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Discussion Starter #1
I have an 88 Samurai and just replaced the timing belt and tentioner. It runs great but when the engine passes between 3,000 - 3,500 RPMs there is a vibration coming from the engine. It is not violent but you can feel it through the seat and hear it. It will do this while driving or sitting still so it is not in the drive train. Did I tighten the belt too tight or something? I changed the fan clutch out with another one and that did not do anything. Could it be a
unbalance or damaged fan blade?

To be honest I do not remember before the new timing belt if this vibration was there or not.

Thoughts are appreciated. Thanks
 

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Discussion Starter #3
When I did the timing belt I did not remove the crank gear....just the pully. Everything went back smooth.....Where are the balancers? Could I have overtightened the TB and would this be a symptom of one? Thanks
 

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I don't recall a harmonic balancer on the front of the 1.3, just a pulley.
 

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Discussion Starter #5
I am thinking of pulling the drive belt off and running it down the street and back quickly to see if the vibration is coming from the fan. I do not think it will overheat in a short distance.
 

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Keep it under 2~3 minutes and you should be fine.
 

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It's not like a harmonic balancer like you would find on a big V8... The cast pulley actually acts as a balancer. You can see on some where small dots have been drilled out on the back of the casting to balance the pulley.



Sorry, I don't have a better picture of the cast pulley here at the office.
 

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Discussion Starter #8
Thanks...now just ship that engine to me. I remember the pully being fairly stout so that makes sense. I just can't figure out why it would start after the TB replacement. There really is only one way to install the pully...
 

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Thanks...now just ship that engine to me. I remember the pully being fairly stout so that makes sense. I just can't figure out why it would start after the TB replacement. There really is only one way to install the pully...
That's the one that went into this:

And then took it to just over 100mph...

I realize that it only fits one way, but I remember that the bolts are not the biggest and if you don't torque them to spec they could back out a little and cause an imbalance. It's the only thing I could think of for that problem.
 

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It's not like a harmonic balancer like you would find on a big V8... The cast pulley actually acts as a balancer. You can see on some where small dots have been drilled out on the back of the casting to balance the pulley.
Yes - there is a cast pulley, but as far as I know it's not a balancer of any sort - and I know several people who have replaced it with lighter & smaller aluminum ones and had no problems whatsoever with vibration.
 

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Discussion Starter #11
Well I removed the crank pully and it still had the vibration right around 3,300 rpms. I even removed the timing belt cover to see how it looked while running....all OK. I checked the flywheel through the small rubber plug on the bellhousing...all tight. I looked through the hole at the flywheel while it was running and there was no wobble. I don't know.....maybe this is normal????
 

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Just my opinion - and it's hard to diagnose sounds/vibration without hearing/feeling them - but it's not normal for the 1.3 to have a noticeable vibration that comes in around 3000 rpm and fade out above 3500.

I've run mine up into that rpm range, both in motion and stationary, when checking oil pressure (the FSM spec for oil pressure requires you to check it at 3000 rpm) and there's no vibration.
 

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Discussion Starter #13
Wondering.....could my problem be with the timing belt...meaning, when I tightened the TB tensioner could it have caused a misalignment between the crank and cam pully? It seems to check out OK on a timing light....I checked the timing and it shows 10degrees at the flywheel. I am just wondering as the rpms go up and the timing advances maybe it gets out of sync or something. Am I on to something? How do I check my thoughts? Or since it checks out on the timing I am just wrong on thinking this may be an area of the problem. Thanks
 

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Discussion Starter #14 (Edited)
Update.....Vibration Cured

OK....after checking timing, plug wires, and scratching my head I finally cured by vibration problem.

While driving over the weekend the vibration was gone.....but I would hear a noise every once in a while...sounded like a metal plate vibrating. I inspected the underside and found that a bolt off of a muffler mount I made was missing...allowing it to hit the catalytic converter. So I replaced the bolt and the original vibration was back. So then it hit me...the muffler mount I made was a solid piece of alluminum which did not allow the muffler to move and transmitted engine noise through the body.

I bought a rubber mount and that cured all my problems.....so the lesson is do not use hard mounts on a muffler system.

I should have known better.
 

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inline 4 cylinder engines are hard to balance. Most inline 4's have 1 or 2 balance shafts to help keep it smooth but as you probably saw the samurai has no balance shaft and so it has a little extra vibration right around 3,000 RPM. You normally don't notice because the engine (as well as the exhaust and transmission) has rubber mounts to keep the vibration at bay.

Your hard muffler mount would have eventually broke or would have broke something in your exhaust system.
 
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