There is nothing hard about it. There is obviously something wrong with the seals tho. They will need to be fixed. I can’t do anymore damage by have the wrong fluid in the diff? I can’t have the machine go down when it’s in use is all. Thanks alot for the link to the o&m manual. It is a huge help.
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1994 cat 928f rear end leaking?
- Thread starter brendin
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kshansen
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The thing I would want to know is does it take one day or one month to leak a gallon of oil in to axle.
If it is passing a gallon a day I would make it a priority to get the leak fixed. But if it takes a month or more I would be looking for time in the work schedule for myself and who ever you are going to have do the work.
Might be able to plan it for a time when machine and mechanic both are more or less free. That way you don't have to air freight in a part that you did not expect you would need.
heymccall
Senior Member
I'm sure that you are all aware that the leak is most prominent when the brakes are applied.
Right way is to disconnect feed line to one side a pump it up with a porta power and gauge. With knowing test spec, I'd call 750psi a good number. If it holds, test other side.
Odds are that only one side is leaking, but there is no way I'd only reseal one.
Does Caterpillar have a brake lining inspection hole on each side like on my Deere machines?
Right way is to disconnect feed line to one side a pump it up with a porta power and gauge. With knowing test spec, I'd call 750psi a good number. If it holds, test other side.
Odds are that only one side is leaking, but there is no way I'd only reseal one.
Does Caterpillar have a brake lining inspection hole on each side like on my Deere machines?
Yes there is a inspection hole to check the brake measurements I’ll do doing that this weekend to see how they are. I ran the loader for 3 hours today and the fluid has not risen any that I can tell on the dipstick. I’m going to keep running it when I have time to see how long it takes to start filling up.
Nige
Senior Member
That’s what I was alluding to in asking how long since the rear axle oil was last changed, because I’m betting that was the last time anyone looked at that dipstick. Obviously because you only recently bought the machine you don’t know. However if you were to discover that the oil was last changed say 18 months ago (for the sake of throwing a number out there) I imagine that might change your perception of how urgent it would be to get into the axle to replace the leaking seal in the brakes, because that would be the length of time that the amount of oil you drained the other day had taken to accumulate.
The oil in the rear axle should be an SAE50 TO-4. To mix small quantities of SAE10 with that wouldn’t do any harm in the short term, especially if the SAE10 was also a TO-4 oil.
The oil in the rear axle should be an SAE50 TO-4. To mix small quantities of SAE10 with that wouldn’t do any harm in the short term, especially if the SAE10 was also a TO-4 oil.
Well I’m going to play it out the next while and if it does not seem to be going up to fast I’m going to drain the axel and fill it with the correct oil. And hope it takes 18 months to fill back up. And if it were my guess I’d say it’s been a long time since it’s been done based on the amount of crud and such on all the drain plugs and the dip stick.
Nige
Senior Member
I think that's a sensible attitude. Until you have a handle on exactly how much oil is leaking in what time frame IMHO it would be impossible to make an informed decision on how urgent it is to make the repair.
When it comes to removing the axle there will be plenty of help available to guide you through the process.
When it comes to removing the axle there will be plenty of help available to guide you through the process.
kshansen
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And if you do come back to ask for the "Remove Rear Axle" instructions be sure to include the S/N in that request even if you have posted above in this thread, save who ever sees the request from having to scroll through several pages of the thread trying to find it.
I would also suggest you do post that request right on this thread to keep continuity to the problem.
good Luck!
I would also suggest you do post that request right on this thread to keep continuity to the problem.
good Luck!
Well I ran the loader on aug 28th for about 3 hours and it’s just been sitting since. The oil on the dip stick for the rear diff has risen about 1/2 and inch. It must be a bad seal leak if it’s leaking while it’s just sitting right? If I run the machine I thought it would fill up faster while I’m running it and using the brakes. It seems to fill up faster when it’s just sitting.
Nige
Senior Member
It can't leak "just sitting" in my opinion. It will only leak when you actually apply the brakes, because it is hydraulic oil from the brake operation side that when you press the brake pedal is leaking past the brake piston seal into the axle housing.
How much did the oil level in the hydraulic tank go down in the same time..?
See the illustration of the differential and one of the brake packs below. The hydraulic piston for the brake is #6 and it has two seals (circled) on it. When you press the brake pedal those two seals are going to be what's leaking, either on one side of the machine or both I don't know. Either way it would be normal to replace the seals on both sides at the same time. The BIG problem about disassembling the brake packs is that it requires the axle to be removed from the machine and stood up in a vertical position, it can't be done horizontally.
How much did the oil level in the hydraulic tank go down in the same time..?
See the illustration of the differential and one of the brake packs below. The hydraulic piston for the brake is #6 and it has two seals (circled) on it. When you press the brake pedal those two seals are going to be what's leaking, either on one side of the machine or both I don't know. Either way it would be normal to replace the seals on both sides at the same time. The BIG problem about disassembling the brake packs is that it requires the axle to be removed from the machine and stood up in a vertical position, it can't be done horizontally.
kshansen
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Have to agree with Nige, seems strange that you say it is filling up more when parked than when being used. Can't see why there would be any pressure going to the wheel brakes with it parked and engine off.
Could it be that the side of the axle with the dipstick in it was just lower than the other side? Maybe when you checked it the first time the dipstick was at the high side and the next time you checked it it was at the low side of the axle.
I thinking the only way to prove it is leaking while parked would be to drain down till it was at the right level and then without moving or running the machine check it after a day or two.
I can see finding the oil level to go up slightly while parked if one was to check it right after running and then check again after it had set for some time which might give time for oil to drain back from planetaries and off the inside of the housings.
Careful checking of both hydraulic and axle oils is important to be sure what is going on. And check it with machine nice a level every time.
As an example we had a Mack truck at the quarry that when parked in shop and oil was checked right at the full mark. Then when parked outside next to shop it would show below the add mark. The dipstick was at the rear of oil pan and where the truck was parked outside looked level to the eye but was actually a very slight grade and truck was facing towards the low end of parking space!
Could it be that the side of the axle with the dipstick in it was just lower than the other side? Maybe when you checked it the first time the dipstick was at the high side and the next time you checked it it was at the low side of the axle.
I thinking the only way to prove it is leaking while parked would be to drain down till it was at the right level and then without moving or running the machine check it after a day or two.
I can see finding the oil level to go up slightly while parked if one was to check it right after running and then check again after it had set for some time which might give time for oil to drain back from planetaries and off the inside of the housings.
Careful checking of both hydraulic and axle oils is important to be sure what is going on. And check it with machine nice a level every time.
As an example we had a Mack truck at the quarry that when parked in shop and oil was checked right at the full mark. Then when parked outside next to shop it would show below the add mark. The dipstick was at the rear of oil pan and where the truck was parked outside looked level to the eye but was actually a very slight grade and truck was facing towards the low end of parking space!
Nige
Senior Member
Thinking aloud I wonder if there is a leak somewhere in the brake accumulator side that is causing a slight residual pressure in the brake system that is just enough to weep it past the piston seals..?
To the OP. Run the machine. Set the oil to the correct level in the rear axle dipstick and carefully note the quantity of oil you drain out. Also note the oil level in the hydraulic tank.
When you have shut down the engine press the brake pedal numerous times until it goes "hard" under your foot. That means that the brake accumulator has been completely discharged. Note how many pumps of the pedal it takes for this to happen.
Leave the machine stand for a few days in one spot and go back and check the hydraulic tank and rear axle oil levels again.
To the OP. Run the machine. Set the oil to the correct level in the rear axle dipstick and carefully note the quantity of oil you drain out. Also note the oil level in the hydraulic tank.
When you have shut down the engine press the brake pedal numerous times until it goes "hard" under your foot. That means that the brake accumulator has been completely discharged. Note how many pumps of the pedal it takes for this to happen.
Leave the machine stand for a few days in one spot and go back and check the hydraulic tank and rear axle oil levels again.
Ok will do this weekend. I drained it the first time to get it to the correct level and I drain out roughly 25L to get it to the correct level. But the hydraulic tank was not low 25 L it was down maybe 12L but I’m not sure what the previous owner was doing.
kshansen
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Good once you get a solid baseline to make judgments from it will be much easier to make an educated guess at how bad the leak may be and how soon you need to be looking into a major repair.
Ok. So I drained about 10l for oil from the diff so it was at the bottom of the add mark. Let it sit. And it is still filling up. Any ideas? I didn’t touch anything else because I wanted to see it was actually leaking when just sitting. Does the park brake have anything to do with these brakes or is it a different setup.
kshansen
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Did you do as suggested by Nige above?:
To the OP. Run the machine. Set the oil to the correct level in the rear axle dipstick and carefully note the quantity of oil you drain out. Also note the oil level in the hydraulic tank.
When you have shut down the engine press the brake pedal numerous times until it goes "hard" under your foot. That means that the brake accumulator has been completely discharged. Note how many pumps of the pedal it takes for this to happen.
Leave the machine stand for a few days in one spot and go back and check the hydraulic tank and rear axle oil levels again.
At least give us an idea how much and how fast it is "filling up." Also is the hydraulic oil also going down?
As for the parking brake, going by SIS it is located on the drive-line just forward of the transmission. A basic drum type brake that is actually your simple mechanical brake. Lever should be to left of operators seat.
No I didn’t not do exactly what he said. I drain it and did not want to start it or touch the brake to see if it leaks sitting. It filled up about 8l in 3 days. 2.5 days. The hydraulic oil was down a bit yes. Where else could the oil come from? I know the seal leaks I’m just wondering why it leaks while sitting. Everyone says it should leak when the brakes are being applied
heymccall
Senior Member
If the seals are really bad, or the piston is cracked, remember, the feed line to the brakes is higher than the axle, and siphoning can occur.
As an aside, does a Cat loafer have recircultor pumps, screens, and coolers like my later Deeres? If the recirculate pumps are hydraulic driven, could that be the source?
Is there a rear differential lock, and, if so, is it hydraulically activated? Could that be a leak source?
It would seem as if the easiest course of action is to disconnect the brake feed to the rear axle and pressurize the brakes with a porta power. Someone else will chime in if the pressure for testing should be 750 psi or not.
As an aside, does a Cat loafer have recircultor pumps, screens, and coolers like my later Deeres? If the recirculate pumps are hydraulic driven, could that be the source?
Is there a rear differential lock, and, if so, is it hydraulically activated? Could that be a leak source?
It would seem as if the easiest course of action is to disconnect the brake feed to the rear axle and pressurize the brakes with a porta power. Someone else will chime in if the pressure for testing should be 750 psi or not.