AN: Update: Rare Pentastar problem
[Originally posted June 25th, 2012; updated July 7, 2012.] In June, several dealers reported that some of the current Pentastar V6 engines had experienced premature cylinder head failure, usually on cylinder 2. While it is rare considering the number of these engines produced, it became an issue for dealerships in some areas due to the lack of readily available service parts. The Pentastar V6 is Chrysler's only current six-cylinder gasoline engine except for the Ram 1500's 3.7 liter powerplant, which will not return for the 2013 model year. Customers were generally given loaner cars while the issue was being resolved, though in some cases there was a considerable delay as Chrysler engineers sought root causes and an effective cure. The issue did not leave customers stranded, as far as we know, but lit the "check engine" light.
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A fix was engineered and entered production by the time of our first report;..
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A fix was engineered and entered production by the time of our first report;..
View the original, full post
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Actually the only revision appears to be to the front casting where the alternator mounts to the front of the block on top of the 2012 Wrangler, and looking at a recent minivan it had the holes and flat places in that front casting already for attaching the alternator where the Wrangler attaches it. So the engine itself appears identical across all Chryslers that use it, with the only difference being accessory mounting (the Wrangler putting the alternator up top). Well, and the computer is tuned slightly differently due to the Wrangler's different exhaust and different operational requirements (a Wrangler needs low-end torque more than it needs top-end power), but if there is a problem it should affect all Pentastars, not just Wranglers. In particular, the driver's side/left side head is the same on all Pentastars.
My guess is that because it appears to be pretty much random, the head issue is a porosity issue. Porosity is a Brownian process (i.e., completely random) that is a given with thinwall aluminum castings. Silicone impregnation is used to deal with this in general, and that works quite well in most parts of the engine, but heads are somewhat special in that they are subjected to extreme heat in the vicinity of the combustion chamber. If a casting is particularly thin near #2 cylinder and passed pressure test due to silicone impregnation, but is subjected to sufficient heat to burn out the silicone... hmm. Now that I think about it, the fact that the Wrangler has a different exhaust system might result in more heat near #2 cylinder, which might be why the Wrangler people are reporting this more often than other Chrysler products (though I've heard about it in other products too, so it's not Wrangler-specific).
But of course this is all speculation. As the owner of an August-build Wrangler, I am of course quite personally invested in keeping track of this issue, and am glad Chrysler has a solution. Not that they had much choice -- if the Pentastar craters, that's the end of the company, since it's what powers everything but their trucks and their small 4-cylinder cars nowadays.
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Seriously. Because it sounds like you will be without a vehicle until they can get the part in. 5,000 more miles until I find if my Challenger is affect, I guess.
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better be offering loaners to people affected. I still have ~8k miles left before I get there.
Looking at the Wrangler forums, the issue has affected people with 3,000 miles, and people with 35,000 miles, so it isn't as if there's a magic number where your engine suddenly just disintegrates. The Wrangler has had the Pentastar only since August and there's already a number of Wranglers affected (not a huge number, maybe one or two per dealership out of the several dozen that each dealership has sold of this amazingly popular upgrade to the Wrangler platform) so clearly the mileage stated is an average (since most of these Wranglers don't have 20,000 miles on them yet), not a fixed number. As with everything dealing with this problem, the mileage at which it crops up seems fairly random and likely related to driving patterns, exhaust design, and random brownian motion of aluminum molecules during head casting.
Loaners appear to be the rule for folks affected by the problem while the dealership waits for a head to come in, so no worries there. So far once the CEL comes on Chrysler has done the right thing.
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I'm curious as to the "why" and "what" engineering-wise. To me, this says production problem, but there has to be an obvious solution. I'm guessing casting revision to provide a little more metal in one area.
It's interesting that the Pentastar has been through one of the most rigorous durability testing cycles, according to them, but production reveals a few quick failing parts with inherent issues. For those of you who have a better grasp on metallurgy, what's the solution? Alloy changes, casting or machining changes ( to thicken an area?), or something else?
It's interesting that the Pentastar has been through one of the most rigorous durability testing cycles, according to them, but production reveals a few quick failing parts with inherent issues. For those of you who have a better grasp on metallurgy, what's the solution? Alloy changes, casting or machining changes ( to thicken an area?), or something else?
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For those who think that this seems terrible... Let me remind you of a couple really bad "stinkers" in the recent past...
Subaru had casting problems that released sand into the crankcase and destroyed engines, and it was a problem that took them a long time to fix, and owners sometimes had a terrible time getting Subaru to permanently fix the problem with a new engine.
The first year of production ( 1994) of the GM 6.5 electronic injection engine had a near 100 % failure rate. The engine electronics were not adequately heat tolerant, among other things. Some blame was offered that at the last minute a plastic shield was placed over the motor that caused temperatuers to rise underneath. Whatever the cause, only months into production, GM began replacing the entire injection pump with a newly redesigned one, that had both mechanical and electronics redesign. We believe that GM actually knew they would fail, but wanted to market the pickup with the "new" engine, as the new engine was required to have a diesel that met emissions for 94.
The Cadillac 4-6-8 V-8 with variable displacement was also a near 100% eventual failure, as it proved to have a failure rate, again, so high that success was more rare than failure.
Cummins had a large number of B engine blocks that failed near the introduction of the ISB. A porosity problem that caused them to leak coolant through the metal. Many owners did not experience failure within warranty, and thus had to fix an 7000 dollar engine on their own.
Subaru had casting problems that released sand into the crankcase and destroyed engines, and it was a problem that took them a long time to fix, and owners sometimes had a terrible time getting Subaru to permanently fix the problem with a new engine.
The first year of production ( 1994) of the GM 6.5 electronic injection engine had a near 100 % failure rate. The engine electronics were not adequately heat tolerant, among other things. Some blame was offered that at the last minute a plastic shield was placed over the motor that caused temperatuers to rise underneath. Whatever the cause, only months into production, GM began replacing the entire injection pump with a newly redesigned one, that had both mechanical and electronics redesign. We believe that GM actually knew they would fail, but wanted to market the pickup with the "new" engine, as the new engine was required to have a diesel that met emissions for 94.
The Cadillac 4-6-8 V-8 with variable displacement was also a near 100% eventual failure, as it proved to have a failure rate, again, so high that success was more rare than failure.
Cummins had a large number of B engine blocks that failed near the introduction of the ISB. A porosity problem that caused them to leak coolant through the metal. Many owners did not experience failure within warranty, and thus had to fix an 7000 dollar engine on their own.
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For those affected by this, a list of past "stinkers" is irrelevant.
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what i meant to say is a revision in the castings were made for 2012 to accommodate the JK's accessory drive. new special tools were released for holding the timing chain tension while servicing the cam sprockets. the old ones wont fit with the new bolt hole boss in the timing cover and head configuration.
i cannot recall if it was the timing cover, head, block, or combination of the above that were changed though.
so far ive done one of these #2 misfires, and another tech here has done one as well. that's all we've seen. mine in a journey, his in a caravan
i cannot recall if it was the timing cover, head, block, or combination of the above that were changed though.
so far ive done one of these #2 misfires, and another tech here has done one as well. that's all we've seen. mine in a journey, his in a caravan
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I hope Chrysler is also looking into some of the timing chains breaking on 2009 and 2010 5.7L HEMI engines. We have had two 2010 R/Ts (automatics with MDS) in our local Challenger club break within the last 2 months. And on challengertalk there are now between one to three new reports a month (since end of last year). All happening during highway cruising (so far all MDS cars). Most of these cars have between 40k and 80k miles on them. Yes, the numbers are low. But shouldn't a breaking chain at those mileage numbers be almost unheard of?
It appears to be the timing chain cover (that's that the front casting is called? Hard for me to to tell, since Chrysler won't give access to mere mortals to their electronic service manuals unless we fork over $$$$ for access to *ALL* service manuals, hopefully next year they'll let AlldataDIY do the 2012 Wrangler) is the only difference. There may have been a block change to add reinforcement for the cover mount bolt holes that were repurposed for the alternator mount, but looking at the preproduction Pentastar photos on the main site, the bolts appear to have already been there to hold on the timing chain cover, just without the flattened surfaces needed to mate with the alternator housing. See, e.g., this photo on the main site from last year:
http://www.pentastars.com/photos/engines.jpg
You will see that the two bolts that are used to mount the alternator are there at the top just inside the vee, but the cover lacks the large flat surfaces needed to mate with the alternator on the Wrangler, which is mounted up top.
There may have been additional things moved in the cover area that affected your bolt holes for your jig (not having seen it, I wouldn't know), but in general Chrysler's engineers appear to have tried to make as few changes as possible to the physical engine itself to support the Wrangler. Which makes sense, because maintaining parts commonality is the only sane thing to do in today's environment. I once worked for a company that didn't maintain parts commonality as much as possible across its product line. That company went out of business because maintaining sufficient parts inventory to meet contractual obligations became a gigantic expense that ate the company alive.
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how many heads in the last 10-15 years have been made or of iron? other than some truck v8's I can't think of any cars since the early to mid 90's that had factory cast iron heads
Yes I'm aware of that, not thrilled about it.
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