I own a 1996 F150 with a 4.9L straight six. It has 210,000 km (131,000 miles) on it. It has been very well cared for. I have owned it since it was brand new and never missed an oil change.

Recently the motor started making a loud tapping noise. It only does this when the motor is started cold. As soon as I put the transmission in drive the noise stops or quiets right down.

What could be doing this? Is it ok to continue driving without getting this checked? I would appreciate any advice. Thanks in advance.

 

What brand of oil filter are you running?

 

I used the Ford Motorcraft oil filter. I let the dealer do the all of the oil changes since it was new.

When I first bought the truck they put 5W30 oil in it. A couple of years ago they started putting 5W20 in it. The manual calls for 5W30 or 10W30. Now I am concerned that might not be good for the motor.

 

You have a dirty, sticky, or collapsed lifter.

 

Add a quart of Marvel Mystery oil in the next couple of oil changes, and run it like normal. I cleared up a 'ticking" I had at start up in a 96 302 a few years back.

 

I'm partial to Rislone for the same purpose. I strongly suspect they're the same stuff in different bottles.

 

Neither - use AutoRX.

 

A carbon shaker by any other name...

 

Well, how do you explain that the tapping sound stops as soon as I put the truck in drive? Even if I put the gear selector back in park immediately the tapping sound doesn't come back.

I added a can of Wynn's engine tune up to the crankcase. It's supposed to free sticking lifters. It hasn't had any effect yet but it hasn't been in long.

It's almost time to do another oil change. I am going to get the oil and filter changed later this week. I will post a message if that helps. If it is a problem with a lifter, do I need to have it fixed?

 

A mechanic took a brief look at my truck today. It doesn't sound to be a lifter noise. He said he thought the sound might be coming from the air pump but he wasn't sure. It didn't occur to me at the time to tell him that the air conditioning isn't working. There is no cold air blowing from the air conditioner. Could the noise I'm hearing be coming from the air conditioner compressor?

 

yep.

 

Only when cold? If left in Park, how long until the noise stops on its' own?
Have you opened the hood to hear this noise firsthand, maybe with someone else starting the truck?

I bought my F-150 new in Dec, 88. Reg cab, long bed, straight six, 5 speed. It's got almost 160,000 miles on it.

 

I haven't left it in park long enough for the noise to go away on its own. I didn't want to leave it running like that long in case it was a lifter. It goes away as soon as I shift it into drive. If the motor is cold and I shift it back into park the tapping noise resumes. If the motor is warm and I shift the truck back into park the noise doesn't come back. It just takes a couple of minutes before it goes away.

I tried opening the hood and listening to it myself. It sounds like it is coming from the front of the motor. It is a metallic sound like the noise an industrial fan would make if you stuck an object in it and the blades were hitting against it.

 

The problem appears to be resolved. The noise was caused by the fan hitting the shroud.