Got a 93 legacy for free, it has been very well maintained, oil always changed every 3 to 4 k, it has 184k miles, and has a knock. i think its a bearing but not sure, it does it really at any rpms, but with more gas, it seams to stop but if you hold it at a certain rpm above 2300 it will make the noise badly. So i believe with more rev the oil pressure goes up and its quiets down. But just took it and it passed california smog with flying colors. So i want to know if theres anyway to find out what it is, and possible fix. How long do i have running it this way. I had it at 6200 rpms before the smog to clean it out and didnt make a sound, until i let up on the gas and tried to hold speed and it made a racket

Probably just the hydraulic lash adjusters. They fill with oil, yet sometimes they seize or get air trapped because a oil passage way is slugged up running them dry. It causes them to give a noise similar to a knock.

 

You can remove them and bleed them. You can also try getting a bottle of seafoam at your local parts store and dumping it in the oil and driving around aggressively hopefully it will clear out the sludge and the HLA's will be nice and quiet. You should only drive around for like 20minutes or so until the noise goes away, THEN replace the oil and filter.

ok will try the seafoam, and see what happens. But what would it take to remove and bleed them?

I'd put the Seafoam in but I would just let it idle or drive it under very light loads with the seafoam in.

 

I spun a bearing with seafoam in the oil. I had put it in and then I had to drive it for 15 miles.

 

It spun a bearing. Read the Seafoam directions.

 

It's great stuff.

 

Also try a quality 5-30w oil.

i have 5w-30 fully synthetic in it now, been in there for about 300 miles. I sure hope its only the valve lash. Will try the seafoam and hope for the best