'98 4.0 w/100k miles, head gasket...

now progressed to in between "weeping" and "seeping". Mobil 1 changes every 3k, no loss of any fluids including coolant except motor oil via head/ block interface, no effect whatsoever on dip stick oil level.

Perfect emissions, stellar performance even w/3.55 and 31's, Platinum fours look like they came out of the box. Nothing bizarre eminating from the tailpipe.

Bought a valve cover gasket but have not installed it after gunking down motor and discovering true source of leak. The only head bolt exposed I think is a twelve point, have not pulled valve cover to see what other bolts are involved. Will delve into the FSM tonite.

Does this portend a major catastrophe, or can the head with existing gasket and bolts be retorqued, or should I just let sleeping dogs lie.

Not panicking yet, but just renewed insurance w/full coverage, saving for a down payment on a new house, do not need something like this, which I cannot do myself, specially given the downtime.

Thanks,

Mike #300

Drain and flush the system, refill with 50/50 coolant mix of mopar and DISTILLED water. That should stop the headgasket from deteriorating any futher from high mineral content provided that the last time it was changed the changer used tap water.
Every once in a while my 98 gets some green coolant near the thermostat housing, not all the time, just every once in a while. No rhyme or reason, just happens.

Re: '98 4.0 w/100k miles, head gasket...long...

Rich, always backflushed using the Prestone "cut-the-heater-hose" kit, then drove around for a few miles with pure distilled water, then dropped that, finally putting in coolant and distilled water, maybe 60/40.

The oil seepage is worse towards the rear of the motor. I was locating/tapping into the gray tach wire going to the coil for a remote starter installation, that's when I noticed that the seepage, which not only moves downward with gravity, but upwards on the head through, what, capillary action?!? It saturated the plastic loom that lies on the coil side of the motor

I don't know what the drivers' side looks like, but the interface between the very front edge of the block and motor reveals not a trace of oil seepage at all.

I'll get under the motor and search further. Can a motor with this mileage but in otherwise showroom condition head be snugged down a bit?

Thanks,

Mike #300

i guess if you have a torque wrench and want to pull the valve cover and see if any of the bolts are loose that might work. but the problems is that most of the bolts have rusted a little giving you a false reading on the torque wrench thus making some bolts tighter than others. if you realy want to fix this problem do a head gasked it's not that hard just takes some time. thinking this thru i would strongly recomend to just let it be clean it up nice nice and check to make sure that the oil isn't coming from somewhere else that can be delt with. EX: (valve cover gasket) (breather hose) then just keep up on the seapage and dont' let it cover the entire engine (if you care about looks)

I originally bought the oem valve cover gasket before I cleaned the top of the motor. I would have sworn it was that gasket that was leaking.

After a thorough cleaning, the seepage was really obvious. It must have been going on for awhile, the starter caught alot of the oil. Tonite I have to lube the front end, still have to look under the mainifolds to see what's going on there.

I dont mind the seepage, I'm just afraid the gasket is going to pop, overheat, and at the very least warp the head and block. This xj has never seen anything but Mobil 1 oil and filter, changed at ridiculously low mileage intervals, and the idle is smoother than when I bought it.

I'll try to take some quality photos of the problem.

BTW, I've never taken the valve cover off, I don't know what the head bolts look like. I think there's one up front out side the cover, rusted to the max.

Thanks,

Mike #300

It is seeping outside of the pushrods, which is only 3/8" thick. It won't have any effect on compression or water leakage as there is no water in that outside edge of the block. I'd just use a little brake clean now and then and it will probably go another 100K.

rsalemi said:

It is seeping outside of the pushrods, which is only 3/8" thick. It won't have any effect on compression or water leakage as there is no water in that outside edge of the block. I'd just use a little brake clean now and then and it will probably go another 100K.

Click to expand...

Ditto on that. A little oil "sweat" on the passenger side of the block is normal on higher mileage 4.0's and is usually caused by small amounts of oil weeping past the head gasket where the pushrod oil galleries are. As Bob said, it won't affect compression and it's far enough away from the water jacket not to be an issue.
You may have a small leak past the valve cover gasket. The cure, quite often, is simply to tighten down any of the valve cover bolts that may have worked their way loose.

Thanks,

Appreciate the help. Still have not lubed the xj and gotten underneath to see ehat the manifold side is doing.

Not going to worry that much, other than wasting $30 on the oem valve cover gasket, which my fsm states is designed to be reused. What the heck, curious to see what 95K worth of Mobile 1 looks like inside the valve cover.

Thanks again, appreciate your experiences, sorry it took so long to get back to the thread.

Mike #300