Seems to be a lot of folks having issues with the Pentastar and back ordered parts:
http://www.jkowners.com/forum/showthread.php?t=71955"I'm not sure this will make any of you feel any better about the problem, but maybe I could offer some insight as to why some engines suffer from these issues and others may not.
I am a tooling engineer/ CNC tooling specialist. I've been working in the automotive industry for some time now and have the pleasure of working with SEVERAL people who formerly worked at the Chrysler plant, (engine plant). I've even had the pleasure of touring The Trenton Michigan plant.
The pentastar is manufactured and assembled in a VERY similar way to the engines I've produced of the last 3-4 years. Each plant would receive raw castings from different locations. For example the Mexico plant would receive there heads, blocks, and cranks from a facility somewhere in Mexico, or Texas. Michigan would receive theirs from a facility in Michigan or Ohio. No more than a couple hundred miles apart. In an effort to keep costs down, and produce more jobs, as well as keep inventory to a neccesary minimum.
Anyway. If there were an issue with the cylinder head castings from one plant, or a tooling issue, then there could possibly be 100,000+ cylinder heads that left the plant defective before the plant was even aware of an issue. The problem could be caused by impurities in the aluminum, or the brand of cam phasers that we're being used at that facility. The head bolts could have been torqued slightly higher, or any number of things. When you are producing 650 engines per day, it is very easy for one mistake to cause a problem on SEVERAL engines before it is realized to be a problem. The modern day "high tech" engine plant is basically automated. There are very few times when a human puts there hands on the engine or it's main components(heads,block,crank), unless there is an issue. The cam caps are attached to the heads by a machine then they are bored out. The bolts are then loosened by another machine. After the cams are placed in the heads the bolts to the cam caps are tightened again by a machine. The entire valve train is installed by a machine which takes all of 7 seconds for all 24 valves springs, and retainers to be mashed in. The head bolts are also installed then torqued by a machine. It is possible that the head bolts could be installed by a human, but the impact wrench they use is very high tech, and the torque is preset. It is incredible how fast and accurate some of the machines and robots are. If you ever get the opportunity to watch the machining and assembly process, it is definitely worth watching. However if the preset torque for the machines or impact wrenches was set incorrectly by just a small amount, or there was a problem with the impact wrenches, it could very well go unnoticed for a long time.
The pentastar is a very high tech engine. The tolerances are extremely tight. The valve seats, valve guides, cam bores, crank bore, and cylinder bore are kept within 4 micron. The drill and tap for the head bolt holes has a 20 micron(+/-10um) tolerance. With overhead cams, cam phasers, 5 timing chains, and so many small parts moving internally, everything must be kept very, very close to specifications. With so many moving parts in a light weight aluminum engine, every single component is CRITICAL. Vibration will tear an all aluminum DOHC engine with DVVT apart very quickly. This type of engine will develop serious vibrations if every part is not working in harmony. Aluminum heads are wonderful for High performance engines, aluminum blocks as well, but every joint face, seal, and port becomes a potential TSB if tolerances are not kept extremely tight. Torque is the yin and the yang of the aluminum engine. Too much or too little is certain disaster. Just enough and you have a 3.6L V6 that screams, with as much horse power as a 2000 SVT Mustang Cobra.
As far as counter measures to correct this issue, they have probably been in effect for some time now. That being said, there are probably several vehicles still on the lot right now that still have the defective engines in them. So be careful when selecting your new wrangler. Chrysler should have been all over this, and I hate that anyone has had to lose trail time, or suffer the headache that is dealership service dept. because of an issue that should have never happened to begin with. I love my Jeep!!. But honestly the knowing that deep down it was just another Chrysler is what has kept me from buying one until now.
I have a 2012 Wrangler unlimited sport, and as of 4100 miles I have not experienced any ticking, or MIL lights, but my fingers are still crossed. Aside from the harsh ride from the metal bumpers on stock suspension, I am very happy with my pentastar JKU. Good Luck Everyone."
Topic: 2012 JK Pentastar Problems (Read 164 times)
