Guys, just want to share this with you. No more Jeep Caps, don't buy em they are junk!! Here is what you do, go to the Junk Yard or to Pick and Pull and locate a Volvo 740 or 940 turbo, there are plenty of em at the JY. Like XJs, 740 and 940 turbos were produced forever. You should be able to recognize the turbo from the non turbo by the additional plumbing. Locate the coolant bottle and make sure it has the green coolant cap. Pull it off and install it on your XJ. I have had the same cap on my XJ for over three years and never had one leak with it.
Here is another trick that you can do, locate a Volvo 240 non turbo and grab the coolant bottle off that, you can grab the cap with it but 240 non turbos had a blackcoolant cap and don't have the higher pressure rating that the green cap, mentioned earlier, has.
The Jeep bottle and the Volvo bottle are pretty close in dimension, also the Volvo bottle seems to be made of a thicker material than the Jeep bottle. The only difference being is that the small inlet hose located on the top of the tank is slightly smaller in diameter than the Jeep tank. I purchased a reduced diameter fuel barb and simply installed it onto the Jeep inlet hose with the reduction end going to the bottle. Install the proper diameter of hose there and you are good to go.
To make the Volvo bottle work on the Jeep bracket you only need to push the bottle inboard (towards the engine) and it will work fine. The rubber hold down strap will now pass over the cap rather than the bottle. I will see if I can post some pics later on
Any questions?? ask away