rv969wf
Well Known Member
Alan Judy's Van's RV-6 with a Lycoming IO-360A1B6 fuel injected engine, CS Hartzell Prob. Approximately 750SMOH. Almost everything inside this engine was NEW except the case and cylinders, cylinders were taken .010" over with New pistons etc. All machine work was done correctly and Yellow tagged, engine was blueprinted very precisely. All clearances within factory specs at overhaul and I did the assembly so I know this engine inside and out. SMOH this engine has always had around 45psi oil pressure +- 2-3 lbs at 190F degree oil temperature at idle 750rpm. In cruise it has always had around 75 lbs +- a 2-3 lbs at 2,450 RPM with oil at 190F degree. I have always been able to maintain my oil temperature plus or minus 5-8F degrees between winter and summer via a controllable oil door, the NEW Vernatherm at overhaul has never caused a problem. Engine has had Exxon Mobil Elite 20w-50 it's entire life after rings were seated. Oil and filter has always been changed around 25-30 hours. Oil samples have always been good and oil filter has always been very clean when cut apart and inspected. Engine is preheated in cooler months so I haven't had any cold starts, I live in the Oklahoma area in the USA. I average 90-120 hours per year and fly mostly cross country with a few short trip, at times I'll close the oil air inlet to the oil cooler get the oil up too 200-210F to boil off any moisture in the crankcase for a few minutes then lower to 190F range. Compression always around 76-79 over 80 at annual.
This is what happened on my last flight, on run up, my oil pressure was normal at the time. I took a 45 minute flight and shortly into the flight I noticed my oil pressure was only 52 lbs at 2,450 RPM, 190F oil, it has always been around 75 lbs +- a couple lbs SMOH at 190F oil temp. After landing my low oil pressure light came on, my low oil pressure sending unit is a separate unit than my oil pressure sending unit and it is set at 25lbs for the light to come on, I then looked at my oil pressure gauge and it was only showing 23 lbs at idle 750RPM, 190F oil. The first thing I did the next day was take the oil filter off and cut it apart to inspect, Tempest #AA48108-2, the filter media was VERY clean with no debris. I build automobile racing engines for a living and few airplane engines so I know what to look for. Oil level in the crankcase was showing 6 1/2 quarts at this time. I have always flown after an oil change with 7 qts total and when it gets down to 6 qts I add one quart, oil burn has always been about 1 qt in 9-12 hours with my steel Lycoming cylinders SMOH. My next step, I installed a New oil filter, 1 more qt of oil added to bring the oil level close to 7 quarts total and I installed a Perma Cal Calibration test gauge directly to the right front oil gallery that is the same oil galley that feeds the main bearings that is at the right front towards the prop to compare oil pressure to the MicroVision VM-1000 cockpit oil pressure. I test ran the engine and documented the start up with oil at 48f degree cold and warming the oil up to 100F. The Perma Cal test guage read 2 -3 lbs higher than the VM-1000 cockpit gauge throughout the test from idle to 2000RPM at various oil temps, test gauge and panel oil pressure corresponded in equal amounts, slight variation but all good. Being this I eliminated the oil sending unit being a problem or possibly the oil fitting at the crankcase for the sending unit that has the .040" restricted hole from being plugged up. For those that don't know, the .040" oil restrictor is there in case the oil line breaks to slow down the loss of oil. While warming up the engine and oil, I had the same oil pressures within 2-3 lbs variation, so the oil filter was not the problem or the oil sending units. My next step was to remove the oil pressure relief, spring, ball and washers. I inspected the seat that the ball seats against in the crankcase oil galley at the #3 cylinder crankcase location, it looked good but I took the time to apply some dye, lapping compound with an old pressure relief ball and lapped the seat, it had a perfect contact pattern and was seating nicely, no issues there. The pressure relief ball had no nicks or signs of wear, I measured it with a micrometer and it was perfect. I checked the bypass spring with a NEW spring, free length was good and it had the same pressure as a new one, I went ahead and installed the new spring and noted how many shims were behind the spring and put the same ones back in. Did another ground test run, started the engine up and there were NO changes of oil pressure at different oil temps or RPMs. I'm not sure what is happening to cause the sudden loss of around 20-25 lbs oil pressure when its cold or at operating temp throughout idle to cruise RPM 2,450. If I had metal in the oil filter I'd be tearing the engine down but I don't see anything in the filter. My next step is to run the engine, warm the engine oil up, drain and take an oil sample and send in for a report. I suspected my fuel pump diaphragm might be going bad and allowing fuel into the crankcase and deluting the oil, but the vent line from the fuel pump has showed no signs of dripping or leaking, maybe the oil sample will help with this. CHT's have always been in the 300-360f range depending on outside temps. Oil temps have always been normal, no changes in fuel pressure, EGTs all good and peak the same. Timing has always been set at 20 degrees because I'm runging 10:5.1 pistons, bore scope of cylinders show no issues, no detonation issues on piston tops or ring lands. 100LL Avgas all the time, 150F -200F rich of peak in climb, cruise 75-100F rich of peak at 65-70% power. Sometimes lean of peak at low power settings. This engine has always been strong and has never had any issues and it makes a lot power. Its still strong, makes no abnormal noises and runs like nothing is wrong other than the 20-23 lbs of oil pressure that I lost across the board. Possible bearing problem? but no metal in the oil filter, possibly oil pump issues but why such a sudden loss of pressure, possibly a crack in oil gallery which if there was, oil pressure should be good cold but much worse when hot as the aluminum expands and should open up a crack in the oil gallery and making it worse at higher oil temps, but I don't think that is the case, the Woodward prop governor works fine, prop cycles normal, oil galley plug missing?, if one was missing it should have zero oil pressure. I don't see any issues with the Vernatherm as my oil heats up quickly as normal and at cruise my oil temps are normal. I have even used a thermal imaging camera to detect how the fluid/heat is flowing through the oil lines, filter and oil cooler and find no issues. Something that I have not done yet is too shim the oil pressure relief with 5 washer/ shims which should raise the oil pressure 25 lbs across the board from cold oil to hot oil for GROUND RUN TESTING ONLY to see if the oil pump will maintain as a test only. If the added shims don't show any signs of raising the oil pressure, possibly oil pump issues or something else has gone wrong inside the engine that is causing the leak of internal oil pressure. I questioned the piston oiler nozzles but they open at around 40 lbs and should not cause low oil pressure at cruise RPM. It's not a heat related issue of any sorts as I don't have any. I'm at a loss and need some professional advise before I do a teardown at 750SMOH. FYI, I used to be on this VAF forum daily on a regular basis MANY years ago and payed my dues during that time but do to life changing things I have not been on here and after posting this I need to send Doug some $$$$. Any GOOD Technical Advice would help. Thanks, Alan
This is what happened on my last flight, on run up, my oil pressure was normal at the time. I took a 45 minute flight and shortly into the flight I noticed my oil pressure was only 52 lbs at 2,450 RPM, 190F oil, it has always been around 75 lbs +- a couple lbs SMOH at 190F oil temp. After landing my low oil pressure light came on, my low oil pressure sending unit is a separate unit than my oil pressure sending unit and it is set at 25lbs for the light to come on, I then looked at my oil pressure gauge and it was only showing 23 lbs at idle 750RPM, 190F oil. The first thing I did the next day was take the oil filter off and cut it apart to inspect, Tempest #AA48108-2, the filter media was VERY clean with no debris. I build automobile racing engines for a living and few airplane engines so I know what to look for. Oil level in the crankcase was showing 6 1/2 quarts at this time. I have always flown after an oil change with 7 qts total and when it gets down to 6 qts I add one quart, oil burn has always been about 1 qt in 9-12 hours with my steel Lycoming cylinders SMOH. My next step, I installed a New oil filter, 1 more qt of oil added to bring the oil level close to 7 quarts total and I installed a Perma Cal Calibration test gauge directly to the right front oil gallery that is the same oil galley that feeds the main bearings that is at the right front towards the prop to compare oil pressure to the MicroVision VM-1000 cockpit oil pressure. I test ran the engine and documented the start up with oil at 48f degree cold and warming the oil up to 100F. The Perma Cal test guage read 2 -3 lbs higher than the VM-1000 cockpit gauge throughout the test from idle to 2000RPM at various oil temps, test gauge and panel oil pressure corresponded in equal amounts, slight variation but all good. Being this I eliminated the oil sending unit being a problem or possibly the oil fitting at the crankcase for the sending unit that has the .040" restricted hole from being plugged up. For those that don't know, the .040" oil restrictor is there in case the oil line breaks to slow down the loss of oil. While warming up the engine and oil, I had the same oil pressures within 2-3 lbs variation, so the oil filter was not the problem or the oil sending units. My next step was to remove the oil pressure relief, spring, ball and washers. I inspected the seat that the ball seats against in the crankcase oil galley at the #3 cylinder crankcase location, it looked good but I took the time to apply some dye, lapping compound with an old pressure relief ball and lapped the seat, it had a perfect contact pattern and was seating nicely, no issues there. The pressure relief ball had no nicks or signs of wear, I measured it with a micrometer and it was perfect. I checked the bypass spring with a NEW spring, free length was good and it had the same pressure as a new one, I went ahead and installed the new spring and noted how many shims were behind the spring and put the same ones back in. Did another ground test run, started the engine up and there were NO changes of oil pressure at different oil temps or RPMs. I'm not sure what is happening to cause the sudden loss of around 20-25 lbs oil pressure when its cold or at operating temp throughout idle to cruise RPM 2,450. If I had metal in the oil filter I'd be tearing the engine down but I don't see anything in the filter. My next step is to run the engine, warm the engine oil up, drain and take an oil sample and send in for a report. I suspected my fuel pump diaphragm might be going bad and allowing fuel into the crankcase and deluting the oil, but the vent line from the fuel pump has showed no signs of dripping or leaking, maybe the oil sample will help with this. CHT's have always been in the 300-360f range depending on outside temps. Oil temps have always been normal, no changes in fuel pressure, EGTs all good and peak the same. Timing has always been set at 20 degrees because I'm runging 10:5.1 pistons, bore scope of cylinders show no issues, no detonation issues on piston tops or ring lands. 100LL Avgas all the time, 150F -200F rich of peak in climb, cruise 75-100F rich of peak at 65-70% power. Sometimes lean of peak at low power settings. This engine has always been strong and has never had any issues and it makes a lot power. Its still strong, makes no abnormal noises and runs like nothing is wrong other than the 20-23 lbs of oil pressure that I lost across the board. Possible bearing problem? but no metal in the oil filter, possibly oil pump issues but why such a sudden loss of pressure, possibly a crack in oil gallery which if there was, oil pressure should be good cold but much worse when hot as the aluminum expands and should open up a crack in the oil gallery and making it worse at higher oil temps, but I don't think that is the case, the Woodward prop governor works fine, prop cycles normal, oil galley plug missing?, if one was missing it should have zero oil pressure. I don't see any issues with the Vernatherm as my oil heats up quickly as normal and at cruise my oil temps are normal. I have even used a thermal imaging camera to detect how the fluid/heat is flowing through the oil lines, filter and oil cooler and find no issues. Something that I have not done yet is too shim the oil pressure relief with 5 washer/ shims which should raise the oil pressure 25 lbs across the board from cold oil to hot oil for GROUND RUN TESTING ONLY to see if the oil pump will maintain as a test only. If the added shims don't show any signs of raising the oil pressure, possibly oil pump issues or something else has gone wrong inside the engine that is causing the leak of internal oil pressure. I questioned the piston oiler nozzles but they open at around 40 lbs and should not cause low oil pressure at cruise RPM. It's not a heat related issue of any sorts as I don't have any. I'm at a loss and need some professional advise before I do a teardown at 750SMOH. FYI, I used to be on this VAF forum daily on a regular basis MANY years ago and payed my dues during that time but do to life changing things I have not been on here and after posting this I need to send Doug some $$$$. Any GOOD Technical Advice would help. Thanks, Alan