Car knocking

i have a 1993 nissan 300zx non turbo and the car has been sitting for 3 months and now that i am ready to drive it i hear a knocking

is this a bad thing?

It certainly isn’t a good thing.

I don’t know - who is knocking? Friend or foe?

There are too many different sounds that might get described as knocking and too many conditions under which these kinds of noises can occur. So you’re going to have to be more descriptive.

Is it safe to assume that you at least checked - if not changed - the oil?

Under what conditions is it knocking?

Oh, and, um, have you checked the oil?

i am changing the oil today, i was told that it sounds like the lifters

its coming from the top of the engine, some say that it might be the lifters since the car has been sitting for so long

i was told that it could be the lifters but dont they tick or do they knock. i dont know,

By conditions, he means does it knock all the time the engine is on, or only when accelerating, and so on.

yes it knocks all the time, i only ran it for about 10 minutes, but if i hit the gas, it got louder. but when it idled down it seemed to get quieter but it didn’t stop.

I would dump a half a can of Seafoam in the crankcase, idle the car for 20 minutes or so and then change the oil. (I’m not sure everyone else would agree).

thanks ill try that tonight and let you know what happens

I agree with the flush, but would recommend simply reading the can and following the directions to the letter.

Yea, but the Seafoam can doesn’t say anything except to add a pint per 10qts. No flush instructions. I was always mystified by that. They imply that you can just drive around with it that way. That would not be my choice.

But, jcc - if you do buy something else called a “flush” - then follow the directions to the letter.

cool will do, but do you think that it sounds like the lifters since the noise is coming from the top?

If you go to Seafoam’s website, they actually have more detailed instructions on how to use it prior to oil changes. I agree that it is very strange that they give almost no helpful advice on the can.

Check their website!

Apparently those engines have hydraulic lifters that are known to stick. Removal and cleaning or replacement may be required, if oil change/seafoam doesn’t work:

I admit to not knowing that. I’ve never personally used the stuff. It is a surprize that they have no directions. I’d think that because of the expensive damage that could occur they’d protect themselves with explicit instructions.

We can’t say what it sounds like since we can’t hear it. If it is up top then it is more likely to be valve train noise rather than uglier lower end things. Get it flushed with some fresh oil and then try to get someone with an experienced ear to listen. Or find a way to record it and post it online somewhere.

If you call them on the phone and ask them I believe they’ll tell you that you can just run it in the oil - i.e. as an additive, not a flush. Like I said, I wouldn’t - but I think that’s their line.

thanks, i’ll try that first since that seems to be the cheapest thing to do first