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Discussion Starter #1
Hi, I am trying to diagnose a noise coming from the engine on a 1991 Toyota 3SGTE. After I rev the engine I can hear a rattling on decel. See the video. Interested to hear what you think.


 

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Discussion Starter #2
I checked valve clearance for intake and exhaust, all checked within spec. Was concerned that it could be rod bearings, checked those and using standard bearings they are within spec.

The crank bearing No. 3 is within spec, but 1,2,4,5 are .004mm out of spec. The crank bearings are also standard size and all measure .038mm for clearance and should be (according to BGB), 0.015-0.034mm. Could this be causing the rattling right after I rev the engine and starts to decel?
 

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How does oil pressure look? Mileage on the engine? Compression? Crank bearings 0.004mm out of spec aren't going to cause any trouble as long as you have good oil pressure. They won't cause that kind of noise in general since they are all supporting the crank together.
Get a mechanic stethoscope and start probing around. Does it make the noise if you hold the RPM or is it only on decel? Does it do it if you hold the clutch pedal in? Could be worn out clutch springs banging around.
 

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Timing belt idler bearing could be going, just finished redoing mine, same type of noise.
I replaced the timing belt, idler bearing about 1000 miles ago. I noticed the old idler bearing turned slightly better than the new one but put the new one in anyway. I can try putting the old one back in. Thanks!
 

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How does oil pressure look? Mileage on the engine? Compression? Crank bearings 0.004mm out of spec aren't going to cause any trouble as long as you have good oil pressure. They won't cause that kind of noise in general since they are all supporting the crank together.
Get a mechanic stethoscope and start probing around. Does it make the noise if you hold the RPM or is it only on decel? Does it do it if you hold the clutch pedal in? Could be worn out clutch springs banging around.
ok. I did use the stethoscope before and couldn't pinpoint the sound but at least found it was in the top end, not the bottom end. It only makes the rattling noise on decel and it ticks at idle, but not loud enough to notice in the video. I am concerned about the ticking too but thought resolving the rattling noise could fix the ticking too. I didn't try it with the clutch pedal in, but did check the springs (on the clutch disc) and they are tight.
 

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I replaced the timing belt, idler bearing about 1000 miles ago. I noticed the old idler bearing turned slightly better than the new one but put the new one in anyway. I can try putting the old one back in. Thanks!
New ones will have more resistance. This is normal.
 

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Hmmm, if it's in the top end it will be hard to track down without pulling the head apart. I ran the 4AFE head in my Tercel for a long time with some pretty scary sounding ticking noises at idle without any issues. I swapped the head for a reman and it solved the issue. Could be valves rattling around in guides?
 

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Discussion Starter #10
Curious how you checked the springs on the clutch disk...
I dropped the engine and transmission a couple of days ago, i checked the springs on the disc by hand and they were tight/didn't move. Is there a way to check the tension of the springs?
 

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I replaced the timing belt, idler bearing about 1000 miles ago. I noticed the old idler bearing turned slightly better than the new one but put the new one in anyway. I can try putting the old one back in. Thanks!
Had this exact sound a month ago. It was definitely timing belt tensioner.
 
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