Knock after startup

[GMTMark]

I hope I’m not dragging up something that’s been discussed and worn out. If so I’m sorry.

My 1998 5.7 has 162,000 mi and runs great. During it’s life it has had a valve job while it was in for intake gasket replacement. Very early in its life it developed a knock or tapping sound after a cold start. It sounds to me like a collapsed lifter that needs to pump up but the sound also seems a bit lower pitched than most lifters I’ve heard. It does drop one cylinder during the sound that lasts about 10 seconds. My question is has anybody else had this problem and is there an additive such as marvel mystery oil or Lucas something that I can use to stop this? I don’t want to tear into an engine that uses no oil. I use Mobil 1 5w30 with either a wix or AC 1218 filter. I’ve tried high mileage oil with no improvement. Thanks in advance.

 

[Schurkey]

WHICH cylinder does it "drop"?

What is the cranking compression of that cylinder when cold?

When cold, pull that valve cover, look for play in the rocker arms of that cylinder when it's rolled to TDC-Compression.

 

[GMTMark]

I haven’t checked compression. I’m assuming you’re thinking deflated lifter? It could be and it’s worth checking but I didn’t include that the noise comes after cranking but after about a 3 second delay. It doesn’t have the immediate tapping upon startup. That’s what confuses me.

 

[kenh]

Are you loosing any coolant. As in the coolant level is dropping but it's not leaking to the outside of the engine. If so a possible head gasket or cracked head. Water in a cylinder will wash the oil of the cylinder wall causing accelerated wear from lack of lubrication. Could have a worn piston????

Ken

 

[GMTMark]

Are you loosing any coolant. As in the coolant level is dropping but it's not leaking to the outside of the engine. If so a possible head gasket or cracked head. Water in a cylinder will wash the oil of the cylinder wall causing accelerated wear from lack of lubrication. Could have a worn piston????

Ken

That’s a possibility. When the intake gasket was replaced it was due to an internal coolant leak which could have gotten into the cylinder. My plan is to replace the cam anyway so maybe I should at least pull the head and inspect the cylinders if not go ahead with a rebuild. Thank you.

 

[kenh]

That’s a possibility. When the intake gasket was replaced it was due to an internal coolant leak which could have gotten into the cylinder. My plan is to replace the cam anyway so maybe I should at least pull the head and inspect the cylinders if not go ahead with a rebuild. Thank you.

That sounds like a plan. Figure out which cylinder is suspect and pull that head. Do have the head checked for warps! I feel that is something many forget to do.

Ken

 

[Supercharged111]

My lifters were gummed up when I got my truck. It would tick on cold morning starts for a few seconds. When I did my cam I cleaned the lifters and it hasn't done it since.

 

[skylark]

My lifters were gummed up when I got my truck. It would tick on cold morning starts for a few seconds. When I did my cam I cleaned the lifters and it hasn't done it since.

On my old Buick someone went way too far with oil changes. I ran 4 quarts of oil and 1 quart of atf at every oil change. It went from my God that is nasty to spotless in about 20k judging by valve cover gaskets to intake swap 20k later. I got it with 130k and the engine finally let loose at 275k when the tranny slipped and I over revved the crap out of it. I'm a fan of the high detergent properties of atf.

 

[Supercharged111]

On my old Buick someone went way too far with oil changes. I ran 4 quarts of oil and 1 quart of atf at every oil change. It went from my God that is nasty to spotless in about 20k judging by valve cover gaskets to intake swap 20k later. I got it with 130k and the engine finally let loose at 275k when the tranny slipped and I over revved the crap out of it. I'm a fan of the high detergent properties of atf.

I went with 4 quarts of Havoline and 1 quart of Marvel Mystery oil after the cam, but have also done the ATF thing like you, but generally only for one oil change.

 

[GMTMark]

Update: I have been driving the truck more regularly lately and I’ve driven it a little harder than the previous owner. I have also treated with Seafoam twice. The after startup noise has almost disappeared. I’m convinced it’s been carbon buildup. The cylinder fires instantly upon startup. I’m happy to report that I firmly believe the issue isn’t a serious problem. Now on to bigger and better things with my project. Thank you everyone for your input.