1998 Ford F-150 Nocking noise under truck_

Tiny
JANAGEORGE
  • MEMBER
  • 1998 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 12,400 MILES
I drive the truck for about 15 minutes. As soon as the engine gets warmed up, I start hearing a knocking noise under the truck. As first I thought it was a rod knocking, but it only does it after the truck is warmed up and sounds more like a part that has come loose and is banging the underneath of the truck. I have gotten under the the truck when it's in park and warmed up and the noise sounds like it's coming from the oil pan, or there about. I went to a muffler shop and they said all the exhaust and muffler, etc. Is intact and the catalic converter seems to be okay too. Do you know what this could possibly be? Is it a rod knocking and it seems to be under the vehicle and really isn't? Thanks for you help. I'm afraid to drive it for rear it is the engine.
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Tuesday, April 21st, 2009 AT 4:08 PM

10 Replies

Tiny
RACEFAN966
  • EXPERT
Does this do it all time once it is warmed up? How is the oil pressure when it starts the knocking noise? Get back to me so I can help. Thanks.
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Wednesday, April 22nd, 2009 AT 10:45 AM
Tiny
JANAGEORGE
  • MEMBER
As soon as the truck warms up, the noise starts. It makes the noise about 95% of the time while the truck is running, but at times, when sitting at a light or something the noise will suside, until you start moving again.

The oil pressure needle doesn't work, but I have plenty of oil, as I check is constantly, so i'm not sure what the oil pressure reading is.
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Wednesday, April 22nd, 2009 AT 1:14 PM
Tiny
RACEFAN966
  • EXPERT
You may have plenty of oil and it may be full but that don't mean you have oil pressure. You need to find out what the oil pressure is weather it be hook up a guage or make your guage work. Also have you taken a long screw driver and held it against the oil pan and put the other end to your ear and listened to the engine? Let me know what you can.
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Thursday, April 23rd, 2009 AT 10:19 AM
Tiny
JANAGEORGE
  • MEMBER
I will go and buy an oil pressure gauge and attempt to check the pressure.

And, I will put the screw driver up to the oil pan and put the other end to my ear and listen to the engine, although I'm not sure what I'm listening for. I'll report back when I've done that, which may be a day or two.

Thanks.
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Thursday, April 23rd, 2009 AT 1:50 PM
Tiny
RACEFAN966
  • EXPERT
What you are doing is listening to see if you hear the noise coming from there. If you listen and hear only whishing noises and such then the noise is coming from somewhere else. You can also buy an automotive stethiscope if that will help to better listen. If you do not hear the noise coming from there then move to the middle of the engine and then the top side. If all that sounds ok with no loud noise then go to the transmission and listen there. It is kinda like when a doctor listens to you heart it helps them to better hear the sounds it makes right. Let me know what you find and we will go from there.
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Friday, April 24th, 2009 AT 10:22 AM
Tiny
DROBB0151
  • MEMBER
Just wanna throw this out there, check your torque converter and make sure the bolts are tight, bought a car that had that problem years ago. Good Luck!
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Friday, April 24th, 2009 AT 10:26 AM
Tiny
JANAGEORGE
  • MEMBER
I had a friend of mine get underneath the truck with a tree branch. He said the same thing. It works as a stethoscope. He said the nosie sounds like transmission or the torque convertor, but was hard to tell which without raising the truck up. I'll have it raised and we'll check the bolts. Hopefully that's the problem. Would sure be nice if it was! I'll let you know the findings. Have a great weekend!
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Friday, April 24th, 2009 AT 11:36 AM
Tiny
RACEFAN966
  • EXPERT
OK sounds great. If all is tight at the converter then I would check end play on the crank too. Let me know what you find.
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Saturday, April 25th, 2009 AT 8:33 AM
Tiny
JANAGEORGE
  • MEMBER
Sorry I haven't been able to get back with you, but I finally took my truck to a mechanic and he said the noise definately was the convertor. I took it back to the muffer shop and it was making the noise when I got there, so he did find that it was the convertor afterall. I had it replaced and it's quiet as a mouse now. Thanks for all your help!
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Tuesday, May 5th, 2009 AT 1:12 PM
Tiny
DROBB0151
  • MEMBER
Congrats!
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Tuesday, May 5th, 2009 AT 3:35 PM

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