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AWheeler 06-24-2013 07:51 AM

99 4.0 - Low Pressure and knock
I have read several threads about this issue, but have not found a similar situation yet...

I was wheelin' over the weekend and had a ball. Ran for about 3 hours in the AM. No issues and everything worked very well. It was warm outside, about 90 or so. Took the Jeep back to camp and had lunch for about an hour. After getting back from lunch, I started the Jeep and hear a ticking / knock sound. Opened the hood and it was coming from the fuel runners / exhaust manifold. So, I immediately thought I had a cracked manifold. The sound kept pace with the RPM's. So, I shut it off, looked under the hood for a minute, then started back up. It made the same noise for about 15 seconds, then went away. Has not made the sound sense. I did notice that while creeping on the trail, the oil pressure got low. At idle, it kept 15 - 20 psi, which is low to me, but OK.

What could this be? I have 145k miles on the motor, so should I go to something like 10w40 or 10w50? I use 5w30 right now.

Thanks all!

WhiteMtnJeep 06-24-2013 02:36 PM

5w-30 is too light. IIRC proper oil viscosity is either 10w-30 or 10w-40.

cruiser54 06-24-2013 02:38 PM

What brand of oil filter are you using?

tinktinkTJ 06-24-2013 02:41 PM

10w-30 is the proper viscosity. Try changing the oil and see if that helps. I do run 5w-30 in the winter but I wouldn't run it in the summer.

WhiteMtnJeep 06-24-2013 03:49 PM


Originally Posted by cruiser54 (Post 15601922)
What brand of oil filter are you using?


cruiser54 06-24-2013 05:30 PM


Originally Posted by FernBchJeep (Post 15602169)

LOL. I meant the OP. I figured you ran a good filter.

esiegler3 06-26-2013 08:36 PM

Change the oil pump, I'm doing my pump this weekend to a high output pump. I have the same problem no pressure.

AWheeler 07-04-2013 02:59 PM


Originally Posted by cruiser54 (Post 15601922)
What brand of oil filter are you using?

ProMotive (Purolator). Sorry for the delayed response...

I have put a few hundred more miles on it and it has not done it since.

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