help diagnose knock

[mtn goat]

Hi all, I need some help trying to figure out what this knock is. a month ago my jeep died on the road and when I got it started there was this horrible knocking. I pulled the valve cover and lifters had died and a pushrod had come out of the arm. well thinking this was the problem I pulled the head, did valves and lifters and put it all back together....STILL KNOCKING BAD. I cant really isolate where its comming from, it doesnt change when I disconnect the spark plugs one at a time. using the tube to ear method it sounds it seems to be comming from the back bottom (almost from the clutch area) but I cant really tell. Help, How should I approuch this know :confused:

[Michael]

You will need to run a compression test on your cylinders. Undoing the spark plug wires one at a time will only tell you part of the time. The knock may be so severe that by doing that it will not be an issue. I am not saying that it is your problem but that is how I would diagnose a dead cylinder.
Is the knock consistant? Like it does it at the same time each time? More than likely you bottom end is going south. But it is hard to tell without really hearing it. If you retard the timing does it go away? Just some ideas to check it out. I am sure someone here could tell you exactly what to look for. Good luck.

[Brown Bear]

If your rig has an automatic tranny, and I believe it does (don't know much about 258's), I would check the bolts that old on the fly plate. Mine came loose and it sounded like I had dropped about 3 or 4 rods. comes from the back bottom also.

[Crazy_Jeepman]

If you had a push rod out from under the rocker then I would have checked as to why that happened. I do not think putting new lifters and pushrods would have been the fix. There was a reason that happend, bad cam, loss of oil presure causing colapsed lifters, to name a few. i would not waste time doing anything else but finding out how the push rod came out, even if you have bad compression it would not knock, a standard shift trans unlikely it would come loose and the knock would change pitch when clutch was depressed. I think it will be a bad cam, or no oil presure at the lifters. Good luck ;)

[ November 11, 2001: Message edited by: Crazy_Jeepman ]

[mtn goat]

Brown Bear, No...My rig has a manual. here are the specs. 258, 120k on the clock, manual hubs and manual tranny. Oil pressure is fine, and she seems to dive strong...only this #%&@! noise. I does sound pretty consistant although when you speed up it is not to regular and sounds like some steel balls in a coffee can. timing helps a little but not enough to make it go. I am giong to do the compression again today (last time I checked all was fine)

Come on guys, I need a flaming briefcase on this one.

[mtn goat]

Crazy, my engine had a lot of sludge in it, the offending lifter had no spring left in it..just stuck to the bottom. I assumed it was just clogged. The oil didnt have metal in it as far as I know, I will pass a magnent through it to find out for sure though.

[64Trvlr]

If you want to know what's really in the oil send some off for an analysis. Then you will know what you have. I think Canyon State Oil on Park Ave will send samples off for you.
:cool:

[Crazy_Jeepman]

Ok the new info helps a little. If your oil presure is GOOD it will not be a rod knock and the pitch never changed removeing a plug wire while running on each cyl. that eliminates a wrist pin. So we are back at the cam and lifters. Since your engine has a lot of sludge in it, and one lifter has already colapsed I would be wondering if the oil is getting through the lifters. I would pull the valve cover and start it up use heavy hammer and beat the rockers and see if it makes a difference, no wait that is for another fix don't do that. Take a hammer (hard wood handle) and press down on the push rod side of the rocker HARD lots of pressure. do this to all of them see if you get a different sound. If you do then I would check the pushrod for being bent, bad lifter, or cam lobe wore off or no oil pressure getting to that lifter pluged oil galley. While it is running and valve cover is off take notice if oil is comeing out of each pushrod under each rocker. ;)

[mtn goat]

Here's a little more info. The noise seems to get worse when the engine warms up(at leist that was the case this morning) it also increases and gets louder with engine speed. I could see the rocker where the lifter died before and its getting plenty of oil from the pushrod side. after letting it run a while there almost seems to be a screetch in the knock..

[Crazy_Jeepman]

OW a screech that is not good. I am not sure what to tell you. Knock that keeps in tempo with engine speed and now a screech, I would have to lean towards a rod. It is possible to maintain good oil pressure and have a knock, if the rod bearing spun, this would give the screeching sound and knock. However really should not run long before complete engine lock up or throw the rod. I guess I would pull the oilpan and look at all the rods. Sounds bad. ;)

[andy d]

hows the inspection plate @ the bottom of the bell hsg doing?

[mtn goat]

There is no inspection plate right now, I think the PO lost it. anyway, the flywheel and teeth look fine, no sign of metal or anything.