**HELP** JCB 803 Slew Motor **HELP**

dhas

dhas

Active member
Hi Folks.
I'm looking for some help on an ongoing issue I am having with my 1995 JCB 803 and her slew motor/gearbox. With several years she has been leaking hydraulic oil through the gearbox. The motor on top forcing hydraulic oil down through the gearbox and on the drive gear on the bottom of the gearbox. We did the seals on the gearbox several times and 3 years ago I replaced the hydraulic motor on the gearbox and re did the seals in the gearbox. Fantastic.. It worked.. For a short while! I have noticed she is yet again leaking hydraulic oil through the gearbox 😭 has anyone had similar problems? Is it a possible pressure issue? I've just had enough of this now 🙈
 
V8Druid

V8Druid

do it as well as you can,but learn to do it better
is the slew supply pump separate to the main pumps, or draws from the main circuit? Mine has its own direct coupled 290 bar pump ... mains are 340bar .... perhaps as you say there is/should be some sort of pressure reduction for it :unsure:
 
dhas

dhas

Active member
is the slew supply pump separate to the main pumps, or draws from the main circuit? Mine has its own direct coupled 290 bar pump ... mains are 340bar .... perhaps as you say there is/should be some sort of pressure reduction for it :unsure:
It's from the one pump I believe. I replaced the main pump several years ago due to a hairline crack in the casing. Straight from the mains. It must be pressure when she hasn't done any work on hilly ground or lifting to put the motor under pressure 🤔
 
V8Druid

V8Druid

do it as well as you can,but learn to do it better
A case drain?
a line direct to tank ...... usually 1/4" ... which will allow any oil that bypasses the motor's internal seals to be relieved direct to tank, with no obstructions and not allow a build up of pressure in the motor's case
 
dhas

dhas

Active member
a line direct to tank ...... usually 1/4" ... which will allow any oil that bypasses the motor's internal seals to be relieved direct to tank, with no obstructions and not allow a build up of pressure in the motor's case
On the directional control valve bolted to the motor there is a small line under this? Two pipes attached and a small line under this black casing. Must be the pressure relief 🤔
 
V8Druid

V8Druid

do it as well as you can,but learn to do it better
On the directional control valve bolted to the motor there is a small line under this? Two pipes attached and a small line under this black casing. Must be the pressure relief 🤔
you mean case drain ? quite poss., but as Rory said .... really need a hydraulic schematic to be sure :unsure:
 
V8Druid

V8Druid

do it as well as you can,but learn to do it better
you mean case drain ? quite poss., but as Rory said .... really need a hydraulic schematic to be sure :unsure:
could try to trace the small line back to the tank, or to a free to tank line - very often tee-ed into other free to tank lines ... me Hydrema is a 'rat's nest' of FTT lines tee-ed into each other .. all over the place !! .... but handy if you needed to tee into one, being all over the place
 
dhas

dhas

Active member
could try to trace the small line back to the tank, or to a free to tank line - very often tee-ed into other free to tank lines ... me Hydrema is a 'rat's nest' of FTT lines tee-ed into each other .. all over the place !! .... but handy if you needed to tee into one, being all over the place
Thanks very much for the help 🙏🏻 I'll check what drawings I have and with my local JCB dealer. Be a couple weeks before I get home to it again but I'll keep you updated 👍🏻😊
 
jd6820

jd6820

Active member
Yeah I'm with the others on this. Was gonna comment earlier but got side tracked. Usually on the slew motor you have three connections. Two bigger lines (rotation feeds) and a case drain back to tank (small line on its own). Every JCB i've worked on has this. Can't find an 803 manual in my collection but 8052 shows drain line to tank.
 
jd6820

jd6820

Active member
Yep, just had a gander at the parts diagrams. It should have a return line to the motor that heads back to the main valve chest, not the tank directly. 1/2" bore low pressure hose. The other two hoses are 3/8 bsp high pressure. Heading to the valve chest nearest the seat. So just check the line isn't kinked or blocked. Fastened with jubilee clips according to parts book. I'd reckon that would be reason for seals blowing, that or relief pressure set too high but very unlikely compared to the alternative.
 
dhas

dhas

Active member
Yep, just had a gander at the parts diagrams. It should have a return line to the motor that heads back to the main valve chest, not the tank directly. 1/2" bore low pressure hose. The other two hoses are 3/8 bsp high pressure. Heading to the valve chest nearest the seat. So just check the line isn't kinked or blocked. Fastened with jubilee clips according to parts book. I'd reckon that would be reason for seals blowing, that or relief pressure set too high but very unlikely compared to the alternative.
Hi jd6820. Thank you very much for looking into this for me. I'll give a gander and trace the lines back along and see what I come up with. I'm hoping it's something as simple as this. I'll keep ye updated 👍🏻😊
 
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