Okay guys, Sorry for the long thread but I am trying to be thorough.
Here are my engine (S2600-A) tests done. Re: previous thread, post injector ignition knock on M4500DT. Engine starts easy doesn’t run rough, has blow-by, if I remove dipstick some bubbling of oil. Only blows a bit of smoke with high revs.
Cracked each injector: engine falters, would indicate injectors not blocked but maybe still post ignition. Removed injectors tested them and each spray fairly well and pop at 1900-2100 psi.
I compression tested a number of times with excellent battery.
Cylinders 1,2, 3 and 5, 380-400psi. Cylinders 4 and 6 at 350psi and 300psi respectively. Oil squirt in #4 pressure goes to 400psi and 6 goes to 350psi. I would think, going by opinions and the manual for over 10% difference in the cylinders, that one or both of these have either very worn or cracked rings. I can’t find what positive test I can do for cracked ring vs worn rings?
I decided to compare oil squirt in good cylinder, goes from 400 to 450psi. This is higher than what a new engine states in the manual, this engine is so old it’s impossible to be so high. I think my compression tester must be reading higher than it should which shouldn’t matter, consistency between cylinders I am told is the key. It obviously doesn’t say to do oil squirt in a good cylinder in the manual. I can see oil test compression wouldn’t increase on a leaking valve because there would be no increase in pressure when the oil is added, however if assuming my 400psi cylinder and piston is pretty good and it raises another 50psi with addition of oil squirt, doesn’t that give out a false positive for the worn/broken compression ring test? To rephrase would a broken ring give out a very low compression reading on one cylinder, more than the difference I see in #4 and 6? My compression tester is reasonable (not a cheapo and does have Schrader valve). The manual says to crank for 5-10 seconds, but the gauge is only getting to 200psi after this time then starts climbing to 400psi after 20 seconds (the maximum pressure reached). I figure that the small 5mm x 10mm port from cylinder in to the firing chamber is not letting enough volume through to reach maximum pressure in this 5-10 second time? Maybe a new engine produces more volume and pressure than a tired one. With some experience testing cars which have an open head directly in to the cylinder, I have found the needle jumps quickly and only needs a few cranks to reach pressure. Not so I have found with the tractor, but I am no mechanic. Further the cylinders 1,2,3 have a clean look with light carbon deposit, but 4,5 have a bit more carbon and 6 has a heavier build up. #6 renowned for being the problem on straight 6 engines (at least with cars it is).
Leak down test using compressor on TDC I can hear air passing in to the sump very slowly on most cylinders. It sounds like a touch more air on #4, and # 6 is noticeably more than the others. Other cylinders seem to release the pressure more slowly, this test done without tappet cover on.
I made a home-made leak down tester, my air compressor goes to about 80-90 psi and most cylinders only drop to 70psi so have 15-20% leak age but to my horror #6 is dropping from 80-90psi down to around 20 psi. 75% leakage which is a huge amount of leakage and no doubt causing what blow-by I have.
I could use a decarbonizing product but if it is broken rings it won’t do any good. I have also read heavy detergents can damage crankshaft bearings as the gunk is pumped through after the detergent does its job, but if this cylinder is leaking down by this amount would it make any difference anyway. My question is can just worn/carbonised rings and bore glazing cause this much leakage? Is there still some life left in the engine or is it ready to go?
I looked at each cylinder with a borescope, there does appear to be light scouring in some cylinders
which I think is from piston skirt scuffing. The borescope only focuses to a minimum of 2 inches so it is hard to see if scuffing/scouring is deep. #6 doesn’t have a hole in the piston or damaged edge on the crown but a bit more scuffing or scouring on cylinder wall than the other cylinders.
I could take the head off and look which would only cost $200 but its unlikely to tell me more, a complete strip down is costly and I don’t think the tractor is worth it. I only do slashing for a half day 3 times a year so I was going to keep it running, listen for any changes and do a compression test and check if the bad cylinder gets any worse over time. With the info given is that ill-advised? If I continue to use it will I blow the piston or would I notice it get worse before that happens?
Here are my engine (S2600-A) tests done. Re: previous thread, post injector ignition knock on M4500DT. Engine starts easy doesn’t run rough, has blow-by, if I remove dipstick some bubbling of oil. Only blows a bit of smoke with high revs.
Cracked each injector: engine falters, would indicate injectors not blocked but maybe still post ignition. Removed injectors tested them and each spray fairly well and pop at 1900-2100 psi.
I compression tested a number of times with excellent battery.
Cylinders 1,2, 3 and 5, 380-400psi. Cylinders 4 and 6 at 350psi and 300psi respectively. Oil squirt in #4 pressure goes to 400psi and 6 goes to 350psi. I would think, going by opinions and the manual for over 10% difference in the cylinders, that one or both of these have either very worn or cracked rings. I can’t find what positive test I can do for cracked ring vs worn rings?
I decided to compare oil squirt in good cylinder, goes from 400 to 450psi. This is higher than what a new engine states in the manual, this engine is so old it’s impossible to be so high. I think my compression tester must be reading higher than it should which shouldn’t matter, consistency between cylinders I am told is the key. It obviously doesn’t say to do oil squirt in a good cylinder in the manual. I can see oil test compression wouldn’t increase on a leaking valve because there would be no increase in pressure when the oil is added, however if assuming my 400psi cylinder and piston is pretty good and it raises another 50psi with addition of oil squirt, doesn’t that give out a false positive for the worn/broken compression ring test? To rephrase would a broken ring give out a very low compression reading on one cylinder, more than the difference I see in #4 and 6? My compression tester is reasonable (not a cheapo and does have Schrader valve). The manual says to crank for 5-10 seconds, but the gauge is only getting to 200psi after this time then starts climbing to 400psi after 20 seconds (the maximum pressure reached). I figure that the small 5mm x 10mm port from cylinder in to the firing chamber is not letting enough volume through to reach maximum pressure in this 5-10 second time? Maybe a new engine produces more volume and pressure than a tired one. With some experience testing cars which have an open head directly in to the cylinder, I have found the needle jumps quickly and only needs a few cranks to reach pressure. Not so I have found with the tractor, but I am no mechanic. Further the cylinders 1,2,3 have a clean look with light carbon deposit, but 4,5 have a bit more carbon and 6 has a heavier build up. #6 renowned for being the problem on straight 6 engines (at least with cars it is).
Leak down test using compressor on TDC I can hear air passing in to the sump very slowly on most cylinders. It sounds like a touch more air on #4, and # 6 is noticeably more than the others. Other cylinders seem to release the pressure more slowly, this test done without tappet cover on.
I made a home-made leak down tester, my air compressor goes to about 80-90 psi and most cylinders only drop to 70psi so have 15-20% leak age but to my horror #6 is dropping from 80-90psi down to around 20 psi. 75% leakage which is a huge amount of leakage and no doubt causing what blow-by I have.
I could use a decarbonizing product but if it is broken rings it won’t do any good. I have also read heavy detergents can damage crankshaft bearings as the gunk is pumped through after the detergent does its job, but if this cylinder is leaking down by this amount would it make any difference anyway. My question is can just worn/carbonised rings and bore glazing cause this much leakage? Is there still some life left in the engine or is it ready to go?
I looked at each cylinder with a borescope, there does appear to be light scouring in some cylinders
which I think is from piston skirt scuffing. The borescope only focuses to a minimum of 2 inches so it is hard to see if scuffing/scouring is deep. #6 doesn’t have a hole in the piston or damaged edge on the crown but a bit more scuffing or scouring on cylinder wall than the other cylinders.
I could take the head off and look which would only cost $200 but its unlikely to tell me more, a complete strip down is costly and I don’t think the tractor is worth it. I only do slashing for a half day 3 times a year so I was going to keep it running, listen for any changes and do a compression test and check if the bad cylinder gets any worse over time. With the info given is that ill-advised? If I continue to use it will I blow the piston or would I notice it get worse before that happens?
