I've been searching what seems like hundreds of threads and videos about thumping noise through the intake/Air cleaner, which is what my 06 F250 is experiencing. I just replaced the injectors and noticed the noise, and am not sure if it was making it prior. The noise appears to be coming from the drivers side only. If I remove the oil fill cap on passenger side, there is no positive pressure, however if I remover the CCV tube, there is a slight positive pressure out the CCV, which makes me think it's a leaking valve. I have AE with ford bundle but it's not great at showing contribution in my opinion. Truck runs good with no noticeable power loss and no codes. Getting ready to pull push rods on that side to see if any are bent and all rocker arms look good. Anything else I should look for?
Ordered an adapter for my compression tester and will check that eventually. None of the threads I've read mention positive pressure out the CCV, so I'm a bit stumped.

 

 

Is this coming from the valve covers of the intake. Sort of clarifying things.
The ideal way to check for blow-by is by plugging the CCV ort and then take
the measurement over on the passenger side oil fill port with the test tool.
Or if you don't have that tool just place the cap on the filer upside down.
If it blows off at idle then you have something that you need to look into.

 

After running some tests on a buddy's 6.0, I've come to realize that the amount of pressure coming out of the CCV is the same on mine as it is on his. My theory was if it was coming out of one side and not the other it could indicate a leaking valve stem on that side, but it appears to be normal crankcase pressure, which isn't much. Plugging the CCV did not change the sound from the intake, so I think I can cross that off my list and pursue valve train concerns. I should have my compression tester adapter soon and will begin the process of elimination. I have not removed the passenger side valve cover yet and will do that today to inspect rocker arms. My previous three trucks we're all 7.3 psd's. This truck has run pretty well and I am a bit **** about maintenance , but I think this will be my first and last 6.0. IMHO, it is probably one of the poorest designed engines I've seen.

 

A cylinder contribution test and a relative compression test can help narrow it down to what cylinder to focus on. Along with a standard compression and leak down test once you know what cylinder(s) to concentrate on.
When you get a glowplug adapter you can put the suspect cylinder up on TDC and pressurize the cylinder with shop air. Then listen @ 1. Intake 2. Exhaust 3. Oil fill to hear any gross leaks around the intake, exhaust valves or the rings/piston.

 

A leak down tester is very handy in that case.
I have not used one on a diesel. I have done air planes and you really want a third hand. A prop can really hurt. The double
gauges come in handy. You rock the crank shaft back and forth and watch the gauge actions. I will have to see if I can find
that video. There is a lot of good info that can be applied to the diesel world.

 

Well, I finally got back to my truck after healing from a few broken ribs over the winter. Hard to work on these truck when it requires laying across the radiator.
Compression test showed an average of 380 on all cylinders, with only about a 2 percent difference between them, and with 152k on the engine , I'm calling that good.
Leakdown test showed less than 5 percent, with cylinders 6 at 5 percent.
I pulled the intake and put tape over intake ports on each head, then cut a small flap on each port. Then I cranked the engine over and found a slight blowback on the rear intake port of number six during the exhaust stroke.
I pulled both the exhaust and intake pushrods and rocker arms, and found no issues with those. Both push rods or straight as an arrow.
So I'm assuming it is either a burnt valve or a bad lifter. Either way I think the head is coming off, unless someone else has other suggestions?