For the last couple of years when I would start my truck I would get a very loud popping noise in the intake. I mean loud enough that people would turn to look over at me. It was intermittent at first, but became more common as time went on. It was especially bad with fresh oil changes until eventually it was popping all the time when running hot or cold, albeit not as loud as when it first started up.

So I jumped on Rockauto, ordered a set of lifters and put them in. The problem lifter was on the passenger rear (#7?) exhaust valve. I couldn't get the pushrods out on that cylinder to check them because of the evaporator case and didn't feel like fooling with it. The problem is fixed except for the faintest little noise until oil pressure pumps up the lifters, so it may have bent that pushrod slightly.

Speaking of pushrods, keep them oriented by cylinder and which end is up/down along with keeping the rockers in the same position as well. Some of the faces the work the valves were a little worn looking but the truck has 233k on it.

Job took me about six hours taking my time, being tedious and very clean. I had to run to the store for RTV and a new fuel pump. I noticed a crack in the top of the pump and it was leaking diesel down all over the underside of the truck. Do yourself a favor and use compressed air to blow all the dirt and debris from the valley pan too. I replaced mine but probably could have reused the old one. I had to cut it apart to get the CDR stand pipe out of it because it was so hardened at the bottom. CDR end was still pliable.

 

Any time an exhaust valve fails to open what ever the cause will make them pop back in the intake.

 

Mine had nearly the exact same problem, except the intake lifter there locked solid, so there was no give to it and the intake valve never seated. Unfortunately I thought it was a head gasket issue, and pulled the heads. Lots of extra labor.