My 466 was 300 miles from home when it started blowing massive blow by and puking out oil at an astonishing rate, to the tune of one gallon to a gallon and a half every 100 miles or so, it came on all of the sudden, as in less than one mile of driving. Made some calls to determine what happened and was told by many I scored a sleeve and piston was most likely the cause or a cracked head, I had air pressure for the brakes and otherwise it ran pretty good. Was told to bring it home and if it started to make any funny noises to shut it off immediately, ran fine the whole way home besides massive blow by and puking out oil at an alarming rate through the blow by pipe and onto the ground. Made more calls when I got home and was assured it was a scored sleeve and piston, didn't quite add up, had other engines do this and they had a miss, this one didn't, didn't match up to a blown piston either because lack of miss, didn't act like a cracked head but had to tear it down just the same. Pulled the engine out of the frame and tore it down, pistons looked great, so did the sleeves, have the head in now waiting its turn to get checked over but first look the rebuild guy had was it looked fine to him, he'd just redone it less than 20k miles ago, the same time the turbo was new, took that in and was told it looked great, brand new and nothing wrong with it. No holes in the sleeves, cracks or anything out of the ordinary we can see. Basically no smoking gun so to speak, so I have asked every repair shop around about the air compressor for the brakes and have been told it can't possibly be the air compressor causing the engine pressure issues and massive blow by. The air compressor is cam gear driven and I've never had one do this before, first can it happen and cause this issue, and next question is, how? Every air compressor I've ever had either worked great or had a massive failure and self destructed so to speak. Everyone ruled out the compressor by asking is there any oil in the air tanks on the truck, checked that and they are dry and no sign of oil soaking anything. Just wondering if anyone has had an air compressor do this to an engine before, I've asked about a scored sleeve in the compressor itself and was told in 300 miles of driving it would have blown apart long before I ever got home if there was a compressor issue of any sort?
While I've never dealt with it first hand I have heard of a compressor having issues and creating crankcase pressure. Wouldn't take much postive pressure to blow oil out like you describe. Too bad it's all torn down and we can't collectively troubleshoot it. Blowby that severe sure would be more than one scored hole, IMO. My 5.9 had one terrible hole and a couple mediocre ones and it only blew a quart per tank of fuel. Being massive like that I sure would expect a major failure somewhere that would stick out like a sore thumb. I could see a compressor doing that but I'd also expect to see a reduction in air supply in the needed areas such as brakes etc. Puzzling for sure. I'll be curious to see what it turns out to be. Junkyard
Too bad you didn't look at the injector nozzles before tearing it down. That would have prompted you to do a compression check. I once pulled a head on a Superior V16 natural gas engine because it sounded like someone dropped a socket in the spark plug hole. We had to shut down the gas compressor facility. Turned out to be detonation from uneven load. Is there some kind of air operated oil pressure relay? Something like a make switch or break switch to prevent the compressor from loading for a couple seconds until the engine has oil pressure?
I'm only on my first cup of coffee but agree this one sounds strange. Short of a dropped valve I find it hard to think of how the problem would be in the head, but then I have not worked on a 466. What does this engine have for crankcase ventilation system? I'm assuming the oil was coming out that system ? Just wondering if there is some kind of baffle that was out of place and letting oil out without there actually being pressure in crankcase. I know it probably seemed to be a no brainer what the problem was but would love to have done a little checking before tear down, especially if it ran good enough to drive 300 miles.
Everyone I knew to talk to assured me it was something with the pistons and rings, several sleeves scored at least and told me to pull the engine out and tear it down, it was so bad with blow by it would be obvious when torn apart.........................so much for that idea. Its not all for a waste, the main bearings and rod bearings were due anyhow. When I pulled the head off and saw the sleeves I knew right away I was in for a strange ordeal, my next thought was broken rings or somehow the rings were aligned and allowed blow by past the rings, or a cracked sleeve or hole in a sleeve I couldn't see with just the head off, turned out not the case. While driving the oil coming out was so bad, it blew it on the exhaust pipe and the blue haze behind the truck had cars behind me slow down so they could see, and that's no exaggeration, we had to stop and buy a short piece of hose to add onto the blow by pipe and extend it down to the pavement past the exhaust piping to eliminate the blue smoke. When we got home so much oil had blown by and under the truck, it was dripping off the back bumper and belly of the truck. It was blowing so much oil out, sitting idling for even a few minutes it left a blown smear patch of oil, at idle the blow by was so bad as it hit the ground it plumed out in every direction and as the oil spewed out, the blow by would blow that dripping oil from a puddle to a smear, at high rpm it would be a solid pipe of pressure coming out. I've had engines score a sleeve and piston before, and it didn't take long and it would blow the dipstick tube out along with blow by, this engine had a screw tight dip stick/fill tube and we'd never run an engine with a scored sleeve and piston long, maybe a few minutes or half hour, this time we ran about six hours, can't tell now if it got worse or not, my main concern was to get it home and worry about it later, we had too many things more important to do and be concerned with at the time. Figured at tear down it would be obvious. I asked all locals if there was anything to test for and they all laughed and told to just tear it down, its a no brainer as to what was causing the problem, they are no longer laughing and are somewhat puzzled, my next question to them is, unless we find something obvious, upon start up after a rebuild, what's plan B if it does the same thing?? There response so far has been, then we can test the engine, my question was for what?? I know I'm somewhat negative in thinking but I've never torn down an engine before that I didn't find an obvious problem right away, so I'm thinking we have not yet found the total problem.
For $hits and giggles tear into the compressor if you haven't yet. It's not common but possible it was creating crankcase pressure. Head checked ok? This is a head scratcher for sure.
Junkyard, I've asked more specific questions locally and nobody seems to know how to even test the compressor for crankcase pressure, nor can or ever has gotten parts for the compressor if I'd even tear it apart, not talked to anyone yet who's even torn one apart, everyone just swaps them out for rebuilt if there's a problem. Only suggestions so far is to put the engine back together and if it still has massive blow by, to put a rebuilt compressor on then. Its a twin cylinder bendix 550 compressor, its been remanufactured but no date on the rebuild, not sure there is anything wrong with it for sure, anyone ever torn one apart or tested one before, waiting for a call back from bendix.
Pull the head off it, there will be a couple little pieces for the unloader valve but other than that it's like a little motor. See if cylinders are scored, busted piston etc. You can pull the plates off the side, just go nuts you can't hurt it. If you see oil on the air side (in cylinders or tops of pistons) that's a telltale sign. Has there been oil in the air tanks? It's a stretch to be the compressor but not impossible. It's like an autopsy! Haha
Does the compressor have a coupler section before it bolts to the front geartrain? If it does, I would think the air would push out there before pressurizing the front case. I have seen them go bad and dump oil in the air tanks, I have also seen them back oil up into their intake pipe- you might be able to find the oil in there. If it somehow blocked its oil return, or even slowed it down, you would be getting all kinds of oil.
No coupler section, it just bolts directly to the back of the front cover, also the oil return to the engine is directly into the front cover as well, through the front of the compressor making it almost impossible to isolate the return even if the engine was running to see if the compressor was making pressure to the engine crankcase.
Turbo?
Turbo isn't that old and I took it in to the local fix it guy and he told me nothing was wrong with it after he looked it over, he also told me at idle the turbo would never produce anywhere enough pressure to cause that much blow by and at full pressure it would only build about 35 psi of pressure. On start up I can check that, I was told all I have to do is take the oil return line off and dump it into a bucket and run the engine long enough to get some oil in the bucket and if it blows bubbles with the return hose routed into the pail, I have a turbo leaking issue. Been reading the air compressor service manual online and I now at least have some understanding how it works, I also know now that what I was told as to how to test it won't work. I'll wait out Bendix and talk to the techs first before getting carried away tearing it apart.
Cracked piston. I have had that happen on a Cummins before. Amazed how much oil can be blown out. Took 10 gal of oil to get 500 miles home! Truck and trailer were both dripping by the time I got it home to the shop. Doesn't take a very big crack either.
By looking at the piston's, they all look fine, but the shop is going to look them over for sure. Finally got through to a tech at Bendix, chatted and asked a lot of questions, some might find this interesting, the compressor I have is a twin piston and when I asked if it was possible for the compressor to cause my engine crankcase pressure issue the answer was "yes", so I asked some more questions and told the guy at Bendix I drove the truck home 300 miles and if the compressor was bad, how did I still have air to run the brakes......................................it took him a few minutes to respond and his answer was this, one cylinder built pressure and the other dumped pressure into the compressors crankcase and thus into the engine crankcase. I asked how do I check the compressor to find out if it is indeed bad, he told me there is no test that would tell me much of anything, since the compressor crankcase dumps directly back into the engine crankcase, I asked about bench testing the compressor and he told me nobody had that ability. As for visually seeing anything if I'd take it apart, his opinion was I might, but probably not, I'd have to check ring gap, cylinder wear specs and everything the rebuild shops do. So between the tech's suggestions and some experimenting this is what I came up with, by hand turn over the compressor as I hold my finger over the outlet port, one cylinder builds pressure and try's to blow my finger off the port, the next stoke has virtually no pressure against my finger and I could hear a hissing coming out of the compressor crankcase as I rolled it over. After some phone calls to my kids, I was told we had a spare compressor somewhere, so after a few hours of looking, found it, also a twin cylinder compressor and tried that one, same technique, but this time I couldn't roll the compressor over completely the back pressure would make it impossible to roll over the compressor, as it built a lot of pressure against my finger, next stroke same thing, I couldn't turn it over completely by hand due to the pressure it was building with my finger over the hole. So armed with that knowledge, I'm thinking the compressor is bad and the main culprit for this whole problem.
Blank off the compressor air outlet and connect shop air to the inlet. That will pressurise both cylinders.
Yes! this would be a very good test! While it will not tell you exactly which cylinder is bad or why if you get anything more than a very faint amount of air going into the crankcase of the compressor you would have your answer. The valves on an air compressor are very simple one-way check valves. If one piston has failed it will not produce enough pressure to open it's exhaust valve. If like on many engines the inlet to the compressor comes from the intake of the engine between the turbo and the intake manifold the turbo boost pressure would be likely enough to open the intake valve on the bad cylinder and with a bad piston that pressure would go straight to the crankcase of the engine. This would overwhelm normal crankcase ventilation system. If you do as Cmark suggest and get lots of air coming into the compressor crank case grab a 1/2 inch socket and ratchet and take the head off that compressor and see what is in there. Be sure to post some good pictures for us!
I started to mess around with the compressor, I pulled the bottom plate off to look inside at bottom portion of the sleeves, both looked pretty good and felt good. Rolled the compressor over and the cylinder closest to the front of the engine had a lot of slop in the piston and I could hear a hissing in the compressor crankcase as I rolled the compressor over. I squirted some oil along the bottom of the pistons and turned the compressor over, pretty sure the first sleeve and piston are the culprit, but I'll sure do as Cmark suggested tomorrow as the compressor bottom is open and its flipped upside down, with some soap and water or oil, it sure should show up without a doubt if there is compression going into the crankcase of the compressor. I'll see what I can do about pictures as well.
A bunch of years ago I worked for the Link-Belt dealer. The hot logging machine in those days was the 4300C2 with the Cummins engine. We had a couple of machines that developed a ton of blow by and leaked all over the back of the machines. We did the inquiries with the machine manufacturer who told us to talk to the engine manufacturer. We did that and they had no idea but they could send out one of their guys at our expense to check it out. That didn't settle well. One machine we brought into the shop and resealed all the gaskets and seals, sent it back out to start leaking a ton again in a week. We knew the engine ran too well to be making so much pressure. Finally we started checking other issues. The axial piston hydraulic pumps in those days were pretty new and engineers didn't seem to connect that it has to be mounted lower than the level of the hydraulic oil in the tank. To solve the problem they installed an air compressor on the engine and plumbed it to the top of the hydraulic tank. There was a pressure reducing valve installed to keep the tank pressure at about 15 PSI. We call the air compressor people who filled in the blanks. It seems the engineers at Link-Belt did the engineering on the air compressor installation. Basically they used engine coolant to cool the air compressor. The people we talked to told us the Link-Belt people put in too small of an output hose for the coolant and the air compressors were overheating. I checked the output temps off the compressor coolant line and found this to be true. Problems was Link-Belt denied all of this and left us holding the bag for the customer. The point is to make sure if you have an engine cooled compressor that you have the right fittings and hose sizes and maybe check the temps after things are at operating temp.
John, thanks for the reply and the heads up on this, but I'm thinking with all the idle time on this engine, and being a remanufactured compressor, it just needs to be replaced due to wear and tear. I hadn't really thought of it, but I could take the block in so they can clean it up and steam it, to be sure there is no blockage or buildup in the water jacket to slow cooling anywhere. I forgot to post, I called just before closing yesterday, my piston's were checked over, they are fine, the cam is good, they checked the crank and its right in the middle of spec for standard and didn't need to be machined, but haven't gotten to the head or sleeves yet.
Followed Cmark's advice and pressurized the compressor, with it flipped upside down and the bottom cover off, yes it blows air into the compressor crankcase, next I took an oil can and squired the bottoms of the pistons full of oil, was obvious as to where the air was coming from, at each ring level, the oil hole behind the ring was letting air at each ring, then around the bottom of the pistons they leaked a lot as well, one piston worse than the other, squirted some water and soap in and the bubbles were so bad I couldn't see into the compressor case. Made another call to Bendix and asked some more questions, first one was how much blow by into the compressor's case is acceptable and how much is excessive.................................was told that was an excellent question, after all there is always some. I explained how I did the test and was told the only true way to test any compressor was with the engine running and time the air buildup as the blow by was monitored. The other way is to do a timed pressure reduction, asked how that works and the guy could explain it, basically put x amount of air into the compressor head as I did, then time how long it takes to drop x pounds of air pressure, and the guy I was talking to had no idea any of the technical amounts, like how long or how many pounds of pressure because its basically never done by anyone, they use the timing to build air method after rebuilding. The techs advise was to wait till the engine was put together and running and time the air buildup, monitor the blow by on the engine and if the time is too long, swap for a rebuilt compressor and repeat the timing process and compare to rebuilt or call and ask for specific times for each compressor to build x pounds of air. I asked how much more crankcase pressure a compressor would build that was actually running on an engine and he had no clue, but thought it was be considerable, but said he's never been asked that question ever before. He told me to take apart the dryer receiver on the truck, and examine it for oil residue, his claim was any compressor shot beyond its capability would shoot oil into the downstream air system, the worse the compressor, the faster it would fill the downstream system. I asked about a rebuild kit and he told me no specs have ever been kept on a rebuilt compressor as to what bearings, rings, pistons or anything was put into them, so it was impossible to know what parts I'd need to rebuild it, some compressors are bored, some honed and some are set back to standard and everything in between. I was hoping to get a pressure drop number and time from him, set up a gauge and some valves and run in x pounds of air, and cap it off, monitor the time it takes for x pounds of pressure to drop x pounds, but that never happened and he claimed had never been done?? Not sure anyone wants to know any of this, but I found it educational just the same. As for pictures, I tried but couldn't get a photo of the bottom of the pistons to show the oil bubbling or how the air shot in through the holes behind the piston rings, it was too dark that deep down and the flash only lighted up the crank, I tried with a flashlight laid down in the case, but that didn't work either, so sorry I tried, but wasn't successful, I'd have had to had a bore scope of sorts with a camera on the end and I don't have one. I shot some soap and water in on top of the oil and have a few pictures of the bubbles overflowing out of the compressor, but it didn't show much air or where it was coming from per say.
I think that the reason you don't get good numbers on this is that nobody in the commercial trucking world wants to mess with air compressors, they just diagnose, hopefully correctly, slap a reman on, and send the truck on down the road. I think in the previous posts that you have pretty well demonstrated that the compressor is junk what with a sloppy piston, uneven pumping, etc. so you might as well just get the reman and continue, shame you had to pull the 466 apart, though.
I will second what vogt said- no one remans these themselves, they just slap another one one and down the road they go, I would think $5-600 should get you a new reman compressor, and I would just go ahead and do that before/ while you're doing the engine, I wouldn't bother starting it with the old compressor and doing the whole leak down/ build up time thing. You may not be seeing any oil in the tanks, if the air dryer is catching it all, but I would think you would have a little coming out of the water trap on the bottom of the dryer. Glad you hear you've figured something out.
Consulted all the locals that told me to take the engine out and tear it down, and a couple told me even though it doesn't help me, it was a nice learning experience for them, none would have bet a dime on it being the compressor and were glad I kept them informed on what I found, won't help me any but might help someone later on down the road to learn from my expense and ordeal. Crazy thing is, in about ten minutes and no money out of pocket, I could have pulled the compressor off the engine and left it hang and ran the truck to see if it was the culprit had anyone given me even a hint it could be the compressor causing the issues. Reman compressor exchange is about 700 bucks, not sure I'm even going to mess with the spare one I have on hand, its laid around over ten years and have no history on that one either. I know its an expensive and time consuming way to go about it, but we are going to get new rod and main bearings, new rings, new rear main seal and wear sleeve, same for the front, new clutch, new receiver dryer and oh yea, remanufactured compressor and all new gaskets and seals in the engine, and we now know a history on the engine and its condition as of today. I'm not expecting the shop will find anything wrong with the sleeves or head either but I think we now have the cause. Just talked to my pump guy and he's going to bench test it, along with the injectors and pin time the pump, but I'm not expecting he'll find anything else.
Maybe it's just me but if that compressor was off the truck and the base was off it I would go one step more and remove the head and then remove the rod caps and pop the pistons out just for kicks to see what things looked like. Might take all of 1/2 hour including sticking it back together to send in for the core credit. I would just have to see exactly what it looked like inside, heck if I was down the street from you I come over and do it tonight no charge!
Yea, I've been thinking about it last night, but all I'm expecting to find is a worn out set of rings from what I saw with the compressed air and the oil on the bottom of the pistons, not yet sure why it did it in such a short time while driving, that is still a question I've been wondering. I'm going to ask more questions before next week, I'm also wanting to pull the piston's out of the compressor and remove some rings and fit them into the bore's just to satisfy my curiosity as to how much gap there is in the ends of the rings, maybe a waste of time, but I am curious anyhow. I'm not expecting to see scored sleeves, what else is there to look for??
Good morning Randy. Just to add another idea. I know back in the day, IH tractors had a problem similar to this. Where is your crankcase breather? In the block? Or valve cover? IH came out with some sort of service bulletin adressing oil consumption. I dont remember the specifics. But a call to a old IH dealer may help. I think the problem was with the breather in the block. Couldnt get oil to separate out. Then changed to valve cover breather system. Good luck.
2nd that Maybe a clod of ice plugged the end or grease/goo. Always cut the tube at a angle. Wont bridge over as easily.
The breather is in the valve cover on this 466, there is a screen over the opening to the pipe to keep oil in the valve cover and engine, the opening in the pipe is towards the top of the cover and the pipe itself is up against the top of the valve cover.