Bobcat T300 Hyd lock wont release.

[CharlieMurphy]

Hello all, I am new to this site and have a question about a t300 im working on. (525412911) (Levers) Runs great. All the lights come on when seated and bar is down and button pushed. All systems go.(No codes) However, there is a hyd lock somewhere. I have looked and looked for a block with a solenoid on it but I cant find one on this machine. I know on wheeled machines it has a magnetic solenoid operated lock that locks the gears, but this machine is all hyd and not gear driven... So its just running across a relief that is open or something. Its gotta have at least 2 or 3 hyd lines running to it as well as a solenoid w/wires.. Right??. Going to give this thing a better bath and look again. If anyone has any ideas please feel free to share.

Thank you for your time.

-D

 

[CharlieMurphy]

I think I've figured it out.. Hyd brake valve by the throttle linkage under the seat. They have it tucked up under there tight. So solenoid has full battery power (12v). Next is seeing if the spool is being shifted by the solenoid.

 

[CharlieMurphy]

K, proper voltage to solenoid. Now throws a "extreme low charge pressure" and will kill. I think either the positive filter is plugged or the screen on the charge pump may be clogged. going to check case drain for debris and also run with case drain lines apart to see how much leakage i have on either side.

So either...
Charge pump is bad, leakage, not supplying enough volume/pressure of oil
Positive filter is plugged, so oil runs across a relief back to tank, not releasing brakes
Screen on inlet of charge pump is plugged (cavitation) which is why they have the fuel solenoid turn off, and machine quits
Check case drain filters, tell me what condition motors are in and how much leakage is present

Im open for Ideas guys. Any help, ideas, thoughts is much appreciated. I refuse to give up and bring it to Bobcat. How the hell am I going to learn is I do that....

Thanks again
-D

 

[crewchief888]

low charge pressure warning could be caused by several things

low charge pressure, bad pump or debris in the charge relief
bad charge pressure switch
bad wiring on connection at the charge switch.

i'd verify charge pressure with a manual gauge, if it's good, replace the switch and/or fix the wiring
if charge pressure is low, dump the hyd filter into a clean container and check for debris (steel is from the drive motors, brass is from the pump)
also check the case drain filter for debris.

charge pressure is on the 8v system along with
seat bar
RH paddle switch
coolant temp
eng oil pressure
hyd charge

any or all of these sensors, may or may not throw the proper code,( especially with old software, it doesnt seem to happen as much with newer software)
pull the case drain filter and check it for debris

if you have a wiring issue it's usually within 3 or inches of the connector. the harness get pulled and twisted, strands of wire breaks inside the (visually) good insulation, or the connector terminals inside the harness get spread open and stop making contact.
oil & moisture inside the sender connection will also cause faults

:drinkup

 

[CharlieMurphy]

crewchief888,

Thanks so much for the reply. I new this was the forum for clear precise, easy to follow information.

There is a T in the charge line, before the brake valve, that has a brass "male" quick couple sticking straight up. I tapped into that with my gauge and at idle it reads 200-250 psi. If I rev it up I can see 300-350 psi max. Then the alarm goes off and machine dies.

When I put my volt meter to the terminals of the wires running to the brake solenoid I have 15.4 volts with the machine running. Too much??

I also noticed when I had it idled up that it threw a too high voltage to the fuel level or something like that.

Your talking about the main Hyd filter right there when you have the cab up right? cant miss it... I will check that tomorrow. ty

Checking the case drains tomorrow as well! ty

Is the charge pump located right in the center of the hydrostat? Charge line runs from back of hydro under the hydro and up to the control valve and break valve right?
Is there a brass cone filter in there too that can restrict? I keep reading about a "positive filter"

Again, Thank you for the help!

-D

 

[willie59]

Welcome to HEF CharlieMurphy. :drinkup

I don't have a manual for a T300 so I can't help much here, but regardless of model, if your getting 15.4 volts on a component, don't be surprised if the main controller shuts the machine down for high battery voltage as well, 15.4 volts is getting up there.

 

[crewchief888]

crewchief888,

Thanks so much for the reply. I new this was the forum for clear precise, easy to follow information.

There is a T in the charge line, before the brake valve, that has a brass "male" quick couple sticking straight up. I tapped into that with my gauge and at idle it reads 200-250 psi. If I rev it up I can see 300-350 psi max. Then the alarm goes off and machine dies.

When I put my volt meter to the terminals of the wires running to the brake solenoid I have 15.4 volts with the machine running. Too much??

I also noticed when I had it idled up that it threw a too high voltage to the fuel level or something like that.

Your talking about the main Hyd filter right there when you have the cab up right? cant miss it... I will check that tomorrow. ty

Checking the case drains tomorrow as well! ty

Is the charge pump located right in the center of the hydrostat? Charge line runs from back of hydro under the hydro and up to the control valve and break valve right?
Is there a brass cone filter in there too that can restrict? I keep reading about a "positive filter"

Again, Thank you for the help!

-D

what voltage are you getting at the battery at full throttle?

you shouldnt see more than 8v on a power wire to any of the sensors.

sensor supply voltage is regulated by the main controller.

:drinkup

 

[CharlieMurphy]

I will check. I think thats the least of this guys worries. Enjoy.

 

[CharlieMurphy]

I got 3 rags full from that case drain filter. I believe that it clogged, creating a pressure differential, compressing the brass bb's together causing resistance to go up which is why the end of that brass filter is blown out. I have no clue now how bad the damage is. I think sense how much worse could it get, is to get 3 hyd filters and a few brass cone filters and 20 gal of hyd fluid and see if I cant flush it out. I know it needs to all come apart to properly flush but, this guy wants a quick fix so he can sell it. Im not sure if this is going to be a quick fix.......

The main hyd filter was full of crap too. parts of an oring, brass, steel, maybe aluminum.

Do you think its worth fixing? guy has 11k in to it. 4400hrs.

Thanks again guys!!!

-D

 

[willie59]

I wager you're looking at two drive motors for that machine and hope it hasn't started chewing up the drive pumps.

 

[CharlieMurphy]

I will keep you guys updated....

Question, Bobcat, they dont make the hydrostatic drives right? They slap there tag on it tho huh....??? Sunsource or parker or eaton. ect is who makes em. right?

 

[willie59]

Well, I can't speak for every Bobcat machine and the components therein which includes your machine. But generally speaking, when it comes to hydraulic components, pretty much any brand, not just Bobcat, has hydraulic components that are produced by companies that specialize in that specific component. Yes, over the Bobcat years, the drive pumps have been supplied by several brands, Vickers, Sunstrand, Danfoss just to name a few. Rexroth made the drive motors for a number of the track machines. But if you're thinking you can pick up an aftermarket source for pumps or motors, you typically run into one of two things, 1) the motor or pump has specific features (spec'd by the end OEM) and those features are not readily available in the "off the shelf" units, or 2) the specific features of a pump/motor are "proprietary", meaning, yes, Rexroth makes the drive motor, but that specific motor with it's specific features are available only through the OEM, they're not available to sell via outside/other vendors.

 

[lantraxco]

Or they used them for two years, were the only customer buying them, and they went obsolete when they updated the model so neither the OEM or the manufacturer supplies replacements or parts any more.

 

[crewchief888]

the last machine we had that the filters were in that condition, cust dumped $20K+ into it.


pumps, motors, sprockets, hoses, cooler, oil ect ect.


:drinkup

 

[CharlieMurphy]

Thanks for all the help guys. I am on hold till the customer tells me what to do. I may try to flush the system with some inline filters in the lines running to the drive motors and see if I cant flush it. The reservoir needs to be cleaned, all the lines, pumps and motors need to come apart to get cleaned. I have access to test benches but I feel the carnage will be too great. There will be more leakage than anything.... I will keep you guys posted. It may be a bit.... The machine may get parted also...

Again,
Thanks guys.
-D