motor knocking sound
03-09-2015, 09:58 PM
#31
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Year: 2004
Model: Grand Cherokee
Engine: 2000 4.0
Not necessarily. There is a check valve that closes to keep them from bleeding down but it does not always seal off completely. Until you get your engine running there is no way to know.
03-10-2015, 05:55 AM
#33
Old fart with a wrench
It's my opinion that you had valve noise before you took it apart. You found a couple of lifters that didn't seem to hold oil very well. If it were my jeep, I'd replace the whole set of lifters and be done with it. JMHO however.
03-11-2015, 07:36 AM
#35
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Year: 1993
Model: Grand Cherokee
Engine: 5.2 318
make sure there,s no slop in any of your connecting rods. The noise sounded to me like a piston slapping the head because of a loose/spun bearing. I had the same sound on my old Nova with a small block in it and I thought it was valve train noise too.
03-12-2015, 04:16 AM
#36
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Idk but I read that spun bearings cause low oil pressure. Mine has perfect oil pressure.
03-12-2015, 05:57 AM
#37
Old fart with a wrench
I was going to say if you had a spun bearing, you would have found debris in the oil pan and little or no oil pressure. With the overheat, you may have lost some bearing material and decreased the overall life of the engine, but if the pressure is good, I wouldn't worry too much. You'd have to have over .003" bearing clearance before you start losing oil pressure. The book says anything over 13 lbs at idle is normal. That would worry me.
03-12-2015, 06:31 AM
#38
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Year: 1993
Model: Grand Cherokee
Engine: 5.2 318
I believe you have a spun connecting rod bearing. It sounds like the piston tapping the head. I had the same sound in the smc in my old Nova and I tore the top end apart thinking that was the problem only to find everything fine up there. I tried to post this yesterday but was unable to for some reason. See if you have any play in any of the rod caps. Up and down play.
03-12-2015, 07:22 AM
#40
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Year: 2004
Model: Grand Cherokee
Engine: 2000 4.0
NO. Main bearing or cam bearing will because they get a direct and continuous supply of oil from the oil galley. Rod bearings get an intermittent shot of oil as crankshaft turns and the oil holes on the main journals line line up.
03-12-2015, 09:28 AM
#41
Old fart with a wrench
The pistons cannot hit the head because there is AT LEAST 0.020" deck clearance between the piston top and the head. If the bearing was THAT loose, you'd have 0 oil pressure and the engine would grenade! Ask me how I know. The only way a piston could hit the head is if the top broke off at the ring grooves and pounded it. At that point you'd have bent valves as well and possibly bent pushrods.
In the beginning, it was running, had good oil pressure, but made that knocking sound, right? From your video, it sounded like a collapsed lifter or a broken valve spring to me. You found 2 lifters that weren't holding oil in them. I think that's all it is. You also said the timing chain had slack in it. That means the valves were running slightly retarded causing a slight drop in volumetric efficiency, meaning a loss of power. The PCM adjusted the spark timing to compensate.
Don't let this guy fool you. Grab each con rod by the bolts and violently shake them up and down. If you hear a clicking, then check the bearing visually by taking it apart. I really don't think you'll find any.
In the beginning, it was running, had good oil pressure, but made that knocking sound, right? From your video, it sounded like a collapsed lifter or a broken valve spring to me. You found 2 lifters that weren't holding oil in them. I think that's all it is. You also said the timing chain had slack in it. That means the valves were running slightly retarded causing a slight drop in volumetric efficiency, meaning a loss of power. The PCM adjusted the spark timing to compensate.
Don't let this guy fool you. Grab each con rod by the bolts and violently shake them up and down. If you hear a clicking, then check the bearing visually by taking it apart. I really don't think you'll find any.
03-12-2015, 12:39 PM
#42
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The pistons cannot hit the head because there is AT LEAST 0.020" deck clearance between the piston top and the head. If the bearing was THAT loose, you'd have 0 oil pressure and the engine would grenade! Ask me how I know. The only way a piston could hit the head is if the top broke off at the ring grooves and pounded it. At that point you'd have bent valves as well and possibly bent pushrods.
In the beginning, it was running, had good oil pressure, but made that knocking sound, right? From your video, it sounded like a collapsed lifter or a broken valve spring to me. You found 2 lifters that weren't holding oil in them. I think that's all it is. You also said the timing chain had slack in it. That means the valves were running slightly retarded causing a slight drop in volumetric efficiency, meaning a loss of power. The PCM adjusted the spark timing to compensate.
Don't let this guy fool you. Grab each con rod by the bolts and violently shake them up and down. If you hear a clicking, then check the bearing visually by taking it apart. I really don't think you'll find any.
In the beginning, it was running, had good oil pressure, but made that knocking sound, right? From your video, it sounded like a collapsed lifter or a broken valve spring to me. You found 2 lifters that weren't holding oil in them. I think that's all it is. You also said the timing chain had slack in it. That means the valves were running slightly retarded causing a slight drop in volumetric efficiency, meaning a loss of power. The PCM adjusted the spark timing to compensate.
Don't let this guy fool you. Grab each con rod by the bolts and violently shake them up and down. If you hear a clicking, then check the bearing visually by taking it apart. I really don't think you'll find any.
03-13-2015, 12:13 AM
#43
Old fart with a wrench
Yeah, book says 0.004 to 0.013" rod side clearance is permissible.
BTW, that 0.020" deck clearance doesn't include the thickness of the head gasket. That deck clearance is designed to allow room for the rods to grow in length because of heat.
BTW, that 0.020" deck clearance doesn't include the thickness of the head gasket. That deck clearance is designed to allow room for the rods to grow in length because of heat.
Last edited by dave1123; 03-13-2015 at 12:19 AM.
03-13-2015, 03:11 PM
#44
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Year: 97
Model: Grand Cherokee
Engine: 4.0
Dave I'm glad you posted that I was thinking the same thing. Plus add .040-.060 for head gasket. There's no way piston would hit the head with out major fail. Would sound a lot worse than just a tap. Dude throw some lifters in the pig an jam on.
03-27-2015, 09:23 PM
#45
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OK guys. so I finally ordered all new parts and should be here by early next week. Any tips? I already have all the torque specs. Any tips would be great.
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