4.0L Engine Cooling Issues
Background Information:With this conversion I needed a different fan assembly because the 4.0L uses a reverse rotation water pump. The engine came from a 1990 Cherokee (XJ) which had the cooling fan mounted on the idler pulley rather than on the water pump. I bought a YJ water pump and idler pulley to replace the XJ parts. I used the fan and clutch from the donor vehicle but it didn't cool very well so I bought a new clutch and found a 7 blade reverse rotation fan in the wrecking yard. The fan clutch was now very close to the radiator and I actually saw contact marks on the fins after one mild off road trip. The next step was to move the radiator to the forward side of the core support and with some 1/8" alignment shims was able to increase the clearance to 1-1/4". The only problem now is the shroud didn't fit well or seal at all so I didn't bother to install it. The engine still ran hotter than I liked so I decided to try an electric fan package. I heard good things about SPAL fans, the dual 11" fan in particular. This fan is 23.25" x 16.25" x 4.25" but it didn't look like there was enough clearance between the right motor and the idler pulley. I ended up buying a unit made by Flex-A-Lite.
This is the Flex-A-Lite #575 fan. Made for the 2" core, centered cap, CJ radiator. The fan measures: 15-1/2" x 26-1/4" x 2-5/8", fits the CJ core perfectly and mounts with the radiator mounting bolts. I used studs in the spring nuts which made it easier to hang the radiator then fit the fan assembly.
Clearance between the water pump pulley mounting nuts and the center of the fan assembly is 1.0"
Clearance between the idler pulley and the fan motor heat shield (the thin aluminum plate attached to the motor) is .75"
Another view of the pulley clearance. Once again, there is only 3/4" between the idler pulley shaft and the right side motor (left side in this picture) Since the mounted depth of this fan is 2-5/8" thick, I could'nt see any way the SPAL fan at 4-1/4" depth would fit. The SPAL fan is 2-3/4" narrower but I don't think I could slide it far enough for the fan motor to clear the idler pulley.
A closer view of the idler pulley clearance. I don't know if there is a difference in the YJ and XJ 4.0L pulley mounting other than the alternator on this engine (XJ) sits lower than one on a YJ.
Impressions and Performance:
This setup doesn't cool any better than the fan clutch setup so I may have other problems such as the radiator. I'm running a 180* t-stat, standard water pump (non-high flow) and the fans keep the engine temp near 200* except for highway speeds then the temp climbs to 220* - 230* with ambiant air temps above 90*. There are many write-ups on using Ford automobile fans and I may look into this some day but for now I'll live with it.
Update 8/2003
I installed a new 3-core radiator, haven't tested the Jeep out on the highway yet.
Derale Fan Control
Instead of using the Flex-a-Lite controller I am using a controller made by Derale, part No. 16759. This setup has a prob that is inserted into the radiator fins just below the upper tank by the hose connection. In the near future I will change this over to a 3/8" mpt sender, part No. 16749, installed in the heater hose from the t-stat to the heater.
Below is the wiring for the Derale controller. The switch is DPDT center off, the diode was one I had around the shop. The diode is a one way device and sends 12 volts to the yellow wire when the switch is in manual on, ignition off.
