I have a 2001 Jeep TJ with a Novak Gen III 5.3L/4L60E conversion. I followed Novak’s recommendations and used their TJ conversion radiator.
Relevant Jeep specifications:
Gen III 5.3L engine with GM PCM
4L60E automatic transmission
Atlas II transfer case
Dynatrac 60 axles
5.13 axle gears
37-inch tires
Hood louvers
New 16-psi radiator cap
Edge Insight CTS3 monitoring the GM PCM
Approximately 2,400 RPM at 70 mph
At speeds below 50 mph, the cooling system works great. I can rock crawl with the A/C running, and the coolant temperature remains under control. I couldn’t be happier with its low-speed cooling performance.
However, highway driving is a different story. During a recent drive with the outside temperature around 85°F:
At 70 mph without the A/C, the coolant temperature reached approximately 216°F.
At 70 mph with the A/C running, the coolant temperature climbed to 230°F before I turned the A/C off.
The engine was running at approximately 2,400 RPM at 70 mph.
The transmission temperature was only around 158°F during the A/C test.
The temperatures are being read from the GM PCM using the Edge Insight CTS3.
At this point, I cannot use the A/C during highway driving without the coolant temperature continuing to climb.
Has anyone with a similar Novak TJ conversion experienced this? Since it cools well at lower speeds but struggles at highway speeds—especially with the A/C running—what should I investigate first? Could this indicate restricted airflow through the condenser and radiator, an overcharged A/C system, or another cooling-system issue?
