Hello, I've been using this site for a long time to learn how to work on my Jeep and I've finally hit a road block big enough that I need some specific help myself. This might be a kinda long post cause I've done a lot already.

I have a 98 XJ with a 4.0 that is overheating badly. At idle it needs the electric fan most of the time to cycle between 215-225 but won't go above that, while driving around my neighborhood it can hold around 225, cools down to 210 while driving downhill, and even less than a mile of a steady uphill grade or driving any faster than 40-45 it starts climbing up around 240 before I shut it off or turn around. A couple times I've boiled over, had to limp home and reached 260+.

These problems started recently after I pulled the head due to a misfire and rough idle. I replaced all gaskets, resurfaced the head and block, lapped and restored the valves, and replaced the oil seals and valve springs. After this repair the engine runs AMAZING. I can't believe the difference, idle is silky smooth, and the car is significantly more responsive. Only problem now is the overheating.

Here's what I've done since then trying to deal with it:
new CSF 3 row radiator
new flowkooler water pump
new thermostat
new radiator hoses
pressurized coolant flush through every hose including heater core
drained coolant shows no oil, drained oil shows no coolant
engine block test shows no combustion gases in coolant
exhaust gas does not have any discernible color or odor out of the norm
compression test showed the following by cylinder each time I ran it 1-140/142, 2-133/133/132/133, 3-145/144, 4-144/146, 5-149/149, 6-146/148
fan clutch has good resistance after running the motor, top half of fan shroud is still in place
temp sensor matches IR reading of thermostat housing
I can't measure coolant flow but I disconnected the heater hose and filled from the radiator cap as the engine ran and the flow from the hose seems substantial enough
vacuum test reads 13 in at idle at 4500' elevation, and shows no sign of exhaust blockage when revved
cleaned ac condenser to try and maximize flow, no significant airflow blockages

I do live in Arizona so it's hot out and my jeep has a decent amount of extra weight in aftermarket bumpers and roofrack along with a small lift and 31s, so the engine has some extra work to do but nothing crazy. I'm at a total loss for where to go from here, all I can think of is to pull the head and just try to redo the job. The only inclination I have of any problem is the slightly lower compression on cylinder 2, but I'm hesitant to tear into it again considering how much my performance has improved since the head repair and the fact that I have zero other signs of a problem with the head or gasket. I'm really looking for any and all suggestions, I need to get this taken care of as it's my daily driver and I'm getting truly desperate lol. If you've made it this far thanks for taking the time to read into my problems, I really appreciate it.

 

Did you ever get a response to this ?. I have an almost identical situation. I’m wondering if I have full flow of coolant through the block and head passageways ?

 

After all that work it turned out the $100 flowkooler water pump I got was just faulty from the start. Replacing it with an $18 gates pump fixed everything....

 

A "high-flow" water pump can often cause a cooling problem.