miata knocking noise, help please
 

my friend started his car up, and it was making a loud knocking noise from idle, and at rev also. doesn't sound like a ping, or lifter noise. any ideas? he said his oil gauge would go all the way down to 0 pressure when he would take it out of gear and into neutral while driving, then all of a sudden at start up was making this noise.

Did you check the oil? It sounds like there's very little in there.

no oil pressure. hmm, I wonder whats wrong

yeah sounds like it's sort of out of oil.

Sounds a little louder than low oil. I'd say low oil caused a bearing to go bad. But also, it's low on oil. Heaven forbid you check the one thing the car manufacturers actually want us to look at...

its not low on oil, and its not my car. i posted this up for a friend, so not sure how frequent the gauge would show low oil pressure. im positive this is caused from the oil not circulating, but not sure what the noise is... im thinking bad bearing also.

I think the thing to do at this point is to change the oil; see what the oil that comes out looks like and what the car does with the new oil. If the issue continues, the best option is probably to look for a new motor and swap it in. You should be able to find a used motor a good bit cheaper than trying to fix a "no oil pressure, loud knocking noise" issue.

ya thats pretty much exactly what i told him to do. what should he be looking for in his oil? just deep black oil, and bits of metal? or are there going to be other things to look out for? i've never run into an issue like this. he doesn't have internet at the moment, or a smart phone, so im doing my best to help him out. thanks for the help.

When he drains the oil he can cut open the oil filter, spread out the pleated filter media and see how much metal is in it. Metal = new/used motor. No metal I'd throw in new oil and see what happens.