Cab Lift Problem and finding Hydraulic Reservoir on 1994 M1078

[D Foster]

Hello All, Went to attempt to lift my cab. It went up approx. half way and had to use the cab manual jack to lift rest of way up. My manual says to check the hydra. reservoir but the diagram they show does not appear to match my truck? I also noticed the manual says: "If Equiped"? I would think all the trucks would have a hydraulic reservoir? Also when I put the cab back down it appears to be working okay so far. Any help would be appreciated.

 

[Suprman]

If you had enough fluid to manually raise the cab maybe your air hyd pump needs a rebuild. It’s behind the cab.

 

[NDT]

What sound did the pump make when it was unable to raise the cab?

 

[firefinder]

I have a very old unit with multiple manual pumps. To my knowledge units that had an air/hydraulic pump had the pump located in the same place. The air/hydraulic pump is located behind the cab and between the spare tire and air filter snorkel. The air/hydraulic reservoir is part of the air/hydraulic pump.

NDT has a great thread on the rebuild of the air/hydraulic pump.

https://www.steelsoldiers.com/showthread.php?137274-FMTV-Air-Hydraulic-Unit-Repair

The air/hydraulic manifold (by the passenger side toolbox) is also a good source for leaks. Almost all of the items can be rebuilt.

Use the search function for a variety of threads on repairing the individual components and troubleshooting ideas.

 

[D Foster]

What sound did the pump make when it was unable to raise the cab?

When attempting to lift the cab with the pump the pump made an empty banging type sound? Someone mentioned NDT had a good thread on pump rebuilding. Who is the NDT as I am not familiar? I will check the pump tomorrow. I now have a good idea on its location. Thanks! PS Will also check the air/hydr. manifold. I did notice I have a lot of air coming out of the bottom right knob (cab air springs)

 

[tennmogger]

As Suprman implied, check your fluid level in the reservoir. Going part way up implies the air/hydraulic pump is working and there are no leaks or blockages. The reservoir is small and if not serviced can run out of capacity.

After you find the pump located behind the cab (literally a black box, usually), there is a round knob that's the dipstick. Unscrew it, check level, and that's the fill point.

 

[D Foster]

Cab Now Lifting!

As Suprman implied, check your fluid level in the reservoir. Going part way up implies the air/hydraulic pump is working and there are no leaks or blockages. The reservoir is small and if not serviced can run out of capacity.

After you find the pump located behind the cab (literally a black box, usually), there is a round knob that's the dipstick. Unscrew it, check level, and that's the fill point.

Hello Suprman, Just wanted to thank you and the others for all the input. As you mentioned after finding the black reservoir box it was very low on fluild. After replenishing with fluid it now is working fine. Also checked for leaks and all looks good. Thanks again!

 

[Wildland]

What is the hydraulic fluid type and weight? My cab raises about 4-6" then stops and I can hear the pump operating. There is some rusty fluid, teaspoons, around the small brass filter/vent on the end of the rectangular reservoir/pump assembly. Thanks.

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[GeneralDisorder]

What is the hydraulic fluid type and weight? My cab raises about 4-6" then stops and I can hear the pump operating. There is some rusty fluid, teaspoons, around the small brass filter/vent on the end of the rectangular reservoir/pump assembly. Thanks.

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Much easier if you start a new thread vs. grave-digging one from 2018.

There is a sticky at the top of this forum with parts, fluids, capacities:

LMTV/FMTV Quick Parts Reference Spreadsheet

https://docs.google.com/spreadsheets/d/1U0XMs6blh-7a6B3IIe-A7GKcAHEj5-6hZEghH_jddgw/edit#gid=0 I just started doing this tonight. I have about 3 or 4 hours into it so far. I am going thru threads and pulling up part numbers people have posted as well as running NSN's myself. If you have any...

www.steelsoldiers.com

You can also consult the Lube Order (LO) in the TM.

The hydraulic system uses MIL-PRF-5606H aviation hydraulic fluid. It DOES NOT use "tractor fluid" or ATF. Not if you want it to function properly.

 

[NDT]

What is the hydraulic fluid type and weight? My cab raises about 4-6" then stops and I can hear the pump operating. There is some rusty fluid, teaspoons, around the small brass filter/vent on the end of the rectangular reservoir/pump assembly. Thanks.

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Slobbering pump vent means it’s time for an overhaul.
I’ve had ATF in service for 12 years now. Seems to be ok.

 

[Ronmar]

The main reservoir is where that vent is located it has a dipstick…. As mentioned, slobber bad…

 

[Wildland]

Thanks, I need to download the TM and print it.

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