'89 Engine Knock! Need advice!
 

One of the kids I mentor has a 1989 Supra N/A with auto trans. I helped him find it and believed he got a good deal. Had 109K on it at time of purchase and now has 119K. Here are the issues that I know of at this time...
- Small oil leak near top front of motor. Lots of fresh oil under car now. Uses a quart every few hundred miles.
- A solid knocking has started in the past few weeks.
- Oil pressure builds but I'm not completely sure what is normal for this car. At idle, the gauge sits at or close to zero, but gradually raises up to around 40psi when put under driving load.
- Coolant seems to be a bit filmy and has some brown particles floating in the overflow tank which means there could be a head gasket leak from the oil side to the water side. (Had this happen to my 85 Celica once. Outcome wasn't pretty)

The car is still running like a champ, but I've told him to drive as little as possible until we can properly diagnose the problem. Any suggestions would be greatly appreciated.

Test the coolant. Drain the oil and inspect for light brown sludge or separated coolant in it. Check inside the oil cap for pudding like sludge.

As for the knock, listen with a stethoscope to determine where it's coming from first.

The oil leak from the upper, front could only be a few things: Valve cover gaskets, cam seals or between the head the lower timing belt cover. Check the valve covers for loose screws (do NOT over tighten them). If that seems fine, pull the timing belt off the cam gears, remove the cam gears and pull the upper rear timing belt cover to inspect the cam seals and the seam where the head comes down onto the lower, rear timing belt cover.

Oil pressure on these cars isn't very high. 5-30psi at idle (kinda broad range there, huh?) and 40+ over 3000RPM.... <---- Not the exact figures, but they're some around there; Look in the TSRM for specific figures if you need.

I have a 1990 7mgte that for a bit I thought had something wrong with the rods or something lower end because it was knocking, turns out I had an oil leak in the same area as you, can't be sure its the exact same place but, I fixed that leak which wasn't cheap, ran me about 300 and I did a bit of the work myself. As soon as the leak was fixed the knock faded out fast and hasn't come back.

My 89 had a oil leak at the back of the head and a knock my oil gauge did the same thing. mine turned out to be a bad rod bearing does the knock happen between 2000-3000 rpm if it does I might be a bad rod bearing I drove mine like that for a year and I still ran fast when I decided to have it rebuild