743B leaking oil into the chain case, which seals are bad

[rogerh]

All, I know this subject has been hashed over several times, but I have reason to believe my 743B is leaking hydraulic fluid into the chain case. (I opened the plug at the front of the chain case to find clean oil (probably hydraulic fluid) gushing out. I used a siphon hose to remove some more fluid and found what looked like water and then some dirty oil started flowing out). So, I removed the drive motors and as per the service manual, removed the removable seal carriers (one on each side). My questions is this, are the seals mounted in this removable seal carrier the ones that need to be replaced to cure the problem (there appear to be two seals in each of these seal carriers). The manual also indicates to replace a large o-ring that fits between this removable seal carrier and the motor carrier ... hopefully these parts come as a kit (2 seals and o-ring). As for how water got into the chain case, anyone have a clue ? I will say that I had to take the engine out to get to a hydraulic leak that I thought was coming from the oil cooler, turns out it was just a hose that connects to the cooler. Anyway, I power washed the engine bay while the engine was out and I could have forced some water in through the chain case breather, other than that I don't know.

 

[Tazza]

With the drive motors off, you should see a shaft that the drive motors shaft goes into, around here is the seal you need to replace. It should be only one seal, there is an O ring that seals the carrier against the drive motor.
The water probably got in through an inspection cover, there is one under the pump and one under the park brake. The gaskets are always failing allowing water in. Use good quality silicone to seal them up, do the bolt threads too.

 

[rogerh]

With the drive motors off, you should see a shaft that the drive motors shaft goes into, around here is the seal you need to replace. It should be only one seal, there is an O ring that seals the carrier against the drive motor.
The water probably got in through an inspection cover, there is one under the pump and one under the park brake. The gaskets are always failing allowing water in. Use good quality silicone to seal them up, do the bolt threads too.

Just went to the dealer to pick up the new seals ... I understand your reply now. The seal carriers I removed from my machine were the original type of seal carrier (the first production type) .... these "old type"seal carriers had flanges on the outside so that you could grab them with pliers and pull them off the shaft ... in the carriers themselves were two seals that could be replaced. The new (replacement type) seal carriers have one seal in the carrier and the carrier is one complete replacement part ... thanks for the input Taza ... now I understand. Minus the tools the dealer has, how is the best way to install the new seal ? Thanks, Roger

 

[Tazza]

Just went to the dealer to pick up the new seals ... I understand your reply now. The seal carriers I removed from my machine were the original type of seal carrier (the first production type) .... these "old type"seal carriers had flanges on the outside so that you could grab them with pliers and pull them off the shaft ... in the carriers themselves were two seals that could be replaced. The new (replacement type) seal carriers have one seal in the carrier and the carrier is one complete replacement part ... thanks for the input Taza ... now I understand. Minus the tools the dealer has, how is the best way to install the new seal ? Thanks, Roger

The tool sure makes it easier, i spun one up on my lathe a few years back.
The hardest part is getting it started. You should be able to use a pin punch and work your way around. A helper would be very handy, get them to hold the opposite side while you get it started or else it may keep trying to flick the opposite side back out.
Lube up the lips that run on the shaft before you install it to prevent it pinching.

 

[rogerh]

The tool sure makes it easier, i spun one up on my lathe a few years back.
The hardest part is getting it started. You should be able to use a pin punch and work your way around. A helper would be very handy, get them to hold the opposite side while you get it started or else it may keep trying to flick the opposite side back out.
Lube up the lips that run on the shaft before you install it to prevent it pinching.

Tazza, thanks for all your help and advice ... one more question, since this is a different style seal than what I am replacing, I want to make sure I install it correctly. The new seal I have is metal on one side and rubber/plastic on the other .... which side is on the motor side, or a different way of asking, which side should I see once the seal is installed, the bronze looking metal, or the black side Thanks for the help, Roger

 

[Tazza]

Tazza, thanks for all your help and advice ... one more question, since this is a different style seal than what I am replacing, I want to make sure I install it correctly. The new seal I have is metal on one side and rubber/plastic on the other .... which side is on the motor side, or a different way of asking, which side should I see once the seal is installed, the bronze looking metal, or the black side Thanks for the help, Roger

If it's the seal i'm thinking of, the metal faces inwards.