4.2 1997 engine knock
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4.2 1997 engine knock
I have a 1997 F150, 4.2, with 200,000 miles, with an engine knock. I just recently replaced the top and bottom intake manifold gaskets, and found the old gaskets were shot. Water was entering cyclinder as evidenced by oil and spark plugs. The knock was there before this repair, and after reading of the potential to ruin the engine, I did the intake gasket repair job. The knock is still there. When engine is cold, knock is not noticable. After a few minutes of warming up, knock is noticable. Sounds like only one cylinder. But, if I increase engine speed, knock goes away. If engine speed drops back down to idle, knock comes back. I've listened, but can't tell if coming from upper or lower engine, but it is coming from right / passenger side.
This is a "farm truck", just used for occasional chores around the property and country roads.
I am hoping that because the knocking sound is only at low RPM's, and disappears at higher RPM's, that this will narrow down the list of probable causes. Any help or advice appreciated.
This is a "farm truck", just used for occasional chores around the property and country roads.
I am hoping that because the knocking sound is only at low RPM's, and disappears at higher RPM's, that this will narrow down the list of probable causes. Any help or advice appreciated.
Lead Driver
Joined: Sep 2006
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Sounds like a rod bearing.
As engine speed increases oil pressure increases.
See what changes if you remove an injector plug so the bearing has no combustion pressure applied.
Trying heavey oil like #40 quits it down or nearly so it's a bearing.
Good luck.
As engine speed increases oil pressure increases.
See what changes if you remove an injector plug so the bearing has no combustion pressure applied.
Trying heavey oil like #40 quits it down or nearly so it's a bearing.
Good luck.
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follow up questions
Bluegrass - thanks for info. A few follow up questions
1. Are you suggesting that instead of 10/30 oil, I try 10/14 oil... or are you saying straight 40 wt oil, or? What about 20/50?
2. Do you know if you can pull the oil pan and get to the rod bearings with engine in truck?
3. Should I also consider replacing oil pump,which I think is accesible as the oil filter attaches to it?
1. Are you suggesting that instead of 10/30 oil, I try 10/14 oil... or are you saying straight 40 wt oil, or? What about 20/50?
2. Do you know if you can pull the oil pan and get to the rod bearings with engine in truck?
3. Should I also consider replacing oil pump,which I think is accesible as the oil filter attaches to it?
Lead Driver
Joined: Sep 2006
Posts: 7,907
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The increase in oil viscosity is to see if the knock subsides as a decision for you to remove the pan for rod bearing check if you want to go further in repair.
If you put substantial loads on the truck, then bearing noise should show up more, so notice that as well.
If you go that far, a bearing could have been wiped from lack of oil, water in the oil etc.
Be sure to mike the bearing surface for being out of round and look at any scoring.
If that is evident, a new bearing won't last as long as you may need it to.
To remove the pan, you may have to drain the coolant, disconnect the hoses and motor mount points so the motor can be raised enough to ge the pan out.
Depends on you model and year.
Good luck.
If you put substantial loads on the truck, then bearing noise should show up more, so notice that as well.
If you go that far, a bearing could have been wiped from lack of oil, water in the oil etc.
Be sure to mike the bearing surface for being out of round and look at any scoring.
If that is evident, a new bearing won't last as long as you may need it to.
To remove the pan, you may have to drain the coolant, disconnect the hoses and motor mount points so the motor can be raised enough to ge the pan out.
Depends on you model and year.
Good luck.
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