No oil pressure and engine knocking
03-02-2017, 10:27 AM
#1
Newbie
Thread Starter
Join Date: Nov 2016
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
No oil pressure and engine knocking
i have a 1996 xj with the aw4 inline 6 4.0. I was driving on the highway one night and once I got off and was doing some town driving at lower speeds I thought I could hear like a knocking sound. Ever since then it has been knocking and I've always had a problem with the oil pressure. I replaced the sending unit once and topped it off with oil (even though I just recently changed the oil) and I had like maybe 40psi of pressure but that only lasted like a week and it went back down. Not sure if the two things are directly related but since you people have more experience than I do maybe someone knows what this might be. Also I was having a shifting problem around the same time where it feels like it's never really in the right gear, I have no power going up any kind of a hill and it's a chore to get up to even 45-50mph. I had a thought that maybe the shifting issue could have cause me to over work the engine trying to get up to speed or something I don't know. I never took it above 3000 rpms though so I kind of doubt it. I would post a video of the knocking sound but the heep is in the shop right now, our mechanic is working on the shifting problem (before you jump to conclusions I already "adjusted" the kickdown cable, it kinda changed the way it was shifting but didn't fix it) anyway I really am mostly concerned about the motor right know, is it a twisted rod bearing? a piston slap? Or something else? anyway hopefully someone who has experience could help me out, thanks!
03-02-2017, 11:44 AM
#2
CF Veteran
Join Date: Nov 2010
Location: In the middle of Minnesota!
Posts: 5,804
Received 99 Likes
on
88 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
How many miles are on this engine? The following is how I would proceed if your XJ was in my garage.
1. Test your oil pressure with a "mechanical oil pressure gauge". It is temporarily installed where your oil pressure sending unit resides. You need some actual hard test data to tell you about your engine and the first and easiest one is oil pressure. This gauge can be rented from many parts stores; call around for availability. The oil pressure spec. for the 4.0 is as follows:
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
2. Perform a compression test on all 6 cylinders. The compression spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.
Testing is the only accurate way to come to any conclusions. Either do it yourself or pay somebody to do it; the above tests are not expensive to perform. Once you have completed these tests, you will have a VERY good idea on what is going on internally with your engine.
Also, an experienced technician will likely be able to help you in isolating that engine noise as noises are difficult to help you with online.
Good luck and be sure to post any testing data that you get for comment!
1. Test your oil pressure with a "mechanical oil pressure gauge". It is temporarily installed where your oil pressure sending unit resides. You need some actual hard test data to tell you about your engine and the first and easiest one is oil pressure. This gauge can be rented from many parts stores; call around for availability. The oil pressure spec. for the 4.0 is as follows:
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
2. Perform a compression test on all 6 cylinders. The compression spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.
Testing is the only accurate way to come to any conclusions. Either do it yourself or pay somebody to do it; the above tests are not expensive to perform. Once you have completed these tests, you will have a VERY good idea on what is going on internally with your engine.
Also, an experienced technician will likely be able to help you in isolating that engine noise as noises are difficult to help you with online.
Good luck and be sure to post any testing data that you get for comment!
Last edited by tjwalker; 03-02-2017 at 11:49 AM.
03-02-2017, 01:35 PM
#3
Newbie
Thread Starter
Join Date: Nov 2016
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
I appreciate the advice, like I said the jeep is currently in the shop, might have my guy go ahead and check that stuff for me. Or I'll do it myself when I get it back. either way I'll be sure to do post the outcome of these tests. thanks again!
How many miles are on this engine? The following is how I would proceed if your XJ was in my garage.
1. Test your oil pressure with a "mechanical oil pressure gauge". It is temporarily installed where your oil pressure sending unit resides. You need some actual hard test data to tell you about your engine and the first and easiest one is oil pressure. This gauge can be rented from many parts stores; call around for availability. The oil pressure spec. for the 4.0 is as follows:
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
2. Perform a compression test on all 6 cylinders. The compression spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.
Testing is the only accurate way to come to any conclusions. Either do it yourself or pay somebody to do it; the above tests are not expensive to perform. Once you have completed these tests, you will have a VERY good idea on what is going on internally with your engine.
Also, an experienced technician will likely be able to help you in isolating that engine noise as noises are difficult to help you with online.
Good luck and be sure to post any testing data that you get for comment!
1. Test your oil pressure with a "mechanical oil pressure gauge". It is temporarily installed where your oil pressure sending unit resides. You need some actual hard test data to tell you about your engine and the first and easiest one is oil pressure. This gauge can be rented from many parts stores; call around for availability. The oil pressure spec. for the 4.0 is as follows:
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
2. Perform a compression test on all 6 cylinders. The compression spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.
Testing is the only accurate way to come to any conclusions. Either do it yourself or pay somebody to do it; the above tests are not expensive to perform. Once you have completed these tests, you will have a VERY good idea on what is going on internally with your engine.
Also, an experienced technician will likely be able to help you in isolating that engine noise as noises are difficult to help you with online.
Good luck and be sure to post any testing data that you get for comment!