New member with 1995 853

[wateka]

O-ring TLDR:
use the backup o-rings. Don't double o-ring it. Details below.

Hydraulic tank sock filter:
order a new one or find a washer/machine bushing with an ID that will fit the sock and an OD that will keep it from falling into the tank but allow the fill cap to screw on, and solder the sock to the washer.

The groove: if you are referring to that triangular shaped raw metal in your picture, is likely from the neutral return spring rubbing against the housing.

The servo spool fix kit you mentioned is what I think is a replacement control sleeve and, if so, is covered in the below attached Service Letter dated 12/14/1995.

O-ring details:
I'm not an engineer, but I did just rebuild my entire 853 hydraulic and hydrostatic system and replaced every o-ring and backup o-ring in there. Part of my learning curve required reading about o-rings to make sure I was ordering the correct size (the "dash number") and material. After learning the function of the backup o-ring, it makes perfect sense as to why they are included, and how the double o-ring idea is not going to achieve the same outcome.

More details at the link and a PDF (of the same link) below:

Backup Rings | Global O-Ring and Seal

Backup rings provide extrusion resistance, preventing o-ring and seal damage when subjected to high pressures, temperatures, and larger extrusion gaps.

www.globaloring.com

 

[Mitch500]

O-ring TLDR:
use the backup o-rings. Don't double o-ring it. Details below.

Hydraulic tank sock filter:
order a new one or find a washer/machine bushing with an ID that will fit the sock and an OD that will keep it from falling into the tank but allow the fill cap to screw on, and solder the sock to the washer.

The groove: if you are referring to that triangular shaped raw metal in your picture, is likely from the neutral return spring rubbing against the housing.

The servo spool fix kit you mentioned is what I think is a replacement control sleeve and, if so, is covered in the below attached Service Letter dated 12/14/1995.

O-ring details:
I'm not an engineer, but I did just rebuild my entire 853 hydraulic and hydrostatic system and replaced every o-ring and backup o-ring in there. Part of my learning curve required reading about o-rings to make sure I was ordering the correct size (the "dash number") and material. After learning the function of the backup o-ring, it makes perfect sense as to why they are included, and how the double o-ring idea is not going to achieve the same outcome.

More details at the link and a PDF (of the same link) below:

Backup Rings | Global O-Ring and Seal

Backup rings provide extrusion resistance, preventing o-ring and seal damage when subjected to high pressures, temperatures, and larger extrusion gaps.

www.globaloring.com

View attachment 5693
View attachment 5694

Thanks for that info. I think I'll re oring first to see if it solves my leak. Those replacement sleeves are $330 each at bobcat.

Only reason I tried to double oring was because i read on this forum that it will help seal the sleeve if the pump housing is damaged from grit riding the oring. Maybe I'm over thinking this and I'll just put the back up oring (the white Teflon washer) on and call it a day.

Also this is the groove I was mentioning, that's probably machined from factory? Just seems strange because the service bulletin in the document says the new sleeve places the oring 0.05" below to seal on a new surface of the bore.

 

[Mitch500]

Ok got everything back together last night. Today I fired it up and noticed the hydraulic pump was slightly whining wrrrrrerrrrrrr sound. Nothing loud or alarming. Machine moved forward and back boom lifted up and down fine and bucket tilted.

But still a slight audible wrrrrrrrr-ing sound. I did notice in the hydraulic reservoir the oil was quite bubbly lots of micro bubbles. I check all the large suction lines and noticed the ones on the back of the pump were kinda loose, they took a good couple revolutions to tighten. So I did all of those. Maybe air was intruding there.

Im going to let the machine sit and let the bubbles rise out and see if the sounds gone.

But I'm wondering if it normal for the first bit for the hydraulic oil to bubble up after hydraulic filter change. I also drained the case and cleaned case filters as well as replaced the o-rings on the high-pressure lines at the left drive motor.

I've only had it running for a few mins, thought I'd consult you guys before doing anything wrong.

Also I did change the steering spool and sleeve o-rings. So far there was no leaks from there. I'd assume the pump wouldn't create vacuum and suck air from those. They seem like they would leak oil from pressure if they were not sealing.

Here's pic of oil in hydraulic tank:

 

[brdgbldr]

Bobcat self purge air that is in the system when it is introduced from oil changes, cylinder rebuilds etc. Let the foam clear, too off oil and go again. It will eventually stop foaming.

Just make sure to keep checking the oil because air can also be introduced from bad seals, loose hoses etc.

 

[Mitch500]

Got around to pulling the pick up tube from the tank. I made a little pry tool and popped it out from under the hydraulic pump. It was missing the check ball and the hose was heavily rotted. Waiting on bobcat dealer to bring the new part in.

Also replaced the drive belt, it had a big split down the middle and was cracked all through the underside.

Installing the new one was a PITA. But I managed to get in on and tensioned. The manual talks about a spring loaded tensioner. I did not have that so I just tightened it snug with about 1/2 or so play.

 

[Tlawdogg]

The small tensioner in center, isn't it spring loaded or not? I know they have two types of "Tensioners" for those years.

 

[Mitch500]

The small tensioner in center, isn't it spring loaded or not? I know they have two types of "Tensioners" for those years.

Mine was not spring loaded, it also didn't have the arrow indicator.