M1078 Hydraulic Controller Box and System Schematics

[Lugnuts]

I guess the simple question would be to ask if there is a Troubleshooting Chart for the Hydraulics System? After reading the Manual I read how to disassemble and reassemble but it never explained the function of the check valves and flows of the oil/
My valves were leaking oil out the front of the unit thus there was not enough oil to operate the system. I could raise the cab high enough by the hand pump to check oil by the starter. Air pump made noise but no oil/
Pulled valve controls and replaced O-Rings on spools, base and stem/
Oil leaks were resolved/ Filled system, primed and pumped and filled hand pump/ Cab is up full/ Air pump was filled and primed/ System is working the way it should/ Up and down 3 complete cycles/
Fourth time up just to gloat on my accomplishment the cab raised fully and in lowering the cab it suddenly stopped and said NO! Wow/ Attempted to raise it in the event that it thought it was loosing oil but it would not raise/ Hand pump felt hard as a rock/ Same way in lowering position/
After time of contemplation (no details on that) I decided the easiest and cleanest way of lowering the cab was to slowly remove the Raise/Lower Cab Valve and let the oil ease out/ Much to my surprise when slowly unscrewing the valve the pressure started exhausting internally in the manifold without dumping outside, cab descended, and I have no idea where the oil went except that it stayed within the system/
With cab down I figured the pressure also was relieved so I switched to Spare Tire Mode and went to used hand pump and it was still hard as a rock/ Used Air Pump and it would make a bump and that was it/ I concluded that I have a Check Valve or oil passage that must be locked up or plugged but I don't have the information to intelligently make a diagnostic.
Again I am turning to the experienced in this area for some enlightenment or diagrams on oil flow and Valve Body functions I appreciate all the help in the past. Thank you!

 

[Suprman]

I keep this handy. There are filters in the control box and one in the hand pump but you have to take it apart to get to it. The ones in the control box are under hex caps on top the caps come off and the filters unscrew with a size larger hex. There are orifices behind each of the 3 top controls they come out with a hex key. Crap gets in the system and gums it up.

 

[Lugnuts]

I keep this handy. There are filters in the control box and one in the hand pump but you have to take it apart to get to it. The ones in the control box are under hex caps on top the caps come off and the filters unscrew with a size larger hex. There are orifices behind each of the 3 top controls they come out with a hex key. Crap gets in the system and gums it up.

Thank you for your reply. Do you have to remove the box completely or can it be dropped down and get to those?

 

[Suprman]

The filters in the box are under hex caps on top of the box. There are some check valves on the back and left side of the box. You can see them in the hyd diagram. Im not sure if they dont allow flow until a certain pressure or what. The orifices you can unscrew the up down valve and it comes out with a hex key. If you unscrew the cab lift control valve, the cab should come down.

 

[Ronmar]

There are 2 different control valve models and they have the filters in slightly different positions, but they are under hex caps as Superman described.

Have you downloaded the manuals from here? There is a section in one of them on accessing filters and orifices(sorry, forget which) For both types of control valves.

there is a checkvalve on each pump output, but those are simply to keep the output of one pump from back-feeding the output of the other pump. The 2 check valves used in the control valve are to steer the returning fluid to the right place. So if for instance you are using the hand pump, the return flow goes there instead of into the air op pump, and when using the air op pump, it will try to send fluid to the hand pump, but since it is sealed and no fluid is being removed from it it quickly builds the few PSI required to open the valve back to the Air op pump Reservoir.

sounds like something got clogged like a restricted orifice. or you have a valve not quite in the right position, like trying to send oil to the suspension compression cylinders that still have the locking pins in place…

M1078 TM's

Listed below are a number of the TM's for the M1078 trucks. To save them to your computer, right click, select "save as" m1078_TM 9-2320-365-10.pdf TM 9-2320-365-10 for the M1078 series trucks. m1078_TM 9-2320-365-20-1.pdf TM 9-2320-365-20-1 for the M1078 series trucks. m1078_TM...

www.steelsoldiers.com

 

[Ronmar]

I guess the simple question would be to ask if there is a Troubleshooting Chart for the Hydraulics System? After reading the Manual I read how to disassemble and reassemble but it never explained the function of the check valves and flows of the oil/
My valves were leaking oil out the front of the unit thus there was not enough oil to operate the system. I could raise the cab high enough by the hand pump to check oil by the starter. Air pump made noise but no oil/
Pulled valve controls and replaced O-Rings on spools, base and stem/
Oil leaks were resolved/ Filled system, primed and pumped and filled hand pump/ Cab is up full/ Air pump was filled and primed/ System is working the way it should/ Up and down 3 complete cycles/
Fourth time up just to gloat on my accomplishment the cab raised fully and in lowering the cab it suddenly stopped and said NO! Wow/ Attempted to raise it in the event that it thought it was loosing oil but it would not raise/ Hand pump felt hard as a rock/ Same way in lowering position/
After time of contemplation (no details on that) I decided the easiest and cleanest way of lowering the cab was to slowly remove the Raise/Lower Cab Valve and let the oil ease out/ Much to my surprise when slowly unscrewing the valve the pressure started exhausting internally in the manifold without dumping outside, cab descended, and I have no idea where the oil went except that it stayed within the system/
With cab down I figured the pressure also was relieved so I switched to Spare Tire Mode and went to used hand pump and it was still hard as a rock/ Used Air Pump and it would make a bump and that was it/ I concluded that I have a Check Valve or oil passage that must be locked up or plugged but I don't have the information to intelligently make a diagnostic.
Again I am turning to the experienced in this area for some enlightenment or diagrams on oil flow and Valve Body functions I appreciate all the help in the past. Thank you!

Re-reading your description again, it sounds like it is probably the 3way selector valve as both pumps sound like they are deadheaded/blocked… Since they are rotating spools and not sliding spools, if they are not properly seated, or loose(can,move in or out) you might be able to rotate them to the right position, but still not be aligning the ports…

 

[Suprman]

So here is how I fixed my issue of nothing wanting to move but building lots of pressure. Initially I believe it was just the orifices behind the cab tilt and spare tire up down valves. I removed each valve and cleaned each orifice they were both visibly dirty. Gave the system some flush to get out any more stuff that was in the box and put the valves back in. The valve o rings were old and had been seated for a long time. When I pulled out the valves I broke the years old seal and the o rings never re-sealed. So I had pressure building on both sides of the function. I swapped in some generic o rings and am back in business.

 

[BERZERKER888]

this may help

 

[Lugnuts]

Re-reading your description again, it sounds like it is probably the 3way selector valve as both pumps sound like they are deadheaded/blocked… Since they are rotating spools and not sliding spools, if they are not properly seated, or loose(can,move in or out) you might be able to rotate them to the right position, but still not be aligning the ports…

When I rebuilt them I made sure all the holes aligned and it was working fine on three cycles. I have watched the video posted and didn't realize I had orifices and ports in the bottom of the spool valves. I am just coming to fact that I need to remove and go through every orifice on the hydraulic unit. They are not exactly a joy to remove and reinstall. Thanks for the input and thought about it.

 

[Lugnuts]

There are 2 different control valve models and they have the filters in slightly different positions, but they are under hex caps as Superman described.

Have you downloaded the manuals from here? There is a section in one of them on accessing filters and orifices(sorry, forget which) For both types of control valves.

there is a checkvalve on each pump output, but those are simply to keep the output of one pump from back-feeding the output of the other pump. The 2 check valves used in the control valve are to steer the returning fluid to the right place. So if for instance you are using the hand pump, the return flow goes there instead of into the air op pump, and when using the air op pump, it will try to send fluid to the hand pump, but since it is sealed and no fluid is being removed from it it quickly builds the few PSI required to open the valve back to the Air op pump Reservoir.

sounds like something got clogged like a restricted orifice. or you have a valve not quite in the right position, like trying to send oil to the suspension compression cylinders that still have the locking pins in place…

M1078 TM's

Listed below are a number of the TM's for the M1078 trucks. To save them to your computer, right click, select "save as" m1078_TM 9-2320-365-10.pdf TM 9-2320-365-10 for the M1078 series trucks. m1078_TM 9-2320-365-20-1.pdf TM 9-2320-365-20-1 for the M1078 series trucks. m1078_TM...

www.steelsoldiers.com

I went through the manuals that I have and didn't see a whole lot that was specific to troubleshooting these boxes. If you recall which TM they were in I sure would appreciate that info. Thank you

 

[Ronmar]

I went through the manuals that I have and didn't see a whole lot that was specific to troubleshooting these boxes. If you recall which TM they were in I sure would appreciate that info. Thank you

Chapter 19, which you will find in the 20-4 manual. 19-4 manifold valve replace, has complete exploded views and disassembly instructions for all the valve assemblies…

 

[Ronmar]

When I rebuilt them I made sure all the holes aligned and it was working fine on three cycles. I have watched the video posted and didn't realize I had orifices and ports in the bottom of the spool valves. I am just coming to fact that I need to remove and go through every orifice on the hydraulic unit. They are not exactly a joy to remove and reinstall. Thanks for the input and thought about it.

And of course the tie breaker for the decision as to which valve has the issue would be to select cab suspension and see if you can move those cylinders. each suspension cylinder has 2 locking pins that must be removed before you can extend them. There were to keep them from leaking down and releasing the axle springs inside an aircraft, possibly damaging it… That circuit does not have restricted orifices in it…

 

[Lugnuts]

Chapter 19, which you will find in the 20-4 manual. 19-4 manifold valve replace, has complete exploded views and disassembly instructions for all the valve assemblies…

I will look into sir and thank you

 

[Lugnuts]

So here are my latest findings and questions.
I pulled everything out of the box and used brake clean in a pressurized can and air to make sure all passages were clean. Pulled the 2 little orifices in the back of cab raise and lower and the spare tire raise and lower. Filters were clean.
The trouble with the schematic that I have, it doesn't say the journey through the different check valves is cv4 to whatever the next location is, they're not labeled so to my best account the flows are there.
I reassembled the unit taking special care as to cleanliness, timing of the valves, and working of the check valves.
I then took an R12 Refrigerant manifold and hooked up to P1 for pressure and air flowed to all the correct positions that were indicated on the valves. My pressure is about a 100psi.
My next test resulted in the question. When you have the P1 port pressurized and the cab lift valve in cab lift raise and pressure is flowing out the cab lift cylinder connection shouldn't you be able to have air go from the cylinder connection for cab lower to flow out you T1 return? That is to say if you have oil going into the cylinder to raise it you would also have to have oil coming out of the other side of the cylinder.
My return side on the box does not seem to be letting return air pass through. Is there not enough pressure on a valve in there to make it work?
Any feed back before I just install it and try it?
Thanks guys

 

[Ronmar]

It should provide for a return path to the reservoirs but there is some steering check valves in there to insure it goes to the right reservoir with the priority insuring the sealed hand pump reservoir is full then if it gets 5psi of back pressure on that path, it opens a check to allow flow up to the aop reservoir

 

[Lugnuts]

It should provide for a return path to the reservoirs but there is some steering check valves in there to insure it goes to the right reservoir with the priority insuring the sealed hand pump reservoir is full then if it gets 5psi of back pressure on that path, it opens a check to allow flow up to the aop reservoir

Thank you for responding.
I feel no air flow out the T1 or T2 return lines but there is a bit of pressure flowing out the one makes pilot. Does this seem right?

 

[Lugnuts]

Does anyone want to sell a controller box?

 

[Ronmar]

Does anyone want to sell a controller box?

Sure I am nearly done with mine, just need to lower the spare one last time…

 

[Lugnuts]

Sure I am nearly done with mine, just need to lower the spare one last time…

I am unclear if this is sarcasm or if you have one to sell? I take it is sarcasm but...? If any one has a Controller Box perhaps an extra that they would like to part with then I am most certainly interested! LOL! I would say smart ass but some might be offended.

 

[Ronmar]

I am unclear if this is sarcasm or if you have one to sell? I take it is sarcasm but...? If any one has a Controller Box perhaps an extra that they would like to part with then I am most certainly interested! LOL! I would say smart ass but some might be offended.

I don’t do sarcasm, I am a very literal person. I am removing all my mid structure and am replacing all the hydraulic control with a hand pump. I literally need to use it to lower the spare tire one last time then I am done with the valve…