Oil pressure adjusting spring for 720D

chas036

Member
I was out bush hogging today with my 720D, and after a hour or so, the oil pressure went from H to M, to finally hold at the L or a little above at high rpm. At idle it would hover below the L.

I already changed the oil to 15-40 rotella and it has a new JD calibrated gauge. My next thing I would like to change is the oil pressure adjusting spring since I have been told that over time they get weak.

Does anyone know where I can get an oil pressure adjustment spring or equivalent substitute that will fit a 720 or 730? JD does not stock the part anymore, and my searches can not locate anything that references that part for a 720 o 730.
 
"I have been told that over time they get weak" (the oil pressure regulating spring)

While NOT impossible, chances are (about a million to one) your low pressure when warm isn't caused by a "weak" spring.

(But we all dream of easy/cheap fixes, I guess, so myths like this persist!)
 
The very first thing I would do is temporarily install a test gauge of known accuracy. Just because the gauge is "calibrated" doesn't mean that it is. I will no longer install a new oil pressure gauge without first testing the gauge. Many new gauges are not in register with what the original pressure was intended, and if your gauge came from mother deere, it is probably wrong. The only place I know of to get the right gauge, properly calibrated is Jerry Trcka (evergreen restoration) BTW, it's highly unlikely the spring is bad for the oil pressure relief. I have a 70 diesel that developed the same problem you're having. Please be in contact if you need more info.
 
Dumb question, but the oil level is okay right? I had a 630 do a similar thing, the right side main bearing seals went bad and the engine pumped oil into the transmission. Luckily I caught it in time.
 

Oil pressure control valve only limits the max pressure . It does not maintain a minimum pressure .
If all else fails try straight weight 50.
 
One time I had one do that and found out diesel fuel was getting into the crankcase.

I also have a 720D that was completely rebuilt. Crank reground, all new bearings to clearance specs. I also installed all new springs in the oiling system since I was there and back then they were cheap. Well after all that I still have oil pressure drop when hot. ( don't really know what it did before ? ) I ended up installing an aftermarket gauge that goes higher so on start up it doesn't ruin it because I bumped the oil pressure up to hold stead at hot idle IIRC 15 psi. Only thing I can figure is the oil pump housing must be worn out ? Too big of job to go back in and worry about it and too long ago to remember what it measured or if I measured it ? I can't image I didn't measure it ? as I think the service manual has specs. on them ?
I have had others that I would imagine the engine was worn out not do that ? so who knows.
 
I agree, pressure relief would apply when cold, if pressure dropping when warm it is not relief issue, is clearance issue
 

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