another winter, more MLS valve problems...

   / another winter, more MLS valve problems... #1  

Rudevette

Bronze Member
Joined
Jan 22, 2009
Messages
99
Location
End of the road, NE South Dakota
Tractor
Bobcat CT235
First off I really don't care if you've had your tractor for 9000 years and ran a billion hours with no mls valve problems.

That said, I just turned 180 hours and my mls valve is done again. This will be the fifth time I have had it out, torn it apart, found nothing really wrong, put it back together, and so far every time it works for awhile after that. It won't go up. If I put the receiver hitch attachment on it it will go up once the oil is warmed up but has a 5 second delay before lifting. With the snowblower on or posthole auger it won't go up at all unless I roll the loader bucket all the way one way or the other to deadhead the hydraulics for a few seconds then let go. Then it will go up about a third of the way, then I have to do it again. So now it's back in the shop to do the same old same old again, and I guarantee it won't last long before it quits working again. :mad::mad:

The three point on this thing is pretty much worthless scrap iron.
 
   / another winter, more MLS valve problems... #2  
Sounds like possibly a pressure relief in the valve stuck open...

Aaron Z
 
   / another winter, more MLS valve problems...
  • Thread Starter
#3  
The part that really chaps my $^*@&($(&$^ is that when I take the MLS apart all I find that is the slightest bit odd is the spools have the tiniest bit of drag to them when I slide them in the bore. All I do is slide them in and out by had for a little while until they drop right in and it's fine...... for a little while. Pretty soon I'm going to chuck those spools up in the lathe and turn them down a tad. What's the worst that will happen? It won't work? That'd just be a **** shame wouldn't it?
 
   / another winter, more MLS valve problems... #4  
reading your signature, Why not a 72 inch box blade?
 
   / another winter, more MLS valve problems...
  • Thread Starter
#5  
If I decide to keep this tractor it probably would be a 72". But I might just as well drag an I-beam behind from a chain because the 3 point won't lift a box blade anyway.
 
   / another winter, more MLS valve problems... #6  
Forgive my ignorance but if taking the MLS valve (whatever that is) apart and putting it back together again restores functionality but only for a short time doesn't that suggest that the problem is actually somewhere else in the hydraulic system? You take out the MLS which I'm guessing would have some effect on the rest of the hydraulics based on your comment that rolling the bucket affects how the 3-pt operates. So possibly a sticking valve somewhere else that comes free when you take the MLS out of the system? As I said, forgive my ignorance if I'm way off base here.
 
   / another winter, more MLS valve problems... #7  
What hydraulic oil are you using?
 
   / another winter, more MLS valve problems... #8  
If I decide to keep this tractor it probably would be a 72". But I might just as well drag an I-beam behind from a chain because the 3 point won't lift a box blade anyway.

Possibly you just hit the problem. If your 3 pt wont lift a box blade, then your Hyd pressure is low. Mine will fully lift a 1000 Lb tiller easily. Have you checked your system pressures, and do you have clean oil in the system.. Also check the hose quick connects. When my FEL started having issues, it came back to several bad quick connects - partially plugged with junk, or totally failed. They check good off the unit, but failed under pressure.

Service guy had a pressure gauge hooked up to a short quick connect to check system pressures at various points. he did need to adjust the pressure relief valve a bit. It was bleeding pressure too soon.

Hope this helps.
 
   / another winter, more MLS valve problems... #9  
Rudevette,
I presume this is on your Bobcat Ct235. If yes I also presume the front loader works fine since you state that you can roll the the bucket back and build pressure.

Since I am not familiar with Bobcat hydraulic system I am going to make a couple of assumptions.

1) This is an open center hydraulic system. I.e Gear pump
2) Pump flow goes to the FEL control and then feeds oil to the 3PH control.
3) The 3PH only has a surge / spike relief and no system relief.

It sounds like you are not getting flow to the 3PH hitch control and that the Power Beyond feature of your FEL control is not working or installed correctly.

I would look at the FEL control to determine where the power beyond port is. Now try and determine where the plug is in the FEL body that is used to convert this valve from non power beyond to power beyond capable. Make sure this plug is installed and that any O-rings are not damaged. This plug isolates the pressure chamber in the FEL valve from the Tank port in the FEL valve. Some use a special fitting, some use a pipe plug installed inside the housing, etc..

good luck
 
   / another winter, more MLS valve problems...
  • Thread Starter
#10  
I use bobcat hydraulic oil and bobcat filters. And have changed it twice.

I can almost guarantee that it's a spool sticking in the Mls because after I take it apart and polish the spools up a little bit with a rag and hydraulic oil it works for a little while. The Mls has a pressure relief built into it.
 
 
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