lmorris Posted March 1, 2012 Share Posted March 1, 2012 Any ideas on why only the exhaust rockers are breaking on these? Our service manager feels they need to be a tad thinker, but the new ones don't seem to be any different. I have found nothing else wrong on a few lately to contribute to the failure, just the resulting damage. They seem to be piling up now. Have 3 in the works as I type this. Edit: During diagnosis this truck had 2 low cylinders. 3 and 6. With the firing order being 12734568 I was a little baffled as to why it flagged #6. Hotline was no help stating I must have a bad injector because the valve train was good. After racking my brain on this I dug into my memory banks to when I was doing my apprenticeship, which BTW was around 18 years ago for engines. Using the chart from memory to calculate which cylinder is on what cycle I was able to determine that when #6 was on the power stroke, #3 was on the exhaust stroke. Seeing as the exhaust valves were not opening on #3 this would slow down #6 and mark it as low. Jim would be so proud. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted March 3, 2012 Share Posted March 3, 2012 Sweet, good find. The power balance on these trucks seems to be very sensitive. I have often had it flag wrong or extra cylinders as well. One that comes to memory was a truck with a seized exhaust valve on the rh bank, and broken rocker/ pushrod. The power balance was flagging another cylinder on the same bank, which ended up being the next cylinder to fire on that bank. I figued it was inhaling (some of) the spent gasses from the cylinder with no exhasut valve operation. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted March 3, 2012 Share Posted March 3, 2012 I pulled one in yesterday that has a dead miss on #1 and the proper codes to confirm. Power balance AND relative compression also show two other cylinders misbehaving at a much lesser degree. In the past, 6.4L engines with a broken rockers have always displayed this. We haven't gotten the covers off but I expect to find the #1 intake has the problem. The engine reacts similar for both intake and exhaust valve concerns but when it's the exhaust valve you get a popping from the intake and the effects on the rest of the engine are more distinct. We shall see on this one. I am surprised that the Hot-Line has no information on this - how one cylinder can affect others in this scenario. I know I have reported this in one or two of my reports and we can't be the only one's to make this observation. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted March 4, 2012 Share Posted March 4, 2012 Leon - haven't seen any failures like you describe (yet) though I have seen a couple of rocker arms missing the ball off the end - as I recall, these were camshaft failures and I'm "assuming" that these were beaten to death due to valve train dynamics. Compared to some of the valve springs I'm used to with our roller cam RB Dodges, the 6.4 valve springs seem a little anemic. I do like your chart revisiting engine basics - something most of us tend to overlook at some point in time or another yet can be useful when forming opinions. The power balance function in IDS can be "too accurate" at times. In years gone by, we would short a cylinder and watch rpm drop. We'd do this for every cylinder and compare the results. Our dwell/tach would smooth the readings. Now, since IDS reads the speed of each tooth on the tone ring, we have the opportunity to get into trouble. And for this I offer broadcast message 4376 as it applies to the 6.2 gas engine. "4376 - 6.2L POWER BALANCE LOSS OF RPM CONTRIBUTION ON CYLINDERS 4 AND 7. SOME 6.2L EQUIPPED VEHICLES MAY SHOW A LOSS OF RPM CONTRIBUTION ON BOTH CYLINDER NUMBER 4 AND 7 WHILE PERFORMING THE INTEGRATED DIAGNOSTIC SYSTEM (IDS) POWER BALANCE TEST. IF NO MISFIRES ARE FELT AND NO DIAGNOSTIC TROUBLE CODES (DTC) OR MODE 6 MISFIRE COUNTS ARE PRESENT TO SUPPORT A MISFIRE ON THESE 2 CYLINDERS, THE CONDITION IS NORMAL OF ENGINE DYNAMICS AND HOW POWER BALANCE INTERPRETS THIS INFORMATION. THIS CONDITION DOES NOT AFFECT THE FUNCTION OR DURABILITY OF THE VEHICLE, CONTINUE WITH NORMAL POWERTRAIN CONTROL/EMISSIONS DIAGNOSIS (PC/ED) DIAGNOSTICS AND TESTING." Just to interject some reality... at 2000 rpm, a crankshaft rotates over 33 times per second.... A piston goes from top dead centre to bottom centre in just over 15 milliseconds. The piston accelerates from 0 feet per second (crankshaft dwell at TDC) to whatever when the crank throw is at 90 degrees (hey, remember I'm a high school drop out!!!) and back to 0 fps at BDC in that time. Add in engine harmonics and I'm left wondering if I should be scratching my head or my nuts.... Quote Link to comment Share on other sites More sharing options...
Mikill Posted March 5, 2012 Share Posted March 5, 2012 I pulled one in yesterday that has a dead miss on #1 and the proper codes to confirm. Power balance AND relative compression also show two other cylinders misbehaving at a much lesser degree. In the past, 6.4L engines with a broken rockers have always displayed this. We haven't gotten the covers off but I expect to find the #1 intake has the problem. The engine reacts similar for both intake and exhaust valve concerns but when it's the exhaust valve you get a popping from the intake and the effects on the rest of the engine are more distinct. We shall see on this one. I am surprised that the Hot-Line has no information on this - how one cylinder can affect others in this scenario. I know I have reported this in one or two of my reports and we can't be the only one's to make this observation. In my experience when they come in with dead misses the push tube is broken in half because of a seized lifter Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted March 5, 2012 Share Posted March 5, 2012 For me it has been all seized valves or worn/broken rockers. Quote Link to comment Share on other sites More sharing options...
lmorris Posted March 12, 2012 Author Share Posted March 12, 2012 We get broken rockers, the occasional bent push rod, mainly from it falling out of place then jamming up and having the lifter push it till it bends. All exhaust. No sticky lifters, no sticky valves. No-one seems to be able to provide any answers. We get told to check the lifters and valves and replace as necessary. When I tell them all is good they say to replace the rocker arm and nothing else. They must be compiling some kind on data base on these, you would think. Quote Link to comment Share on other sites More sharing options...
lmorris Posted March 21, 2012 Author Share Posted March 21, 2012 After getting the all good for 8 sets of rockers for an enhanced short block build, because the pivot foot on everyone was stuck in the rocker and not moving, I had a real good look at these new updated rocker arms. They are about 1 mm thicker and stamped a lot smoother. No rough casting edges for a possible crack to start. Not sure if they did anything with the pivot foot though. Quote Link to comment Share on other sites More sharing options...
Jonathan302 Posted March 28, 2012 Share Posted March 28, 2012 I got one today with a dead cylinder(#1) Broken rocker arm on the intake side. The push rod is ok and the valves is free moving The lifter had no more roller on it. The cam lobe is worn, so the cam had to come out. I know what i have to for the next few days Quote Link to comment Share on other sites More sharing options...
lmorris Posted March 28, 2012 Author Share Posted March 28, 2012 I am really surprised to read about people repairing these engines. If the cam is ground down isn't there the possibility of metal throughout the oil system. At that point we short block them. Same with bent rods, we typically see cylinder scoring or the piston bounced off the crank a few times and left metal all over the place. Quote Link to comment Share on other sites More sharing options...
Aaron Posted March 29, 2012 Share Posted March 29, 2012 I am really surprised to read about people repairing these engines. If the cam is ground down isn't there the CERTAINTY of metal throughout the oil system. At that point we short block them. Same with bent rods, we typically see cylinder scoring or the piston bounced off the crank a few times and left metal all over the place. Fixed that for ya Quote Link to comment Share on other sites More sharing options...
Jonathan302 Posted March 29, 2012 Share Posted March 29, 2012 I am really surprised to read about people repairing these engines. If the cam is ground down isn't there the possibility of metal throughout the oil system. At that point we short block them. Same with bent rods, we typically see cylinder scoring or the piston bounced off the crank a few times and left metal all over the place. No surprise for you here ... The lifter roller pin is broke so the roller fall in the pan with the needles. The cam had only light scuffing on the lobe(but need to be replace),no major damage or metal flake all around the block here. That's why a new cam and lifter will do a nice job here without breaking the bank ... I'm not silly, i do my job conscientiously Quote Link to comment Share on other sites More sharing options...
lmorris Posted March 29, 2012 Author Share Posted March 29, 2012 Originally Posted By: lmorris I am really surprised to read about people repairing these engines. If the cam is ground down isn't there the CERTAINTY of metal throughout the oil system. At that point we short block them. Same with bent rods, we typically see cylinder scoring or the piston bounced off the crank a few times and left metal all over the place. Fixed that for ya Thanks...I guess..... Quote Link to comment Share on other sites More sharing options...
lmorris Posted March 29, 2012 Author Share Posted March 29, 2012 Originally Posted By: lmorris I am really surprised to read about people repairing these engines. If the cam is ground down isn't there the possibility of metal throughout the oil system. At that point we short block them. Same with bent rods, we typically see cylinder scoring or the piston bounced off the crank a few times and left metal all over the place. No surprise for you here ... The lifter roller pin is broke so the roller fall in the pan with the needles. The cam had only light scuffing on the lobe(but need to be replace),no major damage or metal flake all around the block here. That's why a new cam and lifter will do a nice job here without breaking the bank ... I'm not silly, i do my job conscientiously Well there is the issue, I haven't seen many bad rollers yet. The one we did see chewed up the cam pretty bad. I think it's because we get 98% oil field support fleets here and if the truck is drive-able they will drive it to us. It has to be spewing from many orifices before they tow them. Quote Link to comment Share on other sites More sharing options...
Mikill Posted March 30, 2012 Share Posted March 30, 2012 I usually find metal in the filter when there is cam damage Quote Link to comment Share on other sites More sharing options...
Mekanik Posted May 25, 2012 Share Posted May 25, 2012 That chart is genius, and exactly my scenario. I've got a pushrod that's splintered at the top, with the ball laying by the injector and the valve bridge for the #3 exhaust valve. How are you guys checking the valves for sticking? Are you guys just replacing the rocker, bridge, and pushrod? What about the lifter? Quote Link to comment Share on other sites More sharing options...
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