yeah ... I can see 160*F tranny temps in the hot line while on road as well ... they are fed to the supposedly much cooler lower part of the rad ...
The water temp gauge is where? I think in the nearly hottest possible spot, right?
(And ambient air is at around 118*F at noon here at the moment.)
So theoretically the hot tranny oil can add thermal load to a part in the rad which supposed to be even cooler without the tranny oil going through, right?
You are exactly right! The tranny does add heat to the engine coolant. That's how it cools the tranny… by shedding heat into the engine coolant.
The whole existence of the 7-blade OEM fan and heavy-duty fan clutch is solely based on the fact that the 32RH tranny was dumping too much heat into the engine coolant, exceeding the engine's cooling capacity.
When your Automatic Jeep is stopped and idling in gear, the torque converter is generating a lot of unnecessary heat.
Following is the Chrysler TSB that pertains to the OEM 7-blade fan and heavy-duty clutch conditions and solutions.
2001 Jeep Truck Wrangler L6-242 4.0L VIN S SFI
Temperature/Check Gauges Light ON
Engine - High Temperature/Check Gauges Light ON
NUMBER: 07-004-01 REV A
DATE: Dec. 14, 2001
THIS BULLETIN SUPERCEDES TECHNICAL SERVICE BULLETIN 07-004-01, DATED JULY 20, 2001.
High Engine Temperatures Due To Extended In-Gear Idling In Hot Ambient Temperatures
This bulletin involves replacement of the cooling fan and fan drive. Certain 2000 M.Y. Wranglers will also require selectively erasing and reprogramming the Powertrain Control Module (PCM) with new software (2000 TJ - Calibration Level Cal15A).
2000 - 2001 (TJ) Wrangler
NOTE : THIS BULLETIN APPLIES TO WRANGLERS EQUIPPED WITH A 4.0L (ERH)
ENGINE AND A 32RH AUTOMATIC TRANSMISSION (DGG).
Engine coolant temperatures may rise high enough to cause the Check Gauges light to illuminate, indicating high engine coolant temperature. This condition is likely to happen after extended periods of idling, with the transmission in Drive, the air conditioning on, and with ambient temperatures greater than 35°C. (95°F.). If the transmission is placed in the Park or Neutral positions, or if the vehicle is driven, then the engine temperatures will decrease.
NOTE : REFER THE CUSTOMER TO THE RESPECTIVE 2000 OR 2001 JEEP
WRANGLER OWNER'S MANUAL AND TO THE SECTION TITLED: WHAT TO DO IN
EMERGENCIES - IF YOUR ENGINE OVERHEATS. IT IS IMPORTANT THAT THE
PROPER PROCEDURES ARE FOLLOWED TO PREVENT AN ENGINE OVERHEAT
NOTE :INFORM THE CUSTOMER THAT THE REVISED FAN AND FAN DRIVE WILL
CREATE HIGHER SOUND LEVELS FOR A MINUTE OR SO AFTER A COLD ENGINE
START, AND DURING HIGH ENGINE TEMPERATURE CONDITIONS.
**THE FAN WILL RUN MORE OFTEN BECAUSE THE FAN CLUTCH WILL NOW ENGAGE AT LOWER TEMPERATURES.**
NOTE :THE MDS2 AND DRB III(R) ARE REQUIRED TO PERFORM PART OF THIS
REPAIR. WHEN USING THE MDS2 AND THE DRB III(R), THE SYSTEM MUST BE
OPERATING AT CIS CD 2064 OR HIGHER.
1. Verify that the cooling system is in good working condition.
2. Verify that the engine coolant mixture contains the proper amount of antifreeze.
3. If the customer complains of the above condition, and the vehicle is a 2000 Wrangler
with PCM software that is earlier (lower or less) than the calibration listed above, perform the complete Repair Procedure.
4. If the customer complains of the above condition, and the vehicle is either a 2001 Wrangler or it is a 2000 Wrangler with PCM software already at calibration level 15A or later, then perform only Step 1 of the Repair Procedure (replace only the fan and fan drive).
Verify the current PCM software calibration level (2000 Wrangler only). If the 2000 Wrangler PCM software calibration level is earlier (less or lower) than 2000 TJ - Calibration Level 15A, then proceed with steps 2 though 4.
NOTE :THE FOLLOWING STEPS ARE REQUIRED BY LAW.
1. Replace the cooling fan and viscous fan drive. Refer to the appropriate Wrangler Service Manual, Section 7 - Cooling Engine, for detailed fan and fan drive removal and installation instructions. The Service Manual procedures may be found on the MDS2.
2. Reprogram the PCM using the MDS2 (Mopar Diagnostic System) and DRBIII(R) (Scan Tool).
3. Type the necessary information on the "Authorized Software Update Label" p/n04669020 (Fig. 1). Attach the label to the PCM and cover the label with the clear plastic overlay.
4. Type the necessary information on the "Authorized Modification Label" p/n 04275086 and attach the label near the VECI label (Fig. 2).