Farmall 666 Hydraulic Pump

[dm2237]

Hello, My Farmall 666 hydraulics keep loosing prime when the tractor is shut down for a while. First thing I do after firing up the tractor is to turn the steering wheel back and form to essentially prime the system. Also, it appears that the pump is leaking. I wanted to change out the pump, but am not sure what pump it takes. I'm guessing it would take 12 GPM pump? Would the same pump that fits a 766 and 966 fit the 666? Thanks, Dan

 

[used red MN]

Here is a link to the YT hydraulic pump parts available from YT. YT IH 666 hydraulic parts The first pump in the list looks like the one you need, it looks like it is a slight upgrade pump because it says it is 15 GPM the original is 12 GPM. The ones offered as 17 GPM are not for your tractor, the oil filter and tube that the pump suction works through cannot supply more oil than the 12 GPM pump requires. FYI there is a second 9 GPM pump piggy-backed onto the back of the main pump that supplies the 3 point hitch. When the 3 point is not in use the flow from that pump adds to the other hydraulic systems. When you say the pump leaks what do you mean? You can’t really see the pump, only the plate it mounts on.

 

[dm2237]

It seems like I'm getting oil on the TA area. It doesn't seem to be coming from the rear main seal. Was guessing it's coming from the hydraulic pump area. I was wondering if that's why I keep loosing prime in the system. But I know the hydraulics aren't very strong, and I start to loose the power steering when it gets hot. I don't complete loose it, but it gets sluggish. I wanted to replace the pump, and see what else I need.

 

[used red MN]

I take it the leaks are on the outside, on the side or underneath? Can you get some pictures of it? Pics attach through the “Attach files” button. The pumps are internal can’t really leak outside. They are behind the square plate by the steps. See subsection 10-01 in the hydraulics section, all inside. CNHI IH 666 parts catalog Have you changed the filter and fluid?

 

[dm2237]

I might be able to get a picture at another time. It's kinda put away for the winter. I have not changed out the filter and or fluid. I have a new filter for it now, and was going to change it when I replaced the pump. the leak is coming from inside the TA area, and it drips under the tractor.

 

[used red MN]

Is it coming from some holes about 1/2” dia. on the bottom side of the housing about the center of plate cover 13 the filter cover? Reference parts diagram If so bad news, those are drain holes for the dry direct TA clutch cavity, it is in the cavity below cover 7. Seals go bad and then fluid leaks into there. The drains prevent the fluid from filling up the cavity and getting the dry direct clutch oiled down. Secondly, there are 3 seals that can cause this leak. I believe it is one of them that requires the TA be almost completely disassembled to replace it.

 

[dm2237]

Hmmm, but would that cause the hydraulics to loose prime all the time too?

 

[used red MN]

Not related, you just happen to have two separate problems. I assume you keep the transmission/hydraulic fluid at the proper level. Any idea how many hours are on the tractor?

 

[dieselbob]

Another possibility is the hose in the rear end is bad, to get to it you remove the cover for the third arm and look in the hose goes from the top cover to the pickup tube in the bottom of the transmission it is a common problem when they start to suck air

 

[leroy in ne]

I remember reading that some models IH having a problem that many solved by over filling by 5 gallons. IH guys was that for a prime problem and the cure that would apply to this model?

 

[used red MN]

I remember reading that some models IH having a problem that many solved by over filling by 5 gallons. IH guys was that for a prime problem and the cure that would apply to this model?

The 5 gallon overfill is mainly a bandaid fix for some hydraulic gremlins in the hydraulically shifted TA models, 706 and up. This tractor has a mechanical TA.

 

[dm2237]

Sorry for no reply. Was busy at work. I'll try to get the hours tomorrow in the light.

 

[paulsamwel]

Hello, My Farmall 666 hydraulics keep loosing prime when the tractor is shut down for a while. First thing I do after firing up the tractor is to turn the steering wheel back and form to essentially prime the system. Also, it appears that the pump is leaking. I wanted to change out the pump, but am not sure what pump it takes. I'm guessing it would take 12 GPM pump? Would the same pump that fits a 766 and 966 fit the 666? Thanks, Dan

Several places to loose prime;suction tube in diff housing then to filter housing from there to pump,most likely the o-ring at pump(they get real brittle with age)that seals suction tube that comes from filter housing.Does pump squeel a little before it picks up prime?Oil leak likely coming from seal between trans and t/a housing...need to split tractor if thats the case.I have a 1976 triple six with D312 darn good tractor.Don't condemn the pump,check system pressure first.Get a service book...makes working on it much easier.
Paul

 

[dm2237]

Ok, the tractor has 3535 hours showing on the meter. Not sure if it's 100% accurate or not. The tach has always worked since I've had it. The leaks seem to come from the middle of the tractor, not really on 1 side or the other. I was guessing the pump just because it's coming from that general area. Could be something else. I'll pull the filter and check the O-rings to see if it's leaking there. The pump doesn't really squeal when it's building prime, just have no hydraulics or steering. But right now I have it put away for the winter. Will know more when I get it back out. It's been parked since November anyway.

 

[dm2237]

Sorry to bring up an old thread. I found what appears to be the leak. The T shaped cover below the hydraulic pump area wasn't sealed good. They had the old gasket and new gasket both on with a layer of silicon sealant between the 2. Working on big trucks, I know that will leak every time. I took the cover off the back for the top link to look at the suction hose in there. How do I know if it's bad and sucking air. Thanks.