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Old 04-11-2012, 02:52 AM   #1
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Default loud knocking at idle and while revving

My friend's 95 started knocking under load and now knocks all the time. Head and valve train look ok. An inspection camera didn't find anything in the combustion chamber. Compression is 200/180/150/150. Is this a bottom end problem like a bent rod or spun rod bearing?

Engine is stock, no turbo, but it has 200k miles and unknown history from previous owners.

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Old 04-11-2012, 03:20 AM   #2
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Bearing. It's done.
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Old 04-11-2012, 03:22 AM   #3
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yup. time to yank that sucker
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Old 04-11-2012, 07:54 AM   #4
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www.car-part.com

Or rebuild it and force feed it.
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Old 04-11-2012, 09:26 AM   #5
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Bearing. It's done.

just use 75w-90 oil.
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Old 04-11-2012, 10:48 AM   #6
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Ok, that's what we thought. New engine is already being sourced. My ls1 which had 1 spun bearing with only small amount of wear didn't sound nearly this bad, but would barely idle when it was pulled. This thing drove 50+ miles and still idles/revs all while clanking.
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Old 04-11-2012, 11:38 AM   #7
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We do have a 70k mile vvt longblock for sale just fyi
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Old 04-11-2012, 12:34 PM   #8
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Quote:
Originally Posted by orion4096 View Post
Ok, that's what we thought. New engine is already being sourced. My ls1 which had 1 spun bearing with only small amount of wear didn't sound nearly this bad, but would barely idle when it was pulled. This thing drove 50+ miles and still idles/revs all while clanking.
Miata engines are some of the loudest, most baffling, and yet toughest engines I've ever seen.

I've seen a 1.6 lose most of it's coolant (Radiator neck leak), get ran for ~80 miles, leak fixed and filled back up...and it was fine.
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Old 04-11-2012, 01:34 PM   #9
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Just keep running it, see how long it lasts. Not on a track though. You'll ruin the day if you oil down the track.
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Old 04-11-2012, 03:17 PM   #10
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He was driving up to the corkscrew at Laguna when it happened so it's already seen some track time while knocking... While it might be fun to blow it up and possibly add a hole to side of the block I'd rather just swap it out now and open it up.
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Old 04-11-2012, 03:28 PM   #11
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Rebuild it for a shelf spare. Ebay rebuild kits are cheep, if you wanna cost effective diy project.
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Old 04-21-2012, 10:07 PM   #12
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We pulled the motor today. Drained the oil... all 0.5 quart that was left. Spent most of the day swapping parts and redoing all the belts and seals on the new motor. If anyone has an extra carfax I'd appreciate if you can lookup the new motor in exchange for some $$$: JM1NA3536S0610298
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Old 04-22-2012, 12:32 AM   #13
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Give this a shot:
Attached Files
File Type: zip JM1NA3536S0610298.zip (972.7 KB, 83 views)
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Old 04-22-2012, 01:30 AM   #14
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yeah, cause clicking a .ZIP file from a member with two posts is totally a good idea.
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Old 04-22-2012, 01:36 AM   #15
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yeah, cause clicking a .ZIP file from a member with two posts is totally a good idea.
afaik .zip files are pretty innocuous (maybe I'm wrong)? I figured the .xps format wasn't supported by the forum upload software.
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Old 04-22-2012, 01:41 AM   #16
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@orion4096
Can't PM yet, so I'll reply here:
No worries, I had the Carfax left over from car shopping last weekend. Don't worry about paying, it was going to go to waste anyways.
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Old 04-26-2012, 12:02 AM   #17
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Swapped the motor last weekend and it looks to be running good. Haven't had a chance to pull apart the old one, but we did cut open the filter. I think there's more than 4 bearings worth of metal in it:

53c14c94.jpg?t=1335407869
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Old 04-26-2012, 12:27 AM   #18
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Quote:
Originally Posted by orion4096 View Post
Swapped the motor last weekend and it looks to be running good. Haven't had a chance to pull apart the old one, but we did cut open the filter. I think there's more than 4 bearings worth of metal in it:]
Horrible... you should collect up what you can with a magnet & weigh it.
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Old 05-03-2012, 02:29 AM   #19
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What's left of the #4 rod bearing next to another half that looked fine. Nothing else was obviously broken from a quick inspection.

c4a60e15.jpg?t=1336022718
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