• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

thumping sound coming from air intake

L

lt1fire

Member
Messages
26
Reaction score
26
Location
charlotte, nc
Seems like I must have a stuck valve, broken spring or bent pushrod

I've got the thumping noise coming from my air intake. I can only hear it when standing by the passenger side fender or with my head under the hood near it so I’m not sure how long its been doing it but I noticed when I left my truck running to jump out and put something in the UPS mail box on the way to work earlier in the week.

I’ve seen a couple videos and threads on it so I’m pretty sure its one of the three. Is there anything else it could be??????


I’m trying to find my mechanics stethoscope but it seems to have gone missing. Is there another way to isolate the runner it could be coming from??
If not I’m going to pull the driver’s side valve cover to see, hopefully, if it is on that side of the motor. I’m guessing a stuck piston, spring or pushrod will be pretty easy to see.

Anyone have any experience with this before??
 
I picked up a 24" long screwdriver from one of those "on sale" cheap tool bins you see at NAPA and other fine stores. Use it for isolating noises only in lieu of a Mechanic Stethoscope.
Friend of mine lost a rocker button on the intake side and was 'making oil' pushing fuel past the rings so check your levels. Of course he was way down on power too so it may not be that.
Not sure what else to say here friend as it's beyond me.
 
While idling, Crack loose the injector nuts one at a time then re tighten before going on I the next one. You should here a change in the messed up cylinder compared to the others so isolate which one.

You'll get a little diesel spray, it nothing to worry about just garden hose off when done.

Can you post a video?
 
You could use a IR temp gun on the manifold and look for a cold cylinder. Does it hit on all 8? Smoke or other issues? A miss on this engine is clear at idle via a bad shake.

These engines do make this noise warming up sometimes.
 
That's the video of it running. Wasn't quite as loud as it normally was but you can hear it near the air box. Showed the blow by it has also, can't really see it out of the dipstick but some does come out. Going to tack my recycling to the dump tomorrow and will see if I can get a better video.
 
I'm only hearing a little cant tell what I'm hearing because I'm on my phone-my laptop is down for the count. Can you ID a weaker cylinder? You might be popping the valve cover off to see the problem, but try as hard as you can to know what cylinder first or it will be a goose chase.
 
I don't know has anyone tried this to diagnose an exhaust rocker button.... Take off the upper intake and see if it coughs back through the intake. Might even be able to feel the pulse out of a runner or see a gray puff ??????

I had a gasser break an exhaust rocker and it would cough back through the carburetor. Is the turbo muffling the sound?
 
Catch it when it's loud. Kinda not really didn't hear anything unusual. Again is there any performance issues or a miss with the engine?
 
Leo beat me to it. I listened again and was going to post.....

Is it the vac pump being a bit noisy that you are hearing? Mines been off a good while but seems I remember it chuffing a little????

See if you can hear it louder in the passenger tire fender well down by the tire or under bumper. The vac pump is under the compressor. I would think if its a bad rocker button or major valve issue it would be more consistent in loudness and not as fast?
 
I had a thumping through my intake. Turned out the retainer clip in the top of one of the exhaust lifters broke so the pushrod was seated deeper than normal. The pressure couldn't get out of the cylinder and would instead come out of the intake. When I was having the problem I tried both An IR thermometer and a stethoscope and had trouble isolating the problem though I suspected a lifter. Good luck and let us know what it ends up being.
 
You must log in or register to reply here.
Back
Top