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Discussion Starter #1
My first post... hoping to get feedback from anyone else that has had issues... so... I have read that there were many problems with JK cylinder heads around 2012... well I have a 2016 Jk that is in the shop to have the Left cylinder replaced... it only has 17,000 miles on it... I thought that they had fixed the problem...
 

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Well... I found out that my Jk had a code of PO304...#4 cylinder misfire... They preformed a compression test 150psi #4 cylinder ... preformed leak down test 32% on #4 Exhaust less on rest... bottom line... replaced cyclinder head... be aware that this problem that was very common in the 2012 jk models... seems to have not been completely resolved... FYI
 

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I'm not totally surprised, although disappointed. I'm just curious, how do you drive it, easy, or do you get on it right away? I'd also be interested in the Julian date on the head.
 

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I'm not totally surprised, although disappointed. I'm just curious, how do you drive it, easy, or do you get on it right away? I'd also be interested in the Julian date on the head.
Sorry, I do not have the Julian date on the head... My jeep is a 2016 so i would hope that the cylinder head is the newer design... I broke in my engine as recommended... had all maintenance and did light off road stuff... My JK has not had a tough life... I hope that this is a one off problem... what has me a little concerned is that the people at the dealer service department were not surprised that this happened to my Jeep...
 

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Sorry, I do not have the Julian date on the head... My jeep is a 2016 so i would hope that the cylinder head is the newer design... I broke in my engine as recommended... had all maintenance and did light off road stuff... My JK has not had a tough life... I hope that this is a one off problem... what has me a little concerned is that the people at the dealer service department were not surprised that this happened to my Jeep...
I spoke with an friend who owns a machine shop and is familiar with the problem. He felt the problem might be caused by running a cold engine hard, before it was fully warmed up. Over time that would take its toll. He said the cooling passages were poorly engineered in the earlier runs of the Pentastar engine, and them running very hot might have also contributed to the failures. You'll notice in order to service the left cylinder head it's buried trapping heat, unlike the right head.

I'd hope you had the redesigned head, but I have a feeling they might have allowed a certain % of the old heads back into circulation, gambling so to speak rather than scrapping them. This would spread warranty claims out over the years. It would be a stupid practice, real stupid, but nothing surprises me. They also claim not all the heads are going to fail, so maybe they rolled the dice? No one has a straight honest answer. If you had the head build date that might shed some valuable light, which is why I also asked.

Good luck!
 

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My 2014 experienced the problem -- occasional loss of power for about 90 days that felt like you had a tank of bad gas. Then catastrophic failure in May of this year at 15,000 miles. No 6 ate a valve seat, a valve, and then stuck a con rod through the block.

They replaced the long block. Treated me right as far as handling everything (I was 1900 miles away from home; they paid for my rental, flatbedded the Jeep two hours to nearest dealer, car-carriered it home when complete). But I'd rather have been able to finish the trip in MY Jeep rather than a (very, very nice rental) from Twisted Jeeps.

But yeah, problem didn't end in 2012.
 

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My 2017 JK with 30k miles is getting a new cylinder head. Check engine light came on, twice. Code P0304. Dealer replaced plugs and coils. Light back on. Pressure check and going to put on a new cylinder head.
 

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My 2017 JK with 30k miles is getting a new cylinder head. Check engine light came on, twice. Code P0304. Dealer replaced plugs and coils. Light back on. Pressure check and going to put on a new cylinder head.
Welcome to the Forum.

Yep, this defect just continues on..very sad..
 
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