Knock & Low oil pressure at start up.

[jeepboy381]

So this is what happens, 99% of the time when I start my Jeep I get a loud knock for about 3 seconds and no oil pressure. After 3 or so seconds the oil pressure comes up to normal and the knock disapears.....what could cause this?? :fuse:

[RichP]

Fram oil filters will do this.. The jeep motor oil filters from mopar, Mobil-1, K&N among others have a better metal anti-drain back valve in them. The frams are cardboard.

[old_man]

Oil pump taking a hike. Isn't there a anti-drain back valve in the pump or block.

[cherrycherokee]

jeepboy381, hate to break it to you but you are probably describing a worn engine. When there is too much clearance at the bearings you lose pressure initially. When the oil circulates it fills these gaps and eventually builds pressure. Go to a heavier oil and put in a can of super heavy oil (honey thickness) at each oil change. Change the oil as regularly as you can and you'll get some more life from your engine.

[joe_peters]

Your profile says 2000 XJ, would this be the Jeep in question?

Engine? How many miles? Current oil filter, does it have a silicone drain-back valve or a Nitrile rubber drain-back valve? Just curious.

Some interesting reading from the Filter Manufacturers Council (whoever they are): http://www.filtercouncil.org/techdata/tsbs/93-1R1.pdf

[sjx40250]

JP: that was an interesting article. I am surprised they didn't make the suggestion to fill the crankcase then install the replacement filter. This would allow any trapped air to escape through the oil filter circuit. I will change my steps from this point forward.