91 2DR Red, AX15, NP231J, 284,000.

When I drove it and bought it a month ago it was fairly quite. Checked the dipstick and it had fresh oil in there. Didn't pull the oil fill cap. Brought it home and based on sugesstions drained some oil and replaced with a quart of ATF to clean it up a bit. Drained it, 5 qts oil(10w40 due to mileage) and 1 qt MMO. Shortly afterwards got what I thought was a rod knock. It wasn' real loud but it for sure didn't sound like lifter(s) noise. 40 psi cold and 23 psi when at temp. And does not burn oil. I finally looked at the rockers through the oil fill hole and there is a lot of gunk in there. Replaced the t-stat which was basically rusted and it runs 220-225. Idles smooth at 800 rpm at temp. If I run it up to12-1500 rpm the "knock" goes away, sounds like a normal engine, oil goes back up to 40 psi and the temp stays put. I did notice before and after t-stat replacement it seemed to take a real long time for the upper radiator hose to get hot. The heater works real well defrosting real well and plenty warmth for my liking. Now I'm thinking maybe the fan clutch/water pump is what is making the noise. I haven't really had to turn wrenches on a car for 25 years so I'm looking for input.
I do plan to hit the engine with a flush to get rid of the sludge and hope for the best as well as running some Seafoam through the intake as the throttle body was black before I hit that with some cleaner. Figure best case rod & main bearings, rear seal, oil pump, timimg chain replacement if it isn't the water pump/fan clutch. Worst case do the pump, crank and cam kit, timing chain to get it too last another 50k+(it will be driven 56 miles round trip each day for work and putzing around the area. Have a 2003 Wrangler for long stuff) while I put the money away for a rebuilt motor. Either way for right now this is strictly a budget fix as money is hella tight at the moment. Any work will have to be done with the motor in as I have no way to pull or to work on it out of the weather. Not trying to be ghetto but gotta do what I gotta do and I need a second vehicle on the road.

You folks are the SME's on the XJ so your infinite wisdom will be greatly appreciated.

Thanks for putting up with the long post.

PEPPERHEAD

 

could it be your knock sensor?

maybe remove your valve cover and try to clean out the mess.

i've seen somewhere before where a bmw owner hadn't changed his oil for 60k, should've seen what it looked like inside. can't believe it even ran anymore.

 

run some seafoam for about 100 miles and then change the oil again... that stuff will break down all the crap in there...

 

to search for the knock if u dont have a stethascope or whatever the heck... cut off a 2 foot piece of water hose and hold it to your ear and each item on the motor... helps track down where the knock is coming from... which helps diagnosis...