We all know what rod knock sounds like right? Well i do at least cause this is my 3rd motor. I just had it installed 3 weeks ago. Well this past weekend, i get in my car drive down the street 5 mins and i hear a very loud knocking noise coming from the engine bay. I pop the hood and it sounded EXACTLY like the knock when you have spun a bearing. Except it kinda sounded like it was coming from up near the top end. So, i turn it off, go into the store all pissed off thinking the motor is shot. i come back out, start the car and its running perfect with NO NOISE. I drove it a couple more times that day and no noise at all. Then the next day i started it up and it was knocking again, started driving anyway and after 2 minutes of driving it was NOT knocking anymore! ???

The knock DOES get louder/faster with the rpm's.
All fluids are fine.
No overheating.
I have not done a Comp. check.
Dont have an oil pressure gauge, wish i did.

My thoughts...but im no mechanic.
1) Oil pump/pick up... Not getting oil sometimes??
2) Spun a bearing but its ceasing up when it warms up so its not making any noise??
3) Lifter..But it sounds too loud/deep to be a lifter??
PLEASE HELP GUYS! Thanks

pop off the valve cover and take a look, that will rule out rocker arms right away

You could also check the flywheel bolts. If they are loose they can sound VERY much like rod knocking and will be RPM dependant.


Brian

Thanks for the suggestions so far...i'll have both looked at, since i dont have enough time myself. Wouldnt the bolts being loose on the flywheel consistently do it? BUT my biggest problem is that is stops doing it?? i called the guy that put in my motor and i told him about it, what sucks is that what if it doesnt do it when he has it?

My buddy is having this SAME problem with his flexplate bolts, granted he's an automatic. His is intermittant(sp).


Brian

Flex plate bolts not tight? Ugh <cringe>

Put your ear on (or near depending on loudness) the valve cover when you first start it up (cold) if it sounds like its coming from there, might as well replace your hydraulic lifters with PT Cruiser ones.

My turbo DSMs had a lot of problems with dirty or old hydraulic lifters that you could hear 3 blocks away clattering in the morning. Usually when the car heated up it would go away. I replaced all my OEM 2gnt lifters with the upgraded PT ones because of it, before they had a chance to go bad.

Definitely check the flywheel bolts as mentioned. Might have to pull off the timing belt cover and look for objects, as well as the oilpan and inspect the rod bearings.

Thanks guys. It hasnt made any noise since, i swore when i was driving it the other day while it was doing it, it seemed as if something poped off and bounced around under my car, then it stopped. So i guess its a strong possibility that it was a bolt on the flywheel that maybe broke and fell out??? i dont know, thanks to your suggestions, i have a lot of stuff to check.

Originally posted by CustomGS
So i guess its a strong possibility that it was a bolt on the flywheel that maybe broke and fell out???

There are two ways out of the bellhousing for one of those bolts:
1. The thin aluminum access panel/drain at the base of the bellhousing next to the oil pan. Get under the car and look towards the tranny from under the timing belt/oil pan area. You will see the panel and, wait. I have a picture...

It's the panel facing left in this picture, by the red dot on the right. (Directly behind the slave cylinder.)

2. The other way out is, well, through the transmission. Did that twice in one week, last year. You would know if you had this going on.


EDIT:
This is to say, I think Dan is probably right. If one of those bolts comes out, it's not going to stop making that noise at all. The clutch/flexplate assy is rotating whenever the engine is running. It's like a giant saw blade turning in there. If anything is loose in the bellhousing, it's going to be loud and fairly constant. Even if it were the clip on the throw out bearing - it would be ground up and continue to have pieces rattle around in there.

*Drain your oil and check for "glitter" or metal in it.
*Check your bellhousing access panel, it takes about five minutes to yank the bolts holding that plate in place and will let you see if anything is loose in there.
*Be prepared to buy some new lifters and redo your timing belt. :P

Originally posted by DR1665
*Be prepared to buy some new lifters and redo your timing belt. :P

Sweet, thanks for all your help and the pics brian. Im going to tell the F***er that installed the motor to do that shit since he gave me a 90 day warranty. HeHe! But i'll probably give him the pt lifters to put in to try to queit her down a bit. I'm still baffled as to how its not making any noise whatsoever now. past 3 days its been running and sounding great ( other then a bad cat making it sound like a honda )yuk.

check to make sure that your cam gears are tight. this was the knock i had recently on my car in which i couldnt figure out and it was the cam gear banging back and forth cuz the cam gear bolt was a little loose.

Originally posted by eclipse982nrRST
check to make sure that your cam gears are tight. this was the knock i had recently on my car in which i couldnt figure out and it was the cam gear banging back and forth cuz the cam gear bolt was a little loose.

Another good idea, imo. Pretty sure a loose cam gear can shear the guide dowel off the cam and lose all timing, resulting in bye bye valvetrain... :P

Originally posted by DR1665

Originally posted by eclipse982nrRST check to make sure that your cam gears are tight. this was the knock i had recently on my car in which i couldnt figure out and it was the cam gear banging back and forth cuz the cam gear bolt was a little loose.

Another good idea, imo. Pretty sure a loose cam gear can shear the guide dowel off the cam and lose all timing, resulting in bye bye valvetrain... :P

dre, not sure if you followed my NO SPARK thread, but this is what hapened to me. the cam gear bolt cam loose, shreaded the cam dowell right off and had a fucked cam signal alowing it not to even start. however, the valve train was A OKAY!