Ok so i just bought a 1991 Cherokee 4.0L from my sister. besides the basic leaks from about every lower gasket there is this amazingly loud knock coming from either around the bell housing. but only at idle when in park or any gear. Also there is an issue that keeps draining the battery in less than 5 mins. New Alternator and Battery. This is my first jeep with a jeep motor in it. I'm used to working on a Chevy 350 CID in one. I dont know where to start with either problem. I have traced connections and wires through the whole thing and dont know where the drain is coming from or if the knock and the drain are in common. And the Voltage drain doesnt occur everytime either. Please help me. If you have any reccomendations please email me. I'm on the road alot with work
~Levi
I usually use a piece of plastic pipe and listen to various points on the motor to try and localize any knock. It may take awhile, but by repeating and sticking with it you can generally mark the spot fairly closely.
Two possibilities that come to mind are the typical 4.0 piston slap, which IMO can be ignored and is pretty much a trait of the motor.
Another is a cracked flex plate or more likely the bolts backing out of the flex plate or the torque converter. You can remove the inspection plate and check the torque converter bolts (if your plastic pipe and ear search leads you to that area). Sound travels and it can fool you.
I don't know if it's possible to drain a healthy battery in 5 minutes. Chances are it is something in the cables. Most likely the battery clamps and poles. I spray mine with solvent, clean them with a 3M pad or sand paper, spray the clamps and poles again. Get everything nice and shiny then tighten the clamp back on.
The battery ground at the block near the dipstick brace, is a known trouble spot. Corrodes and gets covered in oil, likely to make a poor contact.
I'd check my battery voltage, at the battery poles. Should hold near +/- 13.5 volts or higher, should charge around 14 plus with the motor running.
If it is in fact a drain , the best way I've found to trouble shoot, is to start removing fuses and try to narrow it down to a sub system.
What exactly makes you think the battery is drained? It doesn't crank? Which can be a whole other issue.
The volt gage in the instrument cluster says it's low? The volt gage lies as often as not.
Everything is dark and you have no power at all?
