The oil pressure in my 0-300A is running at 55 psi in cruise. I'm a little confused because in the overhaul manual specifications it calls for 30-45 psi in the 0-300A, B & C - and 30-60 psi in the 0-300D & E. Then in the description of the oil system it says that the oil pressure relief valve is set to 30 - 60 psi. All of the parts for the pressure relief system are the same for all models, so I don't understand how the different models can have different oil pressure specifications. The oil pressure gauge in the aircraft is marked green from 30 - 45 psi and redlined at 50 psi and has been checked for accuracy. What am I missing here?
jc
High oil pressure
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
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GAHorn
- Posts: 21295
- Joined: Fri Apr 12, 2002 8:45 pm
My O300 does the same, indicates 55. My gauge is also correct.
I talked to TCM field rep about this several years ago. ( I was concerned about a TCM Ovhl Manual warning about valve lifters with excessive oil pressure.)
TCM field rep said not to worry. Oil pressure up to 60 is now considered acceptable by TCM. Earlier engines went through several modifications with regard to lifter bodies that provoked differenct comments regarding oil pressure, but since lifter design was finalized TCM has found no problems with oil pressures up to 60.
The only adjustment is the relief spring. If your relief spring is blue in color, then it should be the current standard, which specifies 6.06 lbs to 6.31 lbs pressure when compressed to 1.56" length. (The minimum spring pressure for used springs is 5.75 lbs at that length.) Sometimes a low pressure can be caused by an eroded relief valve seat, but with 55 psi, that is clearly not happening in your case.
Enjoy the pressure.
I talked to TCM field rep about this several years ago. ( I was concerned about a TCM Ovhl Manual warning about valve lifters with excessive oil pressure.)
TCM field rep said not to worry. Oil pressure up to 60 is now considered acceptable by TCM. Earlier engines went through several modifications with regard to lifter bodies that provoked differenct comments regarding oil pressure, but since lifter design was finalized TCM has found no problems with oil pressures up to 60.
The only adjustment is the relief spring. If your relief spring is blue in color, then it should be the current standard, which specifies 6.06 lbs to 6.31 lbs pressure when compressed to 1.56" length. (The minimum spring pressure for used springs is 5.75 lbs at that length.) Sometimes a low pressure can be caused by an eroded relief valve seat, but with 55 psi, that is clearly not happening in your case.
Enjoy the pressure.
Last edited by GAHorn on Thu Oct 30, 2003 3:04 am, edited 1 time in total.
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1SeventyZ
- Posts: 253
- Joined: Mon Aug 11, 2003 2:08 am
I love this site. I was kinda worried about running 55 psi in cruise until I saw this thread. Couple questions for a n00b:
1. Where is the pressure relief spring located on the engine? Is this something that may/may not be replaced during overhaul and therefore "updating" the standard cruise rpm oil pressure for "modern" TCM design considerations? I have a C-145-2.
2. What are the ramifications of high oil pressure? Where are the weak components that could be damaged?
1. Where is the pressure relief spring located on the engine? Is this something that may/may not be replaced during overhaul and therefore "updating" the standard cruise rpm oil pressure for "modern" TCM design considerations? I have a C-145-2.
2. What are the ramifications of high oil pressure? Where are the weak components that could be damaged?
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GAHorn
- Posts: 21295
- Joined: Fri Apr 12, 2002 8:45 pm
The relief spring/plunger is beneath the brass capnut adjacent to the oil pressure line on the right side of the engine.
If your oil pressure is within specs, there is no need to change it out. It should be cleaned, inspected and re-installed/replaced at overhaul.
Excessively high oil pressure is likely to cause propshaft (crankshaft) front seal leaks and failed hydraulic valve lifter/units.
If your oil pressure is within specs, there is no need to change it out. It should be cleaned, inspected and re-installed/replaced at overhaul.
Excessively high oil pressure is likely to cause propshaft (crankshaft) front seal leaks and failed hydraulic valve lifter/units.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
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