Thread: Knock on cold start up

So like the title says, It started out almost sounding like a timing chain rattle until it warmed up and only did it driving between 2500-3000rpm under no load.

So I drained the oil droped the lower pan to see if pickup was blocked. All looked good, no metal shavings or anything so pounded out the pan a bit for extra insurance. put on new filter and upgraded to 15w/40 from the 10w/30 I was running. so next morning I see if it helped at all, and it didnt, sounds worse!

Now it almost sounds like a rod knock and get gradually louder with rpm under a load only up to 3 grand or so then clears up.

Once it warms up it runs great, with no knocking/rattling at all...

So I always thought, if a rod bearing is f'd, its f'd, period and the noise will not go away.

i am hoping it could be a lifter, timing chain tensioner...anything but a rod bearing!!

Any thoughts on this fella's?

Thanks


EDIT: If I start the car cold, let it warm up and when I come back out to it, it has a knock at idle. I rev it up it goes away.

I used a scope to listen to narrow the noise down but proved to be difficult to do. Looking at the motor it sound like its coming from the tranny side, and with the scope i hear the knock more on that side of the valve cover also. I did not hear much from the oil pan or block areas tho and the timing chain area sounded tight as well.

I did the pull a plug wire test to see if the knock went away and only the number one plug wire (passenger side) seemed to make any difference, very hard to tell.

When driving it sounds like its coming from the passenger side, but with hood open and scope on it it def coming from drivers side, NOT tob noise tho.

maybe oil pump starting to take a crap??

I tried posting a video here but i cant ever get it to work right.....in the OP there is a video. Does yours sound like this?

http://www.sr20-forum.com/sentra-se-r/53010-help-me-find-knock.html

No mine does not sound like that... that to me def sounds like a rod knock for sure tho!

I just popped out the timing chain tansioner to inspect. No cracks or anything all looks good. So I can scratch that off the list..

Just switched back to 10w/30 seems to be quieter now, like it was at first. Apperently it didn't like the thicker oil. Now it sounds more like a rattle than a knock.

Could I have a weak oil pump? I do not have a guage yet and the dummy bulb has been removed from the cluster.

And this is only when the motor is cold.

do me a favor an have someone push an hold the clutch in while its running an see if that makes a difference.. i know you said different oils had different results but its a free test..

my TOB makes sounds while my engine is warming up, its been doin this since i changed the trans an didnt relube the bearing, or atleast thats what i think. if i push the clutch in the noise goes away till i left off the clutch, one its warm its quiet. really tripped me out at first.

I put the scope on spots on the tranny and sounded fine. Plus I get the noise while driving until it gets up to full temp. Like 2300rpm to 3000rpm cruising under no load. Like I gas it a bit and let off a bit to cruise and I get a quick rattle. Thinner oil def made a difference, well it went back to how it originally was.

ah, yea mine dont make a noise that i can hear while driving or revving the motor lol.

maybe you have piston slap or something.. i've heard about when that happens its worst when cold an will go away when warm, i think my truck does it in fact.

Yeah I was thinking piston slap also, not sure if the thicker oil would make something like that worse or not.

I pulled a few plugs yesterday and all looked mint besides #3, same issue I noticed before. Top of the piston is wet from oil and plug was all gunked up from it. That could be my bad piston...???

What causes piston slap, bad piston, bad rings, messed up cylinder? Could a hone, new piston and rings correct? Or is a bore necessary?