Case 990 hydraulic system malfunction

After getting my 990 running and water weight in the tires for traction I actually like the old tractor except the hydraulic system is not live, but the diesel is what I wanted in the first place and the 50HP is okay.
Well, after putting 13 hours on the old tractor the hydraulic system is choosing to not work sometimes and it growls and then works sometimes. I parked it and after looking at it I decided that the pump is inside the transmission. So, the steering gerotor needs to come off and then the top of the transmission to get access to the pump inside the transmission after draining the lubricant that is sort of milky even though I replaced the lubricant and filter and both stick boots as I figured that they were leaking water inside the transmission when it rained outside(wish I had a roof). Can anyone steer me in the right direction as I am a decent mechanic? I don't think I have steered wrong so far. I figure that once I get the top off of the transmission I will discover a bit of corrosion from moisture that may have led to damage to the hydraukic pump gears and they will need replacing. Am I right? Help me out if you can?

Pump is in the rear. You need to get a book and study it carefully.

All you have to do is remove the pto housing in the back and you will have access to your hydraulic pump and if
you need a good used one I do have one my e mail is [email protected]

Here is a photo of the hydraulic pump on my 990.

Note: All the service manuals are free and downloadable at the following link:
David Brown Manuals

Thank you my Canadian friend for saving me from removing the top of the transission. It sounds much easier from what you said and I'll keep you in mind if the gears are the problem as I suspect. I have found a new K961694 set on EBay for $346 including freight from Israel. Is that the right set? Gotta get offline as the thunder tells me that the expected storm is on top of me now.

Beautiful. I'll be downloading the free manual and determine if the e-ring needs removing from the shaft sticking out of the upper bearing after I removed the outer housing. I thought that it would be a lot of heavy work and I got out my portable hoist and removed the seat to get at the housing better.
Thank you Joe Stewart. You have been very helpful for an old retired farmer.

I think before you start tearing into things you need to go through the trouble shooting diagnosis in the DB manual. Did you see any aluminum shavings in the sump oil? A mess of them is an indicator the pump is toast. "Not working sometimes" isn't necessarily the pump, but could be several other things. RG Martin is real good at diagnosing these things, hopefully he'll be along and comment.

You need the manuals.

Well, since I changed the trans lube & filter it's a bit late to look for shavings as that was several years ago and there was water in the sump thru the shift boots. This tractor has sat since then. Now that the housing is off and the pump is disassembled I can see the housing chewed along with excessive play in the bushings and the gears have a lot of wear so it's a new pump for this 990 and not just a cartridge assembly, but the whole kaboodle. I DL'd the manuals and they showed what I have been led to expect. Thanks anyway. I always respect others experience concerning what I am about to endure. Ciao.

The E-ring didn't need removing and I realized that early on and it took a come-along hooked to my truck hitch to pull the housing free from the tractor. Everything is as described and after disassembly the pump housing is chewed along with excessive gear and bushing wear and that was the problem and it showed up after 13+ hrs of work. This 990 has over 3500 hrs on it when the hour meter died and it has a new one now along with lot of other 21st century goodies such as a one-wire alternator. I converted a bottle jack to test and adjust my injectors and had the injector pump rebuilt and it'll last till I'm in the grave.Thanks for the assistance.

I DL'd the manuals and they showed me what I needed to know. Thanks.

Hello Jean Claude,
I received a new pump yesterday and this morning found the exact size o-ring for the pump connection as the old one was dried and cracked. Now I have decided that the whole transmission needs to be carefully scrubbed and flushed as the congealed trans lube has left its mark on the walls and it will plug the filter in time and besides it's better to do a thorough cleaning and flushing. The hardest part was removing the rear housing as it was thoroughly stuck after 40 years but I used my truck hitch and a come along to get it unstuck. It's cleaned but I will remove the top of the tranny anyways to clean it as well as it should be as the rest was with residue on the walls that will become dislodged and plug the filter as time passes requiring more filter changes than normal. It appears as if I am on the way thanks to you and other's assistance.

The Selectormatic Control Valve (on the right side, inside the rear axle) is known for getting trash inside, which causes all kinds of hydraulic problems. While you have the rear case off, I would probably suggest that you pull that valve and clean out the trash from that valve. Be careful, there are 1 or 2 screws on that valve the manual specifically tells you not to open for any reason. I replaced the defective hydraulic pump on my (1980) Case 380CK (which is very similar to the 885 and probably the 990) only to find that the Selectormatic Control Valve also had to come out and get thoroughly cleaned and readjusted. Once it is reassembled, adjustment takes a while to figure out exactly how much adjustment the screws require.

I'm thankful that you have made it known about the valve and the problems with accumulations of trash within it. I had been wondering about if I should try to also clean it before closing up the rear end/pump and you solved that problem and I'll take it apart as much as I dare and blow it out if at all possible and I think that I can spot something that concerns the screws that you mentioned. The filter has been cleaned with gasoline twice and now will be installed for another go at filtering. I like the compound filter design that uses a spring bypass when the paper element is plugged up. I think it is one of Case's better design features. This filter has only been used for 13 hours and it became filled with congealed debris that washed off the walls of the tranny. That's why I decided that the whole inside of the tranny needs a good brushing and rinsing with a squirting device using gasoline to rinse the insides of the tranny, saving me a lot more work down the line. Thanks again.

Diesel fuel is probably a much safer product to use than gasoline to clean out everything. Gasoline is far more dangerous due to explosive fumes. The hydraulics can handle very small amounts of diesel mixed with the fluid.

Be sure to precisely count the number of turns for the adjustment screws on the Selectomatic control valve, so that you can get the adjustments back to where they should be, as close as possible. You will probably need to adjust them anyway because the lift arms will probably stay down all the time, or up all the time, until you get the adjustments back to where they should be. Final adjustments can only be done once everything is reassembled.

Don't lose the small ball or tiny strainer inside one of those adjustments or it will never work.

Tighten adjustments down using the locknut. You might even have to make a special bent wrench to be able to tighten this locknut since there is not much room to work once everything is reassembled back inside the rear axle.

The valve that you mentioned is on the outside and to reinstall it will require three new o-rings that I now have in hand. The valve was surprisingly clean of any debris. I'm guessing the filter was functioning as designed and I'm thankful for that. The problem was the pump all along and it was time to die after 440 years. The valve was truly something to disassemble and adjusting everything back to what it was will be easy enough from your instructions. There are three check balls in this assembly that should never be lost or a new assembly is in the budget as they must be irreplaceable.

I've been working outside and so the flammability of the gasoline was no problem as there was no spark around to ignite me. Gas has a bit more solvent ability than diesel does so I found it better in this instance since I was outside where no fumes can collect and ignite. Thanks for the instructions and information.

Hopefully, the 990's Selectomatic Control [u:023f25acbf]Valve[/u:023f25acbf] is external on yours. It is [u:023f25acbf]inside[/u:023f25acbf] the rear right axle on the Case 380CK. See attached 1st and 2nd pictures.

The Selectormatic Control [u:023f25acbf]Mechanism[/u:023f25acbf] is external. See attached 3rd picture. I had to replace the Fork Selector (item #22) inside the Selectormatic Control [u:023f25acbf]Mechanism[/u:023f25acbf] which was melted inside of mine. It was made out of some type of high temp plastic.