Knocking sound! now with video
 

I am hearing a knocking sound coming from the engine. It comes and goes when it wants. Car is running great except for that dam knokcing its gettin annoying but i cant figure out what the hell it is.

if you put your hand on the manifold, can you feel the knock through your hand? Use a screw driver as a stethoscope (sp?) to listen around the engine bay to try and figure out where it's coming from. Rod knock wouldn't be a good thing. You may want to consider pulling your pan and changing those bearings.

Well the sound seems to coming from the left side of the plenum. Iv asked many people what it could be Z owners of course i get i defferent answer everytime. From change the oil, oil pressure regulator,bearings,cam gears. Im so tired of different answers i guess i might try and check the bearing. I will try today and get a camera and take some footage and see if that helps.

on my 1990 300zx i have a knocking sound i was told that my cam gear sliped and that i was one tooth off.. and it made my vavle not open right... .. im going to try some type of good valve stuff ill let yall know how it goes for me bye

good valve stuff?
wtf is that supposed to mean?
if the belt slipped, you need to realign it, period.

An audio/video clip might help a little. Is it really a knock or a tap or a tick? If it's in the upper part of the motor, as you say under the plenum, it could be lifter tick or your VTC springs need replacing. If it really is a knock, have you tried to listen from under the car? Right behind the front wheels is where it would be loudest if it was a rod or main bearing.

Thanks for the info guys, tommarow i will try and listen to what sound it really is.

Took some footage today of that soundwhatcha think? http://media.putfile.com/Picture-571

WOW, initial response would be out of oil. Old pushrod v8's have that sound on initial start-up before the lifters get fully pressurized. Knowing you have oil and all.
You say it comes and goes. And it's running o.k. on all cylinders.

I watched it like 20 times.
The sound is loudest @ #2 (on the drivers side front).
Aside from the tapping sound, I kind of hear a grinding sound.
By the tapping sound, I would say stuck lifter or bent valve.
By the feint grinding sound, I would speculate t-belt idler pulley.
I've heard bad VTC springs will cause some tapping, but that is loud.

Have you checked your oil and is there any metal in it?

Other ideas?

Yep as far as i know, i took it to a shop to have a compression test done they said everything checked out fine. All was changed 100miles ago mobil 1 10w30 dont laugh but i use a fram filter lots of people seem to laugh when you say FRAM lol.

i know...fram has so much goin for them yet they are proclaimed as the worste....original is best, yeha lets blame the tick on the fram filter (o crap i got a fram filter)....i take it back, the fram filter is curing it?

... Fram has the worst filters on the market... don't bother arguing this with me. Like everything else I've argued, I have facts and I really don't feel like posting them for the 1,000,000th time so just take my word for it. (look up my previous posts if you question the legitimacy of my statements please)

As or the sound, it doesn't sound like rod knock, so feel lucky about that (rod knock is much deeper in the engine, that sounds closer to the top, and that's more of a tapping or ticking sound than a rod knock). But it doesn't mean there isn't a problem (and with what I think it is, a compression test is not going to show it). I think you've got bad lifters and/or worn valve springs. The sound is clearly in the drivers side head.

There could be deeper problems though, so hear me through. If you have worn valve springs or bad lifters only on that side, there has to be a reason it's not on the other side too (unless one of the heads was replaced or had work done to it).

Best case, it can be cured just by replacing the lifter(s) and/or spring(s). MAYBE even just adding some "Engine Honey" or using a thicker weight oil and reving the shit out of it to make sure the thicker oil circulates thoroughly. But don't do that until you've diagnosed everything.

Worst case, maybe you have a clogged oil passage to the drivers side head, causing it to starve that particular section of the head of oil, resulting in excessive friction. In this case, replacing the lifter(s) and/or spring(s) is only going to solve it temporarily, because the lack of oil flow is going to kill anything you put in there anyway. DO NOT THINK THIS CAN'T HAPPEN, BECAUSE IT HAPPENED TO ME. (In my case, a dead turbo caused metal shavings in my oil pan, which got sucked up by the oil pump and clogged an oil passage to the drivers side head. This ultimately warped the head and snapped my timing belt, but not before it sounded a lot like your car for about a week.)

Possible causes include, but are not limited to:
- going too long between oil changes (oil breaks down and doesn't lubricate the head properly)
- using bad filters (shavings not picked up by the filter could clog passages causing starvation or simply get into the head and damage things)
- beating the hell out of your car and not using the proper oil (aggressive driving puts extra demand on the oil, so if you drive aggressively and don't use the proper weight or type of oil, it could break down more quickly than your next scheduled oil change)
- using crappy oil (doesn't lubricate properly, breaks down too quickly, or even has bad detergents that don't help clean the engine properly)
- oil leaks (leaks can cause a low oil level, which can lead to starvation if a turn is taken or if the car is accelerated hard and the oil pump runs dry when the oil splashes to the other side of the oil pan, causing dry spouts of oil to the heads most often at high rpms; like I said, during heavy acceleration)
- letting the car sit too long (if the engine sits for a long time, the oil will seep down into the pan from the heads; this will cause a very harsh startup and the heads will run dry briefly)

There are lots of other possible causes, and it could be a combination of a lot of things. My point is, try to figure out the cause of the problem before you fix the problem only to have it come back. There's nothing more frustrating than fixing something only to have the problem come right back because you didn't fix the cause of the problem (think of it like this... a guy who doesn't like you shoots you in the arm, so you go to the hospital to get it fixed. It heals, but the guy still doesn't like you so he shoots you again. Ultimately, the only way to stop your arm from getting shot is to somehow resolve the problem with the guy who doesn't like you. The arm would be your cylinder head and the guy who doesn't like you would be the cause of your ticking... fixing it might not stop it from happening again. Find the guy who doesn't like you, and solve that first.)

Hopefully, for your sake, it's just the lifters and springs, because trying to find and fix a clog in the block is a LOT more labor intensive.

I just don't want to see another Z owner going through all the sh!t I went through back when I was negligent with my first 300ZX. Be thorough.

Don't worry, it's not the fram filter. I got over 350k miles one one car and over 250k miles on two others using fram filters and pennzoil & castrol oils. They were running fine when they departed my posession.

What i said earlier was basically repeated above. If your compression numbers were good, I'd say it's prolly not a bent valve. That leaves you with a lifter problem, oiling problem, broken valve spring and/or possible mushroomed valve tip. I wouldn't totally discount a possible t-belt idler pulley failure either. I'd guess the first decision to me made is, are you tearing it apart, or do you have to have someone else do it? At a minimum, the valve covers are coming off on that side.

I m glad someone made a post about this. I m experiencing a similar problem with my '92 NA. With 178,000 miles on th odometer I know things are gonna start wearing out more and more and need replacing. I have heard the same ticking or knocking coming from the passenger side plenum for a while. I m gonna start buy changing to an OEM filter. I really never seem to notice it until I put the unmentioanble FRAM piece on there. And I ll go ahead and throw a new set of VTC springs on since I know they have never been changed. And they are realitively easy to do too. THanks guys!

All I use is Fram....I've never had an issue with them. In any vehical I've owned.

10/30 oil is pretty light for these cars. You should try something heavier.

winter time...light is needed....to cold very viscous

I think cardboard filters great as well. (not really)

go to my link page and take a look at the filter comparison writeups that i have linked.

Hmmm...Mobile 1 looks more gooder.....

Exact Sound mine makes!!!
 

I took my Z to Nissan. Nissan claims the car needs a new timing belt and tensioners as this can lead to the sound I am hearing. I have noticed that this sound is getting progressively worse. I should add that Nissan told me that should the Timing Belt break while driving the result would be...well...catastrophic.

Have you had this repaired? What is the status of your motor?

Give up the goods man.

If you ever open a Fram filter you will buy another brand, anyhow I have a question.
what weight you put on your cars? 10w 30 or heavier?
also what filters do you use?
thanks:048:

any reason why you asked this in a 4 year old thread?

you must have searched to find this thread, so your search should also be able to find the answers to your questions

I use nissan / nippon filters. I usually buy them in bulk around 10 at a time. lasts awhile.

I am sorry , to much reading I forgot where I was.