This makes me ask the question again, since this has been going on now for several years, has FCA Ram decided it's normal and that is that or is there any activity on their part to remedy the situation? I, like most people prefer a quiet engine to a noisy one so being told this clatter is normal and they all do it would be disappointing to me if I owned one.
Molybdenum, Cam wear and Hemi tick
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Originally Posted By: Shannow
Sonof Joe,
I respectfully disagree on some parts of your post.
Above is a cutaway of the Chrysler Hemi hydraulic lifter...like most hydraulic lifters (formerly referred to as "zero lash" if that shows my age), the clearance isn't reduced by oil pressure "pumping" the lifter, that quite big spring is supposed to remove the lash, then the oil flows in, and is captured by a Non Return valve inside the lifter body, and the oil being essentially incompressible makes the lifter "solid" on the upstroke.
A bad NRV back in my Holden/Chev days would make for a clattery lifter. If u ran it with the valve covers off, you could feel the impact loads as the zero lash ended up with lash...adjusting was back them off until they had lash (felt via placing your finger on the rocker and feeling the impact), then tightening down to zero impact, and a little more. A bad NRV always was bad.
The lifters "bleed" down between strokes, dependent on viscosity and RPM...cold start, and the few that were under load clattered like nothing else until they got refilled after a few seconds of oil pressure.
Later, some enterprising people started the high bleed lifters that bled down excessively at low cycle speeds (RPM), and made the cam effectively smaller duration and lift by bleeding down...at high RPM, due to the rates of theings moving, they couldn't lose as much oil volume as fast, and the cam timing returned to closer to the design.
Chrysler in their MDS system take it that much further...
Cut the oil to the cylinders that you want to de-activate, which implies an almost instantaneous bleed-down requirement, to allow them to be on/off...needs comparatively large volumes of oil to refill them too, and the regular bleed down rate must be necessarily high.
Also means that the roller, instead of following the cam profile is free floating, controlled only by the internal spring, which SHOULD be OK...but then when you starte to re-oil/refill, there's a number of cycles that "bang" turn solid mid way up the upstroke...at the point of maximum acceleration.
Engineering wise, that's bad Mojo.
So I sort of part agree, part disagree.
Interesting. I'm wondering if the people who disable the cylinder deactivation also have the tick?
Sonof Joe,
I respectfully disagree on some parts of your post.
Above is a cutaway of the Chrysler Hemi hydraulic lifter...like most hydraulic lifters (formerly referred to as "zero lash" if that shows my age), the clearance isn't reduced by oil pressure "pumping" the lifter, that quite big spring is supposed to remove the lash, then the oil flows in, and is captured by a Non Return valve inside the lifter body, and the oil being essentially incompressible makes the lifter "solid" on the upstroke.
A bad NRV back in my Holden/Chev days would make for a clattery lifter. If u ran it with the valve covers off, you could feel the impact loads as the zero lash ended up with lash...adjusting was back them off until they had lash (felt via placing your finger on the rocker and feeling the impact), then tightening down to zero impact, and a little more. A bad NRV always was bad.
The lifters "bleed" down between strokes, dependent on viscosity and RPM...cold start, and the few that were under load clattered like nothing else until they got refilled after a few seconds of oil pressure.
Later, some enterprising people started the high bleed lifters that bled down excessively at low cycle speeds (RPM), and made the cam effectively smaller duration and lift by bleeding down...at high RPM, due to the rates of theings moving, they couldn't lose as much oil volume as fast, and the cam timing returned to closer to the design.
Chrysler in their MDS system take it that much further...
Cut the oil to the cylinders that you want to de-activate, which implies an almost instantaneous bleed-down requirement, to allow them to be on/off...needs comparatively large volumes of oil to refill them too, and the regular bleed down rate must be necessarily high.
Also means that the roller, instead of following the cam profile is free floating, controlled only by the internal spring, which SHOULD be OK...but then when you starte to re-oil/refill, there's a number of cycles that "bang" turn solid mid way up the upstroke...at the point of maximum acceleration.
Engineering wise, that's bad Mojo.
So I sort of part agree, part disagree.
Interesting. I'm wondering if the people who disable the cylinder deactivation also have the tick?
Another theory bites the dust!!! Will have to put on my thinking cap again...
PS - glad Shannow has joined this thread. Am also hoping that TomNJ might join in as being ex-Hatco, he might be able to throw some light on things from the Ester perspective.
PS - glad Shannow has joined this thread. Am also hoping that TomNJ might join in as being ex-Hatco, he might be able to throw some light on things from the Ester perspective.
Here's the chrysler MDS lifter...I don't like it.
The upper (to the right part) looks like a regular hydraulic lifter.
The bit to the left are the springs that hold the roller against the cam when the cylinders are de-activated...
That pin part is supposed to disengage a locking mechanism which lets the "lifter within" slide in the bore with the heavy springs holding the roller against the cam.
http://www.autonerdz.com/yabbfiles/Attachments/MDS.pdf
Trying to intuit the locking mechanism, but it looks to me (happy to be corrected) takes that the pin when pushed in "releases" a wire circlip that allows the lifter within to cycle in the outer body.
http://www.dodgetalk.com/forums/showthread.php?t=454857
Says that the MDS solenoid applies only a couple of psi to the lifter normally (locked), and 16psi to push the pin to unlock it.
My conjecture here is that stick/slip of the locking mechanism ultimately leads to surface fatigue and the failures shown in earlier picks.
Maybe the esters clean and keep things clean...and that while Zn and Mo tend to make "phosphate glass" type tribofilms, some of the tribofilms formed with alternate oils can be a little more "squishy"
I don't like it, either. They went about this a decidedly both low tech and also complicated way.
OVERKILL
$100 Site Donor 2021
Originally Posted By: demarpaint
Originally Posted By: Shannow
Sonof Joe,
I respectfully disagree on some parts of your post.
Above is a cutaway of the Chrysler Hemi hydraulic lifter...like most hydraulic lifters (formerly referred to as "zero lash" if that shows my age), the clearance isn't reduced by oil pressure "pumping" the lifter, that quite big spring is supposed to remove the lash, then the oil flows in, and is captured by a Non Return valve inside the lifter body, and the oil being essentially incompressible makes the lifter "solid" on the upstroke.
A bad NRV back in my Holden/Chev days would make for a clattery lifter. If u ran it with the valve covers off, you could feel the impact loads as the zero lash ended up with lash...adjusting was back them off until they had lash (felt via placing your finger on the rocker and feeling the impact), then tightening down to zero impact, and a little more. A bad NRV always was bad.
The lifters "bleed" down between strokes, dependent on viscosity and RPM...cold start, and the few that were under load clattered like nothing else until they got refilled after a few seconds of oil pressure.
Later, some enterprising people started the high bleed lifters that bled down excessively at low cycle speeds (RPM), and made the cam effectively smaller duration and lift by bleeding down...at high RPM, due to the rates of theings moving, they couldn't lose as much oil volume as fast, and the cam timing returned to closer to the design.
Chrysler in their MDS system take it that much further...
Cut the oil to the cylinders that you want to de-activate, which implies an almost instantaneous bleed-down requirement, to allow them to be on/off...needs comparatively large volumes of oil to refill them too, and the regular bleed down rate must be necessarily high.
Also means that the roller, instead of following the cam profile is free floating, controlled only by the internal spring, which SHOULD be OK...but then when you starte to re-oil/refill, there's a number of cycles that "bang" turn solid mid way up the upstroke...at the point of maximum acceleration.
Engineering wise, that's bad Mojo.
So I sort of part agree, part disagree.
Interesting. I'm wondering if the people who disable the cylinder deactivation also have the tick?
I think that's a very important question, particularly given the wealth of information Shannow has just presented.
Originally Posted By: Shannow
Sonof Joe,
I respectfully disagree on some parts of your post.
Above is a cutaway of the Chrysler Hemi hydraulic lifter...like most hydraulic lifters (formerly referred to as "zero lash" if that shows my age), the clearance isn't reduced by oil pressure "pumping" the lifter, that quite big spring is supposed to remove the lash, then the oil flows in, and is captured by a Non Return valve inside the lifter body, and the oil being essentially incompressible makes the lifter "solid" on the upstroke.
A bad NRV back in my Holden/Chev days would make for a clattery lifter. If u ran it with the valve covers off, you could feel the impact loads as the zero lash ended up with lash...adjusting was back them off until they had lash (felt via placing your finger on the rocker and feeling the impact), then tightening down to zero impact, and a little more. A bad NRV always was bad.
The lifters "bleed" down between strokes, dependent on viscosity and RPM...cold start, and the few that were under load clattered like nothing else until they got refilled after a few seconds of oil pressure.
Later, some enterprising people started the high bleed lifters that bled down excessively at low cycle speeds (RPM), and made the cam effectively smaller duration and lift by bleeding down...at high RPM, due to the rates of theings moving, they couldn't lose as much oil volume as fast, and the cam timing returned to closer to the design.
Chrysler in their MDS system take it that much further...
Cut the oil to the cylinders that you want to de-activate, which implies an almost instantaneous bleed-down requirement, to allow them to be on/off...needs comparatively large volumes of oil to refill them too, and the regular bleed down rate must be necessarily high.
Also means that the roller, instead of following the cam profile is free floating, controlled only by the internal spring, which SHOULD be OK...but then when you starte to re-oil/refill, there's a number of cycles that "bang" turn solid mid way up the upstroke...at the point of maximum acceleration.
Engineering wise, that's bad Mojo.
So I sort of part agree, part disagree.
Interesting. I'm wondering if the people who disable the cylinder deactivation also have the tick?
I think that's a very important question, particularly given the wealth of information Shannow has just presented.
I think from a failure standpoint it would be valuable to know at what rate camshaft and lifters fail on the MDS lobes vs normal lobes on the cam. If the MDS lobes are failing at a statistically significant rate greater than non MDS lobes then the investigation of the MDS lifter is prudent. Now if the data shows that both lifter types are equally likely to fail then it's less likely that the MDS function has anything to do with the problem. I dont have any post failure analysis numbers so really I'm just bringing this up with no way to find the answer. Just highlighting a potential way forward to gain a working hypothesis.
That is a valid approach and the data would be useful. I'm sure FCA has the data, but we will never see it ...
OVERKILL
$100 Site Donor 2021
Originally Posted By: FlyNavyP3
I think from a failure standpoint it would be valuable to know at what rate camshaft and lifters fail on the MDS lobes vs normal lobes on the cam. If the MDS lobes are failing at a statistically significant rate greater than non MDS lobes then the investigation of the MDS lifter is prudent. Now if the data shows that both lifter types are equally likely to fail then it's less likely that the MDS function has anything to do with the problem. I dont have any post failure analysis numbers so really I'm just bringing this up with no way to find the answer. Just highlighting a potential way forward to gain a working hypothesis.
I agree entirely, however I think as BrocLuno has pointed out, gaining access to that data will likely not be possible.
I think from a failure standpoint it would be valuable to know at what rate camshaft and lifters fail on the MDS lobes vs normal lobes on the cam. If the MDS lobes are failing at a statistically significant rate greater than non MDS lobes then the investigation of the MDS lifter is prudent. Now if the data shows that both lifter types are equally likely to fail then it's less likely that the MDS function has anything to do with the problem. I dont have any post failure analysis numbers so really I'm just bringing this up with no way to find the answer. Just highlighting a potential way forward to gain a working hypothesis.
I agree entirely, however I think as BrocLuno has pointed out, gaining access to that data will likely not be possible.
I will reach out to a friend of mine who is a mechanical engineer at FCA and see if I can get any information. Perhaps some of the dealership tech's on here that have completed the in service repairs can shed some light as to which lobes they've seen failing.
OVERKILL
$100 Site Donor 2021
Originally Posted By: FlyNavyP3
I will reach out to a friend of mine who is a mechanical engineer at FCA and see if I can get any information. Perhaps some of the dealership tech's on here that have completed the in service repairs can shed some light as to which lobes they've seen failing.
I can ask my buddies at the dealer and see if they can provide some info.
I will reach out to a friend of mine who is a mechanical engineer at FCA and see if I can get any information. Perhaps some of the dealership tech's on here that have completed the in service repairs can shed some light as to which lobes they've seen failing.
I can ask my buddies at the dealer and see if they can provide some info.
I believe that every damaged cam lobe that I have seen was on a MDS cylinder, I have been told that earlier non MDS hemis don't have this problem. The most recent hemi that I repaired had a code for cylinder reactivation failure. We first replaced the MDS solenoid, that normally cures the reactivation code, but on this engine I had to replace the lifters. The camshaft was not damaged this time. The locking pin in the lifter looked to be out of position to me.
Originally Posted By: burla
This is the kind of thing happening over and over with hemi tick. One lob gets wiped out, thus turning into a 7 thousand dollar dealer fix. Hemi tick leads to wear here, downstream at the cam!! The other forum has been testing now nearly 5 years.
This doesn't seem to be a MDS lifter.
This is the kind of thing happening over and over with hemi tick. One lob gets wiped out, thus turning into a 7 thousand dollar dealer fix. Hemi tick leads to wear here, downstream at the cam!! The other forum has been testing now nearly 5 years.
This doesn't seem to be a MDS lifter.
Just wanted to thank all the posters here. Really good stuff, especially seeing internals of the Hemi lifters as well as a better understanding of how the MDS system works. I'm on my 3rd Hemi and I have to say, for me, the 5.7 has been rock solid. I've had no lifter issues and I'm not sure this "cam failure" thing is the epidemic it's made out to be on the Ram forum. I hope this thread keeps going as the knowledge is much appreciated. Again, thanks guys.
Last edited:
2 plus more pages and no comment on my simply MOS2 instead of Redline question?
Originally Posted By: KenO
2 plus more pages and no comment on my simply MOS2 instead of Redline question?
According to OP, it didn't help the Hemi tick. He said that somewhere in this thread.
2 plus more pages and no comment on my simply MOS2 instead of Redline question?
According to OP, it didn't help the Hemi tick. He said that somewhere in this thread.
Originally Posted By: FlyNavyP3
Originally Posted By: KenO
2 plus more pages and no comment on my simply MOS2 instead of Redline question?
According to OP, it didn't help the Hemi tick. He said that somewhere in this thread.
Gotchya. Hard to wade thru this mess
Originally Posted By: KenO
2 plus more pages and no comment on my simply MOS2 instead of Redline question?
According to OP, it didn't help the Hemi tick. He said that somewhere in this thread.
Gotchya. Hard to wade thru this mess
I turn the MDS off most of the time in my Ram. I don't really notice much difference in fuel mileage with it off either. I think I might start turning it off all the time now if it is the reason for the cam failures.
Originally Posted By: xxch4osxx
I turn the MDS off most of the time in my Ram. I don't really notice much difference in fuel mileage with it off either. I think I might start turning it off all the time now if it is the reason for the cam failures.
How do you turn off the MDS? Do you have a tuner?
I turn the MDS off most of the time in my Ram. I don't really notice much difference in fuel mileage with it off either. I think I might start turning it off all the time now if it is the reason for the cam failures.
How do you turn off the MDS? Do you have a tuner?
You don't have to use a tuner, I turn mine off by the gear +/- button. I usually just wait until I'm in 8th gear than hit gear -. This issue may be another good reason to disable mds, I do it because my exhaust(spintech) doesn't sound great with mds on.
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