Brief Knock at Start-Up, Then Low Oil Pressure at Idle When Warm

[kcac_1_157641]

I had a Fram Ultra Synthetic filter on the vehicle when I first noticed the problem. I then did an oil change with 5W-20 synthetic oil and a NAPA Gold oil filter. I had that oil in there for approximately one week when I changed it to 10W-40 synthetic oil and another Fram Ultra Sytnthetic filter. I guess I could try a Motorcraft filter. It is just that I have used mostly NAPA (which are re-labeled WIX filters) or sometimes the Fram Ultra Synthetic filters, with 3K to 5K oil change intervals, and never had engine noise or oil pressure issues in the past.

@JoeMario

First, as Tester noted, connect a mechanical oil pressure gauge to the engine. See what the “hot oil” readings are at idle and at 1500-2000 rpm. Verify the engine can hold pressure. If it can’t, and it’s way off, then ignore the rest of these bullets.

When you say “Verify the engine can hold presure.” what am I looking for? Run the engine at 2000 RPM with an oil pressure gauge and see if the oil pressure remains at a steady level?

[JoeMario]

@kcac_1_157641

@JoeMario

First, as Tester noted, connect a mechanical oil pressure gauge to the engine. See what the “hot oil” readings are at idle and at 1500-2000 rpm. Verify the engine can hold pressure. If it can’t, and it’s way off, then ignore the rest of these bullets.

When you say “Verify the engine can hold presure.” what am I looking for? Run the engine at 2000 RPM with an oil pressure gauge and see if the oil pressure remains at a steady level?

Sorry I was not clear.
Although engine oil pressure ranges may differ, on a hot engine, if you bring it up to 2000 rpm, I’d be worried if the oil pressure couldn’t hold at least 20-25 psi.

The fact that you only have 6 psi with a hot engine at idle is very worrisome. It’s likely excessive clearances somewhere.

If it were my car, I’d try to get as much as I can out of the “thicker oil” route, even if that means adding a can or two of STP. (I’m pretty certain your engine does not have VVT, which is a good thing becase VVT doesn’t like really thick oil.)