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Discussion Starter #1
2000 Mercury Cougar 5spd with a 3.0l Duratec from an 04 Sable. Engine was fully torn down and inspected before install.

It had low compression that was fixed, and did a competition valve job while apart. Has your standard bolt-on I/H/E and the trans has an M-Factory LSD, Spec stage 3 clutch with SVT Contour flywheel. Injectors are 24lb from the SVT Cobra.


What I’ve done to chase down the noise:

  • Replaced all hydraulic lifters on right (firewall) side (no improvement)
  • Replaced 2 rockers, rearranged the remaining lifters to see if noise moved (didn’t notice) on right side
  • Replaced lifters on left side (no difference)
  • Did TSB on 3.0 Duratec exhaust cam chatter. From what I could tell this is done to the left side, tho my cam layout seemed different. Didn’t seem to fix the issue.
  • Tried running a heavier oil (10w40) and running cleaners through in case it’s a clogged oil galley.

I’m literally out of ideas as far as driveway mechanic skills go. I’ve had the top of the engine apart 3 times now and nothing seems out of ordinary or wearing poorly. Has plenty of oil, and the car runs great otherwise and goes like a bat out of hell when you’re in 3rd and in that range.

My only idea is that it’s either something internally I’ll never see w/out a full tear down (timing chain or guide), exhaust leak, or maybe even the tune is causing something with timing.
 

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Take the serp belt off and run it like that for a few minutes to eliminate anything belt related.

Run it with the intake upstream of the MAF removed and listen at the MAF to see what the sound coming out of the intake sounds like. This might help determine if its an internal or an external issue.
 

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I don't believe that is spark knock, especially since you are not under load when the hood is open. If you are positive there is no exhaust manifold leaks then look internal.

Is it getting steadily louder over time? It is possible that a rod bearing is the issue. I would look for metal in the oil next time it is changed. Sometimes you can trace it to one cylinder by holding engine RPM at a steady rate, then disconnect spark plug wires at the coil and see if the noise gets quieter.
 

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Discussion Starter #6
It's been consistent at 3k and that quick noise you hear at startup. It's started to seemingly creep into the high 2,000's from what I can tell. The engine only has about 2k miles on it since the build, and has had the sound almost since the beginning.
 

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I have no idea how you would troubleshoot that without an engine disassembly, but my money is on something piston-related. Drive it till it blows, and start again.
 

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Just as I thought the rod bearings were bad. Either way the bearing didn't have the correct crush based on the wear patterns. Is it possible they put the rod bearings in the wrong way, because the tab part is broken.

Time for new rods. Follow the directions exactly when putting an engine together.
 

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I think I have some stock 3.0 rods (still attached to pistons) in my basement if you want them. I told Tim the same thing on Facebook.
 
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