K on a rebuild and is performing seemingly well. No major leaks, compression is on the lower end of acceptable and it runs well on the highway. This is my daily driver. However, in the last two weeks a noticable knock has developed. It does it whether in gear or standing still. The knock imcreases as the rpms do so I assume it is not drivetrain related.

I keep the maintenance on this jeep up pretty well and it is always full of oil.

I am not in a position to swap or rebuild unless this thing dies. Can anyone tell me what is the likely culprit. Is there anything I can do short of a rebuild. Any comments greatly appreciated.

Hope this is not a stupid question.
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post #2 of (permalink) Old 12-02-2002, 03:46 PM
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Re: Is my 258 knock-knock-knockin on heavens door?

Sound to me like the Bottom end (main bearings) are going out bro.

Take it back to the rebuilder and ask them.
post #3 of (permalink) Old 12-02-2002, 10:18 PM
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Re: Is my 258 knock-knock-knockin on heavens door?

How is your oil pressure? If it is really low than you have a bottom end problem.
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post #4 of (permalink) Old 12-02-2002, 10:36 PM
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Re: Is my 258 knock-knock-knockin on heavens door?

Funny how sounds get interpreted differently.

Your "knock" could be defined from anywhere from a tinny click,
a rattle, to a thud or clunk.
The more like a thud the more expensive.

You may have said something very important -
"knocking sound that appears to be coming from under the
valve cover or that vicinity."
Hopefully it's a simple valve train problem.
Pull off the valve cover and have a look-see.
Could be a rocker got loose, pushrod bent, lifter got stuck
etc.

If you said the sound seemed to come from deep within or
underneath, it would probably be a more expensive sound.

And before doing anything, have a good look at the belts,
one that's got a chunk missing can sound expensive.
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post #5 of (permalink) Old 12-03-2002, 06:01 AM
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Re: Is my 258 knock-knock-knockin on heavens door?

I'd start with the person/mechanic/shop who rebuilt the engine. Unless that was you.
A mechanic's stethoscope can very quickly help you find the location of the problem. If it is coming from the valve train, it'll be pretty easy to pull the cover to see what's going on.
My '89 with 120k, leaks oil, burns oil, has little compression, runs 45lb oil, overheats, has two wrist-pins that have knocked (loudly) since 95k. I dont' want it to die, because like you, it's my daily driver. But sometimes I wish it would, then I would have an excuse to replace it.
Let us know if you can narrow the location down a little more.
post #6 of (permalink) Old 12-03-2002, 09:09 AM
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Re: Is my 258 knock-knock-knockin on heavens door?

sounds very familier, I had the same sound twice a year for the last three until I finaly rebuilt. anyway, it was one of my lifters getting clogged with some crap and not pumping up, eventualy the pushrod will pop off and then it really sounds bad!! Pull off your valve cover and it should be pretty blatant which one it is. you could also pull out the lifter with a dentist probe they usualy come out pretty easy and see if it's clogged.Anyway it worked for me for years till I finaly broke down and rebuilt it.Good luck, I had it down where i could pull my valve cover and be driving again in 25min. I'm sure you'll be the same.
post #7 of (permalink) Old 12-03-2002, 11:31 AM
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Re: Is my 258 knock-knock-knockin on heavens door?

1. It seems there's a lot of guessin' going about what the problem is.
2. Do yourself a favor and buy a $8 mechanic stethascope.
3. Listen at various parts of the engine for the knock.
4. Where is it loudest?
a. Valve Cover - Valve train.
b. Upper Block to head - lifter.
c. Lower block - rod, pistion slap, wrist pin, or main bearing.
5. GET IT FIXED NOW.
6. This won't cure itself over time.
7. Spend a little now... rather than a whole lot later.

In any respect... it's best to know what you're facing rather than guess.
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post #8 of (permalink) Old 12-03-2002, 01:26 PM
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Re: Is my 258 knock-knock-knockin on heavens door?

Same problem with mine; very recent too. Mine is the oil pump. Symptons: very low oil pressure (about 20 - 30psi on start up, and 40psi after running a while). Pinging, aka knocking, engine runs on the hot side of the temp gauge. [img]images/graemlins/crazy.gif[/img]
post #9 of (permalink) Old 12-03-2002, 01:36 PM Thread Starter
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Re: Is my 258 knock-knock-knockin on heavens door?

Now that you mention it, yes the engine is running a tad bit on the hot side. Not extremely so, but it has been hotter than I remember. My needle used to rest on about the left 1/4 side of the scale. Now it is slightly over the middle. Water pump, thermostat, and sensor are six months old so I believe the coolant system is working

As to oil pressure I do typically see 40psi on startup and maybe the first 10 minutes of run. Then it drops to 20 and stays there. I have seen numerous posts that this is the typical operating condition for the 258s.

How did you determine the oil pump was the exact problem? I would not describe my noise as a ping. It sounds as if someone was rhythmicly tapping (lightly)a hammer inside my engine in sync with the rpms.

Did you fix this by replacing the oil pump I assume?

Thanks for you help.
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