2000 XJ, 4.0, AW4, NP242. A/C use is a non-factor in all of the below; I've been trying to figure things out with it turned off.
My radiator blew out a few months ago, so I replaced it with a Spectra unit from NAPA. I don't have the receipt in front of me right now, but I seem to recall that the model number was NR 2736 - basically, the heavy-duty option, which is what my XJ left the factory with.
Here are the symptoms: cooling's fine when moving, and the temperature gauge sits at the right level for the thermostat opening (195degF). Idling, in traffic, or crawling on the trail, it will creep up to about 220-230degF, but eventually comes back down once I start moving again. Coolant level stays OK and there are no signs of loss from, say, a bad head gasket or the heater core. Has not overheated, but runs noticeably above normal.
Replaced so far: radiator, upper and lower hoses, fan clutch (used NAPA part number 272310 to upgrade to the ZJ heavy-duty unit), thermostat twice (originally with a Stant unit; currently OEM with the relief valve), coolant temperature sensor, and serpentine belt. 8-hour and 15-minute flushes have been done and all coolant changed; air is believed to have been removed from the system. Coolant is Prestone 50/50 pre-mix.
Prior to replacing the fan clutch (which was on its way out) this behaviour would be more pronounced at ambient temperatures over 80degF; post-replacement, that bumped up to 90degF, so at least that introduced some improvement. Double-checked that the fan blades are pointing the right way; it'll suck a piece of paper right up to the grille and hold it there, and air is being expelled rearwards over the engine from it.
Pretty much the only thing in the system that hasn't received attention is the water pump. There's no evidence of a weep or bearing noise from it, and pulling the upper hose from the radiator with the engine running shows coolant being moved through at what appears to be a fairly normal rate. Doesn't mean the impeller's necessarily 100%, but at least on the surface things look OK.
With all that out of the way, I'm suspecting that the radiator isn't up to the job given that this started after the original one was replaced. One thing I did notice from the online listing that didn't come up in the store: that radiator is apparently listed as being for a RHD postal model. I can't come up with a good reason why this would affect anything - direction of flow (for example) wouldn't change - but it does have me wondering.
Before I go and pull the damn thing again (this is probably my most-hated job on an XJ), does anyone have any ideas on anything I may have overlooked? Aside from the water pump potentially being borderline or the radiator bad, I'm banging my head off of the wall at this point.
My radiator blew out a few months ago, so I replaced it with a Spectra unit from NAPA. I don't have the receipt in front of me right now, but I seem to recall that the model number was NR 2736 - basically, the heavy-duty option, which is what my XJ left the factory with.
Here are the symptoms: cooling's fine when moving, and the temperature gauge sits at the right level for the thermostat opening (195degF). Idling, in traffic, or crawling on the trail, it will creep up to about 220-230degF, but eventually comes back down once I start moving again. Coolant level stays OK and there are no signs of loss from, say, a bad head gasket or the heater core. Has not overheated, but runs noticeably above normal.
Replaced so far: radiator, upper and lower hoses, fan clutch (used NAPA part number 272310 to upgrade to the ZJ heavy-duty unit), thermostat twice (originally with a Stant unit; currently OEM with the relief valve), coolant temperature sensor, and serpentine belt. 8-hour and 15-minute flushes have been done and all coolant changed; air is believed to have been removed from the system. Coolant is Prestone 50/50 pre-mix.
Prior to replacing the fan clutch (which was on its way out) this behaviour would be more pronounced at ambient temperatures over 80degF; post-replacement, that bumped up to 90degF, so at least that introduced some improvement. Double-checked that the fan blades are pointing the right way; it'll suck a piece of paper right up to the grille and hold it there, and air is being expelled rearwards over the engine from it.
Pretty much the only thing in the system that hasn't received attention is the water pump. There's no evidence of a weep or bearing noise from it, and pulling the upper hose from the radiator with the engine running shows coolant being moved through at what appears to be a fairly normal rate. Doesn't mean the impeller's necessarily 100%, but at least on the surface things look OK.
With all that out of the way, I'm suspecting that the radiator isn't up to the job given that this started after the original one was replaced. One thing I did notice from the online listing that didn't come up in the store: that radiator is apparently listed as being for a RHD postal model. I can't come up with a good reason why this would affect anything - direction of flow (for example) wouldn't change - but it does have me wondering.
Before I go and pull the damn thing again (this is probably my most-hated job on an XJ), does anyone have any ideas on anything I may have overlooked? Aside from the water pump potentially being borderline or the radiator bad, I'm banging my head off of the wall at this point.
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