CASE 310G CRAWLER HYDRAULIC HEAT

I just purchased a case 310G serial puts it at a 68 with the 188 diesel. I have gone from bow to stern replacing worn parts and making adjustments to make it like new for season. It seems to me that the hydraulic system heats up rather rapidly <20 minutes run time to about 140 deg F with minimal to no system operation. It has a D41390 pump from what I can tell, and a VDP 22 control valve for the 6 way with a wet line installed for a removable backhoe that the owner before the owner installed. I was told that he had to have the pump rebuilt because he toasted it and he was told he didnt loop the wet line when not using the backhoe and thats what did it. He has a little 1/2 hose loop that is installed via quick connect to the right of the control valve looping pressure and return to what would go to the backhoe when attached to the tractor. Does anyone have any suggestions, specifications for operating or relief pressures, acceptable pressures and specific locations, etc. It has a pressure gauge installed on the "discharge" of the VDP 22 to the wet line that maintains 400 PSI through the loop-which I would assume is the backpressure of that short circuit, also, there is a small 1/4 hose that goes from a street t at that same area up to the far left top of the VDP 22 (which looks like the top of the relief valve) HELP! I understand 140 isnt too hot for a system without a cooler, however, I havent gotten this machine really working yet as its not at my property and that seems hot for not doing any real work.

Thanks

If it was a basic machine without the backhoe the return from the control valve would be larger bore than the supply from the pump,when plumbed for a backhoe the supply for it comes from the return port from the control valve of the blade through the backhoe control valve and returns to the reservoir,therefore if the hoe is off the supply and return must be looped,if the bore of the lines is less it is restricting the oil flow and it may be building up pressure,ensure the lines are of the correct size and also any quick break couplings or adapters on the circuit.
Good luck
AJ

The looped lines and coupling are substantially smaller and it basically drops down to 1/2 through the couplings and the plethora of fittings. I will get my wrenches and patience out again and enlarge the couplings to the same size as original. I estimate 100 trips to the store for this one. So really, after this it will be fine when im using the dozer without the backhoe on, but a lot of idle time when I DO have the backhoe attached should cause heat buildup again since it will be reducing in size to power that rear valve as I dont have the option to open up that valve anymore. Maybe I just need to loop the circuit with pipe install a pressure and a return and a high pressure valve seperating the two so when not attached I can just have open couplings and when attached if I have long periods without use I just open the valve and it flows full flow?