^^ Distilled Water!!
Too many people use the tap, full of things that like to leave deposits in the block and clog radiator passages.

 

Good stuff, Maynard. Please tell me about the ZJ fan clutch deal. What are the advantages? Is it a bolt-up?

 

Pulls a little more air and its a direct bolt in. One caveat is do not order the HD cooling one, that one will not fit.

This is the correct unit.
1997 JEEP GRAND CHEROKEE 4.0L L6
OMIX-ADA 1710504 (17105.04) Radiator Fan Clutch

 

Pics of what we experimented with.....promptly took off....way too much noise and the butt dyno could actually feel the reduction in power which would probably mean a reduction in MPG as well. Keep your receipt in case u want to take it back. Again, the weak link in the cooling system is the dinky rad.

 

That's odd, my ZJ fan clutch is not that size its about the same size as the stock XJ just much tighter.

 

I run the ZJ clutch in the summer (NAPA #272310 for V8). It's works very well and is a huge improvement in efficiency.
I have a good functioning cooling system (2row, high-flow pump,t-stat and housing). but it cannot keep up with desert conditions driving in soft-deep sand.
I can run 2000 rpm and be going 12 mph in sand that is 120F. The HD fan clutch allows me do drive in these conditions and stay at 210. On the highway at 2K rpm I am going over 60mph.

There are fleet XJ's that also use this clutch.
A little louder at idle if you are outside of the vehicle but not noticed when driving.
Most likely a slight loss of MPG. When winter arrives, I reinstall the XJ clutch and can drive in the sand just fine.
The HD clutch also is a huge help when running the AC or in traffic. Temps do not creep up when at idle, at all.
Overall, the HD clutch stabilized the engine temps in any condition.
It is slightly larger. A 3row radiator may be tight. If you run a TC drop be sure and check clearance of the fan blades and radiator.

 

It's not a ZJ fan clutch.......it is for a '79 Chevy Caprice 9C1. Just an experiment....standard Hayden XJ clutch works fine.