aeon117

The motor was rebuilt, new bearings (main and rod), new piston rings, new headgasket, new head studs because a head gasket blew, and found out coolant dripped down through the pistons and pretty much fried the rings. During the rebuild, bearings and crank were checked out. No damage on the crank, but bearings seemed worn. Rightfully so considering the motor had probably over a 100k miles. Replaced with new bearings, and plastigauge for clearances. Everything seems to check out.

Anyways, after the rebuild, baby the motor for breakin miles. About 150 miles in, start getting rod knock. Open the motor up, sure enough one of the rod bearings are worn.
Replaced all 4 with new, and replaced the rod with the worn bearing. Plastigauge the clearance, same as before.

Now im maybe 40 miles in. Same thing. I heard it on startup, and im pretty sure in another 10 or so miles im going to hear it cruising. What gives?

I've gone through pretty much 2 rebuilds on this motor already, and 1 rebuild on another car due to rod knock. I actually even gave up on the other car and traded it off before finishing it. The car I had after that motor seized due to rod knock, and now I have this car... I'm way over on amount I've spent fixing these damn rod knocks.
I need advice on what is happening, and how to fix for good this time. Maybe it aint rod knock, maybe there is an underlying problem causing the knocks. I don't know, but I am sure getting tired of this problem with apparently every car I've had now.


Relevant information: oil pressure and levels are good. Used new 10-30 oil first rebuild, and running on new 20-50 now

m4xwellmurd3r

What did your bearing clearences measure out to

aeon117

I don't have the plastigauge sheet handy to tell exactly, but I think it was .0015

vtechsjc

Was the crank end of the con. rod blackened from getting hot? If so the hole in the rod is probably egg shaped. During the rebuild did you blow out the oil passages in the crankshaft? I have seen chips of metal from worn bearings collect in the crank oil holes.

aeon117

Oil passages were not blown out. The crank was not scratched, or scored the first rebuild. The second time rod knock appeared (less than 200 miles), the rod was replaced with a remaned rod, and clearances came out to the same as before, with the orignal rods...

I should note that the sound is still only present on long sitting cold starts (like overnight), where you can hear what seems to be rod jingle 3-5 knocks. After that, no sound has been present while driving, idling, or on warm starts. Just about reached 200 miles today.


This is stumping me. The cold startup definitely sounds like beginning symptoms of rod knock, but if it's doing it on start, it should be doing it while driving. Especially now after another 100 miles. I've even revved up to 4k rpms a couple times to just see if it would get worse.

Only thing I can think of is that oil passages are slightly worn out to the bearings, and the bearings gets slightly worn from lack of lubrication on startups. Is it wise to invest in those oil stabilizers or should the block be reopened, and diagnosed?

vtechsjc

If it only occurs when cold then its probably piston slap which is considered normal by Honda. But also make sure you are using a decent quality oil filter that has a anti drainback valve in it. And don't use one of those tiny oil filters as they don't flow enough oil in my opinion. I had a VTEC system malfunction car that I fixed by replacing the tiny after market oil filter with a Honda oil filter.

aeon117

I'm not sure if the oil filter is anti drain or not.

It definitely does it on all startups after sitting at least a couple hours. No noticeable out of place noises while driving. Have revved it out a few times now, and still nothing, so it leads me to believe it's not rod knock. If it was, the high hard revs probably would have done whichever rod in by now, and noise become extremely apparent throughout rpms.

It really is stumping me. I've never heard piston slap before, nor never heard it as being a normal part of the motor function, but the noise im hearing on startup definitely sounds like rod knock.

aeon117

just to update the post with the solution. It was a failing oil pump. Learn from me, and install an oil pressure gauge, or at least check/change out the pump when you have the belts off or pan dropped

1HGEJ2

iTrader: (1)

What was wrong with the oil pump?

aeon117

was on it's way out. Had very little flow at low/medium rpms. Higher rpms, it was usable, but definitely not safe for prolonged times. Whether the pump was just going bad or was clogged, I don't know. I had to get a new crank anyways, ended up getting a whole new d16z bottom for same price as crank, so tested the "new" pump, and switched it out.

I'm guessing the low output at low rpms, was starving the oil galley on rod 4 (the farthest from the pump), which happened to be the rod that repeatedly went bad.