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short story is that I just rebuilt my 3sgte (1st build ever) and it has about 300 miles on the motor and the other night it started making a knocking noise from the engine after driving it on the highway. After going through a T/S check list, I believe it is a spun bearing. So today I dropped the pan and checked the rod bearing and they look fine. Well, is it possible for one of the crank bearings to spin out of position? I going to check tonight. If its not a bearing, it has to be in the head somewhere... When I rotate the crank with a ratchet at the crank nut, something is definitely catching something cause i can feel it through out the 360 turn.



Sad to say this but I think I may sell my MR2 after this. I'm so tired of working on it and shit always breaking...:tear:
 

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It's generally not hard to figure out if it's a valve or a rod bearing; I have heard both numerous times, so if I heard it run for 2 seconds I would know. I think the easiest way is to start the car, let it idle and put you head as close to the valve cover as possible, listen more for how loud than the sound, then lay under the car, if it's louder under it's most likely a spun bearing, there isn't much else down there that could make noise. But Don't let the car run for longer than it needs to if it's louder at the bottom of the motor!!!

If it's louder by the valve cover I found that you can use a long screwdriver or a bunch of extensions connected together, and when the motor is running you put the tool against the valve cover above the cam, then put the other side against your ear. Move the tool around to different spots on the valve cover until it's the loudest. That will help slim down much better which valve is bent...
 

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short story is that I just rebuilt my 3sgte (1st build ever) and it has about 300 miles on the motor and the other night it started making a knocking noise from the engine after driving it on the highway. After going through a T/S check list, I believe it is a spun bearing. So today I dropped the pan and checked the rod bearing and they look fine. Well, is it possible for one of the crank bearings to spin out of position? I going to check tonight. If its not a bearing, it has to be in the head somewhere... When I rotate the crank with a ratchet at the crank nut, something is definitely catching something cause i can feel it through out the 360 turn.



Sad to say this but I think I may sell my MR2 after this. I'm so tired of working on it and shit always breaking...:tear:
well, is there evidence of metallic flaking in the oil? did you do a 'proper' break-in? did you use quality parts for the rebuild? or ebay stuff? there are many reasons why an engine can spin a bearing. and as for breaking stuff...i'll paraphrase something i heard or read from a hotshoe many many years ago:
while many problems may arise, but the main culprit is oftentimes attributed/linked to the nut behind the wheel.
 

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how do you know it not a wrist pin piston slap or crank bearing? try taking the oil cap off and see if the noise comes out of there (be careful because oil might sprinkle out)if it is then its in the head
 

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short story is that I just rebuilt my 3sgte (1st build ever) and it has about 300 miles on the motor and the other night it started making a knocking noise from the engine after driving it on the highway. After going through a T/S check list, I believe it is a spun bearing. So today I dropped the pan and checked the rod bearing and they look fine. Well, is it possible for one of the crank bearings to spin out of position? I going to check tonight. If its not a bearing, it has to be in the head somewhere... When I rotate the crank with a ratchet at the crank nut, something is definitely catching something cause i can feel it through out the 360 turn.



Sad to say this but I think I may sell my MR2 after this. I'm so tired of working on it and shit always breaking...:tear:

A bearing turned out of position is the definition of a "spun" bearing.
You mentioned you inspected the rod bearings, did you check clearance? A bearing need not be "spun" to knock. What about the mains?
 
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