Pump Seal

[nobull1]

I just pulled the motor on my 763 to replace the hydraulic pump seal. After getting the motor out we realized that the replacement seal was incorrect for the pump. In all books, breakdowns, etc it shows a snap ring, seal carrier, seal, oring, and a snap ring to hold the bearing in. In my machine it is snap ring, metal ring seal, snap ring. The seal is for arguments sake 3” od by 1” id on my machine. The seal it shows in the book is 3/4” id by 1.75'” and a carrier to make up the extra 1.25”. Now the problem is the direct replacement seal (and old one) is not a vitcon so will not take the heat well. My guess is that is why they changed to a carrier system and a different seal. Unfortunately the new seal from Bobcat is not the right id for my pump so I don't know if the carrier would work either So with all the work to change this seal I really don't want to have to do this again. My thought is if I was to make a seal carrier the proper od to fit the pump and the proper id to fit a new seal, I can use a top quality vitcon seal and just make the carrier the proper id for the seal and buy the proper fit for the shaft and know I will never have this problem again. The only issue I have is how/and what to make the carrier of so to seal the carrier od to the pump (seal material will seal the new seal to the id of the carrier. An interference fit would be lucky to not have a leak IMO. The carrier will sit against a snap ring in the back with a washer and snap ring in the front to hold it in place. Any suggestions as what to do would be appreciated. I am going to make a decision tomorrow of what to do, as I don't want the machine to be down too long.

 

[skidsteer.ca]

Brian
You can't get a number off the old seal and check and see if a viton one is available in that size?
A seal supplier should be able to give you a spec on how much crush the outside should have if you decide to machine yours bigger.
Ken

 

[OldMachinist]

If you end up making a carrier for the seal cut a o-ring groove in the OD and use a viton o-ring to seal the carrier.

 

[nobull1]

If you end up making a carrier for the seal cut a o-ring groove in the OD and use a viton o-ring to seal the carrier.

Old Machinist
That was the thought if I have to make a carrier. I really don't want to make one if possible because I have to do the motor install before I can test it to see if it leaks.

 

[nobull1]

Old Machinist
That was the thought if I have to make a carrier. I really don't want to make one if possible because I have to do the motor install before I can test it to see if it leaks.

Ken
I will be at the seal dealer tomorrow to see if I can get a Vitcom seal or double lip or 5 mm instead of 10 mm wide and use two. The original seal is hard from heat, I suspect, and I don't know how long it has been leaking, If I thought I could get 1000 hours before it would leak I would be happy and not have a problem using the original type. This would before 3 or 4 years for me. I am just trying to decide what direction to go in if I can't get what I need. Decissions...Decissions
How are things with you Ken? Down here we are at ludicrous speed and getting busier.

 

[skidsteer.ca]

Ken
I will be at the seal dealer tomorrow to see if I can get a Vitcom seal or double lip or 5 mm instead of 10 mm wide and use two. The original seal is hard from heat, I suspect, and I don't know how long it has been leaking, If I thought I could get 1000 hours before it would leak I would be happy and not have a problem using the original type. This would before 3 or 4 years for me. I am just trying to decide what direction to go in if I can't get what I need. Decissions...Decissions
How are things with you Ken? Down here we are at ludicrous speed and getting busier.

If summer would ever come it would pickup. We had 10” of snow a week ago Sat that sogged the ground all up again, and more snow and rain since. My hoe and 773 was out on a job for 10 hours Sun, Mon, but they did all they could and the rest has to wait until it dries up some. My 553 is out installing playground equipment at a local school. First 2 jobs of the summer. Scooped up a new log splitter for $300 and converting it from 3 pt hitch to skidsteer, and putting a new skidsteer QA on our 7710 ford farm tractors loader. Then I'll have Dad fully converted to where we can swap attachments.
Good to hear your busy. Maybe check your oil cooler to see if its clean, my loaders generally run the oil pretty cool. If the seal is hard you might be running warm on the hydraulics
Ken

 

[nobull1]

If summer would ever come it would pickup. We had 10” of snow a week ago Sat that sogged the ground all up again, and more snow and rain since. My hoe and 773 was out on a job for 10 hours Sun, Mon, but they did all they could and the rest has to wait until it dries up some. My 553 is out installing playground equipment at a local school. First 2 jobs of the summer. Scooped up a new log splitter for $300 and converting it from 3 pt hitch to skidsteer, and putting a new skidsteer QA on our 7710 ford farm tractors loader. Then I'll have Dad fully converted to where we can swap attachments.
Good to hear your busy. Maybe check your oil cooler to see if its clean, my loaders generally run the oil pretty cool. If the seal is hard you might be running warm on the hydraulics
Ken

Update

I went to the seal dealer today and found the seal is proprietary (made exclusively for the manufacturer and not available elsewhere). I also found out it is a 150 lb pressure seal as well. This makes me not want to start modifying parts or adding new ones.This day is not starting out very good at all. So I figured I would go to the Bobcat dealer and try my luck there. After a little bit of searching we think we have found the right seal for the right pump. It “appears” that the pump in my machine is the newer version of two that were used. My serial number says the early one, but maybe it was changed years ago or the serial number breaks are wrong. Anyhow hopefully it is the right seal and it will fix the problem for awhile at least, and forever at best. We should have the motor back in and running later this week, if all goes well. By the way the guy helping me and doing most/all of the work had the motor out on the ground in less than four hours, for anyone who cares.

 

[thetool]

Update

I went to the seal dealer today and found the seal is proprietary (made exclusively for the manufacturer and not available elsewhere). I also found out it is a 150 lb pressure seal as well. This makes me not want to start modifying parts or adding new ones.This day is not starting out very good at all. So I figured I would go to the Bobcat dealer and try my luck there. After a little bit of searching we think we have found the right seal for the right pump. It “appears” that the pump in my machine is the newer version of two that were used. My serial number says the early one, but maybe it was changed years ago or the serial number breaks are wrong. Anyhow hopefully it is the right seal and it will fix the problem for awhile at least, and forever at best. We should have the motor back in and running later this week, if all goes well. By the way the guy helping me and doing most/all of the work had the motor out on the ground in less than four hours, for anyone who cares.

4 Hours for engine/pump out on a 763 is not bad time. It's good you're there with him-you'll learn more about your machine on this job than you ever could by just listening to folks.
While you have the engine out, it's also a great time to inspect the pump levers and centering mechanism, and see how it works and the way neutral is set up. Seeing it from the engine out perspective makes the hard-to-explain seem so obvious.
If your shaft seal went dry, I would think about changing the lever shaft seals and quad rings while it's out.
Good Luck.

 

[nobull1]

4 Hours for engine/pump out on a 763 is not bad time. It's good you're there with him-you'll learn more about your machine on this job than you ever could by just listening to folks.
While you have the engine out, it's also a great time to inspect the pump levers and centering mechanism, and see how it works and the way neutral is set up. Seeing it from the engine out perspective makes the hard-to-explain seem so obvious.
If your shaft seal went dry, I would think about changing the lever shaft seals and quad rings while it's out.
Good Luck.

Update
Yesterday we installed the seal in the pump and then the motor into the skidsteer. The hardest part was manipulating the motor/pump assy into the machine. There isn't much room and the pump throws a lot of weight to the back of the motor. In the end four of us manhandled the assy and got it in place. I was surprised at how quick it went back together and running. It only took three hours from start to finish including installing the seal. This was actually faster then coming out (4 hours). The biggest asset was having someone who had done this before. If I had tried this myself without seeing it done I am sure you could double the time. Now I am installing my outside and inside rear view mirrors as well as a flashing light and cab fan. We should have it all done tomorrow and be able to get some hours on it to check for leaks and whatever. The motor removal seems like a big job, but it all come out together and it's just a lot of wrenching.