Lifter or Emissions Noise
Thread Starter
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Tuned
Joined: May 2003
Posts: 261
Likes: 4
From: Montana
Lifter or Emissions Noise
Help! I've already stumped a couple of mechanics here where I live as to what type of noise my '79 351M truck motor is making. Sorry this is so long but here goes...
At idle I can hear what I'm pretty sure is a lifter (it's a higher pitched "tick"). However, when I put the truck into gear a new deeper pitched noise emerges that sounds kind of like an exhaust leak on the drivers side. When the truck is under load or heavy throttle the deeper pitched noise is very loud. When driving the truck and I let off the throttle or am going down a hill with very little throttle applied the noise goes away and I can hear the lifter tick again. Letting off the throttle at highway speed produces soft back-fire and black smoke comes out of the exhaust.
The truck still has all the stock emissions equipment. I removed the EGR and it was packed full of soot so I cleaned it and reinstalled it.
I don't see any type of soot that would indicate an exhaust leak. I've been running Marvel Mystery Oil for the last 3,500 miles and that hasn't helped.
Any ideas?
At idle I can hear what I'm pretty sure is a lifter (it's a higher pitched "tick"). However, when I put the truck into gear a new deeper pitched noise emerges that sounds kind of like an exhaust leak on the drivers side. When the truck is under load or heavy throttle the deeper pitched noise is very loud. When driving the truck and I let off the throttle or am going down a hill with very little throttle applied the noise goes away and I can hear the lifter tick again. Letting off the throttle at highway speed produces soft back-fire and black smoke comes out of the exhaust.
The truck still has all the stock emissions equipment. I removed the EGR and it was packed full of soot so I cleaned it and reinstalled it.
I don't see any type of soot that would indicate an exhaust leak. I've been running Marvel Mystery Oil for the last 3,500 miles and that hasn't helped.
Any ideas?
Senior User
Joined: Jun 2003
Posts: 160
Likes: 0
From: Santa Rosa, Ca
Well, the mystery oil isnt going to help anything, just quiet it down a touch. Your problem may very well be a lifter, my truck has made ticking sounds since seventy thou. Nobiggie, how many miles does she have? Maybe its time for a top end rebuild. maybe a timing chain... easy fixes though my friend. Good Luck! 
Junior User
Joined: Dec 2003
Posts: 85
Likes: 0
From: Kalispell,Montana
My truck has a 400 in it but I experience the same sounds you describe,and as of now I've traced it to my oil filler cap.My cap has the PCV built into it and when tuning it up I replaced the cap with an after market and the noises started.Your description of sounds is identical to mine.If you have the same set up you might isolate the sound there,but I would recommend the compression test as stated in previous reply,if anything you'll find the state of your engine.
Posting Guru
Joined: Feb 2002
Posts: 2,404
Likes: 3
From: Cleveland, WI USA
I agree with Mark A. Do a compression check. If the lifter is ticking it might be a stuck valve. A compression check would verify that.
Lifter noise sounds alot like an exhaust leak. You could idle the truck and feel around the connection of the manifold-to-y pipe and see if you feel puffs of air. However, an exhaust leak wouldn't cause the smoke.
My guess would be a collapsed lifter.
Kevin K.
Lifter noise sounds alot like an exhaust leak. You could idle the truck and feel around the connection of the manifold-to-y pipe and see if you feel puffs of air. However, an exhaust leak wouldn't cause the smoke.
My guess would be a collapsed lifter.
Kevin K.
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
Jason,
Your describing an exhaust leak. Have you ruled out an exhaust leak? The "Tick" noise is usually from a manifold leak. the backfire is from air getting into the exhaust system and allowing high enough oxegyn levels to allow combustion.
Here's how to find it:
1. Look for carbon staining on the head at the manifold connection. this is usually the common way.
2. Pull your dipstick and lightly drip oil on the seam between the exhaust manifold and head. Watch for bubbles. If you've got bubbles, you've got your leak.
3. A cracked manifold will not give the symptoms that you are describing but, since I have made this statement it is a possibility. Cracked manifolds will give a deep noise under load, and a hollow noise at idle.
4. Lastly, if the leak is on the bottom of the manifold, unusual place, you are going to have a much more difficult time finding it.
5. On another note, a cracked or crooked valve seat could case this problem. If the seat has shifted it would not let the valve close all the way. This would cause your lifter to tick. it would also cause a backfire during accel or decels. Compression test should tell the tale.
Consider it.
KingFisher
Your describing an exhaust leak. Have you ruled out an exhaust leak? The "Tick" noise is usually from a manifold leak. the backfire is from air getting into the exhaust system and allowing high enough oxegyn levels to allow combustion.
Here's how to find it:
1. Look for carbon staining on the head at the manifold connection. this is usually the common way.
2. Pull your dipstick and lightly drip oil on the seam between the exhaust manifold and head. Watch for bubbles. If you've got bubbles, you've got your leak.
3. A cracked manifold will not give the symptoms that you are describing but, since I have made this statement it is a possibility. Cracked manifolds will give a deep noise under load, and a hollow noise at idle.
4. Lastly, if the leak is on the bottom of the manifold, unusual place, you are going to have a much more difficult time finding it.
5. On another note, a cracked or crooked valve seat could case this problem. If the seat has shifted it would not let the valve close all the way. This would cause your lifter to tick. it would also cause a backfire during accel or decels. Compression test should tell the tale.
Consider it.
KingFisher
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Thread Starter
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Tuned
Joined: May 2003
Posts: 261
Likes: 4
From: Montana
Thanks everyone for your input. I did a compression test today and all cylinders were around 128psi with a low of 125psi and a high of 130psi. I guess that rules out valve problems.
I'm going to go check out the exhaust manifold and PCV.
Thanks again!
I'm going to go check out the exhaust manifold and PCV.
Thanks again!
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