paulutions

My 98 XJ 4.0 started making a knocking noise. Originally, I dismissed it as the "4.0 Knock." My wife was driving it for the last month or so and one day I happened to be in the driveway when she pulled in and noticed the knock was much worse. It sounds like a rod. Long story short, I briefly checked it out and noticed there was no oil pressure and told her to just park it. No telling how long she was driving it like that for. My question is: if I determine that the oil pump is bad, with that knock, do I even bother replacing it? Or, do I just need to start looking for another engine?

freegdr

Engine my vote.

paulutions

How can I tell without spending $80 on a new pump?

BlueRidgeMark

Start by verifying the oil pressure with a mechanical gauge. You might have a bad sending unit. I picked up a Bosch mechanical gauge at Pep Boys for less than $20.


When I got home with it I:

1. Removed my electric sending unit
2. Connected the Bosch
3. Set it up on the cowl where I could see it from the driver's seat
4. Fired up the engine
5. Read the oil pressure at various RPMs.
6. Put it all back the way it was.

That all took me less than 10 minutes. It confirmed my sending unit was bad.

I would not put a pump in it until you have dropped the pan and looked at your bearings. Plastigauge time. Your pump might be just fine, but trying to push oil past worn out bearings, so is developing no pressure to read.

texastaz38

Drain the oil in a pan and look at it, if it looks like a beautiful metallic black metalflake paint....time for a rebuild or new engine.