BOBCAT T190 CONTROL VALVE PROBLEM

[Philosaw]

I have a foot control T190 that has been having a sticking problem with the lift and tilt control. When I go to lower the bucket, it has a hard pedal which when pushed hard will allow the bucket to lower, but with a very sudden jump. We noticed that when the tilt pedal is touched at the same time, it will make the sticking lowering pedal work a little better. I looked over the linkage and found nothing and determined that it must be a valve problem. Since it's a T190, the lift and tilt spools cannot be removed with the valve body in place, so I removed it and have it on the bench. My question is should I also look to another part of the valve to repair while it's out or would this problem be limited to the lift/tilt spools? I should add that it's only been about 500 hrs since I rebuilt the spools due to a leaking problem and it worked perfectly until now. Any ideas would be greatly appreciated.

 

[crewchief888]

are your pedal pivots rusted and sticking?

 

[Philosaw]

Thanks for answering Crewchief. No, I had gone through it totally but it didn’t change a thing. The fact that the lower only was affected made me think valve. When I’d touch the tilt it would jump down pretty hard.

 

[crewchief888]

rusted detent balls/springs in the lift detent?

 

[bobatack]

or just by chance your aux hydraulics are locked on

 

[Philosaw]

Good idea. I’ll take a look. Thanks!

or just by chance your aux hydraulics are locked on

Good idea but it happens when we're operating with or without the auxiliary on. Thanks for the response.

 

[Philosaw]

rusted detent balls/springs in the lift detent?

I took apart the detent assembly which was missing the dust cap and while it wasn't totally clean, it wasn't all that bad either. Your idea makes sense to me because it feels like there's some back pressure on the lift spool that is relieved when I touch the tilt. I'm kind of afraid to reinstall the valve body without finding something more definite. Not an easy job

 

[crewchief888]

FWTW your aux could be stuck on without being energized. to eliminate that possibility you can try this.
engine running,
PTO button on
aux button on
try your hyd functions,
use the paddle switch on the right hand handle in both directions while operating the hyds and see if it starts working.
IF it does, one of the aux stems is stuck open

 

[Philosaw]

Thanks! I’ll try that when I get it back together. Seems like a good lead.

 

[Philosaw]

FWTW your aux could be stuck on without being energized. to eliminate that possibility you can try this.
engine running,
PTO button on
aux button on
try your hyd functions,
use the paddle switch on the right hand handle in both directions while operating the hyds and see if it starts working.
IF it does, one of the aux stems is stuck open

On second thought, I have the valve out so I’d be pretty dumb not to remove the auxiliary spool and solenoids and rebuild them. Easy now, horrible later

 

[ozarkag]

Easy to access the solenoids with the valve in the machine, as they are on top. We just had a T190 that needed both aux solenoid stems replaced. Had to order the newer ones and matching coils as older ones were not available.

 

[Philosaw]

Thanks, I may just replace them both while I'm this deep into it. You're right that it would be easy installed, but when I put it back in, I sure would like to start it up and just go back to work. I'm going to try not to think about all the unnecessary work I've done if this ends up being the fix, LOL

 

[Philosaw]

On second thought, I have the valve out so I’d be pretty dumb not to remove the auxiliary spool and solenoids and rebuild them. Easy now, horrible later

at the risk of showing how dumb I am, I can’t see what happens when the coil is energized. Is there a ball inside the spool that moves?

 

[willie59]

Not dumb, that stuff is not common knowledge stuff. The auxiliary spool inside the control valve is shifted (moved) via hydraulic pressure bearing against either end of the spool. That pressure is delivered via either of the two proportional solenoid valves on top of the control valve. They're proportional because they will meter how much pressure is delivered to shift the spool from minimal amount to full shift, this allows you to control the speed of the aux hydraulics with the thumb sweep switch on the right drive lever. There's nothing serviceable with the solenoid valves aside from replacing the o-rings that seal them. And don't put 12V on those coils, They work off of a max 9 volt pulse width modulation signal from the main controller.

 

[Philosaw]

Thanks Willie59. I understand that when the coil is energized something must move. I don’t see anything that can move. The spool is fixed to the gland nut so what results from the coil being energized? i Can usually understand mechanical things, but this one has me stumped

 

[Philosaw]

Also, this is necessary for me to understand how the auxiliary valve could be stuck in the open position which seems like the most likely solution to my problem.

 

[willie59]

Farther down, the aux spool is in the main control valve. There are three spools, one for loader arm function, one for bucket tilt function, both of those have linkage connected to them to "shift" them. Above those two spools is the aux spool, no linkage, metal caps on the valve section, that spool is shifted by internal piloted hydraulic pressure from the proportional solenoid valves mounted at the top of the main control valve.

 

[ozarkag]

If you unscrew and remove the stem and look at the end of the stem, and also in the side thru the screen mesh, there is a center piece that moves when the coil is energized. On most solenoids you can push in the center and make sure it moves freely. As far as how it can cause the aux to be stuck, if either one of the solenoids leaks it will shift the main spool and pressurize the aux hydraulics.

 

[Philosaw]

Thank you Willie59 and ozarkag. The first thing I did after removing the valve was to inspect the lift and tilt spools, clean and replace seals. Then after Crewchief suggested the auxiliary might be stuck, I removed that spool, cleaned and replaced o-rings. Then I removed the two solenoids and stems, cleaned and replaced o-rings. I didn’t see a moving part in either the two solenoid stems or the aux spool. The manual shows a plug in the end of the aux spool that can be removed. I skipped that part. Is that where the movement is? Also, the little solenoid stems had o-rings without backing washers but the replacement o-rings came with them. Should I instal the backups and if so which side? Sorry this is so long and I do really appreciate your time spent with me.

 

[ozarkag]

The moving part I was referring to is inside the little solenoid stem. As Willie59 said, they are not serviceable.
Backup washers always go behind the o ring, on the side away from the pressure. I think, but am not certain, that on those solenoids the pressure is between the 2 o rings, or on the side of the stem. So from the end the seals would be backup, o ring,(space) oring, backup. There is a serial break on those solenoids, so make sure you actually have the correct o rings.