743 hydro leak massive cannot pinpoint

[Alan Bechard]

Hi, I have an older 743 and have a massive hydro leak that as peculiar as it sounds I am having trouble narrowing down exactly where it is coming from. I originally thought I had blown the hydro cooler, but after pulling the panels and running it, the oil is down lower and it was blowing up through with the fan. My best guess is that it is at the very back / aft / engine end of the hydro assembly, or one of those lines there, I am just having a real hard time seeing anything forward of the engine other than the oil pouring out the bottom. I have the cab rocked open now, and was going to hotwire it and start it with the cab up next, but even now, I am having a hard time seeing the back of that hydro unit. Anyone have suggestions on what / where to look. Hate to pull the engine and not know exactly what I want to change, hard to troubleshoot if I cannot make it leak. Thanks for any help. Alan Bechard

 

[Fishfiles]

there are some steel tubes that run under the rear of the engine from one side to the other , probally a rust hole in one of those , a lot of pressure washing to get the dirt and grime out of there may help , I don't pull the motor for one of those tubes , run a hydraulic hose to replace it , cut the ends off the tube to give room to make the hose work --------------could be the pump input shaft seal also

 

[Tazza]

there are some steel tubes that run under the rear of the engine from one side to the other , probally a rust hole in one of those , a lot of pressure washing to get the dirt and grime out of there may help , I don't pull the motor for one of those tubes , run a hydraulic hose to replace it , cut the ends off the tube to give room to make the hose work --------------could be the pump input shaft seal also

My 743s lift lines that sit behind the blower housing had a reasonable abount of rust on them when i re-built it. They didn't leak, but in time they would have. Its just the location that allows water to sit with dirt/grease and allow them to rust. As Fishfiles pointed out, the main shaft seal could be leaking too. One way to test for this to with the cab in the air, put your hand to the rear of the pump, see of the housing is wet. Wipe it down with a cloth, run it without using lift or tilt, just drive around, then re-check if its wet, if so, its likley its your pump seal.
Naturally, don't wipe around the pump when the engine is running, you have seen the size of the cooling fan! that and hydraulic oil under pressure is very dangerous if it gets under your skin.

 

[Alan Bechard]

My 743s lift lines that sit behind the blower housing had a reasonable abount of rust on them when i re-built it. They didn't leak, but in time they would have. Its just the location that allows water to sit with dirt/grease and allow them to rust. As Fishfiles pointed out, the main shaft seal could be leaking too. One way to test for this to with the cab in the air, put your hand to the rear of the pump, see of the housing is wet. Wipe it down with a cloth, run it without using lift or tilt, just drive around, then re-check if its wet, if so, its likley its your pump seal.
Naturally, don't wipe around the pump when the engine is running, you have seen the size of the cooling fan! that and hydraulic oil under pressure is very dangerous if it gets under your skin.

Thanks guys, kind of what I was figuring, I will try running it with the cab up and maybe see something. As to seeing if anything is wet,,,,,,,,,, This thing is spewing out about a gallon a minute when running. Maybe a bit more. Everything is wet

 

[Tazza]

Thanks guys, kind of what I was figuring, I will try running it with the cab up and maybe see something. As to seeing if anything is wet,,,,,,,,,, This thing is spewing out about a gallon a minute when running. Maybe a bit more. Everything is wet

The other place they are known to leak is under the control block, look at the hose right at the bottom that loops upwards. This one is a pig to replace and they DO crack and fail, but it should not sling oil onto the cooling fan....

 

[rmo]

Thanks guys, kind of what I was figuring, I will try running it with the cab up and maybe see something. As to seeing if anything is wet,,,,,,,,,, This thing is spewing out about a gallon a minute when running. Maybe a bit more. Everything is wet

Hi Alan, I've been an avid reader & really appreciate peoples input. I have only yesterday had the same problem on my 743B. I haven't been able to locate the large leak yet & was wondering how you went with your issue. What did you find was the cause & how did you go about fixing it. Cheers Rod