JeepMoreDoor

We all have driven our XJs on a hot day then 5 mins later get back in and the temp gauge is past 210F, at about 220+ maybe? Basically cooking our engines while it sits. 4.0s run hot enough so I hate how hot they get when you shut the engine off. I came up with an idea but not sure how effective or possible it would be. First thing is this would involve and electic water pump which idk if they make these for 4.0 XJs.

The idea is to rig up an electric water pump with the electric fan, then have these 2 items rigged to some sort of timer 3-4-5 mins that will automatically shut off. That way the coolant can circulate and the fan cool it and cool the engine while it sits. To some it might seems pointless but I think it's a good idea. Id like to know if anyone has any idea how to actually make this happen, if it even can.

PNWjeeper

Sounds do able to me. I think I've seen electric pumps for xj's somewhere before, you could rig it up to something similar to the delay for your headlights. So it sounds like it might be possible it's just a matter of knowing how the electrical works for the pump and fan. Might need to be hooked up to a switch.

F1Addict

I think it sounds like a great idea for those with an adequate electrical system to handle the load of the pump and fan running.

I think the biggest problem will be finding an electric pump that will withstand 220º-240º water without melting. Also, this pump will need to be able to withstand the ambient pressure of a closed system (some XJs) and not interfere with normal operation of the cooling system when the engine is running. You could just install the pump (if you can find one) and rig an auxiliary timed 12v supply to the existing e-fan on your radiator. Again, the pump and not running out of electricity will be your issues.

F1Addict

Also, I'm not sure if the mechanical pump will allow the free-flow of coolant when not in motion. It may prevent an auxiliary pump from cycling water when it's not spinning.

Kalali

I don't mean to sound unsupportive of the idea but the XJs' cooling systems were designed to handle the load generated by the 4.0 motor and its accessories. You hardly see anyone complain about overheating in an XJ, say with 45K miles. The fact is our XJs age just like their owners and aside from poor design in some cases (0331 head) they just need more care and feed. For example run your fingers down inside an old radiator hose and compare it with a new one. Fortunately most of the cooling system components are relatively inexpensive and changing them every say 100K miles is not all that bad. If I were to use an electric pump in the XJ it would be an electric oil pump on those 25 degree mornings...

djb383

The mechanical pump would not restrict flow at all when the motor is off......can't say that about the t-stat though, 'cause u can't determine when it closes. Stewart Components sells an electric pump that mounts in the rad hose.

w-stev29

The T-stat would stay open until whatever preset tempature for the one you have installed. The mechanical water pump will probably allow a little flow til the t-stat closes. The engine will can handle the increase in tempature from the water sitting after shut off. However a timer set on an electric fan for a few mins after shutoff couldn't hurt even some of the newer cars have it as an option. IMHO.

djb383

....but in a motor that is not running, circulating water will cool quickly, thus closing the stat quickly.

One simple fact still remains.....#1 cause of overheating in any older car is owner neglect.

mike mike

Lots of cars in the 90s early 2000s used a thermal switch on the elect. fan and ran after the motor was shut off.
My motor after shut down sheds heat a lot faster since I put in hood vents.