Alrighty, it's been awhile since I've started a useful thread, so I thought I might do a writeup.
It's been getting pretty cold here lately and since I have a commute of less than 5 miles to work, it's gonna be pretty chilly driving in, unless I let the Jeep idle for a rediculous amount of time. I also run 10W30 year round and it can get pretty cold here in the winters, based on this I figured it might be a good idea to purchase an engine block heater.
After researching the numerous styles I figured that the least invasive would be a Lower Radiator Hose style of heater. Basically it is a metal tube that has a heating element in the center of it and slips inside the lower hose. This means you will have to cut about 1" off the end or in the middle of your lower radiator hose, however it beats finding a place to mount a tank heater or pulling out a freeze plug.
All of the parts used were purchased at a nationwide auto parts store, so others shouldn't have a problem using my part numbers.
I am also a big believer in preventative maitenance, so I took the time to replace my upper and lower hoses along with a cooling system flush and topping the system off with some fresh coolant.
Here's what you will need:
First you need to drain your radiator, and if you're like me you will be suprised how your coolant looks more dark green/brown than the atomic green of the new stuff. I also noticed some deposits around the tops of the cooling tubes.
I went ahead and followed the directions on the back of the container. Basically you dump in the whole thing, top off the system with water then run the Jeep up to operating temps, after that you turn on the heater full blast for 10 minutes. Shut off the Jeep, let cool and then drain system. Once this is done fill it up with straight water and repeat. Again, let cool then drain the system. It was pretty cool seeing all the brown junk coming out of the radiator and even better when the water that was draining turned clear.
Next I replaced the upper hose, unfortunately the new one looks nothing like the old one, however it goes from the water outlet around the A/C compressor and then to the radiator. The clearances are a little tight in some spots, but it should be fine.
Here it is installed:
The lower radiator hose is different as well. Many of the TJ guys have issues with this, however I was unaware that the YJ's were the same way. When the new hose is off the vehicle it looks like it won't work, however it looks like it is just slightly redesigned and fits with no issues at all.
Next you need to cut the lower hose into two pieces. The directions for the heater state it needs to be in a section of hose that rises up towards the water pump outlet (if possible). Where I put mine it has a bit of a rise to it but not much, however it was the only place where it would fit.
Rather than cut 1" out of the middle of the hose, I just cut the side where it attaches to the radiator. Also, do not forget to point the heater element towards the water pump as well. Failure to do this could cause issues with proper heating of the coolant.
I found it easier to put the upper half of the lower hose on first, then slide in the heater element followed by the small piece of the radiator hose.
It is also important that the element is placed in either the 7 o'clock position or the 5 o'clock position (per the instructions), I went ahead and placed it in the 5 o'clock position since that is where the plug was going to be routed.