Well I can't seem to figure out why coolant keeps leaking out coming from the sealant cap off the radiator. I'm on my second brand new cap and still leaking. For some reason the return line isn't functioning as intended to have overflow go back to the coolant tank. I've checked the line and it's not plugged. It only happens as soon as I park it, and seems like there's push back into the cap causing an overflow leak. Any recommendations?

 

Radiator neck is cracked or using an off brand one size "fits somethings" cap.

 

Thanks for the reply. I've looked into the radiator neck and it looks fine, I can actually spot where it's coming from and it's the cap itself. I've been getting the caps from Oreilly's Auto Parts supposedly specific for the XJ. You think these are too universal? Where can I find an OEM besides the junk yard. Thanks in advance.

 

Not worth getting a used one from a boneyard.
for ~$15 new OEM will be good for 15 years...
Morris has some Mopar caps:
https://www.morris4x4center.com/