Bobcat 773G Hydraulic Issue

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I have a 773G. Boom and bucket tilt were operating without issue. The other day I pressed the auxiliary hydraulics button and was messing with controls on joysticks. I plan to use the aux hydraulics in the near future. After messing with the controls, the boom and bucket will no longer operate unless I have the Aux hydraulics engaged. Without engaging the Aux, the engine is bogged down and neither boom nor tilt works. When I turn on Aux and engage, RPMs seem to speed up and bucket and boom function. That is not how it was working before. Any input or help would be appreciated.

 

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[cdmccul]

I have no advise for you other than turn it off and back on... Maybe pull the grand battery cable for several minutes and plug it back in...

But, I wanted to say you gave a very through video with a great demonstration of what it takes to go through the motions, and congratulations on at least bugging out how to make it at least semi function for now.

Again, I know nothing here... But I wonder, did you activate a custom program mode that needs to be un activated? I have a remote start on my family van that gets into a program mode if I cycle the key 5 times in like 10 seconds... Which is also similar to the "key dance" you do to pull engine codes on that van. Maybe that helps give a hint?

 

[brdgbldr]

You may have a stuck valve.

Not sure if the info I'm about to give you will help or you already know it, but here it goes.

First when you press the button to relieve the auxiliary pressure hold it in for at least two seconds after the engine stops. It won't relieve the pressure if the engine is still turning.

After you turn on the auxiliary button. When you press the front "trigger" on the right joystick it turns on continuous flow. If you hold the switch to the left and then press the "trigger" it sets continuous flow in reverse.

If you turn on the hydraulics with continuous flow without an attachment on, or an attachment that does not require continuous flow, the fluid has nowhere to go except through a bypass valve. While this fluid is bypassing the auxiliary, it will lower the pressure to the tilt and lift to where they won't go up and will only lower because of gravity.

I hope this helps you to narrow down the issue.

 

[Schifference]

You may have a stuck valve.

Not sure if the info I'm about to give you will help or you already know it, but here it goes.

First when you press the button to relieve the auxiliary pressure hold it in for at least two seconds after the engine stops. It won't relieve the pressure if the engine is still turning.

After you turn on the auxiliary button. When you press the front "trigger" on the right joystick it turns on continuous flow. If you hold the switch to the left and then press the "trigger" it sets continuous flow in reverse.

If you turn on the hydraulics with continuous flow without an attachment on, or an attachment that does not require continuous flow, the fluid has nowhere to go except through a bypass valve. While this fluid is bypassing the auxiliary, it will lower the pressure to the tilt and lift to where they won't go up and will only lower because of gravity.

I hope this helps you to narrow down the issue.

I know little about these machines. I disconnected the battery for half an hour. Just went out and connected again. Tried operation and same as before. It is not working properly. I bled aux hydraulics several times using your method and nothing improved. Without aux hydraulics running boom will only go up and bucket down. With aux hydraulics on as in the video it appears to function.

What valve do you think is stuck?

 

[brdgbldr]

I would be kinda guessing at this point, so my guess would be a relief valve is stuck open or closed. It's just kind of hard to figure out since the machine only seems to operate when the auxiliaries are in reverse continuous flow.

It would be nice to see what the machine would do with an attachment like a grapple or plow blade attached.

Try turning on the auxiliary hydraulics, and on the right control, only move the switch from left to right. Do not press the trigger. First just move the switch from left to right a couple of times and see if the engine bogs down in one or both positions, then check the curl and lift for operation. If nothing changes, press the switch to the left, and while holding it there see if the curl and lift work then try the same thing with the switch held to the right. This may tell us which side of the auxiliary hydraulics need to be pressurized for the curl and lift to work.

 

[Schifference]

I would be kinda guessing at this point, so my guess would be a relief valve is stuck open or closed. It's just kind of hard to figure out since the machine only seems to operate when the auxiliaries are in reverse continuous flow.

It would be nice to see what the machine would do with an attachment like a grapple or plow blade attached.

Try turning on the auxiliary hydraulics, and on the right control, only move the switch from left to right. Do not press the trigger. First just move the switch from left to right a couple of times and see if the engine bogs down in one or both positions, then check the curl and lift for operation. If nothing changes, press the switch to the left, and while holding it there see if the curl and lift work then try the same thing with the switch held to the right. This may tell us which side of the auxiliary hydraulics need to be pressurized for the curl and lift to work.

So I made another video attempting to try what you suggested.

 

[brdgbldr]

First it looks like your auxiliaries are stuck on.

It would really help if you could get an attachment or gauges hooked up to the hydraulics.

At this point it's hard to tell. It could be a bad solenoid that is not disengaging the auxiliaries or the valve / spool that the solenoid is on is sticking. I don't think it would be your switches since the auxiliary seems to be stuck on after the machine is turned off.

It seems like when the auxiliary is running "forward" (switch to the right) everything bogs down and it gets stuck there. Then when you "reverse" flow (switch to the left), it pulls the valve back just enough to disengage the auxiliary but not far enough to actually engage the "reverse" flow. If it was actually engaging the "reverse" flow, it should bog down the engine.



It would really help to be able to tell if the "reverse" is actually engaging or not. Either with an attachment or a gage hooked up to the male port. You could also tell if the "forward" was disengaging with a gage hooked to the female port.

I would check the auxiliary "Pressure Release Valve" since the pressure does not seem to be releasing. This could be a bad solenoid or a stuck valve. Also, find the auxiliary solenoid and check it and check the valve / spool for movement. Best scenario you have a bad solenoid.

I would suggest looking at the parts manual for your particular machine. Enter your serial number and the search "auxiliary":

Bobcat Parts Catalog - Find Diagrams for Your Equipment - Bobcat Company

Locate all parts and component information about your Bobcat equipment with detailed visual diagrams and illustrations with parts numbers and add to your list.

www.bobcatpartsonline.com

This should help you find the auxiliary solenoid and the pressure release valve.

This is one of those problems that could be any number of things. Not only mechanical but electrical. I hope this helps and I hope that maybe someone else on here could chime in with another perspective.

 

[Schifference]

Thank you for your gracious replies.
Here is what I have done and noticed.
I disconnected the 2 AUX Solenoids from their power and started machine. Same issue. Only thing is now when I press Aux hydraulics they don't respond as I would think.
Next I lift up on red emergency relief and RPM's speed up and as long as I keep relief up the bucket will obviously continue to come down but will go up and down and tilt both directions and RPM's sound as they should. No bog or strain on engine.

 

[Schifference]

More information from 3 years ago when I actually tried using Auxiliary hydraulics. I posted this on another forum and never got any response. This might be part of my problem today. Regardless, I have not used the auxiliary hydraulics since the harley rake. Here is what I wrote in 2020.

More details: I put a Harley Rake on my recently purchased Bobcat 773 utilizing the Auxiliary hydraulics for the first time. The Drum on the Harley will only rotate in one direction. I removed both coils and switched them this did not fix the problem or make it turn only the other direction. I changed the wires from and attached them to the opposite coils. Then the drum still rotates only one way in the same direction as previous but is controlled by turning the joystick thumb switch the other direction. I have concluded that both coils are good and joystick switch is good. I read somewhere prior to joining the site that if the coils were good and the switch was good, that the Stem was the issue and could be cleaned. I removed each stem and did not notice any serviceable parts inside it.

I used the Harley rake by changing the fittings on the rake so it turned the direction I wanted.

So If I am going to order a set of $1,000 brackets from Bobcat, with free shipping and the ability to return, I would like to get items that could be responsible for these hydraulic issues.

Thanks for your help.

 

[brdgbldr]

So if it isn't electrical It has to be a valve /spool issue.
There are seals on the pressure release valve that can be replaced but since the pressure seems to stay I doubt that is the issue, but it could be stuck.

The auxiliary spool has a couple of springs on it that can go bad or break. The spool can also get scored and not work properly.
The auxiliary load check has a spring in it also.

You may want to call a dealer and see if they will help with diagnoses. Some dealers are real good with this, others not so much. If you take it into a dealer they charge, at least my dealer, $140 per hour plus parts. A mobile tech is $160 per hour plus parts and travel time. The advantage is that they can hook up a diagnostics computer to the machine and they have gages to check the hydraulics.

A backhoe may work on your machine since the hydraulics seem to get stuck on in the forward position. But if you can't release the pressure in the auxiliary hydraulics you will not be able to hook up the couplers.

 

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So I got the lift and tilt to work as designed. What did I do? I removed both hydraulic spools, I checked to see that spring and mechanism was working. They are sucked in and will pull outward. I replaced them in the opposite location that I took them out. I started the machine and the Boom and tilt worked as designed. No need for Aux Hydraulics to operate boom or lift. Then I turned Aux Hydraulics on again and boom and tilt stopped working again. Except, this time, Aux hydraulics and trigger and toggle left nor right would render boom and or tilt operational. The emergency relief being turned and pulled up would. So then I once again took the spools out and changed location back where they were initially. I started the machine and boom and tilt function as designed. I have not turned on Aux Hydraulics again. Seems like something with the spools or??? is causing other hydraulics to not function properly and as mentioned a few years ago Aux Hydraulics only worked one way.

If you wouldn't mind continuing the brainstorming, I would appreciate it. I would rather fix it myself if possible. I sincerely appreciate your input.


Gosh you seem to know the Bobcat parts. I am not objectionable to purchasing spools if they are not too costly. If you think that could be it, would you be willing to point me as to where to look for a spools for 773G?

Thanks again.

 

[brdgbldr]

You need to take a look at the auxiliary spool and springs. It should have a cap on it instead of a boot and I think it is on the left side of the control valve.

A new auxiliary spool from Bobcat is about $80. Order a couple of filters with it to get it over $99 and to get free shipping to your doorstep.

But again, here is the link to the parts catalog because you really need to look at your specific serial number for parts. I show 11 different control valve setups depending on serial numbers and controls.

Bobcat Parts Catalog - Find Diagrams for Your Equipment - Bobcat Company

Locate all parts and component information about your Bobcat equipment with detailed visual diagrams and illustrations with parts numbers and add to your list.

www.bobcatpartsonline.com

I attached one of the 11 control valve schematics. It should be close to what you have. It may give you a better idea as to where the auxiliary spool is.

I also included a schematic for the pressure release valve for the front auxiliary. I still think that this could be faulty and once you activate the auxiliaries the pressure is not releasing and locking up the spools. Make sure the solenoid is working on it. I would not open this up until it is a last resort because you will probably need a seal kit to put it back together.

Right now my money is on something being wrong with the auxiliary spool. Hopefully just a spring gone bad.

I'm no expert on control valves. I do know however that if one thing goes wrong in it the pressures go to other parts and cause other symptoms.

 

[brdgbldr]

I'm sorry, the more I look at your video the more it looks like you swapped valve stems and not spools. It is always hard for me to see in photos and videos when I'm comparing to whats on paper. The orientation on paper is screwing me up.

I think the spools are going to be on the left side of the control valve and the auxiliary spool will be on the left side top. That's if I have my orientation correct.

Take a look at the control valve schematic I attached above. Find the auxiliary spool and check it.

 

[Schifference]

I'm sorry, the more I look at your video the more it looks like you swapped valve stems and not spools. It is always hard for me to see in photos and videos when I'm comparing to whats on paper. The orientation on paper is screwing me up.

I think the spools are going to be on the left side of the control valve and the auxiliary spool will be on the left side top. That's if I have my orientation correct.

Take a look at the control valve schematic I attached above. Find the auxiliary spool and check it.

So I found a PDF Service manual I must have downloaded a few years ago. I think I found the relevant pages to what you are trying to explain. Please take a peak and tell me what you think I need to do again.
The link you furnished to find the correct parts is awesome! When you hover over a number it highlights it on the diagram.
Please recommend what you think I should order so I have them on hand when I take this apart.
I don't mind spending couple hundred dollars if it will fix the issue. If I can replace all suspect parts for a couple hundred dollars I would rather do that then do it more than once. I guess my goal would be to take it apart and already have the replacement parts so I can just put it back together.
I am no mechanic but am mechanical and try to utilize logic.
Once again I appreciate all your input in my problem.
No hard feelings if you suggest something that doesn't work.

Thanks!

 

[brdgbldr]

Before digging into the control valve I would rebuild the "Pressure Release Valve". Definitely check or replace the solenoid. Since your pressure doesn't seem to be releasing this valve could be the whole problem. If the pressure is not releasing it could be binding other parts and not allowing them to move. It should be located near the control valve but is on its own bracket. Number 27 on the photo I've attached.

If the "Pressure Release Valve" is not the problem then move to the control valve.


As for the control valve auxiliary spool and valves, I would get all of the seals and O-rings for sure. They do have seal kits listed in the parts list but they will be for the entire control valve. Not sure what all they include.

As for hard parts, I think the springs for sure and all of the washers and sleeves. Don't forget that there are springs on both sides of the spool.

A new solenoid if you think the old one may be bad.

I'm not sure I would bother getting a new auxiliary spool or not. There is a chance something could be wrong with it, but if there is, chances are it has messed up the housing it goes into also. It wouldn't hurt to have it on hand and if not used could be returned in the allotted time frame.

If you are going to remove the control valve to work on it I would definitely look at buying a seal kit and replacing all of them. This will also give you a chance to inspect the other spools anns springs. Also, you may want to think about looking at the load checks and springs.

Just make sure you have all of the O-rings you need. For some reason Bobcat never seems to include them with rebuild or parts kits.

 

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[cdmccul]

If all you have in your hand is the coil, you won't feel anything unless you have a magnetic finger.

10 ohms sounds about right.

 

[cdmccul]

The screw driver getting pulled in... That's still power applied, right? That's normal and correct operation.

 

[Schifference]

The screw driver getting pulled in... That's still power applied, right? That's normal and correct operation.

Yes under power. I was going to pull the valve that the solenoid was on but it appears that hydraulic oil would need to be drained. I have been trying to troubleshoot and narrow down. I don't know a thing about these machines. Any input is appreciated. If replacing parts require draining oil, I kinda would like to replace whatever affordable parts that could be the issue especially if I have to remove control valves and other parts from the machine.

To recap:
3 years ago when I acquired the machine the Auxiliary Hydraulics only worked in one direction but when on did not inhibit any other hydraulic function. I have not used the Auxiliary Hydraulics since then. Actually the machine sat unused for a couple of years because it kept locking up hydraulics because of a seat bar issue that drove me nuts. Last year I sent the control board to be looked at and it was the problem. It was repaired and no more issue with seat bar.

Over last year I used machine lightly to move pallets, and some bucket work. No issues with lift or tilt.

Recently I acquired a 709 to dig a few trenches around the property. In preparation for the 709, I turned on the hydraulics to see if they bogged down the engine in both directions. I was curious if the auxiliary hydraulics still only worked one way. After doing that for only a minute or two, I noted the lift and tilt was not working as designed. In order for lift and tilt to function, I had to have the right hand trigger pulled and auxiliary hydraulics in reverse. Without the aux hydro in reverse and turned on the engine was loaded/bogged down and lift and tilt would not work.

Yesterday I removed what I thought was the forward and reverse aux hydro spools/valves/whatever and switched them. The lift and tilt worked as designed until I turned on Aux Hydraulics and then engine bogged down and lift tilt no longer worked. This time, turning on Aux Hydraulics, pulling the trigger and trying to engage forward or reverse did not relieve the bog down nor allow the lift or tilt to function as designed. I was able to turn and pull up on emergency relief valve and while holding up get the lift and tilt to work. I then took out the aux hydro spools/valves/whatever and put them back where they were originally. After that the lift and tilt once again functioned as designed. I did not turn on Aux Hydraulics again to see what would happen.

Today I tested the solenoid for the Front Aux Hydraulics Pressure relief. The solenoid appears to function normally.

I guess it is possible if a machine was hooked up to the Auxiliary Hydraulics it would act different than no machine but I doubt it.

Furthermore, when pressing the relieve pressure on the left upper control panel and holding it, it stalls the engine as designed.

Any input appreciated. Thanks in advance.