OK Mark,
To check your cooling system, you need to pressure it up to about 15 psi.
Usually, folk take it to a shop and get charged a fortune and then ripped for repairs.
Thats not the XJ community. We do it ourselves and save a fortune.
So, to do it ourselves, we need to collect a few basics. I used shit laying around the house, plus a few Ebay cheap items and one Rockauto cheap item.
I still have this Stant Lever Vent radiator cap on my Jeep and love it. Its cheap (less than $10), you can blow off steam if you want, and you can also perform a pressure check with it! The reason is because it blows off steam, you can also pump pressure back the other way with the lever in the up position.
How you do this is keep the Lever Vent radiator cap on tight, but have the lever up. Then get your hose that goes to the plastic overflow bottle. At the bottle, take the hose off. Use an old bicycle inner tube valve cut to size and jam in into the hose and use a small hose clip to get it nice and tight. Also make sure you have a hose clip on the other end. We dont want any air leaks.
Next, buy, or use a bicycle pump that has a pressure gauge on it.
Pump it up to about 15 psi. It should hold pressure.
I do it at night and use a $7 Ebay black light. These make things glow. Believe it or not, coolant glows under a black light.
https://www.ebay.com.au/itm/UV-Ultra...frcectupt=true
So do it at night and sneak around with your black light looking for eerie green leaks.
Worked for me and i found a few weeps around my heater hoses, and that would of meant i was also loosing pressure and cooling efficiency!
Once you have this setup, you can use it on all your vehicles and perform the task regularly to check the condition and function of your entire cooling system.
Here is the 16 psi Stant cap on Rockauto. Only $6.95 Aud.. Great cap...
https://www.rockauto.com/en/moreinfo...180314&jsn=517
Hope this helps.