rod knock - F150online Forums


rod knock


Old 07-03-2006, 05:00 PM
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rod knock

hi there, this is my first post here so here is my problem. during my devorce my ex-wife had someone empty most of the oil out of my 99 f150 w/ a 5.4 v8 with 82000 miles on it. (it also has a 9" lift and 36" tires)
not knowing this i drove the truck about 12 miles. i started to hear the knocking noise so i stopped at the parts store for some oil. i put in two quarts and it didn't even touch the tip of the dip stick. i filled the rest up with a quart of lucus and 30 weight.
now when i start the truck it will knock if i drive away with out reving it up to 2000 rpm for 2-3 mins. as soon as the knock goes away i can drive the truck at any speed w/o the knock. but as soon as i turn off the truck it will come right back. i have had to use the truck about 4 times approx 50 miles but now it is parked. i am very thin in the pockets after my devorce.
now here is my question... do you think that i could just pull the pan and replace the rod bearings to patch or repair this problem and how hard is it to remove the oil pan and replace the bearing shells on this motor. do you have to pull the motor off the mounts to remove the pan? any help would be great. thanks
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Old 07-03-2006, 10:30 PM
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Are you sure its rod Knock? It would always knock if a big end bearing was wiped. Big ends and main bearings need lots of oil flow. I would suggest it might be a cam follower as reving fills it with oil and stopping lets it drain. You might be able to swap main and big end bearings but the crank will also show signs of damage.
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Old 07-04-2006, 12:50 AM
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it sure sounds like a rod knock to me. but i could be wrong. i have herd droped lifters and it dosen't sound like that to me. it is a hard slow heavy knock and the lifters is faster tap tap tap. (i also put in 1/2 qt marval mistory oil just in case it was a dirty lifter when i put in the lucus) i think it is the same though that the jurnal/bearing is dry (worn) and then it gets pressure the knock goes away. i read in some other listings that it could be a wrist pin noise or pistin slap that is common in the 5.4 could that possibly be this noise??? i have never heard those so i have nothing to compare it to. i dont realy want to get rid of the truck but if it is too expencive to fix that my be my only course.
what about the oil pan do you have to lift the motor off the mounts or can you just drop the bolts then the pan. all of my motor exp is on vw air cooled engines (built about 40 of them) but no v8s thanks
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Old 07-08-2006, 08:15 AM
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A little info on bottom end engine noises:

Main Bearing Knock:
Main bearing knock is usually apparent when the engine is pulling hard, when an engine is started, during acceleration, or at speeds above 35 mph.

Loose Flywheel or Broken Flexplate:
A loose flywheel or broken flexplate can usually be detected by this procedure:
1) Advance engine idle to 2000 rpm.
2) Turn off the ignition switch.
3) When the engine has almost stopped, turn the switch on again.
4) Repeat this procedure several times.
5) If the flywheel is loose or the flexplate is broken, a distinct knock will be heard every time the ignition switch is turned back on.

Harmonic Balancer:
A separated harmonic balancer will generally produce a heavy rattling noise that can be heard at low speed.

Rod Knock:
Excessive connecting rod bearing clearance noises are usually a light rap or clatter much less in intensity than main bearing knocks and the loudest when the engine is "floating" or running with a light load at from 25 to 35 mph. The noise will become louder as engine speed is increased. By grounding out each of the spark plugs, one at a time, you can determine from which cylinder the noise is coming. The noise may not be eliminated entirely by grounding, but it will be reduced considerably in intensity. The easiest way to ground out the cylinders is by inserting a 1.5" piece of 5/32" vacuum hose on each terminal on the distributor cap, and then placing the spark plug wires over the vacuum hose. With the alligator clip end of a non-powered 12 volt test lamp attached to ground, touch the test light tip to the vacuum hose to ground out that cylinder.

Piston Slap:
Piston slap is loudest when the engine is cold, and lessens or disappears after the engine is warm. When driving the vehicle (at from 25 to 30 mph) the noise will increase in intensity as the throttle is opened and additional load is applied. To detect piston slap, try the following procedure:
1) Pour several ounces of 40 weight engine oil into the suspected cylinder(s).
2) Crank the engine for several revolutions with the ignition turned off. This will allow for the oil to work itself down past the rings and act as a cushion.
3) Install the spark plug(s).
4) Start the engine.
5) If the noise is eliminated, the engine has a piston slap condition.

Piston Pin Noises:
Piston pin noise is usually the result of excessive piston pin clearance. This will cause a sharp, metallic, double-knock sound most noticable when the engine is idling. Sometimes the noise is more audible at car speeds of from 25 to 35 mph. To test for excessive piston pin clearance noise, use this procedure:
1) Run the engine at idle speed.
2) Retard the spark to reduce the intensity of the knock.
3) Return the spark timing to the normal setting.
4) Short out each spark plug, one at a time. The double-knock sound will become more audible at the cylinder with the loose pin.
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Old 07-08-2006, 11:38 AM
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Start by changing the oil back to the factory spec oil. 5W30 for yours I believe.
The soup that you have in the crankcase is not helping. The tollerances in these engines doesn't allow for heavy 30wt oils. After this is done you can listen for noises.

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Old 07-08-2006, 12:46 PM
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Location: Vienna, Georgia
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Originally Posted by PKRWUD
How is he gonna advance and retard the timing? Where's the distributor on a 5.4?
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