New Here- I'm having issues with my 853 Bobcat even after changing the gear pump

[Climber405]

Hi All,

My name is Caleb and I'm from Piedmont, Oklahoma. I tried posting this in the Bobcat section but it disappeared on me twice so I can only assume it got deleted? I thought maybe I have to make an introductory post first----

I recently purchased this 853 Bobcat and it was working great. I put 'universal' fluid in it (about a gallon) and 15 min later had almost no hydraulic power. I could move the arms up at full throttle but if I operated the bucket at the same time everything would stop. Bobcat told me the universal fluid wouldn't hurt it but I emptied the system and put AW46 in which did not fix anything. Since then I've put a new gear pump on it. This machine was the tandem pump even though its not an 853H. Bobcat says its a 96 which I think is the last year of the 853 so maybe they added some upgrades? I also changed the main pressure valve. I had a hard time finding the valve because it wasn't where the diagram shows on the main control valve. Instead, there is a hard line coming off the main control valve that goes to a block on the left side of the machine where the pressure relief valve is at. Same symptoms with the new valve- I adjusted it incrementally until it was all the way closed but still showed no more than 1000 PSI at high idle.

I'm completely at a loss of where to go from here. Any help would be much appreciated. When I changed the pump I pre-filled all the lines and the pump had oil inside it already. I bumped the key on the machine half a dozen times but didn't let it start to cycle some fluid through before allowing the machine to come to idle. Also, the only pump did have about 10 thousands wear inside the main body and on the face of the gears. I was getting some chatter in the pump before replacing it but haven't had any chatter or odd noises with the new pump.

TIA- Caleb

 

[fortworth-cowboy]

Hi All,

My name is Caleb and I'm from Piedmont, Oklahoma. I tried posting this in the Bobcat section but it disappeared on me twice so I can only assume it got deleted? I thought maybe I have to make an introductory post first----

I recently purchased this 853 Bobcat and it was working great. I put 'universal' fluid in it (about a gallon) and 15 min later had almost no hydraulic power. I could move the arms up at full throttle but if I operated the bucket at the same time everything would stop. Bobcat told me the universal fluid wouldn't hurt it but I emptied the system and put AW46 in which did not fix anything. Since then I've put a new gear pump on it. This machine was the tandem pump even though its not an 853H. Bobcat says its a 96 which I think is the last year of the 853 so maybe they added some upgrades? I also changed the main pressure valve. I had a hard time finding the valve because it wasn't where the diagram shows on the main control valve. Instead, there is a hard line coming off the main control valve that goes to a block on the left side of the machine where the pressure relief valve is at. Same symptoms with the new valve- I adjusted it incrementally until it was all the way closed but still showed no more than 1000 PSI at high idle.

I'm completely at a loss of where to go from here. Any help would be much appreciated. When I changed the pump I pre-filled all the lines and the pump had oil inside it already. I bumped the key on the machine half a dozen times but didn't let it start to cycle some fluid through before allowing the machine to come to idle. Also, the only pump did have about 10 thousands wear inside the main body and on the face of the gears. I was getting some chatter in the pump before replacing it but haven't had any chatter or odd noises with the new pump.

TIA- Caleb

Hello,

first off, the Main Relief Valve is always on the Control Valve, sounds like you changed the Relief Valve from the Bucket Positioning Valve.
That might be your problem, if the Main Relief Valve is wide open, all of the hydraulic pressure will go right back to the Tank.--> Path of least Resistance.
Do you have a Serial Number?
I am not worry about the hydraulic Oil, you would have heard if you damaged the pumps.
Could you take Picture of the Main Relief Valve, you think, you adjusted? And also a Picture, where do you check the Pressure with a Gauge.

 

[Climber405]

Would love to hear your thoughts on these pics. As you can see, where the main relief should be on the main control block on the right side of the machine there is a hard line that pipes over to a block on the left side of the machine- You can see the valve I pulled out and the new one I got from Bobcat that while not a perfect match is very close and I know they updated that part since 96 when the original one would have been installed. I checked the pressure with a gauge on the aux hydraulic line. It was 800 with the old pump and 1000 with the new one.

Thanks! Caleb

 

[fortworth-cowboy]

Would love to hear your thoughts on these pics. As you can see, where the main relief should be on the main control block on the right side of the machine there is a hard line that pipes over to a block on the left side of the machine- You can see the valve I pulled out and the new one I got from Bobcat that while not a perfect match is very close and I know they updated that part since 96 when the original one would have been installed. I checked the pressure with a gauge on the aux hydraulic line. It was 800 with the old pump and 1000 with the new one.

Thanks! Caleb

Serial #?

 

[Climber405]

Serial #?

512821372 Sorry I thought I included that before.

 

[fortworth-cowboy]

Thats were the main relief should be

 

[Climber405]

Thats were the main relief should be

Exactly. I've looked at many pictures of the main control valve and at every schematic available. In pictures 2,3 and 4 I uploaded you can see the spools (one of mine is green) and then where the relief valve SHOULD be, there is a hard line running over to where I have my finger on it on a block on the left side of the machine.

Also, this machine is a regular 853 but for some reason I have the tandem gear pump, same as the high flow. 6665552 is the part number for the pump I have.

 

[Climber405]

This is the spot where your picture shows the main relief should be- but instead its a hard line and elbow.

 

[fortworth-cowboy]

View attachment 8991 This is the spot where your picture shows the main relief should be- but instead its a hard line and elbow.

That's your main relief. I marked it on that other picture

 

[Climber405]

That's your main relief. I marked it on that other picture

The main relief has an elbow on it then and a hard line... is that possible? The one you marked is the same one I marked with the blue circle.

 

[Climber405]

That's your main relief. I marked it on that other picture

I have the machine at Bobcat now and the pressure relief I changed is for the Aux Hydraulics. However, this machine has a older style main control valve and the main relief is actually on the front side under the two pins that goto the peddles. Bobcat doesn't have and cant get the main relief to fit the old valve.

Finding a main relief valve is now the task at hand but they don't even have a part number.

 

[fortworth-cowboy]

I have the machine at Bobcat now and the pressure relief I changed is for the Aux Hydraulics. However, this machine has a older style main control valve and the main relief is actually on the front side under the two pins that goto the peddles. Bobcat doesn't have and cant get the main relief to fit the old valve.

Finding a main relief valve is now the task at hand but they don't even have a part number.

Ok, I run into that before too. Tell the Dealer to ask by Lippert.