2000 XJ, 4.0, 331 head. Bought it 140k, now has 175k. When I purchased it, the coolant was murky, radiator was leaking, and oil was very black. Oil guage always says 80 (I realize it is bad). Replaced radiator, hoses, and thermostat. Runs great, has never overheated, coolant stays green, and oil stays black. No creamy foam under cap.
Last week I changed the old leaking valve cover gasket and checked the prone 3-4 cylinder area and found a crack.
I've lost small amounts of coolant in the past and could not find a leak but could never see anything through cap hole. I borrowed a coolant leak down tester, applied 15lbs for about 15 minutes. Found coolant leaks at thermostat housing and two hose connections. I've just previously driven it to work for the last 17 days (1700 miles) and have had no coolant loss. Also found two needle head size bubbles starting to come out of the crack. I installed a manual oil gauge and read 25lbs cold and 2 lbs hot idle.

I'd like to think its a small enough leak that damage wasn't done and pressure is more of an oil pump issue. I still plan on replacing the head with new aftermarket as well as the pump.
What I'd like to know is:
Since I'm in there, what other things can I do that are worth it as preventative maintenance given the amount of potential miles possibly left. Journals, bearings , etc. I'm new to this, have never pulled a head before, and not sure of everything I can do with motor still in as well as overall costs.
I don't mind spending extra now and doing it. I'd rather just do it once rather than changing oil pump only to find there was more damage my untrained eye didn't see.

 

I should add that it's valvoline high mileage 10w30 and a Chrysler filter. Mechanical gauge installed using a tee at the sensor location. Sensor on the run of the tee and gauge at the bull.

 

Given those oil pressure readings I'd plastigage the bearings as long as you're in there.

 

Thought about your post for awhile and it seems the best for you would be to just pull the engine and do a complete overhaul with all the machine work done to the block also. This isn't a huge cost factor and once its out you can take care of a lot of small things very easily.

This is what I'm having done with my engine rebuilt professionally, the rebuild does cost you his labor but the machine work has to be done anyway. But labor wise you have done a good chunk with the engine being removed and delivered to the builder/machine shop.

I have found over the years that if you tighten up one end of an engine top or bottom the other will usually give up soon due to the extra strain put on them by the new work on the other.

The cost for rebuilding the 4.0 is very reasonable for parts and even labor if having it done, compared to many engines. We are lucky to have this workhorse in so many of our XJ's and then going 250-400k mi. isn't uncommon. Others may not feel this way but after going this far it seems counterproductive to not do a complete overhaul and leave no weak points undone.

JMHO

 

i agree

 

How much does a rebuild on the 4.0 typically run (including labor)?

 

It varies from area to area (labor rates) and quality of the parts used in the build and machine work required.

 

The only other thing you can really do in there is lifters, however some people frown upon new lifters on an old cam. however 2-24 psi for oil is pretty dang low, that means the coolant has been slowly eating the bearings over time. There can still be small amounts of coolant in the oil without it becoming chocolate milk but enough to do some damage over time.

 

Ive had some time to think of this. Not that im right by any means but the ole curiosity got me you said that the oil was very black. was it thick or thin? the reason i ask is that its possible that you oil pump pickup may be clogged. If and when you decide to pull it down or just the pan its worth the look. Ive seen in the industry a couple times with oilchanges that were overdue by 15-25K clog up with cheap oil. Also ive seen them rust if there was moisture in the crankcase... Just food for thought... these 4.0's are tough as nails my 92 went 400k before it coughed up a rod with little or no maintenance

 

Thanks everyone for the advice. I've been working a lot lately and haven't had a chance to get to it. I think in going to pull the pan, replace the oil pump with a high volume, replace rms, as well as the related steering components and bushings that I'll pull for better access.
I'll check the engine internals while there. Google and you tube are helping me in my research.

This is a stock XJ I use as a third vehicle and winter commuter. I live in the middle of a cornfield in the snow belt of NW Indiana. I've always wanted an XJ and really enjoy driving this one.
I think I 'll also be looking into junk yard engines to rebuild as a standby. I'm still on the fence about a Junkyard Tupy or a new Clearwater.

 

be carfull using a high volume oil pump, if it suplies too much oil to the top you could starve your bottom end