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What would cause this?? - JMBT - 11-27-2021
[attachment=8210][attachment=8209]Hello all, I have a 2012 Volvo with a CM2250, and 855k miles. I just popped the top to do an overhead. It has been about 95k since the last overhead I did. Everything up there is nice and clean. All of the cam lobes look beautiful, but on the first three sets of rocker followers, cylinders 1,2,&3 there are lines staring to form. The back three still look great. I cannot feel any of the lines with my fingernail so I don’t think they are very deep yet, but I was wondering what would have caused this? And how worried should I be??
Thanks in advance! JMBT
RE: What would cause this?? - Signature620 - 11-27-2021
Cummins call them 'white bands'. They are harmless and will show up on nearly every ISX overhead.
RE: What would cause this?? - JMBT - 11-27-2021
Thanks Signature620!, and thanks you for the fast reply, that helps my OCD mind!
RE: What would cause this?? - Nostalgic - 11-27-2021
(11-27-2021 )Signature620 Wrote: Cummins call them 'white bands'. They are harmless and will show up on nearly every ISX overhead.
Brand new valve cam and all new rockers and had white bands showing up on just about all of them in less than 10k. Supposedly caused by oil oxidation according to Cummins. Not sure how my oil oxidized that quickly, but whatever... Might as well just toss a couple scotch pads in next time I do an overhead lol. <<-- Sarcasm, just in case someone took it literally.
RE: What would cause this?? - tree98 - 11-27-2021
Gear oil doesn't keep them from appearing?
RE: What would cause this?? - Nostalgic - 11-27-2021
(11-27-2021 )tree98 Wrote: Gear oil doesn't keep them from appearing?
Didn't on any of mine for whatever reason. I've been using Sta-Lube from day one.
RE: What would cause this?? - Rawze - 11-28-2021
(11-27-2021 )JMBT Wrote: Hello all, I have a 2012 Volvo with a CM2250, and 855k miles. I just popped the top to do an overhead. It has been about 95k since the last overhead I did. Everything up there is nice and clean. All of the cam lobes look beautiful, but on the first three sets of rocker followers, cylinders 1,2,&3 there are lines staring to form. The back three still look great. I cannot feel any of the lines with my fingernail so I don’t think they are very deep yet, but I was wondering what would have caused this? And how worried should I be??
Thanks in advance! JMBT
Letting road dirt get onto the rollers while performing an overhead valve adjustment or re-installing the engine cover and its got dust/dirt on it is a very common cause of that streaking. that or the valves are riding the cam because the overhead is not adjusted often enough vs. the amount of head wear. Should be done every 250k miles or so .. or roughly 4,000 engine hours. Maybe more often if you idle a whole lot or have a lot of low rpm PTO.
Mine never got those streaks in them like that. Valve cam made it 1.3 million miles .. number 6 started to get a bit flaky finally, but rest of it was still looking really good. Injector cam still looked mostly new, but i went ahead and replaced them both at 1.3-mil.
- I always also ensured everything is extremely clean + cleaned the cover really well + washed any dust off all my rollers/cams, etc. with a bit of WD-40 spray each time I adjusted the valves, just before putting the cover back on. I also cleaned the ledges around where the cover sits too, usually scrape all the dirt and dust off while using a tiny shop-vac.
- I also make everyone who comes here do this when they are over here and do overhead adjustments too.
RE: What would cause this?? - SemiSweet - 11-28-2021
Mine developed those frosted bands almost immediately after I replaced my cam and followers and I suspect it’s from fine dust during install. Although, I had it apart recently to replace the rocker shafts and it seems like they are disappearing maybe since I've been doing frequent oil changes and adding gear lube. As long as you can’t feel anything with your fingernail it’s nothing to worry about. I always use compressed air to blow the edges of the valve cover before removing , those followers are very close to the edge of the head and dirt pretty much just falls right onto them if it’s not cleaned up.
RE: What would cause this?? - Rawze - 11-29-2021
(11-27-2021 )JMBT Wrote: Hello all, I have a 2012 Volvo with a CM2250, and 855k miles. I just popped the top to do an overhead. It has been about 95k since the last overhead I did. Everything up there is nice and clean. All of the cam lobes look beautiful, but on the first three sets of rocker followers, cylinders 1,2,&3 there are lines staring to form. The back three still look great. I cannot feel any of the lines with my fingernail so I don’t think they are very deep yet, but I was wondering what would have caused this? And how worried should I be??
Thanks in advance! JMBT
MORE causes of this, and/or overhead cam failures in general ...
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* LOWER THAN NORMAL OIL PRESSURES!. If the oil pressures are falling off due to excessive soot buildup in the enigne, or are lower than normal all the time...
- Anything less than about 28 psi or so oil pressures at idle is considered lower than normal oil pressures.
- If the oil pressure falls below about 33 psi or so while at speed (engine above 1300 rpm or so) is also considered lower then normal oil pressures.
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* USING SYNTHETIC OILS + extending oil changes + bypass filtration = A MAJOR contributor towards repeating overhead cam failures! .. and especially if your using synthetic oils and extending the oil change interval out more than 20k-miles+ on oil changes because your combining synthetetic and bypass oil filters. THE ISX DOES NOT LIKE SYNTHETIC AND EXTENDED OIL CHANGE INTERVALS!!. Everyone that I have met so far of that does this bulls$it to their ISX ends up replacing the overhead cams 2-3x more often that they should be.... and a lot of them are too god-damn stupid to realize that syn+extended oil changes is engine abuse!
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* THE CRANK CASE FILTER SYSTEM IS OFTEN THE PROBLEM. Any buildup of pressure.. even small amounts of pressures.. CAUSE THE OVERHEAD CAMS / valve train TO FAIL PREMATURELY! bacuase they are getting starved of what little oil pressure gets to them to begin with.
-- If the engine is getting old... THE paper-element style of crank case filter WILL NO LONGER KEEP UP with the amount of blo-by in the engine. ANY BUILDUP of crankcase fumes in the enigne IS REALLY BAD FOR THE OVERHEAD CAMS AND FOR THE TURBO!. i HAVE SEEN COUNTLESS ENGINES where that paper-style crank case filter was not keeping up on older engines.. Especially when often also combined with the truck owner not changing the filter often enough.. and it caused cam failures.. and the top-end to get starved of oil.
INSTALL A MAINTENANCE-FREE FILTER A.S.A.P! -- ref: http://rawze.com/forums/showthread.php?tid=1051&pid=8950#pid8950
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ANY RECENT CAM/VALVE train replacement work? .. If the valve rockers, cam(s)., etc. was replaced recently.. or the components were removed / re-installed. etc.. OR the head was replaced... Then a second adjustment is requires about 30-50k miles later to ensure everything has the proper clearances once everything has run a bit.
here is an older post that is related to this as well: http://rawze.com/forums/showthread.php?tid=141&pid=783#pid783