M816 Main Hydraulic Pump Leak Fixed

My M816 had a known hydraulic fluid leak when I purchased it. (the previous owner informed me of the leak and it's severity, so it was not a surprise)

As the leak was a static leak, the hydraulic pump seal was the main suspect. I removed the pump, and found the seal to have been damaged upon original installation. The seal still had the OEM light green paint on it so I could assume that it has had a leak since this particular pump had been installed.

An easy job, other than the pump seeming to account for at least half of the total weight of the wrecker. I had to use a chain come-a-long to get the slippery thing out of the hole it was in.

The old seal spring was found separated from the seal, and the seal lip torn. The Chicago Rawhide number was still on it, so I was able to find a replacement.

I lapped both the upper and lower pump end plates. The scoring was slight, and cleaned up quickly with a little lap work. The pump should be good for quite awhile.

The filter was found to be quite filthy, but as the filter element is metal, it was easily cleaned.

The leak is fixed, now on to the hoist gearbox...

Nice work 54 glad to hear you got that fixed.

I would of never figured that out. Great work and great documentation on the fix Brian. Now you can actually use that thing. Don't forget to check the gear oil in the gear box under the turn table that the PTO shaft connects to.

Fine job on that.. So now that your good at it when are you coming up to do mine?

Thanks guys.

The most difficult part of this was the re-installation of the suction line. I ended up removing the bolt-on block that it threads into, and screwed the pipe fitting on the work bench. Then the block/hose is installed once the pump was in place. If you do it this way though, the O-ring in the base of this block will need to be watched so that it is in the groove fully. I had my brother there to help on reassembly, and the second set of hands really helps.

I usually work by myself, but after having to lay down on the M816 rear deck with my arms in the boom base and my foot working the come-a-long to remove the pump, I decided to ask for help on reassembly.

halftrack said:

I would of never figured that out. Great work and great documentation on the fix Brian. Now you can actually use that thing. Don't forget to check the gear oil in the gear box under the turn table that the PTO shaft connects to.

Click to expand...

Will do Jason, the next step after I fix the hoist gear case is to go through the entire machine and change all of the fluids.

Not looking forward to that one, these things have a lot of gear cases!

citizensoldier said:

Fine job on that.. So now that your good at it when are you coming up to do mine?

Click to expand...

How bad is yours leaking, and will it leak while the truck is just sitting?

The Chicago Rawhide part # for that seal is still current: CR 14940. Ran me about $14.

It is easier to remove the lower end plate of the pump, and install the new seal then. Prior to re-installing the lower plate (with the new seal in place), wrap the shaft with some shim stock (about 0.005") to prevent the shaft step from tearing the new seal.

I'm not real familiar with the 816 pump mounting. Would it be possible to replace the seal without removing the pump? Just slide the coupling off?

Dennis

Stretch44875 said:

I'm not real familiar with the 816 pump mounting. Would it be possible to replace the seal without removing the pump? Just slide the coupling off?

Dennis

Click to expand...

I wish that had been the case, it would have saved the time involved with removing the hoses, pump, etc.

The pic in the first post will show the pump mounting location from the top (in between the boom support frame plates). The pump mounts directly to the PTO gear case that sends the power to it, so there is no way to reach the lower part of the pump without removing it.