Considering getting back into a Jeep. I was looking at TJs, as I know their 4.0s are pretty stout.

I keep seeing some JKs for not much more money though.

I know 2012 has the updated pentastar; how “bulletproof” are those?

Any known rust issues on them?

Any other things to watch out for?

 

The JK is a great platform, and the 3.6L is a pretty decent engine, though it does have it's issues, primarily with the VVT. I would stay '13+ tbh as the '12's had some head issues. If you can do your own work on the jeep and even remotely find your way around an engine, I'd say there's nothing to shy away from. The biggest issue with these engines are 1) rocker arm bearings that fail and cause the common 3.6L tick, 2) the oil coolers (under the intake and in the valley of the two heads) will leak, and 3) the 5W20 oil that is recommended is just too thing for these VVT systems and start to throw all sorts of cam codes. The VVT is just too dependent on oil pressure. Use 5W30 and you'll be much better off. Outside of the engine we have common radiator or thermostat issues like any other car. On the '12s and '13s the oil bypass was build into the filter housing and was common to get brittle and break which could lead to catastrophic failure if any of that plastic got down the pickup tube. The '14 redesigned that part......which is also when the leaking oil filter housings became an issue . They how have aluminum units. Typically the leak was just o-rings but sometimes it was the actual unit.

Best of luck in your search. I'd look for something that has not been modified. Most people do a shit job of lifting these.

I'd add that I rebuilt the timing on my jeep. First vehicle I've ever done that on but it was very straightforward. I mention that cuz the engine is just pretty easy to work on.

 

My 2014 was the most problematic vehicle of 45 I’ve owned. It was a semi-daily driver for the first 7 years, meaning I had other cars and so it being down wasn’t catastrophic for me. But at 10 years old I only have 45,000 on it. From memory, I replaced:

Entire engine (long block) when a valve seat dropped into No. 6 cylinder at 15,000 miles
both catalytic converters (one because oil flooded it from the No. 6 failure)
radiator which started leaking
evap canister
drivers Seatbelt retractor
drivers seatbelt latch receiver
pax seatbelt retractor
steering wheel clock spring
clutch slave cylinder
no doubt a few other things I’m forgetting

I sold the Jeep in 2021 after ordering a Defender because driving a JK from Atlanta to Moab every year is a very tiring proposition.

2 years later I still missed it and bought it back from him last May.

Took it for emissions inspection and it failed because two of the 8 “registers” weren’t reset — they weren’t failing, they just weren’t reset, indicating somebody had cleared them all for a fault recently and the required 40+ miles hadn’t been driven for the computer to reset them. I spent 3 months trying to repair myself (replaced evap can again, as well as all O2 sensors (I think there are 4), and then taking to the Jeep dealer who kept it for 5 days and gave it back saying “We don’t know what it is; we’ll try by replacing the entire fuel system from the tank forward if you want.” . Then I took it to my indy who works on my more high-end cars and was confident that “he had a guy” who could run down anything like this and get it sorted. Two days later nada. Mind you, it hadn’t even thrown a code or shown a CEL.

Finally I got tired of running around with expired tags and registered it at our beach house which is in a county that doesn’t require emissions testing, where it continues to be registered because of being unable to do so in Atlanta. A year later it still won’t show those two registers as “Ready” which is required to pass an emissions test anywhere.

Between repairs of things that broke after warranty, and all the mods (rubicon transfer case, 4.56 locked diffs, new G2 D44 axle up front and G2 half-shafts in back, fancy 2.5” lift with all control arms and the rest to be able to properly align it, and then all the usual lights and winch and 1/2 doors and bikini and a 2nd set of offroad wheels and 37s and TrekArmor seat covers and blah blah blah, I’ve spent about as much on it as I paid for it new, which was $24,480.

And I still love the crap out of it.

 

Definitely a love/hate relationship there. I took care of all the engine issues by going V8. Still get stupid Jeep related CELs (like low fuel pressure) occasionally so I simply turn the codes off for checking. They don't stop the Jeep from driving so they are just an annoyance

 

Well, a v8 swap isn't in the cards, lol.

Still have 3 I'm checking out, with a fourth TJ in the mix (looks the part, but rocker panel rust has me shying away).

One is a 2011, (3.8, new interior). One is a 2016. Third is a 2008 (old interior, old motor... more palatable price).