Need Help With Jeep 232/258(long post)

[jwoelfle]

Any experienced Jeep wrenches out there that can help diagnose a knocking sound in my 232?



I don't believe it to be rod knock but since I've never had a vehicle with it, I can't say for certain.



The noise appears to be coming from the oil filter housing area, where the distrib goes into the block and into the oil pump. It is a hollow knocking sound... not very loud but gets louder as the engine heats up. Gets quieter as the oil pressure/rpm drops... as in idling in gear. Oil pressure is 45-50(mechanical guage) at idle in park, 60-70 at 40 mph top gear, ~20-25 idling in gear.



Knock got fairly loud yesterday while driving around. Did an oil and filter change this morning and the knock is much better now, but still present.



Motor still runs smooth and strong... just like usual. Nothing else abnormal except that I don't remember the oil pressure being that high... at idle or at cruise speed... seems to be at least 50% higher than I remember.



Approx 1 week prior to the new knock, I did the GM HEI distributor conversion. It has run better than it ever did before. I used a wrecking yard distrib but replaced that tonight with a new one to rule out bearing slop in the used distrib. Knock still there.



I don't believe it to be rod knock for the following reasons:



does not get louder with load

pulling plug wires one by one on each cylinder yields no change in noise

knock got quieter immediately after an oil change

knock cycle is too fast to be in the lower rotating mass... sounds to be at twice the speed if not more like 6 times... too fast to actually count the number of knocks in a given time period.



I'll be checking the flexplate tomorrow as I've heard that a cracked plate can cause a similar noise, but I doubt that's it.



Any ideas?



Thanks,

Jim

Wylie, TX

 

[srowland]

Just as a check you might want to use the old screw driver trick and check for piston slap. Had a somwhat similar sound from a Jeep 4. 0L this last year, it would go away at idle but got louder under load. Hopefully yours isn't that major.



I know the distributer is directly connected to the oil pump on a jeep engine, but I just had one apart and I can't think of anything that would knock. It might pay to drop the oil pan and take a look. Changing the oil pump is alot easier than changing engines.



Good luck.



Isaac

 

[jwoelfle]

I assume you are talking about the screwdriver to the ear trick to help pinpoint the source of the noise. I used a rubber hose to the ear version of that trick... that's how I found it was coming from the oil pump/filter housing area.



I thought about dropping the pan and replacing the oil pump, but this motor is in a postal jeep that my wife uses for delivering mail here in town. I can't afford the downtime right now... maybe in a week or so.



Thanks,

Jim

 

[B.G. Smith]

I would look at the distributor drive gear if the noise is at a faster rate than the rpm. bg

 

[jwoelfle]

good suggestion... I just glanced at it when I had it out last night and it looked ok, but I'll pull it again today and give it a critical inspection.



Jim

 

[B.G. Smith]

Another thought, try loosening the distributor hold down bolt with the engione running, could be length problem witht the dist. shaft, pushing down on oil pump drive. bg

 

[jwoelfle]

Another excellent suggestion... thanks.

 

[krs]

Sturdy engine.



The flexplate cracking was very common on postal jeeps with 232 engines, and a little more common in the DJ5B and DJ5C (1970 thru '73) with Borg-Warner trans than in the later DJ5D and DJ5F ('76 and '78) with Torqflite trans. It would usually show as a hairline crack around, or partway around the center of the plate and is hard to see through the inspection cover. The knocking is just as you describe it except that it wouldn't get better with an oil change. It's a tough knock to locate because it can seem to be coming from anywhere along the length of the crank, and it can come and go sometimes.



I spent ten years as a mechanic for the Postal Service starting in 1974. Those jeeps still habitate my nightmares.

 

[jwoelfle]

Looks like it was a problem with the oil pump itself. Heard the banging and clanging from the living room when my wife pulled into the driveway this afternoon after finishing her route. I now have first hand experience with what rod knock sounds like. The oil pump quit less than a mile from home... zero oil pressure. #1 cylinder is banging and clanging hard... which is NOT the sound the engine was making before. I've got until 9am Monday morning to get a new motor swapped in. What a way to spend my weekend.



I guess the mystery sound is solved now... or at least doesn't matter anymore. I'lltear it apart later to see just exactly what killed it.



Jim