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I own a 1999 Mercury Cougar, running the 2.5L Duratech DOHC V6. I was recently out with a friend drifting (not the smartest idea, especially since my engine was already running rough), and while drifting my engine knocked. However, this was not surprising, but the surprising part was how loud the knock was. I've never had it knock this badly before. Ever since this night it has been ticking. The ticking sounds like a card being run through bicycle spokes. It's steady at idle, gets worse as I accelerate, and the severity of the tick increases or decreases depending on how much throttle I give it. Anyone know any possible reasons as to why this could be happening?

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    Was the oil level low - did you check? How does the tick relate to engine speed - same (crank rod issue) half speed then cam... – Solar Mike Aug 1 '18 at 5:50
  • Can you take a video, upload to youtube and then post it here? – Captain Kenpachi Aug 1 '18 at 7:11
  • And what do you mean by "knock"? Do you mean pre-detonation, or something else? – Captain Kenpachi Aug 1 '18 at 7:13
  • The oil level was a bit low, and I added some and have kept it at the right level since. As far as a video goes, I can give it a shot. And as far as the knock goes, I am uncertain as to whether or not it is pre-detonation. It only knocks under certain conditions (i.e. when I shift gears too early and give it too much gas, if I'm at a stop and getting going in first and give it too much clutch, etc.). The knock is not constant. Also, as far as how the tick relates to the engine speed, I am uncertain. When the oil cap is removed there is a rod or shaft that is visible, it ticks once per rotation – CarGeekWannabe Aug 1 '18 at 11:19
  • Pre-detonation sounds like a marble rattling in the engine. – Captain Kenpachi Aug 1 '18 at 11:44
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It is almost impossible to tell you exactly what it is, but from what you're describing I am going to suggest it is a valve making the noise.

  • I am wondering if you are a mechanic? It is not because I am trying to be rude, but it would help me trust this advice a bit more if you were a mechanic or have experience working with vehicles – CarGeekWannabe Aug 1 '18 at 11:21
  • I am a software developer who does EFI tuning of Mitsubishi and Subaru turbo vehicles as a side-hustle. So no, I am not a mechanic. – Captain Kenpachi Aug 1 '18 at 11:39
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I'm going to describe what the worst case is: the bottom end of your engine is ruined. However, I cannot tell based on limited information if this is really the problem.

The worst case is that the engine was low on oil (as you described), and hard cornering caused the oil to slosh to one side of the oil pan, thus leaving the oil pump with not enough oil. The compromised lubrication has caused damage to the engine internals. The momentary "not enough oil" event could have caused the rather loud knock that you described wasn't permanent.

In particular, the "tick" you are stuck with now could be piston slap. This happens if the pistons and/or cylinder walls have worn. The best fix is replacing the short block, i.e. the cylinder block, pistons, crankshaft etc. An alternative could be to replace the entire engine with a used part.

It could also be rod knock. This is even more fatal than piston slap which is more of an annoyance, but I wouldn't exactly describe it as ticking. You can fix this too with a new short block or a used engine that doesn't have the issue.

On a 19-year old vehicle, you probably either have to choose a used engine as the replacement, or scrap the car if you hate the ticking sound. An alternative is to learn to tolerate the sound and drive the car until it ultimately fails. With piston slap, it can last a surprisingly long amount of time.

And before you ask, I'm not a mechanic so don't trust this advice unless it gets plenty of upvotes... In particular, I would like the more experienced users to give information whether rod knock or piston slap is the most likely result if lubrication fails. I only have experience with piston slap (and occasionally hearing some other car engines with different sound that I identified as rod knock), and that piston slap was the result of a design fault in an engine, not being low on oil.

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