Hello,

So after dealing with a knocking torque converter and getting rid of the clutch fan, I'm hearing a new knock in the engine. It actually sounds kind of bad when i use the screwdriver stethoscope method.

it seems to be coming from the front of the block (link to video attached, sounds way louder than it is, also fans and ps pump noise in the background). Knocking starts when the engine gets up to temp. Some times it's louder than others.

It doesn't sound like any of the previous knocks i had to deal with (collapsed lifters and wiped out camshaft).

I pulled the spark plug wires one by one and no change in rhythm or volume, just few more burns on my hands.

​​​Also just for clarity all bearings have been replaced except the wrist pin bushings. Entire valve train has been replaced except valves (those were lapped), valve seats and guides. Used all oem parts (no comments on this plz).

New* piston rings. Full compression on all cylinders. Haven't done a leak down test.

I don't think it would be possible for the liners to slip b/c they seem to be held in place by a lip at the bottom (might be an illusion though)

Spark plugs are clean, gapped to spec, NGK iridium whatever it is supposed to be. New* coil. New* plug wires. No misfires.

Coolant is not leaking (same level for last two years, never had to add any, and looks very clean). No coolant in engine oil either. New(ish) head gaskets. Hasn't overheated since engine rebuild. Normal oil pressure. All oil galleries have been thoroughly cleaned during rebuild.

I understand that saying new and expecting it to last more thank 20k miles is wishful thinking - i am fully aware that any of the "new" parts could have gone bad already - nothing will surprise me on this car anymore


Thank your for any pointer,

* New = replaced in last 1-4 years or so.

 

Most likely a slipped cylinder, no year was immune. Given the fact you just redid everything that is the only thing left. How is the oil pressure? What temp does it start knocking at? Suggest always running below that temp.

 

Sounds internal, unfortunately. First thing to check is the oil pressure. Does the knock sound change with RPM? I assume it knocks faster but does the sound lessen with more oil pressure? You can also get it up to temp and take off the serpentine belt, then run the engine for a couple seconds to see if the sound changes. Unlikely to be too revealing however.

 

I'll drop the oil pan once i get a chance and take another looksee.

I'd say it starts few minutes after getting up to full temp. I have the 175* thermostat and the efan is starting right at that temp as well. The fan will cycle couple of times and the knock kind of eases in...

I will need to do a fresh oil pressure take off (sadly i burnt through my pressure gauge hose while checking the transmission pressure, lol), but last time i checked it was per manual.

It does seem to quiet down a little at higher rpm, but im not sure if it's actually quieter or is the engine just louder

 

Welcome to loose liner land.

 

Ugh, sounds exciting...

 

My main question, assuming the liner has slipped, is how long can i drive like this: days, weeks, months. I have two big projects coming up and will be driving around quite bit. Also, I already had the truck sitting still for 2 weeks for transmission repair so if my "finance department" hears any more about car fixing, I'll be walking around.

 

@miron Generally liners slip from overheat - so not random events. The few times I have seen videos with liners slip it was more of a thud, but those maybe worse case.

In your video it seemed to get louder as you went forward and almost had a "ringing" note to it. I would check the oil pressure, pull the belt and check all the pullies as well.

What oil are you running ?

 

I'm pretty positive it has never overheated on my watch, so my quiet hope is that's it not a liner issue. I'm going through youtube and searching for someone with similar knock and the closest "sound" i can compare this to is a failed wrist pin.

I'm using rotella T4 and always dump bottle of zinc additive any time I change oil (i'm really not interested in breaking in a new camshaft again). Once i fix my pressure gauge (and it stops raining) I'll check the oil pressure.

 

Do you need to add zinc to Rotella? I switched to Rotella or Delvac because I thought they had enough zinc already.