2012 GT, LOUD knocking/tapping from top of engine

Discussion in '2011+ Mustang GT 5.0L Tech' started by infinitenexus, Nov 25, 2020.

  1. infinitenexus

    infinitenexus Junior Member

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    I had the faint ticking sound for a short bit, not loud at all but the common sound that so many people seem to get. Just recently it started making more of a "tapping" noise from the engine once it warmed up, loudest around 2500RPM. I only drove it a few short trips once it started making this noise. Last time I drove it everything was fine, then right as I was coming home it suddenly got louder. I pulled into my driveway (which is steep) and as I was balancing the gas/clutch to slowly go up the hill I stalled out like a bozo. Well, it wouldn't turn back on, because the battery was dead for some reason. So I charged the battery and cautiously tried turning the engine on. It started right up but it has a very loud knocking noise that sounds like it's coming from the drivers side top of the engine. I haven't pulled anything apart yet because I wanted to see if anyone else had any experience with this noise. I have been told by some car guys that it doesn't sound like a rod knock, that it sounds like valvetrain noise or the piston hitting something. The car is a 2012 GT, always well maintained, usually driven easily, oil changed on time, 69.5K miles. Only mods are an exhaust and X pipe.

    Here's a short video of the sound.
     
  2. jewc75

    jewc75 forum member

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    I damn sure wouldn't let it run like that. Pull a valve cover and look for broken stuff and drain the oil and look for metal. Id start with the valve cover.
     
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  3. infinitenexus

    infinitenexus Junior Member

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    That's our next step. We removed the serpentine belt and started it really quickly just to rule out broken accessories. Obviously it still tapped, so we're putting the belt back on now and we're going to pull off the driver's side valve cover.
     
  4. jewc75

    jewc75 forum member

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    The more you run it the more damage is happening.
     
  5. eighty6gt

    eighty6gt forum member

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    oof
    junkyard motor
     
  6. infinitenexus

    infinitenexus Junior Member

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    Totally understand that. I'm just trying to figure out what's wrong with this engine. So far I can't pin it down. I'm trying to avoid having to completely tear it apart, because I simply can't afford that. A junkyard engine might be the direction I have to go.

    Has anyone heard a sound like this before? Any ideas as to what it might be? I know these engines are known for all the various noises they make but this sounds like metal striking metal.
     
    Last edited by a moderator: Nov 25, 2020
  7. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

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    that's some serious knock, to me it sounds like rod knock, very similar to what I heard when I lost the motor in my Shelby
     
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  8. infinitenexus

    infinitenexus Junior Member

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    I've never personally heard rod knock before, but my dad also said it sounds like rod knock. I posted the video on grassroots motorsports and they said it sounds more like a valvetrain issue. I dunno. We pulled the driver's side valve cover off, since it sounds like the noise is coming from that side. We saw no evidence of damage there, no bits of metal or anything, the cams looked perfect (to the naked eye at least) I want to take a quick video of the engine turning over a few times with the valve cover off so I can see if the sound lines up with the cams, since they turn at a different speed than the crank. Tomorrow our plan is to do that, and to drop the oil pan and check the bottom end of the rods. Fingers crossed it something I can fix without having to tear it all apart.
     
  9. ford20

    ford20 forum member

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    That's what my car sounded like when I had rod knock. It started off very faint for a bit and then it just increased in sound. I would drain the oil and see what kind of metal you have in there. It is a bit easier than pulling the valve cover.
     
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  10. jewc75

    jewc75 forum member

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    Who is this ghost?
     
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  11. infinitenexus

    infinitenexus Junior Member

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    I was actually surprised at what a pain in the rear removing the valve cover was. Hopefully tomorrow we can drop the pan and figure something out.
     
  12. eighty6gt

    eighty6gt forum member

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    why not just remove engine
     
  13. Steve Burry

    Steve Burry Junior Member

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    Sorry to hear about your problem. Unfortunately, it sounds exactly like the problem we had last year. Different platform - '07 GT/CS convert auto, 4.6L 3V, 113K miles, 2nd owner 4 years now, occasional driver. Started out as yours - soft tick, mostly noticeable when letting off the throttle. Evolved into a louder tap around 1,800 rpm with no load. Then, a fairly loud clatter similar to yours at any rpm. Tried to trace the source - valve train problem? cracked flex plate? rod bearing??? Seemed to be on left side but couldn't isolate it. Decided to do a piston "bump-down" test. Removed the spark plugs (be careful - they twist off easily in some engines - had 2 twist off. You don't want to learn how to remove these if you don't have to.) Anyhow, started around the engine by rolling it over by hand until the crank was pulling the piston down in the cylinder. Used a sleeve from the spark plug removal tool to guide a socket extension down onto the piston, set a dial indicator on top of the extension, and added a short extension to tap on. Tapped on the top extension to see if the piston would move down in the cylinder. All were about 0.001" except for #6 (2nd back left side). It dropped 0.030"! Repeated the test several times. That was a clear indicator that the bearing had spun. Pulled the engine. All the rod bearings were in similar condition, just waiting their turn. Even found the rods weren't all the same. Someone had patched the engine before we got it. Other damage was so extensive (cam journals in right head were scoured so bad the head was junk) I decided to buy a remanufactured engine from Powertrain. Easy to work with. Engine runs smooth and quiet. Into the second oil change with no problems. So, long story short, I know how it feels to hope you haven't spun a rod bearing. Try the "bump-down" test to see if there's play in the bearings. Don't pound on the tool you use - just enough to move the piston if it's loose. It will actually sound different if the bearing is spun - kind of a thud instead of a metallic ping. Good luck.
     
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