pentastar head problems?
JK Enthusiast
Joined: Dec 2011
Posts: 115
Likes: 0
From: Connecticut
If the engine stops in a position such that a camshaft lobe is facing in a direction parallel to the valve, the hydraulic lifter for that valve will be under pressure of the valve spring. This pushes the oil out of the lifter. When the engine is started, the lifter needs to fill with oil again in order to operate normally. The amount of time this takes varies depending how much oil was pushed out of the lifter, what position the lifter is in, the viscosity of the oil in the engine, the temperature of the engine oil, the amount of time it takes to build oil pressure, etc. People usually notice it more in cold weather because the oil is thicker and it therefore takes more time to enter the lifter.
There are tons of other non-Chrysler vehicles with hydraulic valves that tick when they're started. There are forums all over the internet dedicated to this topic. After doing a quick search and following a few links I see reports of Chevy trucks, Corvettes, Lexus', Lexus', and BMWs exhibiting this behavior. Here's a Silverado with 4k on it that ticks on startup:
https://www.youtube.com/watch?v=4lB9bKDKSms
Once you understand why it's happening, you'll also understand why it would not exclusively affect high-mileage engines.
In the case of SabFanInked84, I can't say for sure whether there is a problem with his engine or whether the ticking indicates a potential problem. I don't think we could know that for sure without tearing his engine apart. I know if I were him I wouldn't lose any sleep over it, though.
There are tons of other non-Chrysler vehicles with hydraulic valves that tick when they're started. There are forums all over the internet dedicated to this topic. After doing a quick search and following a few links I see reports of Chevy trucks, Corvettes, Lexus', Lexus', and BMWs exhibiting this behavior. Here's a Silverado with 4k on it that ticks on startup:
https://www.youtube.com/watch?v=4lB9bKDKSms
Once you understand why it's happening, you'll also understand why it would not exclusively affect high-mileage engines.
In the case of SabFanInked84, I can't say for sure whether there is a problem with his engine or whether the ticking indicates a potential problem. I don't think we could know that for sure without tearing his engine apart. I know if I were him I wouldn't lose any sleep over it, though.
If you were to ask if I believe my JKR 3.6L engine will start ticking again; yes I believe it will at some point. I don't think there are very many Pentastars that have reached high mileage; 80k or above. I've seen first hand my valve train apart at my dealer. I don't believe it's a very robust design; hopefully I'm wrong and my engine will be trouble free out to 200k. Keep your fingers crossed because after 5 years or 100k miles we're on our own.
JK Super Freak
Joined: Mar 2012
Posts: 1,476
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From: Mile High Colorado
JK Enthusiast
Joined: Dec 2011
Posts: 115
Likes: 0
From: Connecticut
[QUOTE=lank;3185169]I disagree with this. I do not believe that the plunger return spring can just freely push the plunger out to increase the length of the lifter assembly... It would work that way if the chamber inside the lifter was filled with air or something compressible, but we have to remember that it is filled with oil. Oil is essentially incompressible. Its ability to compress/expand due to pressure is so small we can disregard it.
In order for the plunger to move outward from the body of the lifter, oil needs to enter the chamber in the lifter (the existing oil in the chamber can't expand). In order for the plunger to move inward, oil needs to exit the chamber (the existing oil in the chamber can't compress). Right? The oil passages on the lifter assembly are extremely small and when the oil is cold and viscous (engine is cold) and oil pressure hasn't built up to steady state yet (engine was just started), it makes sense that it would take some time for the oil to enter the lifter. The oil can't just rush right in immediately. In the short amount of time it takes for the oil to pump up the lifter, the valve is not operating with zero lash. This is just a consequence of hydraulic lifter design and, to the best of my understanding, is not indicative of a problem.
Maybe I'm wrong, but that's the way I understand it to work. US patent number 6021751 "Hydraulic valve lifter with lash" is an invention that was designed to prevent the opposite problem: oil not leaving the lifter quickly enough when the engine is cold so the lifter ends up holding a valve open. The invention itself is not totally relevant to our discussion, but much of the information in the patent document supports what I'm saying here:
"During start up of a cold engine, oil viscosity is high and exhaust valve growth is rapid so that hydraulic elements which use a spring biased plunger may not provide a sufficient leakdown rate to avoid holding the valve off its seat on the cam base circle, a condition sometimes called thermal pump up."
--US Patent number 6021751, page 5, "Background of the Invention" (emphasis mine)
Interesting conversation. It does make sense that oil will not give when pressurized. Maybe there's some kind of valving going on internal to the lifter that relieves some of the hydraulic pressure.
What I do know from first hand experience was seeing and feeling the failed lifter. Both cams, rockers/followers were removed. I was able to compress the end that protrudes, adjusts, and moves up against the rocker/cam follower very easily. I'm talking about a force of the weight of my finger. That's how weak the lifter had become. If the only force supporting this plunger at that moment was hydraulic it wouldn't have moved in a linear motion and returned to the exact pre-depressed length. As we know the oil would have damped the force that I was able to apply very easily. The fact that there was no oil pressure within the engine, the engine had not been run in about two days, there would have been very little, probably no, hydraulic resistance remaining. Internal valving, if present, may have retained some oil. As I said if there was any oil left in the lifter there would have been some damping, but here wasn't
As I said the plunger end did positively rebound back into position retaining the exact length equal to all the other lifters. The only known way for this to occur is from a spring; at this point a very weak one. By the way all of the other lifters were impossible to depress no matter how hard I tried.
In order for the plunger to move outward from the body of the lifter, oil needs to enter the chamber in the lifter (the existing oil in the chamber can't expand). In order for the plunger to move inward, oil needs to exit the chamber (the existing oil in the chamber can't compress). Right? The oil passages on the lifter assembly are extremely small and when the oil is cold and viscous (engine is cold) and oil pressure hasn't built up to steady state yet (engine was just started), it makes sense that it would take some time for the oil to enter the lifter. The oil can't just rush right in immediately. In the short amount of time it takes for the oil to pump up the lifter, the valve is not operating with zero lash. This is just a consequence of hydraulic lifter design and, to the best of my understanding, is not indicative of a problem.
Maybe I'm wrong, but that's the way I understand it to work. US patent number 6021751 "Hydraulic valve lifter with lash" is an invention that was designed to prevent the opposite problem: oil not leaving the lifter quickly enough when the engine is cold so the lifter ends up holding a valve open. The invention itself is not totally relevant to our discussion, but much of the information in the patent document supports what I'm saying here:
"During start up of a cold engine, oil viscosity is high and exhaust valve growth is rapid so that hydraulic elements which use a spring biased plunger may not provide a sufficient leakdown rate to avoid holding the valve off its seat on the cam base circle, a condition sometimes called thermal pump up."
--US Patent number 6021751, page 5, "Background of the Invention" (emphasis mine)
Interesting conversation. It does make sense that oil will not give when pressurized. Maybe there's some kind of valving going on internal to the lifter that relieves some of the hydraulic pressure.
What I do know from first hand experience was seeing and feeling the failed lifter. Both cams, rockers/followers were removed. I was able to compress the end that protrudes, adjusts, and moves up against the rocker/cam follower very easily. I'm talking about a force of the weight of my finger. That's how weak the lifter had become. If the only force supporting this plunger at that moment was hydraulic it wouldn't have moved in a linear motion and returned to the exact pre-depressed length. As we know the oil would have damped the force that I was able to apply very easily. The fact that there was no oil pressure within the engine, the engine had not been run in about two days, there would have been very little, probably no, hydraulic resistance remaining. Internal valving, if present, may have retained some oil. As I said if there was any oil left in the lifter there would have been some damping, but here wasn't
As I said the plunger end did positively rebound back into position retaining the exact length equal to all the other lifters. The only known way for this to occur is from a spring; at this point a very weak one. By the way all of the other lifters were impossible to depress no matter how hard I tried.
JK Enthusiast
Joined: Dec 2011
Posts: 115
Likes: 0
From: Connecticut
[QUOTE=Sunkist Rubi;3185881]
I'm taking back what I said about oil not giving under pressure. I also partially disagree on your statement on oil being incompressible.
The cam rotation force acting upon the followers directed to the lifters will be known. The other end of the lifter plunger could be made any size within the head constraints in that area. What I'm getting at is hydraulic pressure is based on the area the oil pushes against; psi. The pressure of the oil running through the engine is also known. All you do is make the opposite plunger end, that interacts with engine oil, the size you want to create just enough force, to be just slightly overwhelmed by the cam rotation force. This keeps everything at zero lash with no gaps or tics. How Chrysler designed this to work based on what I said is unknown to me.
I disagree with this. I do not believe that the plunger return spring can just freely push the plunger out to increase the length of the lifter assembly... It would work that way if the chamber inside the lifter was filled with air or something compressible, but we have to remember that it is filled with oil. Oil is essentially incompressible. Its ability to compress/expand due to pressure is so small we can disregard it.
In order for the plunger to move outward from the body of the lifter, oil needs to enter the chamber in the lifter (the existing oil in the chamber can't expand). In order for the plunger to move inward, oil needs to exit the chamber (the existing oil in the chamber can't compress). Right? The oil passages on the lifter assembly are extremely small and when the oil is cold and viscous (engine is cold) and oil pressure hasn't built up to steady state yet (engine was just started), it makes sense that it would take some time for the oil to enter the lifter. The oil can't just rush right in immediately. In the short amount of time it takes for the oil to pump up the lifter, the valve is not operating with zero lash. This is just a consequence of hydraulic lifter design and, to the best of my understanding, is not indicative of a problem.
Maybe I'm wrong, but that's the way I understand it to work. US patent number 6021751 "Hydraulic valve lifter with lash" is an invention that was designed to prevent the opposite problem: oil not leaving the lifter quickly enough when the engine is cold so the lifter ends up holding a valve open. The invention itself is not totally relevant to our discussion, but much of the information in the patent document supports what I'm saying here:
"During start up of a cold engine, oil viscosity is high and exhaust valve growth is rapid so that hydraulic elements which use a spring biased plunger may not provide a sufficient leakdown rate to avoid holding the valve off its seat on the cam base circle, a condition sometimes called thermal pump up."
--US Patent number 6021751, page 5, "Background of the Invention" (emphasis mine)
Interesting conversation. It does make sense that oil will not give when pressurized. Maybe there's some kind of valving going on internal to the lifter that relieves some of the hydraulic pressure.
What I do know from first hand experience was seeing and feeling the failed lifter. Both cams, rockers/followers were removed. I was able to compress the end that protrudes, adjusts, and moves up against the rocker/cam follower very easily. I'm talking about a force of the weight of my finger. That's how weak the lifter had become. If the only force supporting this plunger at that moment was hydraulic it wouldn't have moved in a linear motion and returned to the exact pre-depressed length. As we know the oil would have damped the force that I was able to apply very easily. The fact that there was no oil pressure within the engine, the engine had not been run in about two days, there would have been very little, probably no, hydraulic resistance remaining. Internal valving, if present, may have retained some oil. As I said if there was any oil left in the lifter there would have been some damping, but here wasn't
As I said the plunger end did positively rebound back into position retaining the exact length equal to all the other lifters. The only known way for this to occur is from a spring; at this point a very weak one. By the way all of the other lifters were impossible to depress no matter how hard I tried.
In order for the plunger to move outward from the body of the lifter, oil needs to enter the chamber in the lifter (the existing oil in the chamber can't expand). In order for the plunger to move inward, oil needs to exit the chamber (the existing oil in the chamber can't compress). Right? The oil passages on the lifter assembly are extremely small and when the oil is cold and viscous (engine is cold) and oil pressure hasn't built up to steady state yet (engine was just started), it makes sense that it would take some time for the oil to enter the lifter. The oil can't just rush right in immediately. In the short amount of time it takes for the oil to pump up the lifter, the valve is not operating with zero lash. This is just a consequence of hydraulic lifter design and, to the best of my understanding, is not indicative of a problem.
Maybe I'm wrong, but that's the way I understand it to work. US patent number 6021751 "Hydraulic valve lifter with lash" is an invention that was designed to prevent the opposite problem: oil not leaving the lifter quickly enough when the engine is cold so the lifter ends up holding a valve open. The invention itself is not totally relevant to our discussion, but much of the information in the patent document supports what I'm saying here:
"During start up of a cold engine, oil viscosity is high and exhaust valve growth is rapid so that hydraulic elements which use a spring biased plunger may not provide a sufficient leakdown rate to avoid holding the valve off its seat on the cam base circle, a condition sometimes called thermal pump up."
--US Patent number 6021751, page 5, "Background of the Invention" (emphasis mine)
Interesting conversation. It does make sense that oil will not give when pressurized. Maybe there's some kind of valving going on internal to the lifter that relieves some of the hydraulic pressure.
What I do know from first hand experience was seeing and feeling the failed lifter. Both cams, rockers/followers were removed. I was able to compress the end that protrudes, adjusts, and moves up against the rocker/cam follower very easily. I'm talking about a force of the weight of my finger. That's how weak the lifter had become. If the only force supporting this plunger at that moment was hydraulic it wouldn't have moved in a linear motion and returned to the exact pre-depressed length. As we know the oil would have damped the force that I was able to apply very easily. The fact that there was no oil pressure within the engine, the engine had not been run in about two days, there would have been very little, probably no, hydraulic resistance remaining. Internal valving, if present, may have retained some oil. As I said if there was any oil left in the lifter there would have been some damping, but here wasn't
As I said the plunger end did positively rebound back into position retaining the exact length equal to all the other lifters. The only known way for this to occur is from a spring; at this point a very weak one. By the way all of the other lifters were impossible to depress no matter how hard I tried.
The cam rotation force acting upon the followers directed to the lifters will be known. The other end of the lifter plunger could be made any size within the head constraints in that area. What I'm getting at is hydraulic pressure is based on the area the oil pushes against; psi. The pressure of the oil running through the engine is also known. All you do is make the opposite plunger end, that interacts with engine oil, the size you want to create just enough force, to be just slightly overwhelmed by the cam rotation force. This keeps everything at zero lash with no gaps or tics. How Chrysler designed this to work based on what I said is unknown to me.
JK Junkie
Joined: Nov 2007
Posts: 2,192
Likes: 2
From: SoCal
wheel hard
OK Sunkist Rubi and lank ( and this is just a suggestion ) because you both have Penastar power plants, lets take off our lifter hats for awhile and start thinking of how to transfer heat off the engine and evacuate heat from the engine bay. This just might be good info other forum members (who wheel hard and engine load is on the upper end ) to read.
One Idea ronjenx did the OEM Mechanical Fan Retrofit on his 3.8
Read Here:
https://www.jk-forum.com/forums/modi...trofit-235132/
A
running motor is a happy 
motor
what do ya think ?
33
One Idea ronjenx did the OEM Mechanical Fan Retrofit on his 3.8
Read Here:
https://www.jk-forum.com/forums/modi...trofit-235132/
A
running motor is a happy motor what do ya think ?
33
Last edited by 33 williys 77; Aug 29, 2012 at 08:30 PM.
JK Enthusiast
Joined: Dec 2011
Posts: 115
Likes: 0
From: Connecticut
OK Sunkist Rubi and lank ( and this is just a suggestion ) because you both have Penastar power plants, lets take off our lifter hats for awhile and start thinking of how to transfer heat off the engine and evacuate heat from the engine bay. This just might be good info other forum members (who wheel hard and engine load is on the upper end ) to read.
One Idea ronjenx did the OEM Mechanical Fan Retrofit on his 3.8
Read Here:
https://www.jk-forum.com/forums/modi...trofit-235132/
A running motor is a happy motor
what do ya think ?
33
One Idea ronjenx did the OEM Mechanical Fan Retrofit on his 3.8
Read Here:
https://www.jk-forum.com/forums/modi...trofit-235132/
A
running motor is a happy motor what do ya think ?
33
JK Junkie
Joined: Nov 2007
Posts: 2,192
Likes: 2
From: SoCal
Thermostatic valve
Automatically regulates oil temperature
Provides quicker warm-ups to operating temperatures
Prevents over-cooling in cold climates
For use with transmission coolers and engine coolers
180°F the thermostatic valve closes, allowing 95% flow through the oil cooler.
Do they make an aux cooler for the pentastar ?
Bad idea to remove thermostat, coolant won't stay in the radiator long enough to transfer it's heat.
Automatically regulates oil temperature
Provides quicker warm-ups to operating temperatures
Prevents over-cooling in cold climates
For use with transmission coolers and engine coolers
180°F the thermostatic valve closes, allowing 95% flow through the oil cooler.
Do they make an aux cooler for the pentastar ?
Bad idea to remove thermostat, coolant won't stay in the radiator long enough to transfer it's heat.
Last edited by 33 williys 77; Aug 30, 2012 at 09:32 AM.
JK Enthusiast
Joined: Dec 2011
Posts: 115
Likes: 0
From: Connecticut
Thermostatic valve
Automatically regulates oil temperature
Provides quicker warm-ups to operating temperatures
Prevents over-cooling in cold climates
For use with transmission coolers and engine coolers
180°F the thermostatic valve closes, allowing 95% flow through the oil cooler.
Do they make an aux cooler for the penastar ?
Automatically regulates oil temperature
Provides quicker warm-ups to operating temperatures
Prevents over-cooling in cold climates
For use with transmission coolers and engine coolers
180°F the thermostatic valve closes, allowing 95% flow through the oil cooler.
Do they make an aux cooler for the penastar ?
JK Newbie
Joined: Oct 2009
Posts: 37
Likes: 0
From: NW Georgia
UPDATE - Just got back from the dealer. Much to my amazement, the dealer I bought from has yet to fix a Pentastar (still hard to believe). That said - the dealer tried to be as helpful as they could. The Restricted Status was present on my Jeep for BOTH HEADS as well. Also note - the Restricted Status on the system now has a note next to it to "Contact S.T.A.R. for further instruction."
Once they tested it - they confirmed something is wrong (ticking, lower power, etc.) and contacted S.T.A.R. And...(Wait for it)....S.T.A.R. told them to (verbatim off my service order) "...Contacted S.T.A.R. - recommend driving to see if problem has any change." My service advisor, apologized profusely and said they want to help but S.T.A.R. told them not to. W-T-F?!
I immediately called Chrysler Customer Affairs and I now have a case number. This is absolutely absurd.
JJ
Once they tested it - they confirmed something is wrong (ticking, lower power, etc.) and contacted S.T.A.R. And...(Wait for it)....S.T.A.R. told them to (verbatim off my service order) "...Contacted S.T.A.R. - recommend driving to see if problem has any change." My service advisor, apologized profusely and said they want to help but S.T.A.R. told them not to. W-T-F?!
I immediately called Chrysler Customer Affairs and I now have a case number. This is absolutely absurd.
JJ