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Is something wrong with my flexplate?

Discussion in 'The Garage' started by JHG, Aug 19, 2004.

  1. JHG

    JHG 1/2 ton status

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    Ok, this is not /forums/images/graemlins/k5.gif related, but my K5 is resting so now I am thinking about another car /forums/images/graemlins/smile.gif

    I have an 86 TA with 305 HO Crate engine (with rollers etc, cant understand why they bought 305 but not 350 but thats another story).

    When I bought this car in 1998 I heard a strange sound (klonk klonk) right after I started it up (cold) but it did go away in few seconds. If I start it and the engine is hot then you cant here any noise.

    First I was worried but after when it did not increase, and nothing happened I stopped to think about it. Finally I decided it must be a piston slap.

    Few days ago a friend told me he thought the flexplate was not like it should be. If its so I would think this sound would alwais be when the engine is running but not only right after startup.

    Other than that the engine works very well (but will be replaced when my 406 is ready /forums/images/graemlins/woot.gif ).

    So to sum it up, the sound is only when I start the engine and its cold, disapeares in few seconds, and does not exists if I start the engine Hot.

    Thanks, Jon H.
     
  2. Thunder

    Thunder 3/4 ton status

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    A cracked/bad flex plate will make a clicking sound when accelerating. Usually wont make noise at startup.
    Noise at cold start up is usually lifters. Could also be piston slap or a rod.
     
  3. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    my flex plate made a ba noise one start up, not so much anyother time. it was cracked through all the bolt holes.

    my friends motor did the same thing, bad noise on start up. when we pulled the motor the flex plate stayed with the converter /forums/images/graemlins/eek.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    The symptoms you describe sound like "dry knock"--that is,a main or rod bearing that is slightly loose and has no oil under enough pressure to quiet it until it starts up,then the oil fills in the space between the loose parts and prevents a knock.Fords do this a lot,and changing the oil filter to one with an anti-drainback valve helps stop it on fords(because the filter is mounted horizontally and oil can drain back into the crankcase),this makes the bearings loud until the filter fills up and oil pressure is restored.I think your filter is vertically mounted,so no check valve is nessasary.I've had many engines that did this only after sitting overnight,and the oil drains off all the bearings--the reason it doent do it after its warmed up is the crank expands a little,just enough to "tighten" it up a litte,when it cools off enough it does it again.Some motors go for years with this noise,some dealers even claim its normal.Crysler "K" cars were notorious for this noise also,they built the motors kinda "loose" and used high oil pressure to quiet them.I remember a lot of engine failures in those cars due to a cheap oil filter blowing its seams when it couldnt handle the high oil pressure upon a cold start,and the oil would pump out into the ground,and well--you know what happenned then!.If it only does it for a few seconds only when cold,I wouldnt loose too much sleep over it,just dont race the engine when it first starts cold,let it run at fast idle for a moment or two.Changing oil to a lighter grade might help quiet the noise because it will flow faster upon startup,but may also encourage a loose bearing to fail when it gets up to temparature,I noticed a ford my friend had did this worse with 20w50 than it did with 10w30,but he also had 10 lbs less oil pressure when it got warmed up--I think the thicker oil and a warm up period is better off in the long run,loose bearings need the "cushion" heavier oil provides.But again,I drove a buick nailhead for two years and 30,000 miles with the same noise and it was no worse when I sold it!.I think your flexplate would make noise most all the time if it were cracked,warm or cold. /forums/images/graemlins/crazy.gif
     
  5. tomseviltwin

    tomseviltwin 1/2 ton status

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    You'll know for sure if you pull off the tranny inspection cover and look for grooves on it where the converter bolts are hitting it. Sounds like a flexplate to me and no they don't all make noise at the same time. At least you could rule this out.
     
  6. JHG

    JHG 1/2 ton status

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    Thanks all, I will check the flexplate, and if thats seems OK then I will stop worry about it
     

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