1586 steering pump

The 1586 IH seems to lose prime to the steering/brake pump after it is shut off a while and always when it sits overnight. If I wind the engine up to 1800 or so it starts working and doesent bother once it takes off. It start doing this last fall but didnt bother throughout the winter, now that it is getting hot it has started to get worse.

Do you think it is just the pump getting bad or might I have other problems. Don't see any leaks and once it takes off it steers fine. I swithced one years ago on the 1466 but that one quit all together. Also is there anything in particular to be careful with if I switch out the pump, I know its behind that left side cover but other than that I don't know much about it.
Thanks for any help with this.

It sounds like the pump.After replacing it you,should consider the kit that gits rid of the supercharge line from the aux. valves.When this valve gets bad it can let the MCV pump suck air and take out your new pump.It will be like the 66 series low pressure system then,but the extra flow from your brake lube will be used for more lube in the TA & trans systems.

With the oil warmed up, with braking applied, do you lose brake assist and/or does the TA downshift when turning at low idle? If you have those problems then the pump is suspect and should be repaired before it leads to rear end failure. If the hydraulics are Okay then the problem is an air leak in the suction side of the pump. The leak will be either at the O-ring between the center section and the rear frame or where the pickup tube enters the filter cavity. To compensate for the leaks simply run the tractor with about five gallons extra oil in the transmission. That is enough to cover either leak so that air does not enter when the tractor is not in use.

(quoted from post at 21:10:29 06/27/10) It sounds like the pump.After replacing it you,should consider the kit that gits rid of the supercharge line from the aux. valves.When this valve gets bad it can let the MCV pump suck air and take out your new pump.It will be like the 66 series low pressure system then,but the extra flow from your brake lube will be used for more lube in the TA & trans systems.

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The supercharge line has nothing to do with brake lube or the amount of oil going through the MCV pump. It should have oil flow in it only when neither the hitch nor any aux valves are being used. When ever there is demand for oil from the rear pump the return flow is dumped to reservoir and not to the supercharge line. The reason for it being there is so that you do not have to draw 29 GPM of cold hydraulic oil through the filter. It was bad enough with the older tractors using 21 GPM. A better solution may be the kit to run two hydraulic filters.

The operation oil for the steering, brakes, TA, seat, and diff lock are all controlled by the size of orifice in the MCV assembly. 06 through 66 series use a three GPM orifice, 86 and newer use a five GPM orifice. The extra oil in the 86 series is used to send one GPM to each brake for lube. The TA, brakes, seat, and diff lock are all closed center valves and only use oil when actuated. Three GPM minus leakage losses are available to lube the TA. Any oil in the TA lube circuit that is at pressures above about 18 PSI get dumped back to the reservoir.

The 86 series tractors use a 12 GPM pump on the MCV. Any oil flow above the 5 GPM that goes for controls is routed to the front oil cooler and then back to lube the differential and range transmission upper shaft. The 5 GPM is priority flow so when the pump gets weak and the flow drops off less oil goes to the rear frame. When it gets to the point where you notice a loss of braking or the TA lube light comes on you have NO lube going to the differential. That is why it is important not to continue to use a tractor with a worn out MCV pump.

Thanks for the information, I will try the brakes tommorow at idle, but I think they work fine once it is primed up after starting it but I will check. I do have a small leak on the right side up by the control valves, I didn't realize the hydraulic valves were related to the mcv pump. I have to look for sure where it is coming from, but has been dripping more than it use to and noticed a bit of oil on the ground when it sits over night on the right side. When I first start it the 3pt goes up and down with the lever, but it doesnt help prime the mcv pump.
If i remember right the light only comes on when i push the clutch in and when it doesn't prime up when it first gets started, once the steering and brakes work I havent noticed the light come on. The 15 is an 80 model and it is the open center type hydraulics, don't know if this makes any difference as far as the MCV. My neighbor has an 81 model that has the closed center hydraulic pump. Also could I open the small plug under the oil cooler lines to help prime it up in the morning? I have to open that plug to bleed my 1466 after i change the hydraulic filter, don't know if thats normal or would help me out for this one? I have some road mowing to do with it tommorow after that it will be back home and maybe I should put a new pump in to be on the safe side. If the light is off is there enough pressure for the tractor, or can the light be off and the pressure be too low for the rear end? Thanks again for the help.

Actually there will be no or very little oil flow to the rear in any of those tractors at low idle. You have a 12 GPM pump at rated speed, 2400 - 2600 RPM. When you drop to low idle at around 800 RPM you are running only 1/3 the rated speed. As a result the pump is also only going to flow 1/3 as much. That gets it down to about 4 GPM, less than the orifice will flow so all the oil goes to the steering. This really is not a problem since the tractor is not able to put much stress on the drive train at low idle.

The reason for testing at low idle is because by turning the steering all the way to stop in either direction it causes the oil pressure in the system to rise from about 250 PSI to 1800 - 2100 PSI. A weak pump will not flow enough oil at those pressures at idle and as a result the TA lube light will come on, the TA will down shift, or you will notice loss of braking assist. If the pump passes at idle it will be serviceable at higher RPMs.

The problem you have is air getting into the suction side of the system, most likely the seal ring between the center section and the rear frame. The MCV pump is completely submerged so the air is not entering there. Installing a new pump may help because it will be a little better at moving the air out of the system but it will not repair the main cause of the problem. On your tractor with the supercharge line it may help if you do not move either the hitch or the auxiliary valve until it has purged.

Finally got back to the tractor today, it was about ten miles from home where I had some road mowing to do with it. The brakes seem to work fine at idle, went to watch the light, but it must have burned out. I know it was on the other day when I had the clutch pushed in, I will have to get a bulb for it and try it at idle to see if it comes on, but like you said I think its just an air leak. I did not move the 3pt when I started it and it seem to prime up at a lower rpm. I also left the 3pt down when I shut it off and left the lever in down position so it doesnt try lifting when it starts, it has been going down overnight and when it starts the first thing it does is lift the 3pt, so maybe this is taking away from the super charge line. The oil is about 1/2" over the full mark, I will probably try adding to that and see if it helps. Still think I might switch the pump if we get a rainy day. Thanks for the help.