782 Hydro Leak Help

[Jacob Michael]

My dad and I have been doing some serious wrenching on my red '79 782 lately. We knew it was leaking hydraulic fluid, so we dropped the transaxle and put in a new gasket between the transmission cases and a new cork gasket(those things are the work of the devil). We Put the tractor back together, and it runs and drives just like it should, but the transmission still leaks about a drop every 90 seconds, but only while the engine is running. We did the replacement all Saturday, (now it's wednesday) and waited til now to run the engine so the cork gasket could soak up oil.
The new leak is toward the top, right under the tunnel cover, beneath where the hydraulic lines tie in. Does anyone know what we can do to fix this leak? Will it go away with time? Or did we put in too much hydraulic fluid(we measured out 7 quarts like the manual said, but that overflowed)? I would love to hear your input on this issue :]

 

[-CӞ]

i’m certain Jacob that you did your 782 profile pic right,

but i can’t help with hydro leaks. fingers crossed a member of this community is familiar with a solution. -C3

 

[glippert]

I'm certain the leak won't go away with time. Probably the relief valves are leaking. If they are, check MachTech Direct on facebook or the web. Also, on my 782 I found one of the metal lines that go to the hydraulic cylinder was leaking at the nut, where it attaches to the hydro. I tightened it, but no improvement. When I removed the nut, I found the flare was completely broken off the end of the tube. I also had a leaky seal at the trunion shaft, which required disassembly of the hydro unit, as the seal is replaced from the inside. There's also a FAQ on how to find a hydro leak if you have trouble isolating the source of your leak. Good luck.

 

[mgonitzke]

Post a pic of the leak. From your description it sounds like the input shaft seal is leaking.

 

[Jacob Michael]

I'm certain the leak won't go away with time. Probably the relief valves are leaking. If they are, check MachTech Direct on facebook or the web. Also, on my 782 I found one of the metal lines that go to the hydraulic cylinder was leaking at the nut, where it attaches to the hydro. I tightened it, but no improvement. When I removed the nut, I found the flare was completely broken off the end of the tube. I also had a leaky seal at the trunion shaft, which required disassembly of the hydro unit, as the seal is replaced from the inside. There's also a FAQ on how to find a hydro leak if you have trouble isolating the source of your leak. Good luck.

Thank you for the feedback, grippers. We did notice that the leak seemed to be coming from the top of the unit, and I felt dripping under the hydraulic lines. Maybe we'll have to take them off and wrap them with Teflon tape.

 

[mgonitzke]

DO NOT use Teflon tape there. Those fittings are flared. The flare must seal, so not only will that not help, if a piece of tape gets into the charge pump it will ruin the hydro unit. Make sure the flares and fittings are not damaged. You may have a fitting that is not tight enough, but more likely the input shaft seal or release valves are leaking. A picture is worth 1000 words here.

 

[dschwandt]

Did you replace the filter as well when you re-filled the unit?
Clean everything off well and let dry.
then sprinkle thoroughly w/baby or talcum powder trying to get it everywhere there may be oil leaking, then wait or run the tractor a bit until the issue presents itself.
The powder will usually indicate and leave a trail to right where the leak is originating from.

 

[tkhoffman]

If you say it's coming from the very top of the unit...I vote it's leaky Relief Valves.

 

[Jacob Michael]

DO NOT use Teflon tape there. Those fittings are flared. The flare must seal, so not only will that not help, if a piece of tape gets into the charge pump it will ruin the hydro unit. Make sure the flares and fittings are not damaged. You may have a fitting that is not tight enough, but more likely the input shaft seal or release valves are leaking. A picture is worth 1000 words here.

Tank you for this crucial piece of advice. Luckily my dad and I haven't gone anywhere near my tractor today. We are both new at working on hydros. All we know is from a video by the youtuber Wood And Metal Shop Time.

 

[Jacob Michael]

Did you replace the filter as well when you re-filled the unit?
Clean everything off well and let dry.
then sprinkle thoroughly w/baby or talcum powder trying to get it everywhere there may be oil leaking, then wait or run the tractor a bit until the issue presents itself.
The powder will usually indicate and leave a trail to right where the leak is originating from.

Yes, we replaced the filter, which we got from a local Cub Cadet dealer. Sprinkling the unit with talcum powder seems to be a good idea to me, but I'm worried it could get into the system and mess it up if the leak is on top.

 

[Jacob Michael]

If you say it's coming from the very top of the unit...I vote it's leaky Relief Valves.

Thanks for the input. What do we need to do to fix the relief valves if that is the problem?

 

[Jacob Michael]

Thank you for the feedback, grippers. We did notice that the leak seemed to be coming from the top of the unit, and I felt dripping under the hydraulic lines. Maybe we'll have to take them off and wrap them with Teflon tape.

Sorry, the spell checker wouldn't let me type your username.

 

[Jacob Michael]

The hydro as seen from below. There is a little bit of oil on the filter. All this was clean Saturday afternoon.

 

[mgonitzke]

Yes, we replaced the filter, which we got from a local Cub Cadet dealer. Sprinkling the unit with talcum powder seems to be a good idea to me, but I'm worried it could get into the system and mess it up if the leak is on top.

It's not going to get sucked into the transmission through a leak. If there was suction, there would be no leak.

Need a picture from the top with the frame cover off, since you've said the leak is coming from that region.

 

[Jacob Michael]

It's not going to get sucked into the transmission through a leak. If there was suction, there would be no leak.

Need a picture from the top with the frame cover off, since you've said the leak is coming from that region.

 

[dschwandt]

If you are ever going to find the leak, you must get it all clean and dry first!
It could be coming from most anywhere and running the tractor, the fan blows it all over everywhere.
Spray the area down w/some mineral spirits and blow dry, then go from there using the powder.
You say it leaks when the tractor is shut off, correct?

 

[tkhoffman]

The two large nuts you show in the picture and the relief valves. They appear to be very dry.
Post #3 has a guy , Mach tech, who will take your valves, cut them open and fix them.
But they looked dry.

 

[Jacob Michael]

If you are ever going to find the leak, you must get it all clean and dry first!
It could be coming from most anywhere and running the tractor, the fan blows it all over everywhere.
Spray the area down w/some mineral spirits and blow dry, then go from there using the powder.
You say it leaks when the tractor is shut off, correct?

Incorrect. The transmission only leaks when it is under pressure, when the engine is running, for example.

 

[Jacob Michael]

The two large nuts you show in the picture and the relief valves. They appear to be very dry.
Post #3 has a guy , Mach tech, who will take your valves, cut them open and fix them.
But they looked dry.

Yes, I knew those were the relief valves. How do I do business with this Mach Yech character? Also, how much does he charge? I'm only 14 and still trying to track down a steady job so cash is an issue.

 

[dschwandt]

Incorrect. The transmission only leaks when it is under pressure, when the engine is running, for example.

OK, I stand corrected.
But the same leak discovery procedure still applies.
You won't need to run it very long either for it to shoe up if that's the case.
Good luck.