Coconut350Track

Hello,

I just recently purchased a 2003 350z track. I bought the car sight-unseen which I would typically not do but the price was right so I was under the assumption that I could take care of whatever was being thrown at me. I've been able to fix the small problems the car had but I just can't seem to pinpoint the cause of this motor noise. If any of you have experienced this or know what it may be, your input would be much appreciated.

Upon cold start you can only slightly hear a knock/tic. The knock/tic is rhythmic and I can feel it through the shifter. It increases with rpms but becomes less distinguishable above 3k rpms. At this point (cold) oil pressure is around 40psi at idle and above 60 when moving.

I can hear the tick/knock turn into more of a knock than a tick while warming up. After the car is warm the knock becomes pretty loud. It seems to be coming from the top side of the engine. As described earlier, it increases with rpms and at this point it rattles my shifter unbelievably loudly. It can be heard very clearly inside the car and fairly clearly outside.

Once the oil has had time to get hot (~15 min. of driving) the knock becomes very clear. It only seems to knock once for a particular cylinder. i.e. it doesn't knock once for every one cylinder fire. It seems to be about 3 knocks per second at 700 rpm idle.

It also makes a very distinguishable rattling sound under very light throttle. I haven't been able to pinpoint if this sound is coming from the top end or not or if it is related to the knock. It does seem to replace the knock sound when it is happening though. It could just be drowning it out but I'm not sure. My oil pressure is just above zero after the oil has completely warmed up. It reaches 30 psi under normal driving shifting between 2400 and 2800 rpms. I've attempted different oil weights (within reason) and lucas additive. I have seafoamed it with no change whatsoever. I am willing to do what needs to be done to fix this I would just like to pinpoint the cause before I get into a big project like this.

This is my first Z and I absolutely love it but this noise is very bothersome. I am currently driving the car. I have heard rod knock before and I am almost positive that is not the cause but I may be wrong. Now that the weather is getting warmer it seems to be getting worse.

Again, any help is much appreciated. Flame if absolutely necessary but please refrain from comments regarding whether my purchase was stupid or not.

Thanks,

Michael

EDIT: Also forgot to mention: no engine trouble codes present.

0jiggy0

iTrader: (13)

The motor sounds "tired," that is some high mileage and who knows how it was taken care off. Once warmed up the oil pressure sounds low. I know there is a certain spec range ( can probably google it) that is considered nominal. If the noise is more of a loud knock, then tick I am going to assume rod knock.

This obviously sounds like something that needs to be inspected further, maybe torn down. How does the oil look?

stuartc323

1. Next time reevaluate purchase of almost 200,000 mile Z.

2. Go get a diagnostic run on car, dont post on forum asking if we know, we cant scan your car over the internet.

3. Next time reevaluate purchase of almost 200,000 mile Z.

Coconut350Track

It has been serviced by nissan all the way up to my purchase of it at 192k. It had an extended warranty from the previous owner that ended at 175k. The oil pressure is technically in spec. It is just under minimum spec at idle. It sounds more of like a "matted" knock rather than the typical piercing rod knock sound. I've had a few people listen to it including a dealer and most say it sounds like the lifters. I do have a short 10 second clip from when I seafoamed it. The car was at operating temperature in this video but it definitely a bit louder than this with a little more run time. I will round up the youtube link and post it.

And as for the comment about buying a 200k mile z... I bought the car at a price that would enable me to go as far as having a new engine put in with my overall investment still under wholesale value. Sure it's a headache to keep up with a 200k mile z but I don't feel that the purchase reevaluation is necessary. You and I are both entitled to our opinions though.

oldschool350z

iTrader: (1)

I share the same opinion as him as well 200K is too much.

That said, compression check on the cylinders and an oil analysis are needed.

Coconut350Track

Syner

I was actually going to suggest this before I read any of the other posts. Never heard it in a Z (mine only has 55,000 km) but pretty typical of high-milers.

Coconut350Track

That's my guess. The fact that it is coming from the top-end really makes me think it's the lifters. I want to just replace them but I don't want to throw money at it without other opinions. The only thing throwing me off is the rattling noise. I didn't think lifters would do that but I may be wrong. Also, the car has plenty of power across the entire band.

2004Black350z

iTrader: (37)

How much money did you buy it for?


How much are you willing to spend to fix it?

Coconut350Track

I'd rather not give my purchase price. I may want to list it FS on this site at some point and would prefer to keep that private.

I am willing to spend no more than the cost of a new motor plus installation, obviously. Basically whatever it takes. I just don't want to throw money at a 200k mile motor if a new one will be more reliable and cost effective.

samsniss350z

I really don't want to post a depressing message, but the VQ33DE was designed to do 200,000 miles so it sounds as though it is due for a rebore and rebuild, hence 'being the right price'. If you could take it to a competant and trusted independent mechanic and get them to give it a compression test and a general once over you'll be in a better position to know what your outlay is going to be. Have you driven any other Zeds for a comparison on power and torque? This could give you an idea as to the general state of your motor. Good Luck.

Coconut350Track

Thanks for your input. I will be having a compression test done hopefully within the next week or two. I have a buddy with a z who I had drive it. He said he couldn't tell a difference in power, only in the noise haha. So as far as I'm concerned compression is okay but I will be finding out soon.

It sounds as the one in this video does just not near as loud and more of a "matted" knock sound. Also, shouldn't rod knock happen when cold as well? I can see his car is not to operating temp yet but is very loud. Mine is hardly distinguishable when cold. Could this still be rod bearings?


I'm expecting the worst. I do all of my car work myself which is why I havent taken it anywhere yet but this is over my head so I guess I'll just have to take it to someone willing to get elbows deep in a vq because I'm sure not. I could replace the lifters myself I just can't be sure that's my problem.

mr. sparco

iTrader: (13)

That sounds like in need of a complete rebuild. Goodluck, just be honest when you try to sell it here.

drvqz33

iTrader: (10)

I would begin looking for a new/used motor. 200k is a lot and you really don't know whether the motor was beaten or well maintained within its life span. But props trying to keep this motor alive. Keep us updated OP

Coconut350Track

I agree and that's what I'm headed for. I live two miles away from Dynosty so I'll probably drop by tomorrow and see what they think. A rebuild/new motor sounds great but is there anything else I should think about when throwing that kinda money at a 350z chassis with that many miles? I've been underneath the car a lot and it looks good plus it has a nismo shocks/struts but should I go ahead and have the clutch replaced? Any tranny preventative maintenance I should have done?

stuartc323

Well from what your telling us the motor is going out, you bought a high mileage car like this meaning that every OTHER part of the car is also at 200k. One thing Ive always learned with cars is replace something brand new on one area of the car and eventually something around that new part is going to break.

All i was saying is reevaluate your purchase because your probably going to end up paying twice the purchase price of the car for repairs and restoration because you never stated the condition of the interior either.

Either way it goes you have already stated your true intention of flipping this car and you already wont release details of your purchase because you want to sell. That sounds shady, please be honest when you sell, because karma is a *****.

FWM69

My last Z made the same exact noise!!! Although I didn't feel it through the shifter.

PerfZ

iTrader: (3)

Seems buying a used motor might be the best option - a simple swap should be less than the cost of rebuilding. You're going to need the money for other "wearable" parts at 200k. My tranny is still going strong at 130k but if I were swapping the motor I would look for that too - close to half the cost is in labor. Clutch for sure. Sounds like what you have is a project car......

Tracktimeplz

I think, first step as mentioned above, Compression check.

If the compression looks pretty good, id send in the oil, for an UOA (Used oil Analysis) This can tell you almost as much about the condition of your engine as a full tear-down.

If the engine is in good shape, id replace the valve springs, retainers, and shims. Its not too bad of a DIY(If you have the tools) and it could be the source of your "multiple noises"



*Edit
Btw all of these are fairly cheap, and definitely worth trying, before jumping right to a new engine, IMO

Coconut350Track

Well, the motor failed on me this morning. Had just gotten on the interstate, my oil and battery light came on with the engine light flashing, started knocking louder than normal, oil pressure dropped off and it died immediately. Looks like its time for a new motor. It needed one anyways so I'm not completely distraught...