Jim I am going to try what you said and swap injectors this weekend. I understand if the noise follows it then it is the injector. If the noise doesn't move could it still be the injector pump timing causing the nailing? Or do I then check if its caused by play in the big end bearing?
Engine Knock M4500DT
- Thread starter Fishfarmer
- Start date
If the knock doesn't follow an injector, I would do a compression test. A leaking injector can cause a burn through of a piston crown, or you might have a burned valve that's making that cylinder a dead one.
Put tractor together after all the tests run it doing “Brush Hogging”, what we call “Slashing” in Oz. Knock is still present especially idling, can’t hear it under load.
Injectors popped okay and sprayed well, One a little bit uneven. IP seems to spurt evenly. Oil lamp flickering on and off at idle after it got to hot running temp. Manual says this is okay, idle 7.11 psi and running 42.7-64 psi and allowable limit 35psi. I put an oil pressure gauge on it and when cold runs at 60-64psi, then as it gets hot drops to 50, then 40, then down to 20psi when fully hot. It idles at 10psi. if I hit the revs full for a couple of seconds it goes to 30 and for a short burst hits 40 psi. Manual says at rated speed. All I can see the speed is in a different section as “Maximum bare speed” 2800rpm.
There are no silver flecks in the oil. It doesn’t burn oil, hit high revs under load or no load there is a puff of grey, or sometimes black and grey. I did a piston push down test and there was zero movement. JohnDB suggested that he thinks there would only be movement when the lower piston rod bearing was really bad. Spun bearing with a lot of clearance. I tend to agree with him, therefore it’s a poor test for a very worn but not quite (yet) ruined bearing. Please correct me if I am wrong but the point I am making is I still think the knock is from the bad piston that has the lower compression and not an injector(see my other posts). For the oil pressure to go so low when hot would indicate to me that oil is losing pressure past the bearings and causing rod knock on the bad one.
Injectors popped okay and sprayed well, One a little bit uneven. IP seems to spurt evenly. Oil lamp flickering on and off at idle after it got to hot running temp. Manual says this is okay, idle 7.11 psi and running 42.7-64 psi and allowable limit 35psi. I put an oil pressure gauge on it and when cold runs at 60-64psi, then as it gets hot drops to 50, then 40, then down to 20psi when fully hot. It idles at 10psi. if I hit the revs full for a couple of seconds it goes to 30 and for a short burst hits 40 psi. Manual says at rated speed. All I can see the speed is in a different section as “Maximum bare speed” 2800rpm.
There are no silver flecks in the oil. It doesn’t burn oil, hit high revs under load or no load there is a puff of grey, or sometimes black and grey. I did a piston push down test and there was zero movement. JohnDB suggested that he thinks there would only be movement when the lower piston rod bearing was really bad. Spun bearing with a lot of clearance. I tend to agree with him, therefore it’s a poor test for a very worn but not quite (yet) ruined bearing. Please correct me if I am wrong but the point I am making is I still think the knock is from the bad piston that has the lower compression and not an injector(see my other posts). For the oil pressure to go so low when hot would indicate to me that oil is losing pressure past the bearings and causing rod knock on the bad one.
If the “knock” occurs only after initial start-up…and stops after increasing RPM…it’s likely OIL PRESSURE problem or indication (or lack thereof). CHECK OIL PRESSURE.
My error of grammar. The lack of oil pressure is not causing the rod knock, the worn bearing is causing the knock and the low oil pressure is the sign of that's what the problem is. ( thinner oil getting past the side of the bearings instead of being forced through the oil passages in the journal. Geohorn the knock is there on startup when i have 60psi oil pressure ( not just initial startup) It goes away or at least I cant hear it under load or revs, yet when I decelerate you can hear it most as it slows to idle, more so after its hot slowing to idle. I am not an experienced mechanic but people have said rod knock is heard more when the load is off the problem piston and the knocking is more pronounced because it is free floating and slapping the journal at TDC. When the pressure is on from combustion it is hard against the journal and harder to hear, although still probably there. At least that's the explanation I have always been given.
The oil pressure, is what it is. The pump must be working fine to push out 60psi when its cold and it should push out 40psi when its hot. I wouldn't think it is oil pump related for it to suddenly perform so poorly at a higher operating temperature, rather it would seem to me to be worn bearing related. So to check the oil pressure you suggest, I can only see by stripping it down could rectify this. Is this what you mean? I am using 14w 40 oil but I read that a heavier grade oil (20W-50 or 50W) can help raise oil pressure and maintain the protective oil film between the bearings and their journals ? Thanks for your input.
If you confirm you have 40 psi of oil pressure or greater… then the knock I was thinking-of…(valvetrain related) will not be the problem.
The viscosity of the oil you choose to use is not the problem and changing oil viscosity or brand is not going to solve it either.
It’s difficult to diagnose serious/deep engine problems over the internet...so it’s time for you to have an experienced diesel mechanic/technician look at it, IMO. The problem will not go away on its’ own and continuing operations will only add to the possibility of serious damage.
The viscosity of the oil you choose to use is not the problem and changing oil viscosity or brand is not going to solve it either.
It’s difficult to diagnose serious/deep engine problems over the internet...so it’s time for you to have an experienced diesel mechanic/technician look at it, IMO. The problem will not go away on its’ own and continuing operations will only add to the possibility of serious damage.
You might want to get an oil sample analyzed. If you have a bearing going south it will surely show up in the oil analysis. All the guessing and theorizing what it might be won't get you to an answer. Take some action. Analyze the oil or pull the pan and check the journals.
kubotafreak
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If there is no discernable metal in the oil, then it is more than likely the lower end is fine. The knocking could be piston slap (hard to physically test due to the need to rock the top and bottom side of piston crown). Wrist pin loose, or other piston deformity. The posted oil pressures seem on the loose side though. The 20 at rated speed is way too low (35lbs min). Did you crack injectors loose one at a time to locate the cylinder causing the noise? I think I would pull the timing cover and inspect the pump. Also check the orings/plugs behind the timing cover. What was the compression?
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I have M4500DT i acquired it for about 8K with Loader and Tiller , it was starting with starting smoke and a good amount of blowby i was told it would need piston6 rings , so i went ahead and did oil changes , filters and anything it required (Still to do GP and INjectors) but after i put in 15W40 it doesnt want to start it smokes a lot and then cranks a rolls over but doesnt want to start , the battery loses juice after some time , could it be that 15W40 is too thick for it to start ? Any inputs from your side is appreciated.
North Idaho Wolfman
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The older Block heater in it doesn't work so i am going to swap that block heater and will try again today
and will update how it goes , after which i will try an oil change.