Rod knock?
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Senior User
Joined: Apr 2016
Posts: 197
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From: Atlanta
Rod knock?
Engine is making a knocking noise when cold, most pronounced under load at around 1500 RPMs. Can't really hear it at idle, and not as loud under light or no load. Knock slowly diminishes as it warms up, and is gone after 5-10 minutes. Does this sound like it could be rod knock, or something else? It sounds too low/solid to be lifters, and I would think piston slap would go away faster than that.... but I could be wrong on both counts.
For background, van is 2006 5.4L with 72,000 miles. Seems early for this kind of failure.
For background, van is 2006 5.4L with 72,000 miles. Seems early for this kind of failure.
Fleet Mechanic
Joined: Aug 2004
Posts: 1,276
Likes: 7
From: NE Tennessee
What weight oil are you using? Being colder if your using a thicker weight it may be taking a bit to thin out. Even 10w-40 is like molassas when it gets cold. I have a '99 express and it knocks a little on cold mornings. I always let it get warmed up for a couple minutes before taking off. It has 150k on it though.
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Senior User
Joined: Apr 2016
Posts: 197
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From: Atlanta
Just an update... still driving the van daily, have put several more thousand miles on it. Knock is progressively getting longer before going away with warmup. Once it's warm it's fine. Switched to 5w30 (from the specified 5w20) and it's not as loud but still there for same amount of time.
Next update will be when it grenades.
Next update will be when it grenades.
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Senior User
Joined: Apr 2016
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From: Atlanta
So kind of a crazy follow up.... the knocking had gotten progressively worse over the last several months. Not any louder, but lasted longer after startup and warmup. I was just biding time anticipating the eventual failure.
My alternator failed on the way home last weekend (see other post), and I replaced with a rebuilt unit. I've noticed over the last few days that the knock is gone at startup and I only hear a little high pitch valve clatter for a minute or two. The noise was the alternator? I never would have even thought it as a consideration.
One other problem that went away with the alternator change was problem with high idle. Over the last two weeks or so the engine would idle at around 950rpm instead of the normal ~600rpm. I assumed that was a vacuum leak and was not looking forward to tracking it down. That also went away with the alternator change.
Three for one! Woo-hoo!
My alternator failed on the way home last weekend (see other post), and I replaced with a rebuilt unit. I've noticed over the last few days that the knock is gone at startup and I only hear a little high pitch valve clatter for a minute or two. The noise was the alternator? I never would have even thought it as a consideration.
One other problem that went away with the alternator change was problem with high idle. Over the last two weeks or so the engine would idle at around 950rpm instead of the normal ~600rpm. I assumed that was a vacuum leak and was not looking forward to tracking it down. That also went away with the alternator change.
Three for one! Woo-hoo!
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Senior User
Joined: Apr 2016
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From: Atlanta
I'm running Motorcraft 5w30, which I think is okay considering how hot it gets here in the summer and having some miles on it.
Lead Driver
Joined: May 2004
Posts: 5,040
Likes: 137
From: Maryville
Well 5W is thinner than 10W, they claim it's due to oil passages but I know better, it's to increase the MPG by decreasing load, they aren't concerned with it lasting, they want to sell more.
Tuned
Joined: Mar 2010
Posts: 425
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From: Fayetteville, TN
Not a 5.4L, but my uncle has a Mercury Grand Marquis and a Ford F150 both with a 4.6L. He bought them brand new and has been using Rotella 15w40 since their first oil changes. He buys it by the 55 gallon drum and runs it in everything he owns. The Grand Marquis has almost 200k miles and the F150 has over 200k miles and they both run great with zero engine issues. My uncle worked for GE for many years helping to design and make high speed electric motors. He said he spoke to a lubrication engineer and he told him the thinner oils is for better MPG and less emissions and using the 15w40 would not hurt the engine. He's 84 years old and still does his own oil changes.
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