Truck is a 97 F150 4.2 V6 169XXXX miles Auto Trans. When truck is idleing in gear (drive or reverse) it makes a knocking sound. When put into park it does not knock and even reving the engine in park it sounds like a strong motor. I can slightly hear the knock under light acceleration when driving but it either goes away or is drowned out by the sound of the truck. Got under truck with a stethoscope and the noise is definitely coming from the oil pan area. I run 10W40 oil because of the high miles and it does not burn or leak oil or coolant. I have had the truck for about a year and it has done it pretty much ever since I've had it. When I first got it the oil pressure gauge would bounce like crazy but that problem has not been an issue for months since i ran some seafoam into the oil and I change the oil at about 2800- 3000 miles religiously.

If anyone has an suggestions that would be great since this thing has been driving me crazy ever since I've had. Truck has never broke down or never not started and the only bad thing about it is this knock and the A/c has a small leak somewhere.

Thanks

 

Hey Dude u need to drop the pan and to install new rod and main bearings. A good thing to do is to change the lower intake gaskets they will leak into the cylinders and hydro lock destroying the engine. It happened to me.My old girl is running fine with the new engine in her. Good luck.

 

Yeah I've been afraid that's whats been wrong. Well definitely don't have the time or money for it at the time so prolly just gonna have to keep going like I am. Maybe I can make her last for awhile or sell as is and go back and get another 5.8. Had 238k on my 95 and only ever replaced a water pump.

 

I wouldn't drive that truck another inch until you replace those gaskets. Mine caused a bent rod and cracked the block. Had to buy a new 0-mile engine for $4,000

 

The 97 and 98 4.2's had a lot of issues. Drive it till it blows up, then go find a good used 99+ replacement.

 

i just figured that the truck would knock all the time if there was a problem with the rods or bearings but pop it in neutral or park and the truck sounds fine. you can rev it all day up to 4 or 5k rpm or let it idle and no knock or anything. is it possible the oil pump is bad or maybe my pickup screen is gunked up in the oil pan? might explain my oil gauge bouncing once upon a time.

 

Ford's oil gauges aren't real gauges- they are dummy check lights. If it moves, then there is a serious drop/spike in oil pressure.

I've noticed a *slight* reduction in the knocking of my valves/pushrods after switching from 5W-20 to 5W-30. So there is a possibility it has something to do with the oil.