Yet another Gravely L Oil Pressure Problem

[gmulhollan]

I have a Gravely LI, serial number A-12456 (1945?). This tractor and Gravely in general are new to me. I have read through the old threads and the service manuals on this beast, but need some more detailed advice. When received, it would start right up (still does), but the oil pressure gauge read on the low side and as the motor warmed up, its reading and the oil stream under the fill cap would diminish. I have changed out the filter (spin-on type, with gauge on the output of the filter; this is as I received it). I took off the gauge and tested its response with my air compressor. The 'red' block tops off at 15-20 PSIG (poor resolution on my compressor's gauge) and 60 or so is just past 12-noon. So I know the gauge is working. New filter, 30 weight oil and no reading, but tilting just like in the manual and bang! high pressure in the gauge. :thumbdown:But...the oil pressure still decreases as the motor warms up. To my uneducated mind, this implies the oil gears are worn and as they warm up the gap between them becomes too big to pump the oil. Does this sound correct or are there other (cheaper, easier to get to) items that I should attend to first?

 

[FlaDon]

I have a Gravely LI, serial number A-12456 (1945?). This tractor and Gravely in general are new to me. I have read through the old threads and the service manuals on this beast, but need some more detailed advice. When received, it would start right up (still does), but the oil pressure gauge read on the low side and as the motor warmed up, its reading and the oil stream under the fill cap would diminish. I have changed out the filter (spin-on type, with gauge on the output of the filter; this is as I received it). I took off the gauge and tested its response with my air compressor. The 'red' block tops off at 15-20 PSIG (poor resolution on my compressor's gauge) and 60 or so is just past 12-noon. So I know the gauge is working. New filter, 30 weight oil and no reading, but tilting just like in the manual and bang! high pressure in the gauge. :thumbdown:But...the oil pressure still decreases as the motor warms up. To my uneducated mind, this implies the oil gears are worn and as they warm up the gap between them becomes too big to pump the oil. Does this sound correct or are there other (cheaper, easier to get to) items that I should attend to first?

The A in the Serial Number indicates a 1957 model. In 1957 the pump would have been the low volume version. Cold oil could reach 30+ pounds in those. Cold oil in a high volume pump can result in 45-50 PSI at WOT when cold. All of them drop back when warm. 10 to 15 PSI drop is common on them. Check and make sure the relief valve is set at 15 PSI and you should be good to go.

 

[schmism]

this implies the oil gears are worn and as they warm up the gap between them becomes too big to pump the oil. Does this sound correct or are there other (cheaper, easier to get to) items that I should attend to first?

metal expands as it warms up, not shrinks.

likely the oil thins out as it warms up and as it thins out it just blows past the worn bearings in the bottom end.

youll find worn out bearins before you find worn out oil pump gears

 

[al b]

Would it help to use some 40 weight or 50 weight?

 

[jdboy4410]

i would hook up a good mechanical test guage to it to get an accurate reading and then compare specs.cold engine is going to run higher oil pressure,as the engine warms up,definitely could see a drop of 10-15 psi.the engine only needs 5 psi at an idle to maintain lubrication,at WOT,you should see 25-30 psi.if your not seeing those pressures,i would be checking bearing clearances.too much clearance bleeds off the pressure fast and won't let it maintain good consistant pressure.if the rod bearing is within spec,put a new oil pump on it.

 

[mark4472]

I have 2 gravely's and had the same problem on one. I took the relief valve out and stretched the spring. It made the oil pressure increase alot.

 

[FlaDon]

Would it help to use some 40 weight or 50 weight?

40 wt was the recommended oil in the days when it was built. That will raise pressure both hot and cold.