s14 sr20det making a tapping noise around 3k rpm

[dwadia]

I am trying to determine what the cause of this noise is. It happens generally around 3k rpm under very light throttle (typically if i ease off but don't completely release the throttle), and as far as i can tell goes away after that. If i accelerate hard or let the car decelerate with no throttle at all, i can't hear any sound. However i can't say for certain that there is no sound under hard acceleration due to the increased engine/exhaust/road noise which might be covering it up, and the rapidly changing rpm's.

The noise sounds like a metal tapping or clacking, definitely loud enough to hear when cruising but not excessively loud either. It is absolutely not present at idle. If any of you guys are familiar with the VTC rattle on s14 sr20's, it sounds sort of like a mild VTC rattle. That's not what it is though, because that goes away when rpm's and oil pressure increase and is most noticable at idle.

A good mechanic, but one unfamiliar with the sr, said he thought it sounded like some sort of problem with my bottom end. He thought there was a little play in one of the bearings on the rods where it connects to the crank and that when the engine is not under any load it is loose enough to cause a rattle I've never heard of such a problem, although i'm not discounting the possibility. However, the car makes full power and it seems like it does occur under a slight load (maintaining 3k rpm) so this seemed unlikely to me. Another thing that crossed my mind was that the timing chain could be slapping something, although i know for sure it's not touching the upper chain guide and the tensioner is new. Do you guys have any experience with this or ideas?

[((sr)) kelly]

sounds like you need a new rod bearing...

[Z U L8R]

zomg rod knock >_<

[dwadia]

Ok, so if it's a rod bearing, what will happen if i don't replace it immediately? Will it get louder and louder, or is it more likely to suddenly fail in some way?

Also, can the rod bearings be accessed by dropping the oil pan (the large, upper portion i mean) or does the engine need to be completely removed and disassembled?

[fliprayzin240sx]

Are you 100% sure its coming from the bottom end and not the VTC rattle crap?

Rod knock has a tendency to be persistent at certain rpm, and goes with the rpm. If it is rod knock, time to look for another bottom end or rebuild. STOP DRIVING or starting the engine. Its not just noise, you are effectively destroying the engine the more you let it run. Hope your crank isnt FUCKED yet...also, chunks of rod bearing is falling down onto your oil pan. They will clog your oil sump and kill your oil pressure. No oil pressure, watch and see the rods make a new oil drain for your block when it EXPLODES!!!

[dwadia]

Well, i'm not 100% sure of anything, but i am pretty certain it's not a VTC rattle because i had that problem, replaced the intake sprocket and it went away. Like i said, i was thinking (sort of hoping) it was timing-chain related, or i'm not sure what else could make an rpm-related tapping, but from your description it does seem like it may well be rod knock. I don't get it though, i've used the engine for only ~2k miles max and it was your typical JDM engine with supposedly low miles (i don't believe it had 40k but how high could it be???).

Is there some way i can be more certain of whether it's rod knock before deciding to have my engine rebuilt? Does it have to be diagnosed from sound alone?

[fliprayzin240sx]

Drop the oil pan to see if you have a present...if you drop it and theres pieces of brass in there, those are pieces of your rod bearing.

If it makes you feel better, you jinxed me cuz I think I just heard my rods knocking last night. Im prepping to drop my oil pan to check later on today and see if I got rod bearing chunkage at the bottom of my pan.

[nxpoweredsr20]

i just had my motor fully rebuilt about a thousand miles ago and i have this exact problem....i was thinking timing chain too but from the sound of it i have bigger problems......im going to take it back to the shop who built my motor and bitch!!!!

[dwadia]

Drop the oil pan to see if you have a present...if you drop it and theres pieces of brass in there, those are pieces of your rod bearing.

If it makes you feel better, you jinxed me cuz I think I just heard my rods knocking last night. Im prepping to drop my oil pan to check later on today and see if I got rod bearing chunkage at the bottom of my pan.

No it doesn't make me feel better, sorry to hear that, but thanks for the suggestion. Are you talking about just the small lower oil pan or the entire thing? Because had the lower pan off recently and it was free of metal. How big would these chunks be? And if there's no chunks does that mean the rod bearings are ok or it doesn't necessarily mean anything?

i just had my motor fully rebuilt about a thousand miles ago and i have this exact problem....i was thinking timing chain too but from the sound of it i have bigger problems......im going to take it back to the shop who built my motor and bitch!!!!

That sucks, please let me know though when you find out what it is... and being that it was just rebuilt, WHY???

[nxpoweredsr20]

beats the shit outta me man lol. It barely has a thousand miles on it and its only at like a certain rpm then goes away....but i put up a screwdriver and listen into the end of it(sounds wierd but it works ) and the sound is comming far away from the bottom end so im betting its timing chain or maybe vct...ii just changed the oil yesterday and the oil didnt look bad at all...my dad wants to cut up the oil filter and check for pieces of brass..would they be in the filter too?but ill keep u updated and u do the same?

[nxpoweredsr20]

idk man. The motor has only a thousand miles on new pistons rods cams machined block and everything else. The noise sounds like its comming from rite up top under the valve cover. When i put a large screwdriver on the side of the head or on top of the valve cover(wierd but it works) it sounds like its in there. I just changed the oil yest and my dad wants to cut up the oil filter and check it for bits of brass...if brass was presant it would be in there also correct? ill keep u posted and u do the same...thx

[nxpoweredsr20]

sorry about those posts i didnt think the first one posted

[dwadia]

NX, sorry man i completely didn't notice there were any more posts on this thread! Anyway i'm not really sure what to think of my car, and between not wanting to make it worse and being sort of lazy about trying to fix it i just haven't been driving it much lol. So i can't say i found out anything new. Have you gotten anywhere with figuring out what's wrong? Find any brass pieces?

[ArcherV20]

Wow.

I've just started to notice the problem myself in the last few days. However, it tends to go away after awhile, or if I'm lucky it just won't show up. I'm really hoping it's VTC, I don't have the time or money to rebuild or reswap the engine at this point in the game :P.

[dwadia]

Hmm... if it is a rod knock, from what i've found out thus far (and as people have responded in this thread) it would definitely be best to address it ASAP. Although there is lots of labor involved, it doesn't need to be a full rebuild if it's very early on. I spoke to someone about repairing my engine, and he explained if it was in its early stages there was a good possibility that just the rod bearings could be replaced without needing to remove the head, and the crankshaft might still be salvagable. Just to give you an idea he estimated ~$1600 to do this job including parts (assuming no crank), and that's with removing and reinstalling the engine from the chassis (no doubt cheaper if you can pull your own engine). Nonetheless i've opted to reswap it because i want an s15 and it makes sense to do it now under the circumstances :boink:

By the way, i had VTC rattle. It's directly related to oil pressure, so it should not be brought on by an increase in rpm. On the contrary, it should decrease and/or go away as rpm's increase. If you sometimes have the sound at idle and it goes away after a period of time (or when revved) that could very likely be VTC. It will get worse if nothing is done about it and become more consistent and persistent, but from what i understand it won't hurt anything, aside from your ear drums and perhaps your ego when people think you're driving a diesel-powered 240sx. In any case, good luck and let me know what happens.

[ArcherV20]

Why is the VTC rattle such a poorly address subject? It seems fairly common in the S14 SR20DET. Are these ridiculously hard parts to find or something? Or is it just difficult to diagnose.

[dwadia]

I've wondered the same thing myself, and what i think is 1) although there are some s14's and s15 engines in the US, the vast majority are s13. Hence far fewer people have experience with or concern about VTC. 2) Of the ones that do, many may opt to take a simple and less expensive "solution" to their problem by simply removing/disabling the VTC system. If you want, all you'd need to do is put in an s13 intake cam sprocket (stock or aftermarket) and you're good to go. 3) As you suggested, the parts can be very hard to find, and also expensive. It is NOT hard to diagnose though.

Zilvia is a very informative forum but for this particular topic you might want to try http://www.nissansilvia.com/. It's an Australian forum, and those guys have a LOT more experience with VCT. And fortunately for us they are probably the only such country which speaks English!! I actually asked similar questions to what you're asking and got some great responses, including testing methods and even a link to the sprocket, which i eventually determined to be bad. Here: Nissansilvia.com -> s14 vtc solenoid replacement questions - Hardtuned.net (http://www.nissansilvia.com/forums/index.php?showtopic=296508&pid=4252213&st=30&#entry4252213) You might need to become a member first though, but that's easy. And make sure to search all the threads on that topic, not just the one in the link.

I was in luck to get a used sprocket from someone parting an s14 motor, because the new one will run you about $500 shipped! That's from Japan of course. There's no way around that if it's new. It really is that much even directly from Nissan (if you could even get hold of it). I can dig up a link for the parts if necessary. Read up as much as you can, and if you run into any dead ends or have any more questions let me know. Good luck.