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Need help diagnosing engine prob (long)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mofugly13, Jun 20, 2003.

  1. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    I posted this in the Garage also. But I need to fix this quick as this is my daily driver and now I'm afraid to drive it except to and from work. This problem is cutting into my summertime weekend roadtrips!

    I have a "clacking" noise coming from under my blazer. It changes with motor rpm. When I crawled under to check it out the noise sounded like it was coming from the flexplate. I inspected the flexplate al the way around with a strong light and can see NO cracks. I just had the tranny rebuilt and a new flexplate installed 7 months ago. It is still under warranty so I took it to the tranny shop. As soon as I drive in the guy says "sounds like your flexplate." They kept it for a day and did numerous test drives to try and diagnose the noise. The guy tells me he cant see that its anything wrong with the flexplate, but drive it until it gets worse and bring it back and he'll check again. So now I think it's something internal to the engine. I made sure all the rocker arms were tight. Stuck lifter? Collapsed lifter? I've heard of this but do not know the symptoms. It started quietly about a month ago, but now it's gotten pretty loud.

    Here are the symptoms.
    1. "clacking noise that sounds like a cracked flexplate
    2. does not make noise on startup, but as blazer comes up to temperature, the noise gets louder.
    3. noise goes away when I accelerate, and when I decelerate (coasting w/ my foot off the gas)
    4. noise is loud when I get up around 50mph and am giving it just enough gas to maintain speed
    5. at idle it only makes noise in 'ParkP and 'Neutral.

    So it makes the loudest noise when there is little to no load on the engine, or when engine braking. So my questions are:
    1. What is the most likely causeof this noise (besides the flexplate)?
    2. What do I have to do to fix it.

    If it turns out that it is something internal to the engine then I just want to quick fix it so it lasts long enough for me to save for a GM crate 350.

    A little background on the engine:

    According to the PO it's a rebuilt 327 with 8,000 miles on it. But he said the same thing 'bout the tranny and that took a $hit two weeks after I bought it. The oil dipstick the PO had on it was way longer than stock, it practically was laying in the bottom of the pan. Which, now that I think of it 's a pretty sweet mod 'cause then you're NEVER low on oil. The first time I drained it I think about a quart and a half came out. The valve stem seals were shot and I changed those. While readjusting the valves I find that my #7 intake lifter is collapsed. When this noise first started I dropped the pan to take a look and change the oil pump. When I had the pan off I decided to check out a rod bearing and the bearings were worn down to the copper; the journals had grooves in them resembling the edge of a dime. So it's definitely had oil starvation problems before.

    To those who try to help me, Thank You. /forums/images/graemlins/thumb.gif
    /forums/images/graemlins/usaflag.gif
     
  2. imiceman44

    imiceman44 1 ton status

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    OK so you say that the bearings were shot, did you take care of that problem?
    Did you just slap some newer bearings on the bad crank and go?
    The only other thing I can think of other than the flexplate is the bearings, or the wrist pin on the pistons.
    But my first guess would still be the flexplate, exactly the symptoms you describe.
    You can not see it if you try and check it while the tranny is on, it usually cracks right around the bolts on the crank.
    I actually changed a tranny and didn't see it cracked and drove it for a few more weeks with the noise until it broke off completely and then I found the problem.
    As for the tranny shop, I would go back to them and ask them to take the tranny off and check it and also check the tabs on the tranny pump, that hapened to me too before. they broke off and the would still engage on the edges but most of the time they would skip and make the same noise.
    I definitely wouldn't want to have my tranny worked on at that place you mentionned, this is not good customer care. /forums/images/graemlins/thinking.gif
     
  3. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    Thanks for the reply. The tranny shop I took it to is very reputable. He spent a good 3 hours trying to diagnose my prob. The flexplate is NOT covered under the warranty on the rebuilt tranny. He didn't charge me a thing for looking at my truck, and he could have been making money for that three hours instead of farting with my truck.
    Anyway, I sure hope your right about it being the flexplate. I unbolted the flexplate from the TC and was able to move the TC about 3/16 toward the tranny which gave me a little better access to the flexplate for visual inspection. I turned the flexplate 3-4 complete turns and used a STRONG flashlight to look for cracks all around the crankshaft bolts...nothing. If it is a crack I cant see, It's hard to imagine such a small crack making such a loud noise. The tranny shop said he'd fix it for whatever he pays his guys; ~$30/hr + the cost of a new flexplate, but he doesn't wanna make me spend the money unless it's the flexplate for sure.

    Oh, and yes, I did slap some brand new rod bearings in there on the chunged up crankshaft. Prolly shoulda checked my mains too...
     
  4. rampage

    rampage 1/2 ton status

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    Care to give the name of this shop? In return I could give you the name of someone NOT to go to /forums/images/graemlins/tongue.gif
     
  5. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    Powell Hydramatic.
    I got many recommendations for this shop, it was pricey tho.
    Hope it's not the shp yer talkin' about.
     
  6. rampage

    rampage 1/2 ton status

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    Nope, E&R Transmission on San Bruno Ave. (don't even consider going there! /forums/images/graemlins/angryfire.gif)
    I'll have to check out Powell for my next tranny needs. /forums/images/graemlins/thumb.gif
     
  7. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    They're on S Van Ness in the City. Cost me $1600 though. OUCH. They did throw in a free flexplate. WhoooHooo! They do the trannys for all the city owned vehicles.
     

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