What are symptoms of rod knock/spun bearing?
03-11-2012, 03:04 PM
#1
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What are symptoms of rod knock/spun bearing? Before I get the smartass response "a knocking sound," hear me out haha. 
Lol.
I've got a 99 LS1 (in a Nissan 240sx), with just a cam/longtubes/exhaust. At certain rpms I have a knocking sound coming from the car. Is there a definitive way to figure out if a knock is coming from the motor? At this point I'm leaning towards the headers or trans vibrating against the chassis of the car as it's very tight, but I wanted to know if there's a way to make sure. Also, would your power level be decreased with a rod knock/spun bearing?
I took the car out today and it was missing some, or just down in power generally, from about 4-4k rpms on up. I just put new plugs and MSD wires on it because it was doing this and I assumed it was the stock wires. I'd like to hope that this problem is from either a coil pack half going bad, or clogged/dirty fuel filter, or bad connection to a coil/spark plug, but that's why I was wondering if the power level would be noticeably decreased with a rod knock.
Lol.I've got a 99 LS1 (in a Nissan 240sx), with just a cam/longtubes/exhaust. At certain rpms I have a knocking sound coming from the car. Is there a definitive way to figure out if a knock is coming from the motor? At this point I'm leaning towards the headers or trans vibrating against the chassis of the car as it's very tight, but I wanted to know if there's a way to make sure. Also, would your power level be decreased with a rod knock/spun bearing?
I took the car out today and it was missing some, or just down in power generally, from about 4-4k rpms on up. I just put new plugs and MSD wires on it because it was doing this and I assumed it was the stock wires. I'd like to hope that this problem is from either a coil pack half going bad, or clogged/dirty fuel filter, or bad connection to a coil/spark plug, but that's why I was wondering if the power level would be noticeably decreased with a rod knock.
Last edited by TurboGoKart; 03-11-2012 at 03:24 PM.
03-11-2012, 03:14 PM
#2
If you believe you've got rod knock, you can drop the oil pan & attempt to jiggle the rod caps. If any of them moves, you can be sure that there is a problem.
I've had spun bearings that caused a 'woosh, woosh' sound, and also have had spun bearings that made no sound at all.
Have you checked your crankcase oil? Any particles in the oil?
More evidence can be gathered by cutting open the oil filter with either a can opener, or a pair of cutters. See if there's any material in there other than oil.
And, while this isn't conclusive, changes in your normal hot & cold oil pressure can be indicative of trouble.
About the percieved power loss...sounds like you have misfire at certain speeds, but I can't tell from here. Do you have any video?
I've had spun bearings that caused a 'woosh, woosh' sound, and also have had spun bearings that made no sound at all.
Have you checked your crankcase oil? Any particles in the oil?
More evidence can be gathered by cutting open the oil filter with either a can opener, or a pair of cutters. See if there's any material in there other than oil.
And, while this isn't conclusive, changes in your normal hot & cold oil pressure can be indicative of trouble.
About the percieved power loss...sounds like you have misfire at certain speeds, but I can't tell from here. Do you have any video?
03-11-2012, 03:43 PM
#3
Ive heard spun bearings that sound like a hammer hitting the block. Ive noticed that rod knock is usually quite noticeable at idle. rod knock also traces the RPM's. drain your oil into a clean bucket then look for stripper glitter (it will be noticeable if its spun a bearing). As gMAG mentioned low oil pressure can be a symptom of a spun bearings. Knocking could be alot of things. it would help if you posted a video
03-11-2012, 07:24 PM
#5
Wanted to add that any rod knock I've experienced, happened when backing off of the gas. As long as pressure is applied to the piston via acceleration, the loose rod cap/rod/bolts are not as evident. The moment you decelerate, the pressure is removed from the piston, and the slack of those components become evident.
03-18-2012, 12:14 PM
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Pics from the filter.
Don't mind the shavings around the top; that was from cutting it open. The oil didn't look bad either. How much "stripper glitter" am I supposed to see? Obvious? Or have to look hard.
Don't mind the shavings around the top; that was from cutting it open. The oil didn't look bad either. How much "stripper glitter" am I supposed to see? Obvious? Or have to look hard.
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03-18-2012, 08:42 PM
#8
Hose that filter off with brake clean and catch the stuff in a clean container. You really should have cut it apart with something other than a hacksaw.
You can even strain the liquid with a coffee filter.
Anyway, a rod knock will quiet a bit if you remove the plug wire from the offending cylinder.
You can even strain the liquid with a coffee filter.
Anyway, a rod knock will quiet a bit if you remove the plug wire from the offending cylinder.
03-19-2012, 01:22 AM
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^^Yeah, after I posted those pics I realized what gMAG said lol. Oops.
Before I did this, I had it out and made a couple pulls with it. It seemed like it was taking forever for the rpm's to increase above 5800rpms. It almost seemed like it was starving for fuel, i.e. the pump not being able to keep up with the demands of higher rpms, but doing fine at normal driving. But I have an Aeromotive Platinum series pump (rated to 700hp), and it's hard wired, so probably a little higher. I was going to change out the fuel filter and try it again, but at this point I'm not sure if I should bother since it's hard to tell by the filter since I was retarded and cut it open the wrong way.
I just put a new filter on it, should I drive it some more and re-check the oil/filter? I mean, if it IS a spun rod bearing, I'm not really going to 'hurt' anything worse lol. Right? It's not as if I'd plan on micropolishing the crank/using a larger rod bearing and re-using anything.
Before I did this, I had it out and made a couple pulls with it. It seemed like it was taking forever for the rpm's to increase above 5800rpms. It almost seemed like it was starving for fuel, i.e. the pump not being able to keep up with the demands of higher rpms, but doing fine at normal driving. But I have an Aeromotive Platinum series pump (rated to 700hp), and it's hard wired, so probably a little higher. I was going to change out the fuel filter and try it again, but at this point I'm not sure if I should bother since it's hard to tell by the filter since I was retarded and cut it open the wrong way.
I just put a new filter on it, should I drive it some more and re-check the oil/filter? I mean, if it IS a spun rod bearing, I'm not really going to 'hurt' anything worse lol. Right? It's not as if I'd plan on micropolishing the crank/using a larger rod bearing and re-using anything.
03-19-2012, 01:27 AM
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Oh, and after those couple pulls the knock definitely seemed to get louder/more obvious. But shut it down and restart, and it's back to normal. Ugh. Lol.
Thinking ahead, if I do just get a new bottom end, I can't upgrade to an LS2 block because of the reluctor wheel difference right? Or I suppose I could lengthen/reposition the sensor, but using the Gen III PCM will I have any issues? Just use the same 02 Camaro map on HPT that I'm using, and tune from there?
Thinking ahead, if I do just get a new bottom end, I can't upgrade to an LS2 block because of the reluctor wheel difference right? Or I suppose I could lengthen/reposition the sensor, but using the Gen III PCM will I have any issues? Just use the same 02 Camaro map on HPT that I'm using, and tune from there?
03-19-2012, 02:25 AM
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I wouldnt call a spun bearing yet. If this car is fuel injected then there is a good possibility that a motor mount is bumping or a header is hitting something the lose of power could be due to the knock sensor picking this sound up and pulling timing. Anyone that has a F body with a bad passenger motor mount where the ac compressor will lay down on the rack knows about how sensitive the knock sensors are.
03-20-2012, 12:44 AM
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Booo. Wideband is on the way to check a/f to see if it's a fuel problem in higher rpms.
Like I said too, I was retarded and a lot of that crap *could* be from cutting it open the wrong way. First time I've needed to do that and I didn't think about it. Oops.
Like I said too, I was retarded and a lot of that crap *could* be from cutting it open the wrong way. First time I've needed to do that and I didn't think about it. Oops.
04-01-2012, 03:26 PM
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Well I found the cause of the upper rpm hesitations. Put the wideband in and it was running lean. Took the fuel filter off and found this:
Yikes! Looks like the fuel cell foam was breaking down for some odd reason. It's just over a year old with only 93 octane run thru it. Beats me.
The knocking sound is still there. Pretty sure it's just my exhaust. It'll make that noise even when I'm on the throttle. I would guess its my exhaust but I'll have to fiddle with it to confirm it.
Yikes! Looks like the fuel cell foam was breaking down for some odd reason. It's just over a year old with only 93 octane run thru it. Beats me.
The knocking sound is still there. Pretty sure it's just my exhaust. It'll make that noise even when I'm on the throttle. I would guess its my exhaust but I'll have to fiddle with it to confirm it.
