Magnum hydraulics. cold oil BYPASS

Hello there. I figured I would pick everyone's brain out there since we all have a vast spectrum of knowledge. With temperatures hovering around -40 here in northern Saskatchewan this week, starting tractors outside in the cold can be interesting. We have a Caseih 7120 magnum that has blown the auxiliary filter up 2 times now. From the looks of the hydraulic schematic this oil comes from the front gear pump and feeds the pto valve as well as the cooler circuit. There is a oil cooler pressure relief in the pump set for 1525-1625 PSI but the filter and housing are only rated for 1000 PSI burst pressure. There is a plugged filter bypass in the filter housing but that would not keep the filter from blowing as it is a bypass not a pressure relief. What am I missing here... I do not see a cold oil bypass anywhere in the circuit. Has anyone else had this problem with cold oil. Yes if we had the facility it should be in a warm building but that is not an option. Synthetic oil is hardly an option at 14 bucks a liter... and that would be 190 liters at total cost of 2660$ CDN bucks. Is there anyone here with experience on these tractors?

Ranch

If the filter bypass is plugged then that is your problem.Oil is too thick to get pushed through the filter at those temps,it needs to bypass the filter until it is warm enough to go through the filter.
Paul

Have you contacted a case IH dealer ? I'd have them see if there were any service bulletins on that issue. Also ask if Case IH offers a low viscosity hyd oil like JD does and try that. Also see if they offer a hyd. oil heater option. Are you running aftermarket filters ? sometimes OEM filters are different.

There is one hose in and one hose out of the filter base... the filter bypass is not much good if the oil can not get through the cooler/ or pto valve fast enough... it pressures up the filter base and blows off the filter or last year it even cracked the filter base. is there a cold oil bypass?

Ranch

Filter housing should have a bypass built into it.Make sure it's working correctly if it does.
Paul

I looked in my service training manual on early magnums. Two different filter bases with a differetn style filter bypass valve but both filter bases are supposed to limit the oil pressure to the filter at 120 psi and filter is rated at 1000 psi. Oil bypassing the the filter is directed right back into the inlet side of the charge pump. Not sure where it joins pump but diagram shows it is after the screen filter down in transmission housing.

I see you busted a filter base so it seems unlikely you would have two bases that the bypass valve would not function. I would do some double checking to make sure there is a outlet from base back to the inlet side of that pump.

The high pressure relief or bypass from the smaller gear pump to oil cooler should not have any effect on the filter. Been many many years since I worked on those magnums and never enough work on them (they were quite trouble free except for getting wrong signals from sending units etc) ti get a lot of experience on the hydraulic problems.

There were several changes made along the way so actual plumbing etc depends on serial number and age of tractor.

I realize it should work in cold weather. Is it possible to put a heater under the tractor with a tarp behind it to hold the heat for a bit if it is not needed only a few times during the winter.

If the oil after the bypass isn?t moving fast enough then the whole filter housing and filter would pressure up. Also this is not the main filter that is busting it is the auxiliary filter that feeds the oil cooler loop and the pto valve. The smaller gear pump feeds this filter. It seems our CNH dealer would rather support the farmers with millions of Dollars to spend and offer very little support to us small farmers who use 30-40 year old equipment. We do not even call there for parts anymore. Cause I ? can order ? the parts too.

Ranch

Ranch

Switch to a Synthetic Hydraulic oil. They flow at much lower temps than petro fluids. Look for a Amsoil Dealer in your area. He can get you fixed up.