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A new noise developed in my oil pan - care to help diagnose it?(((UPDATE)))

Discussion in 'The Garage' started by BorregoK5, Jul 7, 2003.

  1. BorregoK5

    BorregoK5 1/2 ton status

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    Cracked flexplate - a welcome sight over the engine, but still a PITA!

    An interesting noise developed in the oil pan this morning and I'm a bit at a loss as to what it is. Haven't dropped the pan and probably wont have the time to do so for a bit. I've heard just about every kind of noise from a small block but this one is different. It sounds like something rattling around near the crank main and towards the rear of the engine (stethoscope tracked it down). It sounds similar to a dust shield rattle and is definitely not a knock like rod bearings produce. It only makes the rattling noise when at 650rpm but immediately vanishes at anything above that, whether under load or not. The truck runs just fine, not stumbling , no hesitation and rev'd up to 2000rpm sounds great, as if nothing is wrong. Oil pressure is as it has always been but the noise sounds like its coming from that general location. There are a few things which I have not experienced before and I'm wondering if it could be one of these; oil pump on the way out or pickup worked loose, cracked flex plate or sloppy wristpin on the 7 or 8 cylinder. If I had to guess what the noise was I'd be leaning toward the oil pump pickup just barely making contact with the crank because of the hollow type sound. Any thoughts?
     
  2. 69K5

    69K5 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    [ QUOTE ]
    If I had to guess what the noise was I'd be leaning toward the oil pump pickup just barely making contact with the crank because of the hollow type sound. Any thoughts?

    [/ QUOTE ]

    that was the first thought that popped into me head to. probably just worked a little loose or got jarred and spun to one side.
     
  3. BigBurban350

    BigBurban350 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    You say you only hear it at 650 rpms, so it could be something loose that rattles at that frequency, like the shield or the pickup.
     
  4. Beast388

    Beast388 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    It could be a couple of things....

    I have seen the baffles in the pan come loose, the spot welds break and then it flops around and contacts the other baffles, crank or pan.

    It could be the oil pump pickup....but you mentioned your pressure is fine, so it probably hasn't come off the pump.
    Is your pickup a bolt on? If not, did you braze the pickup to the pump? I suppose it is completely possible that it has moved upward and is being hit by the crank counterweight.

    In my experience, when you have a cracked or loose flexplate, it makes noise whatever the RPM is. But this could be your problem, it is easy to check so you might as well eliminate this possibility.

    Hopefully it turns out to be something minor....I'd hate to see that 415 go south on ya. /forums/images/graemlins/eek.gif

    Good luck! /forums/images/graemlins/thumb.gif
     
  5. BorregoK5

    BorregoK5 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    I figure the faster the crank turns, the harder the oil is flying off it and maybe thats pushing whatever it is out of the way, but at idle, its contacting the counterweights of the crank. The more I think about it, it does sounds like the oil pan baffle plate. Every once in a while when I slam the brake, I notice the oil pressure drop then rise back up... wonder if thats related... has been doing that for a long time though. hmmm I did braze my pickup on the pump.. but it could have come loose.
     
  6. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    All the other things i've read seem on track...
    I had a similar rattle noise at idle that i tried to track down for months, thought maybe a cracked flexplate... turned out to be the exhaust system rattling and one of my header pipes was cracked at the 4 into 1, I finally realized it when i was changing a collector gasket and could see some daylight around one of the tubes... Replaced the headers and it went away.
     
  7. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    I would just about lay money down that it is a broken flexplate. They crack around the bolt circle and also between the 6 large holes. I have had a broken one in the past which only made noise at idle but never any other time.
     
  8. BorregoK5

    BorregoK5 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    So looking under the inspection plate, the flexplate has a wobble to it at idle. I assume you pulled yours before it broke and found it cracked. Any idea why it cracked?
     
  9. BorregoK5

    BorregoK5 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    You nailed it! I finally got it rotated to a spot that the flashlight could find it and sure enough, cracked accross the bolt holes (explaines the wobble I noticed this morning). Off to go get another one. I've never had one break before, do the more expensive flexplates help combat this or are there other things I should be looking for?
     
  10. Beast388

    Beast388 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    Whew! /forums/images/graemlins/rotfl.gif At least it isn't internal. /forums/images/graemlins/thumb.gif
    SFI approved flexplates are thicker and less prone to cracking. I would suggest getting one, especially with that healthy 415! /forums/images/graemlins/thumb.gif
     
  11. BorregoK5

    BorregoK5 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    Man, youre telling me. I spent quite a bit of time on that 415 and just couldn't imagine something going wrong internally. I'm especially dependent on the 415 now because its casting number designates it as being built between 1970-73 so when I get the new chassis registered, I'll be smog exempt.

    I though I bought a TCI SFI aproved flexplate which was 0.035" thicker than stock already, matched my TCI low stall converter. Maybe some previous stress from my bell housing explosion caused this and it took this long to develop. I can't exactly cork my 415 up any more than it is.. detuned ignition, stock small valve heads, stock intake, stock q-jet, stock exhaust manifolds and a 2 into 1 exhaust with 2" single pipe out!!! I've got headers, holley dual plane intake and a new set of heads dying to go on!
     
  12. Beast388

    Beast388 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    Do I see a "super-thick" flexplate for Chevy engines being added to the Echobit product line? /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/thumb.gif
     
  13. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    There are cheap thicker SFI approved flexplates available and then there are also more expensive real thick SFI flexplates available. The most common reason for them to crack is from somewhere in the past the tranny bolts coming loose and allowing the engine and tranny to seperate and stress the flexplate.
     
  14. scrappyk5

    scrappyk5 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    jeez , LOL. too bad i didnt read this sooner . thats how
    my flexplate sounded when it cracked. anyways i have been
    messing with mine since. i think mine cracked becouse the
    nub of the converter was bottoming out in the crank hole
    before the converter lugs would make contact with the flexplate. so , when i would tighten the three bolts , it would slightly distort the flexplate and soon after driving
    for a while it would crack the flexplate. i am not sure if
    that is your problem , but mismatched engine/tranny/flexplate/torque converter , caused me to
    research to get the right things to make things operate without breaking.
     
  15. 1972Blazer

    1972Blazer 1/2 ton status

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    Nice thing about the real thick weighted flexplates is they tend to generate more lowend inertia/torque, which is great for rock crawling. Jegs has the the JW Perfomance(ultra bell) 4 lbs heavier flexplate for $175.99. The only problem is that a 400 small block is externally balanced unless you had a machine shop internally balance it, so make sure you get the correct 168 tooth flexplate. Insure that you get one that has the dual bolt patterns for the torque converter, this has been a nightmare before at the end of an installation. If I was there I would give you a hand swaping it real fast.
     
  16. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: A new noise developed in my oil pan - care to help diagnose it?

    [ QUOTE ]
    You nailed it! I finally got it rotated to a spot that the flashlight could find it and sure enough, cracked accross the bolt holes (explaines the wobble I noticed this morning). Off to go get another one. I've never had one break before, do the more expensive flexplates help combat this or are there other things I should be looking for?

    [/ QUOTE ]


    Around these parts, Scott (4x4HIGH) is like E.F. Hutton.........when he talks WE listen!!!! /forums/images/graemlins/thumb.gif
     

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