Compression sound from the intake
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Tuned
Joined: Nov 2002
Posts: 348
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From: Benson, AZ
Compression sound from the intake
Hello again,
My 6.9 a couple years ago my brother in-law decided to "clean out" the air cleaner with starting fluid. I was not there but I was told that the RPMs went up to about 5000. Ever since he did that there has been the Compression noise from the intake. The noise only happens when I run the truck at high speeds on the highway (65 @2500 RPM) then when I slow down the noise continues for about 10 minutes then slowly goes away. I added Marvel Mystery Oil and it did help. Not the motor only makes the noise at high speeds. Any ideas about what it could be would help.
Thanks for the Help
Scott
My 6.9 a couple years ago my brother in-law decided to "clean out" the air cleaner with starting fluid. I was not there but I was told that the RPMs went up to about 5000. Ever since he did that there has been the Compression noise from the intake. The noise only happens when I run the truck at high speeds on the highway (65 @2500 RPM) then when I slow down the noise continues for about 10 minutes then slowly goes away. I added Marvel Mystery Oil and it did help. Not the motor only makes the noise at high speeds. Any ideas about what it could be would help.
Thanks for the Help
Scott
Posting Guru
Joined: Mar 2005
Posts: 1,701
Likes: 0
From: KY
Sounds like you floated a lifter and it is not going to come back in.
Also an intake noise can easily be an exhaust valve issue. What happens if the exhaust valve is late it can not allow enough of the exhaust gases out so when the intake opens it comes out then. There is a very fine line.
Some motors are worse then others about how late a valve can be before you have this issue. It will depends on their cam duration.
I tell you a motor that is real sensitive to this is the inline 6 tractor "Brazilian" motor that was common in Ford medium sized trucks. These motors are common about getting increased valve lash as they wear. Some motors are common about the valves lash tightening. Well when the valves get extra lash they will be "late" in their valve timing and they will sound like somebody is playing the drums in the intake.
If you completely loose and exhaust valve train then it will sound be very loud in the intake because all of the exhaust gases will come out of the intake and I have heard some motors loose an exhaust push tube or lifter and actually run with a miss that isn't noticable at all but it will sound like a train wreck.
Also an intake noise can easily be an exhaust valve issue. What happens if the exhaust valve is late it can not allow enough of the exhaust gases out so when the intake opens it comes out then. There is a very fine line.
Some motors are worse then others about how late a valve can be before you have this issue. It will depends on their cam duration.
I tell you a motor that is real sensitive to this is the inline 6 tractor "Brazilian" motor that was common in Ford medium sized trucks. These motors are common about getting increased valve lash as they wear. Some motors are common about the valves lash tightening. Well when the valves get extra lash they will be "late" in their valve timing and they will sound like somebody is playing the drums in the intake.
If you completely loose and exhaust valve train then it will sound be very loud in the intake because all of the exhaust gases will come out of the intake and I have heard some motors loose an exhaust push tube or lifter and actually run with a miss that isn't noticable at all but it will sound like a train wreck.
Last edited by catfish101; Sep 25, 2007 at 09:52 PM.
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