Starting this post because it is getting cold outside and some XJ's do not put out the heat like a new XJ would.  There are some tricks to get a little more heat out of her.  I thought that the one that I am suggesting was common knowledge but someone I was talking to this weekend did not know it.  So it inspired this topic.  Feel free to add anything that you do to your XJ to help get it a little more warm.

I have always used a simple peice of card board.  You cut it and shove it in the front of the radiator.  The warmer the XJ's engine the warmer your heat will be.  I think, but do not know for sure, that our XJ's pull their heat from the engine.  So kinda the opposite of the summer, you need to get them to keep their heat up. 

The other night the XJ's engine temp was under 160 while driving down the highway.  The outside temp was about 20.  When I would stop the heat would climb some but would stop about 170.  So to make you engine run warmer and better in the winter add card board.

The first thing to do is to take the plastic grill off.  There are 8 philips head screw that hold it on.  Here is a pic of the front of the XJ without the grill on.  You can see the 8 tabs where the screws go.



Here is the grill removed:



Here is a pic of the peice of cardboard.  If I recall from about 2 winters ago 3/4 of the radiator was covered by the card board to reach the happy medium.  This piece will probably be a little long.



Here is the pic after I painted it with flat black.  You can leave it or paint it.  My theory behind painting it is that it will help it survive the elements a little better.



Then you just put the cardboard back in between where the grill screws back on and the grill.  Here is a pic with it installed.



Here is a closer pic of the side so that way you can see where the cardboard is and how you can't notice it even there.



That is it.  Only take about 20 min to do.  Will work great.  I will update the amount of heat change that I notice.  I will warn you that this is not an exact science.  The first time that I do this every year I take a screw driver with me just in case I have covered to much so that I can take it off on the side of the road if the engine is getting to hot.  I have had to do this before, and I just folded the card board in half and shoved it back in.  Then it was just fine.  So you might have to play with the size of the cardboard depending on how much highway/city driving you do.  I do almost all highway.  Hope this helps some people stay warm this winter. 

Feel free to add other things or correct what I have put up here.