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Old 11-06-2011, 01:18 PM   #1
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Default Spun rod bearing??

Last night I was driving my 1999 Miata and I noticed it started making a loud chatter/knocking sound between 2,000 and 3,500 rpm on accel and decel. I stopped at a red light and the car died. When I tried to crank, it was cranking very slowly, like it was struggling to spin. Now when the car starts, it knocks, stops until 2,000, and starts again. Is this a spun rod bearing or something else?

Last edited by AdamSM33; 11-06-2011 at 08:16 PM.
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Old 11-07-2011, 08:50 PM   #2
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Sounds like something very wrong in the motor. Pull the valve cover off to make sure it is not something catastrophic in the valvetrain first. If it looks normal, I would think it is in the bottom end like a rod or main bearing.

Please do not start the motor again. If it is making loud noises, you need to shut it down as soon as possible. Continuing to run a motor that is knocking will eventually cost you a whole lot more money to fix. If something comes apart, you will end up losing your block and or cylinder head as well.
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Old 11-15-2011, 02:39 PM   #3
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Before you pull motor do this

look at harmonic balancer

look at alternator bolt

test battery voltage

look at your pulleys and **** on front of motor
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Old 11-18-2011, 04:22 PM   #4
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I know it sounds stupid, but do you have oil in it? Sounds to me like it ran dry, spun a bearing and is knocking. It's having a hard time cranking because of the terrible amount of friction on the crank. It sounds like you are perfectly describing what my car did when it ran w/o oil. Look at it as a way to upgrade the bottom end.
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Old 11-18-2011, 07:16 PM   #5
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Oil level looked good on the dipstick. But I haven't drained it yet. I haven't really bothered since I've got a fully built 1.8 motor built by Gas Head Motorwerks on the way lol.

By the way, what's the selling policy on here? I know on some forums you need to be a member. I have some Eagle forged h-beam rods I need to sell. Brand new.
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Old 11-18-2011, 07:58 PM   #6
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Spun rod bearing with be easily evident throughout the ENTIRE rev range. From idle to red line. When mine went, it sounded like a card in the spokes of sorts. Could easily be heard at idle all the way to red line, no difference in volume, only speed of click obviously.
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