Pictures of Dodge Pentastar 3.6L head

[wwillson]

Another trip to my friend's shop, another set of pictures.

This is the head from a 3.6L Pentastar from a Jeep with 90,000 miles on the clock. One of the middle exhaust valves was leaking and no compression in that cylinder. No idea why the valve leaks. It was cheaper to get a new head w/valves already installed, than it was to try to fix the old head. [edit] The new head with all new valves and springs was < $375, it was cheaper to get a new head than it was to send the bad head to a machine shop.

I was surprised how light this aluminum head is, my guess is it might weigh 20 pounds as is. Note the cast in head exhaust manifold. The intake valves were a super clean because of the port fuel injection. The head was really clean, except for the dirt and debris from removal.

 

[Elroy the Brave]

How did the spark plugs look at 90k miles? They look like they need to be replaced or not much / little gap wear?

 

[wwillson]

How did the spark plugs look at 90k miles?

I didn't look that closely :-(

 

[demarpaint]

With 90K on the engine is he changing the other head as well?

 

[wwillson]

With 90K on the engine is he changing the other head as well?

No, the other head is fine

 

[michaelluscher]

Did anyone ever get to the bottom of why Pentastar cylinder heads fail?
I heard chatter about how it's the exhaust port routing overheating the valve area?
My dad's 2013 300 needed one side at 77k, the other at 97k
Newer 2017/2018 models are just as ticky and tappy at idle

I could live with the oil cooler issue, but dead misfires and major open engine surgery under 100k is a joke at this point in history

 

[demarpaint]

No, the other head is fine

Years ago, 1970's I was taught to do them in pairs if the engine had more than 20K on it. That can open up a can of worms in this day and age, like a thick vs. thin war now.

 

[The Critic]

Years ago, 1970's I was taught to do them in pairs if the engine had more than 20K on it. That can open up a can of worms in this day and age, like a thick vs. thin war now.

That philosophy is about as dated as replacing wheel bearings and struts in pairs.

 

[demarpaint]

That philosophy is about as dated as replacing wheel bearings and struts in pairs.

The cost today would be a deterring factor I'm sure.

 

[Fla]

I have no experience with that particular engine so take this with a grain of salt. But it seems strange to me that one of the exhaust valves in the center cylinder is noticeably lighter colored than the other five exhaust valves. The intake valves in that cylinder are also lighter than the others.

I would find out try to find out if one of the exhaust valves really was leaking and if so why. A leaking valve shouldn't cause a cylinder to have no compression and I suspect that there's something else amiss. (A sticking valve or broken spring?)

Keep us posted on what you're mechanic finds.

 

[Number_35]

I have no experience with that particular engine so take this with a grain of salt. But it seems strange to me that one of the exhaust valves in the center cylinder is noticeably lighter colored than the other five exhaust valves. The intake valves in that cylinder are also lighter than the others.

I would find out try to find out if one of the exhaust valves really was leaking and if so why. A leaking valve shouldn't cause a cylinder to have no compression and I suspect that there's something else amiss. (A sticking valve or broken spring?)

Keep us posted on what you're mechanic finds.

A burnt exhaust valve will typically cause a popping sound, heard at the tail pipe. That would be my first check.

 

[Number_35]

Another trip to my friend's shop, another set of pictures.

This is the head from a 3.6L Pentastar from a Jeep with 90,000 miles on the clock. One of the middle exhaust valves was leaking and no compression in that cylinder. No idea why the valve leaks. It was cheaper to get a new head w/valves already installed, than it was to try to fix the old head.

I was surprised how light this aluminum head is, my guess is it might weigh 20 pounds as is. Note the cast in head exhaust manifold. The intake valves were a super clean because of the port fuel injection. The head was really clean, except for the dirt and debris from removal.

View attachment 156362

Is it usual for the exhaust valves to be larger than the intake valves? I thought it was usually the other way around. (Certainly not my hill to die on - I am basing this on my memory of replacing the head gasket on an old Mazda 3-valve 4-banger. There were two smaller intake valves, and one larger exhaust valve. I assumed the two smaller valves had greater area than the one larger valve, but also realize that circular area increases with the square of the radius, so the one larger valve may have had greater area.)

 

[paulo57509]

Hard to tell, but what's going on here?

 

[wwillson]

Is it usual for the exhaust valves to be larger than the intake valves?

The exhaust valves are the smaller valves you see and are on the same side as the single exhaust port.

 

[tiger862]

Did anyone ever get to the bottom of why Pentastar cylinder heads fail?
I heard chatter about how it's the exhaust port routing overheating the valve area?
My dad's 2013 300 needed one side at 77k, the other at 97k
Newer 2017/2018 models are just as ticky and tappy at idle

I could live with the oil cooler issue, but dead misfires and major open engine surgery under 100k is a joke at this point in history

Dodge claimed running 87 octane was the problem. They dialed back timing for 87 but while you don't seem to hear it the motor is pinging causing head problems.

 

[michaelluscher]

Dodge claimed running 87 octane was the problem. They dialed back timing for 87 but while you don't seem to hear it the motor is pinging causing head problems.

...did they plan on telling the owners?
TF Chrysler

 

[4WD]

Dodge claimed running 87 octane was the problem. They dialed back timing for 87 but while you don't seem to hear it the motor is pinging causing head problems.

Are you running mid grade gasoline ?

 

[SC Maintenance]

Years ago, 1970's I was taught to do them in pairs if the engine had more than 20K on it. That can open up a can of worms in this day and age, like a thick vs. thin war now.

Years ago I had a Ford 4.6 that burnt up one valve at just under 100K - wore out the guide, etc. Must have been bent. Just one valve.

Sent to the machine shop, replaced that one guide and valve, ground all the valves - didn't even remove the other side. Sold it at 180K. The rest of the car was falling apart but engine was still fine.

 

[demarpaint]

Years ago I had a Ford 4.6 that burnt up one valve at just under 100K - wore out the guide, etc. Must have been bent. Just one valve.

Sent to the machine shop, replaced that one guide and valve, ground all the valves - didn't even remove the other side. Sold it at 180K. The rest of the car was falling apart but engine was still fine.

Back then 100K miles was an accomplishment to many w/o doing some kind of engine work. Today it is a walk in the park.
Edit: I was referring to the 70's when I was in auto shop.

 

[SC Maintenance]

Back then 100K miles was an accomplishment to many w/o doing some kind of engine work. Today it is a walk in the park.

2002?