Hello I’m new to the world of forums looking for some information guidance. I have a t200 bobcat I pulled it in the shop to replace a bottom roller and lift spool seals while I had the track off of the right side I replaced a drive hose “wasn’t leaking just had a worn place on it” put it back together and now it moves about 50 feet and the right side drive motor locks down I had a suspected a brake problem and sure enough I found one brake disc had chewed some teeth off. I cleaned all of the metal out and rebuilt the brake on that side ”seals,discs and piston” put it all back together and same thing so checked charge pressure 315 psi at idle ran for two min and pressure dropped to 250 and was falling when the low charge psi signal popped up Would a charge pump go out all of a sudden or do I need to be looking for a leaking spool or relief valve? Any help is appreciated
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Bobcat t200 low charge pressure
- Thread starter Cb4020
- Start date
Im not familiar with this particular model of Bobcat but, if you didn't have that problem before you started doing what work you did, it is more likely that something was either damaged during assembly or not assembled correctly. Loss of charge pressure is leakage in the system. If your charge pressure also runs your brakes, I would suspect that the brake piston seal may have been damaged when assembled. Hopefully someone will come along that knows this system better than I. Its unlikely your charge pump is failing unless hoses in the drive system were contaminated when replaced.
mikebramel
Senior Member
If you got any dirt in the hose you replaced that will give you low charge pressure
crewchief888
Senior Member
you may want to check the case drain filter.
follow the case drain hoses from the drive motors you'll find a round aluminum filter housing with several small hoses connected to it.
since you had a brake failure, any debris will find it's way to that filter.
in addition you had a leaking control valve, and probably ran the machine low on oil in the past.
both leaks can, and do cause, damage to the charge pump. you may also have a piece of crap stuck under the seat of the charge pressure relief. sometimes removing the charge relief and letting some oil run out will "solve" the problem. i believe the charge relief is shim adjusted on that pump.
follow the case drain hoses from the drive motors you'll find a round aluminum filter housing with several small hoses connected to it.
since you had a brake failure, any debris will find it's way to that filter.
in addition you had a leaking control valve, and probably ran the machine low on oil in the past.
both leaks can, and do cause, damage to the charge pump. you may also have a piece of crap stuck under the seat of the charge pressure relief. sometimes removing the charge relief and letting some oil run out will "solve" the problem. i believe the charge relief is shim adjusted on that pump.
I’ve checked the case drain filter and it wasn’t bad at all few specs of dirt but still shiny brass. My pump has a block on the back of it and bobcat didn’t show a diagram or hose route for it. I checked pressure at the drive hoses only have 800 psi at right side I need to find out if this is due to the low charge pressure or just series of crazy bad parts
crewchief888
Senior Member
block on the back of the pump?
power bobtach valve?
power bobtach valve?
Low charge pressure will effect all your hydrostatic drive.
crewchief888
Senior Member
is this block about 4 inches square and bolted to the back ( engine side) of the hyd pump?
Yes sir. I’m trying to find an outlet to check pressure straight out of the pump I need to know if my pump is actually weak or if I’m bleeding pressure off thru my main controll valve or a stuck relief valve kinda want to start at the source and work out but bobcat info is hard to find
crewchief888
Senior Member
i believe you are confused, the 4x4 steel block on the back of the hyd pump is the power bobtach valve, and has nothing to do with charge pressure.
the charge pump is internal to the hydrostatic pump. you should see charge pressure at the charge pressure sending unit. off the top of my head i'm not positive exactly where the sending unit is located.
but if you look at the engine oil pressure sender it looks very similar and uses the same 3 pin connector. the senders are NOT interchangable
the charge pump is internal to the hydrostatic pump. you should see charge pressure at the charge pressure sending unit. off the top of my head i'm not positive exactly where the sending unit is located.
but if you look at the engine oil pressure sender it looks very similar and uses the same 3 pin connector. the senders are NOT interchangable
Ah. Now we are getting somewhere I was told that gear pump did both charge pressure and aux functions. My sending unit reads 315 at startup and drops to 250 in just a couple of mins. Could I dead head a gauge in the incoming line at the tee where the sending unit is to see if I’m bleeding pressure off down stream or would that hurt the pump?im trying to rule out a leaking valve downstream of the pump. I’ve already tested the brake pistons and neither of them seem to be the problem
crewchief888
Senior Member
if you remove or disconnect the charge sensor, once the engine is started the bobcat controller is going to sense engine RPM and zero charge pressure, and will shut down in 15-20 seconds.
i'm not positive what the charge pressure should be on your machine, but it should be tested at full throttle. bobcat has no specification for charge pressure at idle. you engine @ low idle should be approx 1000-1100 rpm.
on a side note a bad sender or wiring can cause low pressure shut downs.
check the terminals in the harness connector, make sure they arent spread open too far, when you disconnect the sender if there is any oil inside it, replace it, it's leaking internally and will not send the proper signal to the controller.
i'm not positive what the charge pressure should be on your machine, but it should be tested at full throttle. bobcat has no specification for charge pressure at idle. you engine @ low idle should be approx 1000-1100 rpm.
on a side note a bad sender or wiring can cause low pressure shut downs.
check the terminals in the harness connector, make sure they arent spread open too far, when you disconnect the sender if there is any oil inside it, replace it, it's leaking internally and will not send the proper signal to the controller.
I teed a manual gauge in line with everything on the charge pressure circuit it is showing low even locks my right drive motor down I’m guessing pressure loss is letting brakes engage could a peice of trash be starving the charge pump on the suction side causing my pressure loss?
crewchief888
Senior Member
you could always cap off the drive hoses at the pump and see what happens to the charge pressure. do 1 side at a time.
i dont think you'll see much of a change with the drives capped off, unless you have a really big leak in a motor.
if it was my machine i'd shim up the charge relief and stick a for sale sign on it.
i dont think you'll see much of a change with the drives capped off, unless you have a really big leak in a motor.
if it was my machine i'd shim up the charge relief and stick a for sale sign on it.
I did what you said capping off the drive hoses with gauge ports and about 800psi was all I had on right side left side has always operated fine. All this just started at once. Had just been piling brush with the machine and pulled it in to replace a bad roller prolly should have let the hyd leak just drip lol