Bad Main Bearing??
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Joined: Jan 2003
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From: Lacey USA
Bad Main Bearing??
Hey all. Ive got a 1988 F-250 with the 351 EFI. There is an ominous tapping under the hood when Im on the throttle. It only seems to happen when the truck is on the road, i.e. when its in neutral, I can rev it all day the the tapping isnt there. Also it goes away when I coast in gear. All I know points to a bad main bearing but it doesnt sound right for that. Any Ideas?
Thanks all
EJ
Thanks all
EJ
Posting Guru
Joined: Mar 2003
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From: Cloud USA
Bad Main Bearing??
It may be a cracked exhaust manifold, I had a 87 with a 302, sounded like it was a bad lifter but it was the manifold. A rod or main you would here more when the engine isnt under load. Harmonics are worse with no load on the engine. Just a thought.
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Joined: Mar 2002
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From: Charter Oak, Iowa
Bad Main Bearing??
Crossman is pretty close by your description. Bad bearings tend to be quiet when loaded and rattle when unloaded. Also check any breaks in your EGR piping. Manifolds would be the first thing to check tho.
Randy
Randy
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From: Lacey USA
Bad Main Bearing??
C_rossman and PigFarmer. I took another close listen and the manifold noise and the tap are two distinct noises. The tap starts when the truck warms up a little and goes away when its not under load. The good news, maybe, is I dumped a can of Engine Restore oil additive in figuring it cant hurt, and the noise pretty much is gone..... We will see in a few thousand miles 
Any more thoughts? If not, thanks for the info.
Any more thoughts? If not, thanks for the info.
Posting Guru
Joined: Mar 2003
Posts: 1,349
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From: Cloud USA
Bad Main Bearing??
I have used a quart of Tranny fluid 500 miles before I changed it to cure a sticky lifter. Tranny fluid has a lot of detergents, maybe it does more harm than good but it worked on my Taurus.
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Joined: Sep 2002
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From: US
Bad Main Bearing??
If your interesed in the exhaust manifolds, i have a set off my 94 they have the dual air injection conections. Im shore you could plug them
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From: Lacey USA
Bad Main Bearing??
C_rossman - thanks for the help
Tsheriff - Money mandates that I pass on that for now, the issue isnt exaclty pressing. Thanks though
Tsheriff - Money mandates that I pass on that for now, the issue isnt exaclty pressing. Thanks though
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