Hello all, I wanted to post a message here before I followed my mechanics advice regarding my Jeep to see what everyone here had to say about his advice. Let me explain. My 99 Jeep is now at 40,000 miles, but at around 30,000 (of course) after one oil change one day a slight knocking appeared. Slight, not always there, sometimes loud, but nevertheless a knocking coming from the block area where one shouldn't be. Now I know this is BAD meaning a bent rod, most of time, but I have ignored it, til recently when my mechanic noticed it and asked me about it. He looked up the pressure for my Jeep and said that at around 1600 rpms my Jeeps pressure should be around 75 or 80 but it tends to float around 40 - 50 all the time. He suggested that maybe the oil I was running (Mobil 1 Full synthetic 10W - 30, what the owners manual states) is a bit too light, and that I should switch immediately to a 20W - 50 grade. He didn't want to entertain the idea of a bad oil pump with me at all. Now I am not all that familiar with the grades, and not a mechanic in the slightest meaning of the word, but understand it is a heavier oil. I guess he is hoping it would get rid of the knock, as he was feeling that the pressure was a bit low at times, but I guess my question to you all is, do any of you think that this is a good idea? Mobil 1 doesn't make that grade, so looked into Castrol Syntec, but can't find it anywhere, so the next best thing I have found is Vovo (forget spelling) something, started with a 'V'. I was also considering going with Mobil 1's 15W - 50. I am lost here any comments?? Thank you as always. You are all a bunch of help and a wonderful resource for all us jeepers out here.
Greatfully,
Melvin

First off, what is the power train warranty on the jeep. Were they offering the 7/70,000 power train warranty in '99? If so, thake it in and make them fix it....In my personal opinion I don't believe that changing to the 20/50 is going to do anything for you...

No, warranty is 3/30,000. The pressure tends to hang around 50 all the time. What should I do? Does anyone have any suggestions on what it could be or if the pressure seems low to them? Thanks.

hey there
you are saying it is coming from the rear of the motor? if thats the case you might have a cracked flywheel, or one that has become two pieces clunking around in ur bellhousing area. trust me man I seen it happen before and auto tranny's with cheapy flexplates and torquey a$$ starters will rip them into two. I am not saying this is ur problem it's just an idea also ask your mechanic to get in the engine area with a stethascope and probe the engine area (all over the place) and try to trace the noise to find out where its really coming from. I also do not believe your oil pressure is to low. what the ratio is for every thousand RPM, the oil pressure should be @ 10 psi. atleast thats what I have been told at school, and a normal operating motor will have any where from 10-60 (maybe more than 60)psi at normal operating conditions somewhere around there. But first and foremost stick to what the manufactures recommend remember they built and made the jeep to their specifications, second probe the engine comparment to locate the source of your noise and then go from there.

Thanks, Sounds like a rod to me, (lifters area, top engine block), but my mechanic said no. I am going to take it to a engine shop and see what they think. The sound is really annoying to me since it is what my beaters I had when I was 17 sounded like. It only has 40,000 on it? What could it be??

UPDATE:
Took it to a engine place today, they said it is either (as previously said) a cracked fly wheel or bad rod. They don't work on engines still in vehicles, so I was referred to another shop. I will let everyone know how things go. I shouldn't be having this problem with only 40,000 miles on it. I am a bit disappointed over the reliability of my Jeep lately.