5.7L engine trouble - opinions needed!

Discussion in 'GM Powertrain' started by hihoslva, Aug 5, 2008.

  1. hihoslva

    hihoslva New Member

    I just recently bought a '99 Suburban with 143k miles. Very clean, runs great but has an engine "tick".

    A few days ago, I noticed the "tick" sounding like drivetrain noise, and audible in the cabin. Unfortunately, it's incredibly hot here in AZ, so I'm not sure if the noise has always been there because it is drowned out by the AC fan going full-blast all the time.

    I shut the fan off briefly and heard the ticking while accelerating. I've also done a recent oil change to full-synthetic.

    My mechanic is calling it a "death knock", and believes the engine is on its way out. Full diagnosis would require an expensive tear-down of course, so he's recommending replacement at a cost of $2500-$4000 (depending on used or new engine). He also states that it's possible the little car lot I bought the truck from had doped-up the oil to hide the noise and it came about after I changed the oil. But again, I don't know if the noise was there before, or just started recently. The engine had a very typical Chevy 350 "tick" when I bought it, but I don't know about hearing it INSIDE - The AC fan is always going when it's 115 outside......

    However, I've found this tech bulletin on the internet: http://answers.edmunds.com/question...ine-warms-oil-pressure-drops-80-40-18770.aspx

    The symptoms listed are the EXACT that I have. Quote from the bulletin:

    Some customers may comment about a "ticking" sound coming from the
    engine compartment while the vehicle is being driven. This noise may be
    described as similar to valve train noise or detonation, and most
    noticeable when the engine is completely warmed up (hot) and driven
    under load (2nd gear, 30-40 percent TPS, 1800-2500 RPM).


    The cause is an "exhaust pressure wave" according to the article, and there is a test as well as a fix listed. Really simple hose-related stuff. Interested parties can read it in the linked bulletin.

    So what do you guys think? I trust this mechanic, and I can say this: The noise is not pleasant (though not extremely loud in the cabin) and I was in agony over his diagnosis until reading this article. I don't think the guy's a scammer at ALL. Could he be THAT wrong? Has anyone ever dealt with this issue listed in the bulletin and had success?

    Thanks for any/all opinions and replies.
     
    Last edited: Aug 5, 2008
  2. k.daddy1

    k.daddy1 Rockstar 100 Posts

    I bought a suburban that done sort of the same thing. I bought it knowing it had this problem. The previous owner had the transmission rebuilt a year or so earlier. The shop never tightened the transmission bell housing correctly. Anyway the bell housing bolts were loose and caused the flex plate to crack around the bolt hole pattern. It would tick under a load all the time, especially if I'd hold the brake and give it a little gas. Just another tid bit of info.
     
  3. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    If it were me (and I have a little tick as well) I wouldn't rebuild the engine until it was on it's last leg. I use mine as a daily driver and for out of town trips, but usually less that 900 miles at a time. If you are planning a 2500 mile trip then you might want to have it checked out a little more before taking off. I would definitely get a second opinion before dropping that kind of cash.
     
  4. Davandy

    Davandy Moderator 5+ Years ROTM Winner 1000 Posts

    I would check the flex plate first. If there's a crack in the flex plate you hear a ticking sound when you drive. :neutral:
     
  5. collinsperformance

    collinsperformance Epic Member 5+ Years 500 Posts

    run seafoam in the fuel and intake and some in the oil and see if that helps clear it up. i just turned 350,000 miles so you should have more life unless it had a hard life....mike
     
  6. hihoslva

    hihoslva New Member

    Thanks for the replies, fellas.

    I trust this mechanic - even if he's wrong. Because his advice was to dump the vehicle and not bother with the engine swap.

    So that's what I'm going to do.

    I've already bought another '99 (damn these things are everywhere and cheap these days!), and I'm going to sell the problem child.

    The new '99 runs much stronger and even handles better. Had I known a bit more about Suburbans before buying the problematic one, I'd have passed. It's a rattle-trap with vague handling and just doesn't feel that good. The new one has a few more miles, but is a better-running vehicle. It's also in very good cosmetic shape (as was the one with the engine noise).

    Hey - the problem might be minor or serious, but I don't wanna deal with it either way. I know a high-mileage vehicle will eventually need major repair, but I'm not going to stick with a truck that might blow any second. I plan to take the Burb into the mountains for camping, etc., and although any vehicle can break down, I need a sense of confidence in it no matter what. So out with the old, in with the just-as-old-but-runs-better. ;-)

    Thanks again for the replies and advice. All good info!
     

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