963B mystery hydrostatic leak

I have a mysterious hydrostatic leak on a 963B track loader. The oil level in the transmission drops when it is operated and the only evidence of external oil leak I can find is coming out of frame weldment all the way up by the forward cab pivot (behind the lift arm pivot pin) The machine has consumed about 15 gallons of oil in 1 hr of operation. Transmission divider box is slightly overfilled but the oil definitely did not all go there. My only thought is it is the left hydraulic brake circuit or left track drive motor shaft seal is leaking into the cavity between the final drive and track motor and I have filled the entire machine frame with oil. Not looking forward to pulling either the final drive or track motor but was wondering if there is any test to perform to ascertain which component is leaking and if I should pull the track motor or the final drive. Neither of which looks like a particularly fun project. As long as the oil in the transmission is maintained at the proper level the machine operates normally.

Thanks for any advice.
Tom

Check the oil levels in the planitary drive hubs, a nice easy one to do.

I got an opportunity to check the planetary drive oil level and the planetary level was correct/not overfilled.

I guess that rules out the brake leaking into the planetary so the options are:
1. the brake leaking externally towards the motor shaft
2. either of the the brake lines or o ring fittings leaking
3. drive motor shaft seal leaking

Can anyone confirm if that cavity pictured below is actually vented up through the machine frame weldment?

I think my next idea is to try monitoring track motor case pressure and see if case pressure ever spikes enough to push the oil up high enough to where it is coming out of the frame near the cab pivot. I think based on the height differential it would need 2-3 psi which would be above case drain spec.

The 2 lines to the brake are for the air vent so once the machine goes brakes off the pressure should build and brake hydraulic flow should go to zero? Maybe I could add an external flow meter near the HPCU to see if brake circuit is continuously flowing oil indicative of a leak?

In the pictures i found below, it almost looks like the motor shaft seal could be repaired with the final drive off. Can anyone confirm this is possible? Although my experience with leaking motor shaft seals is normally due to high case pressures indicative of other problems. Definitely could not service the brake lines by removing the motor with final drive in place.

Due to the amount of disassembly involved I'm just trying to diagnose the problem first to make sure I'm attacking from the correct side.

Thanks for any help. Tom

I've had this one before. It was a long time ago and I recall it was only discovered when the battery box bolts were removed and a geyser of oil shot 10ft in the air.

I don't think we were able to pin it down to one thing, but we resealed everything we could. A few pointers:
The brake pack is easily unbolted and resealed.
In your picture I don't see any O ring around the drive shaft? This is important.
The motor seal carrier can be removed and the seal replaced. Don't be concerned about excess case drain pressure. If this was happening you would have other problems besides.
Try putting air pressure on the brake lines to check for leaks.
The two seals where brake pressure goes through the split line are unique I think. Use genuine parts.

Checking for flow to the brakes is the right kind of idea, but a leak will to small to register. A good strategy is to install a shutoff valve and pressure gauge. Build pressure in the system, close the valve and watch for the pressure to decay. Beware though, in this situation the machine will be in a permanent Brakes-Off state.

Cmark
Thank you for the insight. Nice to know the battery bolts go into that same cavity. The photos I posted are not my machine, just pictures I found trying to help locate my problem. From the parts book it looks like the motor shaft lip seal actually seals on the outside of a female splined socket and the o-ring you mentioned that is missing in the picture would seal the brake input shaft into the motor socket. I'll definitely use OEM parts and like you suggested reseal everything while apart. The cost of the seals will be minimal compared to the labor of getting the final drive off. It definitely sounds like attacking this from the final drive side is the way to go compared to dropping the belly pans and pulling the track motor.

I like the idea about adding a gauge and valve to check the brake circuit for leaks. I think this is pretty accessible at the air purge valve right under the cab. My machine has some custom forestry brush guards that must be removed to tilt the cab and I have never had to do it in the 12 years we've owned the machine. I'll be sure to find some level ground and apply the front mounted earth engaging parking brake before playing with the brake circuit.

Thanks again Tom

Yes, you're correct on all your points and there is absolutely nothing to be gained by removing the motor. The brake release line is right there in front of you when you open the LH door, but I think that if you remove the final drive, your problem will be obvious.

It's been many years since I did a '63 but I'm fairly certain that you don't need to undo the track frame like in the photo. The procedure actually isn't too arduous.
Remove the track.
Remove the sheet-metal guards around the sprocket.
Remove the rear track guards.
Remove the sprocket segments (for clearance, and to add some lightness)
Remove the F/D.
Putting it back, you will find it useful to make some guide bolts.

I thought I might drive the machine up on some cribbing before breaking the track so I can let the track drop down in the rear to disengage the drive sprocket. I think then I'll only need to remove one sprocket segment for clearance along the front. Or possibly breaking the track and then backing the machine up to get the sprocket clear of the track rails. I'd prefer the stability of the machine sitting on its tracks instead of being jacked up like in the picture
I posted. I think guide bolts will be a must and according to my service manual it sounds like CAT actually provided some tapped holes for jacking bolts to separate the final from the frame. Despite the size of everything I really like the design of being able to pull the final as a unit without having to remove the track frame. Thank you again for the information. Now I feel like I have the knowledge to tackle this problem and will get started on it once I get everything planted on the farm.

Thanks again Tom

Do you have a Parts Manual.? If not it might pay you to get hold of one.
If your Serial Number prefix is 9BL then the manual is Cat Publication SEBP2393.
Here's one on eBay although it's an original Version 0 book dating from 1995 - a new one (Version 45) would be about $115 from Cat. https://www.ebay.com/p/1832625662

Hi Nige.
I do actually have both the parts manual you referenced and service manual SENR5302-04. I was a little confused if these were the correct manual because the cover references 9BL1-Up. My machine is 9BL02214. Is CAT's reference of 9BL1-UP actually 9BL00001-? The manuals seem to match my machine. The manuals were the first place I went but could only find the diesel fuel block and hoses in the area where I had leaking oil which confused me even more.

I have been patiently waiting for someone to recommend drilling and tapping a hole in the frame to run a hose return line back into the HPCU but regardless of the level of additional filtration added I do not think i would ever be comfortable doing that.

sjspecialty said:

Hi Nige.
I do actually have both the parts manual you referenced and service manual SENR5302-04. I was a little confused if these were the correct manual because the cover references 9BL1-Up. My machine is 9BL02214. Is CAT's reference of 9BL1-UP actually 9BL00001-? The manuals seem to match my machine.

Click to expand...

Your assumption is correct. It's Cat shorthand, they always miss out the zeros. So 9BL1-Up does actually mean 9BL00001-Up and the documents you have are applicable to the machine you're working on.

With the guidance of members, I managed to break the track and pull the final drive. Not too bad of a job maybe 3-4 hrs and I didn't even need to remove sprocket segments or the rear track guard, just the sprocket covers. I decided to leave the machine on the ground and back it off the track to disengage the sprocket once the track was broken. The frame cavity did have oil in it but to my surprise was also about half filled with water and about 3/4 inch of mud at the bottom.

I didn't find a smoking gun regarding the oil leak. I am taking Cmark's advice and resealing everything while I'm in there. One of the special brake port orings was a little pringle shaped, the other was either missing or more likely fell into my oil and water recovery drum when the final came off. The 90 degree hydraulic fittings into the parking brake were not particularly tight and on one of the fittings the jam nut should have been backed off and the fitting inserted another full turn. It looked like the oring was pushed down into the fitting threads instead of the smooth area of the fitting. I did not see much sealant on the final drive flange face but it does look like it was relatively sealed. The only dirty areas on the mating surface were around the dowel pins one of which stayed in the machine and the other came out with the final.

The parking brake frictions and steels look new and there was plenty of clear sealant on the brake housing. About half of the final drive bolts seemed newer so I think someone was into the finals not long before we bought the machine in 2008.

My question now is how is the water getting into this cavity and is this cavity supposed to be drained in some manner? We have run the machine through some mud but I never recall operating it in deep water. Obviously the cavity is open up at the top where I had oil coming out and but it is mostly covered by the cab. Is the water just rainwater dripping in. Is there some other area that should be vented to let the water drain? Do other people find water in this area when pulling the finals? Based on the dirt and rust at the top of the brake housing the water has been pretty high at some point but it does look like the big oring did it job keep water out the the track drive motor. I would think freezing could be a big issue if water is allowed to sit in this cavity, replacing the seals should keep the oil out of the cavity and in the transmission.

I've never seen dirt and water in this compartment before. The only thing I can say is clean the mating surfaces properly (I like to rub them over with an oil stone to check for nicks and burrs) and use a good sealant.

*Edit. I wonder if you have a crack in the frame somewhere?*