I need this help badly, we just re-do our engine on a D8H and now my transmission pump wont suck fluid to the transmission, and it wont move, anyone know what I have to do to fix it? I have tried two other old pumps but same result. But when you remove the bleeding bolt and fire the engine, it will pump but when you put bolt back or slack it, it wont pump any fluid.
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transmission pump wont suck fluid on D8H
- Thread starter Joeisibor
- Start date
AmerIndependent
Site Sponsor
- Joined
- Nov 4, 2009
- Messages
- 359
- Location
- Riverside, CA
- Occupation
- Caterpillar Powertrain Rebuild & Repair Specialist
Sounds like a suction leak possibly created when you disturbed hoses during engine R & I. Look for moisture around hoses and listen for a high pitched sound and possible foamy oil.
John C.
Senior Member
I don't know how old your machine is but you probably have either a strainer housing just forward of the transmission pump or if a real old D8 you will have the suction strainer down in the main frame of the cross shaft right where the pump suction hose hooks up.
You didn't mention why you changed the pump. Did you take the old pump apart to see what was wrong with it?
You didn't mention why you changed the pump. Did you take the old pump apart to see what was wrong with it?
Its a 1967 D8H and I have to change the pump for the same problem of not sucking fluid.
Took the pump apart and it was fairly OK
John C.
Senior Member
You have to make sure you are not sucking air through a bat O ring or hydraulic hose. As I recall the hose from the rear case to the suction strainer or pump was real bad for getting leaks in it.
I would attack the problem this way. Make sure the strainer is clean. Check the O ring on top of the strainer housing and at the suctions port of the pump. If you have the strainer at the cross shaft housing, then pull the belly pan and make sure you have that strainer clean and the hose is not leaking anywhere. I have had the problem of those pumps not picking up a suction so all the ones I have worked on had a gauge port plug on top of the pump. You can crack that plug loose and you should see oil come out of it. Probably to start with it will be nothing but air. If you get just oil out of the fitting you probably have a problem in the transmission control valve and you will need to do some testing with gauges.
Good Luck!
I would attack the problem this way. Make sure the strainer is clean. Check the O ring on top of the strainer housing and at the suctions port of the pump. If you have the strainer at the cross shaft housing, then pull the belly pan and make sure you have that strainer clean and the hose is not leaking anywhere. I have had the problem of those pumps not picking up a suction so all the ones I have worked on had a gauge port plug on top of the pump. You can crack that plug loose and you should see oil come out of it. Probably to start with it will be nothing but air. If you get just oil out of the fitting you probably have a problem in the transmission control valve and you will need to do some testing with gauges.
Good Luck!
Yes, I do get air when I crack it open then high pressure oil
but when I turn the engine off, and replace the plug and start the engine, it will stop pumping. Thanks folks for the help so far
DPete
Senior Member
67' should have a magnetic filter by the pump, it has an oring and plate on both ends, make sure the orings are good and plates are tight, I've seen them suck air there and not leak oil.
tctractors
Senior Member
I have just sorted the same fault on a D8K, I popped off the belly guard and found the suction hose from the bottom case to the pump screen to have rubbed a good size hole in on the belly guard as it was not clamped into its set location, A few times though on other tractors I have found that the housing where this suction hose bolts to the case is blocked solid with brake band bits, stopping the oil getting to the hose and onto the pump, I always strip out the pump, screen and all the pipe work involved to check things and fit new O rings, inside the pump you need to be firstly looking at the bushings the gears spin on, the drive side bush I always change also the shaft seal, I then prime the pump with oil and vent air through the trans filter lid via a test port and oil line, when things are pumping good I stick a pressure test onto the port and check thing through the shift lever also checking the drive shaft for slip.
tctractors
tctractors
Just found out the magnetic filter O-ring is cake out on both side, and other o-rings too are bad. There is this suction hose from the filter housing to the pump that has several obvious sign of cracks on the out side, but I dont know about the inside, I will just have to replace them all in a couple of days and let all of you know how it panned out.
Thanks guys