I recently took my 2018 Pacifica Limited with just under 66k miles to dealership for a check engine light code p0303 (cylinder 3 misfire). The car would idle roughly. clearly distinguishable. No other OBDII codes. No overheating or coolant issues. The dealership mechanic diagnosed and determined a blown head gasket and requested to conduct a full engine tear down. I approved and now the dealership is having Mopar inspectors to check engine. Since I bought from a dealership in 2020 as certified pre-owned, it is still under a 7 year or 100k warranty. As anyone had any issues with getting mopar to honor the warranty? The dealership service rep is hinting that mopar sometimes will not and find ways to say the owner has not properly followed the EXACT manufacturers recommended maintenance. For example getting oil changes every 3k miles. I mean with synthetic oils, do you really need them every 3k? Also, it seems the blown head gasket is common for pacificas at such relatively low mileages. Any other owners have similar issues?
2018 Blown Head Gasket
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mikepacificasandiego
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I'll have to remember this fix for that oil filter and oil cooler. I dislike that the manufacturers moved to plastic parts like this on vehicles. They are everywhere.
That document doesn't make any sense. Displacement and Bore x Stroke are identical between the two engines in that document. It appears whoever made that document typoed the compression ratios backward comparing the engines. Have you read the links I provided?
"The Atkinson cycle modifies that process by leaving the intake valves open for the first moments of the compression stroke, as the piston travels toward top dead center, which effectively lowers the compression ratio of, say, 10:1 to something more like 8:1, or so. That adjustment reduces the force on the piston on the power stroke. "
"What Atkinson did is that he lowered the compression stroke of the engine whereas increasing the power stroke. This meant attaining more efficiency since: "
"The compression stroke then has less work to do to compress the mixture."
"But the question arises that less fuel means less power right? Well you are probably right because an Atkinson cycle produces about 30% less power than an Otto cycle. "
Ok, I hear ya.
My guess is this is "a failure to communicate". Since the specs don't account for the various strokes maybe that's just the power stroke instead of the compression stroke? With the Otto engine there's no difference between strokes but not so with the Atkinson.
Compression ratio has to do with the shape of the combustion chamber and piston top. They alter compression ratio by changing pistons and /or heads. They do not change the stroke of the motor.
Atkinson cycle motors use high compression to increase the motor's efficiency. They use the late intake valve timing to blow off some of high compression and prevent detonation. The result of this is lower torque and hp, but better fuel economy. Many automakers do this with their hybrid powertrains.
Atkinson cycle motors use high compression to increase the motor's efficiency. They use the late intake valve timing to blow off some of high compression and prevent detonation. The result of this is lower torque and hp, but better fuel economy. Many automakers do this with their hybrid powertrains.
Good to know. Thanks for the technical explanation.
The Atkinson cycle uses a longer power stroke than compression stroke. That is what increases the efficiency of the cycle over the Otto cycle. It is true that higher compression ratios increase efficiencies in thermal engines, but the real compression ratio is limited by the detonation characteristics of the fuel so the real compression ratio cannot be increased over an Otto cycle engine using the same fuel.
Rather than mechanically vary the compression and power stroke, the trick used is to delay the closing of the intake valve, which makes the the actual compression ratio less than if the valve was closed at the bottom of the intake. This technique is sometimes referred to as the Miller/Atkinson cycle.
I was surprised to see the 12.5 compression in the specifications. I suspect that ratio is the what it would be if the intake valve was closed at the bottom of the intake cycle.
Rather than mechanically vary the compression and power stroke, the trick used is to delay the closing of the intake valve, which makes the the actual compression ratio less than if the valve was closed at the bottom of the intake. This technique is sometimes referred to as the Miller/Atkinson cycle.
I was surprised to see the 12.5 compression in the specifications. I suspect that ratio is the what it would be if the intake valve was closed at the bottom of the intake cycle.
Which stroke does that correspond to here:
- Intake Stroke – The air-fuel mixture is sucked in to the cylinder as the piston moves from top dead center (TDC) to bottom dead center (BDC).
- Compression Stroke – The mixture is then compressed as the inlet valve closes and the piston moves back to TDC from BDC. This marks the first revolution of the crank shaft.
- Power Stroke – Now the spark plug produces a spark and ignites the air-fuel mixture inside the cylinder. This produces a gas at high pressure which pushes the piston down back towards the BDC, producing power.
- Exhaust Stroke – The piston then moves back towards the TDC as the exhaust valve open to push out the burnt gas as exhaust. This marks the second revolution of the crank shaft.
I think the 12.5 ratio in the specification is the ratio of the volume at BDC divided by the volume at TDC. However for the Miller/Atkinson cycle the delayed intake valve closing makes the actual compression ratio the volume at the point in the compression stroke where the intake valve closes divided by the volume at TDC, which of course is lower. However, this makes the expansion during the power stroke to be longer in comparison to the actual compression stroke, even though the mechanical stroke of the piston is the same.
The classical Atkinson cycle makes makes the power stroke expansion longer than the compression mechanically, e.g. the animation in the following--
Miller came up with the trick of delaying the intake valve closure to have about the same effect as the more complicated Atkinson mechanism. Clever, and the hybrid is a good application.
The classical Atkinson cycle makes makes the power stroke expansion longer than the compression mechanically, e.g. the animation in the following--
Miller came up with the trick of delaying the intake valve closure to have about the same effect as the more complicated Atkinson mechanism. Clever, and the hybrid is a good application.
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Model Year:
2017
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Gas
Trim:
Touring L
The progression of your issues are very similar to what I'm going through on my 2017 Pacifica right now. P0303, Spark plugs, coils, something odd with coolant tank, PCV replacement and now the light is back on again. I'm waiting on ChryslerCares to tell me which repair shop in my area has expertise on this matter. I was told in no uncertain terms, there was no issue with my head gasket the last time I dropped it off at the dealer. I only have 69,000 miles on my Pacifica right now. Did you get the engine replacement?
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Model Year:
2017
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Gas
Trim:
Limited
I'm waiting on parts and tools to disassemble my crankcase/shaft and examine the head gaskets for the left bank 1/3/5.
new to the forum, but our Pacifica had check engine light on temporarily, so dealer could not replicate, so we took a trip from Tulsa to Cincinnati, and now our car is sitting at a dealership up there with cracked cylinder head, also under extended warranty.
Thankfully yours is under warranty.
The dealer had to get a code after your check engine light came on. Did you happen to find out what it was?
Don’t know the code but number four cylinder cracked and allowed coolant leak.
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So frustrated with my issue. Brand new engine and radiator which is all under warranty. New radiator and engine and i'm still pouring quarts of coolant into the coolant recovery system. I fill it up between min and max. Drive it for 10 minutes and BAM the coolant system is empty. I got no idea where it's all going! No leaks on the ground when parked! This is the most unreal thing I have ever seen. Two weeks of this **** so I just started to fill it with water today since I don't want to waste the money of expensive coolant. Maxed out the water in the coolant recovery system, drove it less than 3 miles. Got back home and it was empty again! WHERE IS IT ALL GOING? Zero leakage on the ground.
What is your mechanic saying?
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It's the dealership that has removed and replaced the engine and radiator under warranty. $15K which was under a warranty we bought when we purchased it. We had to pay about $3200.00 or so which was better than 15K. This issue has begun only since the new engine and radiator were replaced. I would say we have put almost 2-3 gallons of fluid into the recovery system and still it drinks it! We have a dealer apt on the 19th. We'll see what happens then with a new service rep and hopefully a new mechanic!
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My head gasket blew on my Pacifica. Does anyone know of a reasonably priced mechanic close to Pilsen or 60608? frazierwuan@gmail.com
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Model Year:
2017 & 2021
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Hi @frazierwuan. Sorry to hear of the blown head gasket in your Pacifica. Can you please provide a few details as to how you came to this conclusion. I might then add your username to this thread.
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Username is Fraz. I took my Pacifica to a garage for a diagnostic because it was running hot. The mechanic told me because of the nature of the 'Bubbles' and their orientation indicated the presence of certain gases found in blown head gaskets. My regular mechanic also told me it was a blown head gasket and he took the thermostat out so I could make it home. Also, there is no smoke visible from anywhere.
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