I have never had a problem with master cylinder on 4 different ones with total of about 800,000 miles between them now. One did have a leak in line going to right from caliper from rust which started pretty slow then later got massive just replaced that small section of line on both sides .
I would strongly consider taking the advice to go ahead and change the belt and water pump etc. This is an INTERFERANCE ENGINE so if the belt breaks or just gets a little too stretched and skips a few teeth you hopefully will only break a few rockers and if the rockers dont break as designed then you will bust pistons etc making it more economical to replace with a used engine if you can find a good one. Easier to change glow plugs with more access then too they run around $80 a set. This is drastically different from a timing belt break on a non interference engine.
Believe me you do not want to even have to replace the rockers unless they are very worn its adds at least 12 hours of work for a first timer to the Timing Belt job and maybe as many as 20 hours not to mention the rockers etc for over $400 with gaskets. (We won't even talk about the other things you should do to Bulletproof if you do have to remove the valvecover. The Timing Belt job alone for a first timer is probably around 12 hours. For experienced DIYers around 7 hours. Save yourself a lot of grief and do the timing belt job very soon like NOW. You can check out the intercooler at the same time if you want to but bet if it doesn't have silicone hoses its most likely a hose leak.
Here is a pic of what a broken glow plug tip does to the head see all the peck marks . On full compression position there is only a few thousands clearance between the valves and the piston notice that the valves are actually recessed above the head surface a bit. Its just luck whether or not you get worse engine damage when a tip breaks off. I had one engine with 140K that had 3 broken tips and didn't damage it but still a chance you dont want to take.
https://imgur.com/AjZpmGNIn this pick you see the three tips that were broken off to varying degrees one with whole tip off compared to non broken or replacement ones
https://imgur.com/fkaWRq9Your Jeep has made it this far why take a chance for about 12 hours work and less than $500 when it is about 8 years late already? If I bought your jeep now I wouldn't run it at all after loaded and unloaded on trailer without doing this first its very cheap insurance!!