4.7 stroker consistently runs hot

[MasonMcK]

I've been having issues keeping my newly built 4.7 stroker within the normal temperature range. I've read dozens of threads both on this forum and others but haven't found anything that seems to be the problem for me. My jeep is a 1995 Cherokee (OBD1)

For starters, everything in the cooling system is brand new within the last year with the exception of the heater core which is original. When I first got the jeep it had a cracked radiator so I replaced it with a Spectre aluminum 3 core radiator from Napa along with a new 16 psi cap and 195 degree thermostat. This setup ran fine for the year or so that I had the old motor in for. Temps never reached above 215 even during the summer.

Fast forward to now, my new stroker has been in and running for a little over a month now. Once it's warmed up, the lowest temp it will ever cycle to is 215 and that's a rarity. Usually it runs from about 220-240 or so. When I put the motor in I reinstalled my 1 y/o T-stat because it tested to be good still. I just decided to change it out this week for a new one (tested good). I also checked the 1 y/o one again and it had gone bad in the 250 miles I put on it so far. Still made no difference in temps between the two thermostats. Both were 195* thermostats.

Currently my cooling system is as follows:

Spectre 3 core radiator (1 y/o)

16 psi cap (1 y/o)

195* thermostat (new)

Flow Kooler high flow water pump (new)

Upper rad. hose (new)

Lower rad. hose (new)

Heater hoses (new)

Heater control valve (new)

Stock mechanical fan (age unknown but in great condition)

Stock e-fan (original; currently not functioning due to PCM short; but when wired straight to battery has no effect on ECT's)

Block and head were both hot tanked while apart

No cooling system leaks

Serpentine belt (new, not slipping)

Coolant temp sensor for PCM (new)

Coolant temp sender for gauge (new)

I'm pretty stumped by this. I even flushed the system out a couple times including the heater core and the radiator to little advantage. Any ideas? Suggestions? I'm going to be ordering a new PCM soon so I will have a functioning E fan again but it had no effect on the coolant temps when I wired it straight to the battery for testing.

Any help is appreciated.
-Mason

[Cherokee77]

Have you verified engine temps with a infared gun? Ive been down this road to many times with 2 different cherokees, 3 different engines, different radiators, thermostats, water pumps, fans, oh hell im getting pist just typing all this. Lol.
I have tried different sending units, and factory mopar is the best, I do know now that my factory gauge is 20 to 25 degrees hot compared to 2 different ir guns. I even installed a mechanical autometer gauge and low and behold that reads hot to.
Grab a ir gun and verify your temps.
I have spent so much time and money chasing this problem with mine its ridiculous.

[letitloose06]

Where did you source your new temp sending unit for the temperature gauge?

Many of the aftermarket ones from Advance Auto, Autozone, etc tend to read 20 degrees higher than the OEM ones. OEM sending units (P/N 56027012) are the only reliable ones.

[Russ Pottenger]

^^ This ^^

[MasonMcK]

I went to my buddies house today to use his IR temp gun but he couldn't find it. I'm going to see if I can find someone else nearby that has one that they'll let me use to verify temp readings.

My sending unit is a Crown automotive. Should I switch it out for the official OEM one? My original one broke so I bought the Crown one thinking it would work fine.

Thanks
-Mason

[Russ Pottenger]

Mason,

The Crown sending units are junk
Get a OEM.

[joshm]

]my temp sender on my 4.2 took a crap last year. i cleaned out the radiator and threw a water pump on it. it still was running hot. i found the problem by reading the temp with a IR therm. Check the temp at the thermostat housing, top and bottom of the radiator, and the temp sender on the block. The back of the head/sender will be the hottest spot.

[joshm]

generally you should see a 20 or 30 degree drop in the radiator inlet and outlet temps. this will tell you your system is functioning properly.

[MasonMcK]

Thanks for all the input guys. I don't have an IR thermometer so I used small mechanical one instead. Can't really attest to how accurate the values were but there was about a 20 degree drop. I'm going to get a better thermometer and try again. My new mopar temp sender should be here today or tomorrow as well so I can see if that fixes the problem.

Does anyone know what temps my hoses and temp sender area should be? Also what coolant temp should the E fan kick on at?

Thanks
-Mason

[Cherokee77]

The E fan should kick on around 217 degrees. Hard to get a good reading on the back of the head where the temp sender is, it is the hottest reading you will get though. T stat housing is good place to get readings from. Also when you get a ir gun you can check the freeze plugs in the block also.

[MasonMcK]

Thanks for all of the help guys. Turns out it was the temp sender. My new Mopar one arrived today and my temp gauge went back down to 195-205 degrees when running.

[joshm]

good to hear man, glad you got it straightened out.