Hey guys I’m new here didn’t know where else to look for help. I recently purchased a 1994 cat 928f with 5200 hrs on it. Everything was pretty good on it besides a bit of a rusty cab and I had to fix some wiring issues with the lights. Now I ran the machine maybe 5 hrs since I bought it and it’s been sitting in the shop. I noticed a large puddle of what looks to be hydraulic fluid under the rear end so I crawled under and cleaned it off. It looks like it is coming from 2 small fittings on the rights side? One looks like a male air line fitting but smaller and the other is almost flat. They could be turned so I tightened them but it’s still leaking. Any ideas on what’s going on? Thanks for the help ahead of time.
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1994 cat 928f rear end leaking?
- Thread starter brendin
- Start date
Nige
Senior Member
First - Serial Number. Help to identify Part Numbers
Take a photo and post it so we can see what you're looking at. Maybe take one from a distance as well for context.
Take a photo and post it so we can see what you're looking at. Maybe take one from a distance as well for context.
partsandservice
Senior Member
When oil is coming out there it is an internal brake seal leaking. You can probably observe the oil coming out while holding the service brake pedal.
partsandservice
Senior Member
I ran into this once many years ago on a 928. It appears the be a bleeder fitting but it is not, it is an indicator of brake seal failure. I am not an expert on that machine . So shortly after repairing the cat axle a had a John Deere come in, every time the service brake was activated oil would come of of a similar looking bleed screw. I removed the axle and tore it down but could not find any issue with the brake seals, turns out on the Deere it was actually a bleeder screw and the only thing wrong with it was the bleeder was loose.
heymccall
Senior Member
Left fitting bleeder for removing air from brake circuit.
Right fitting is breather for axle oil. When brake disc orings leak, brake oil is introduced into the axle oil, filling up the housing. That's where the oil exits after the axle housing is completely full.
Brake job time.
Right fitting is breather for axle oil. When brake disc orings leak, brake oil is introduced into the axle oil, filling up the housing. That's where the oil exits after the axle housing is completely full.
Brake job time.
heymccall
Senior Member
First and foremost, verify whether the axle is filled to the correct level.
Do you have an operators manual?
Do you have an operators manual?
heymccall
Senior Member
Oil only transfers when the brake pressure is sufficient enough to squeeze past the worn piston seal. So, a little oil is added everytime the brake pedal is depressed hard enough.
Nige
Senior Member
If you want an Operation & Maintenance manual then you can download one from the web in pdf form for less than $50, probably the best money you'll ever spend
I agree with HMC. The oil is likely coming from the "flat" fitting on the RH side of your photo which is the relief fitting for the axle housing. To the best of my knowledge only one side of the axle has that fitting, the other side will only have a brake bleeder like the npple of the LH side of your photo - please confirm that. If the brake piston seals are leaking and oil is going into the axle then the oil is coming from somewhere. Is the hydraulic tank level low or has oil been added to the hydraulic tank recently that you know of..?
Try doing a test to prove which fitting the oil is coming out of. Clean the area of all the accumulated oil, start the engine, and then have someone press and hold the brake pedal down while you go under the machine with a light and see where the oil comes out. After that check the axle oil level, pretty well guaanteed it will be over-full.
I agree with HMC. The oil is likely coming from the "flat" fitting on the RH side of your photo which is the relief fitting for the axle housing. To the best of my knowledge only one side of the axle has that fitting, the other side will only have a brake bleeder like the npple of the LH side of your photo - please confirm that. If the brake piston seals are leaking and oil is going into the axle then the oil is coming from somewhere. Is the hydraulic tank level low or has oil been added to the hydraulic tank recently that you know of..?
Try doing a test to prove which fitting the oil is coming out of. Clean the area of all the accumulated oil, start the engine, and then have someone press and hold the brake pedal down while you go under the machine with a light and see where the oil comes out. After that check the axle oil level, pretty well guaanteed it will be over-full.
The oil is not coming from the flat fitting it is coming from the bleeder. And it slowly drips oil when the brakes are not pressed. Just sitting it will slowly leak. I’m buying a new bleeder screw to make sure that one is not defective for some reason.
Thanks
Thanks
Nige
Senior Member
Is the oil coming from the bleeders on both side of the rear axle or just one of them..?
If you have to replace it the Cat Part Number is 5H-3701. Price about US$5.
A suggestion while you're in round that area. Remove the flat fitting and make sure you can blow through it from the inside. I've seen lots of them seized by paint or rust and that can cause other big $$ problems. If you want to replace it you need 8T-0336, about $2.
If you have to replace it the Cat Part Number is 5H-3701. Price about US$5.
A suggestion while you're in round that area. Remove the flat fitting and make sure you can blow through it from the inside. I've seen lots of them seized by paint or rust and that can cause other big $$ problems. If you want to replace it you need 8T-0336, about $2.
kshansen
Senior Member
- Joined
- Mar 11, 2012
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- 11,165
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- Central New York, USA
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- Retired Mechanic in Stone Quarry
Have you tried turning the bleeder ? It's basically the same as a bleeder for just about anything with hydraulic brakes, be it a Cat front end loader, Ford pick-up or even my Harley Sportster, heck even my wife's Vespa has fittings like that! I would replace with one from Cat as that way you know it's the right thread and length. Also not a bad idea to replace the other "flat fitting" just to be safe. Cost to replace all them will be less than the gas money to drive to the dealer!
kshansen
Senior Member
- Joined
- Mar 11, 2012
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- 11,165
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- Central New York, USA
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- Retired Mechanic in Stone Quarry
When you remove the one that is leaking I would be very careful to clean out the hole and make sure there isn't some crap down in the hole or guges in the seat area for the end of the bleeder valve.
Well I went to cat and got the new bleeder valves. They were leaking but the vent is also leaking very slowly so like someone said above it’s probably the brake seals went and are filling the axel. Cat said worst case of I bring them the diff 10k awesome Friday
kshansen
Senior Member
- Joined
- Mar 11, 2012
- Messages
- 11,165
- Location
- Central New York, USA
- Occupation
- Retired Mechanic in Stone Quarry
Well that sucks! Hate to say that if you don't have the means to safely remove and support the axle while working on it you might have to hire that job out.
I came close to having to do that job on I believe a 950F. I was asked to go to another plant to diagnose the oil leak on the machine and it was just like this 928F, coming out the vent/breather. But someone in upper management decided to farm that job out, I was actually hoping to get the job. The shop at the quarry has a 40 ton overhead crane, fork truck and carry-deck crane among other tools to work with so the size of the parts was nothing we/I could not handle!
Heck we had no trouble loading a 980G with a dead motor on a lowboy or swapping rear axles between two 988B loaders parked back to back in the shop among some other large things like stone crushers! Oh yea, back in the day it was nothing unusual to split 988B on two to have line boring of the center pins done!
But no! I could not handle a "big" job like dropping an axle out of a 950 F! Things like that were one of the deciding factors in retiring at 65.