Setting pressure relief valve on my 853

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perry

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Aug 22, 2006
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I installed a new pressure relief on my 853, I purposely backed out the adjuster so not to have to much pressure, I was told to much pressure would ruin the pump. I bought a 5000 psi gauge and fittings to connect to aux. hyd.
How do I set the pressure?.
Thanks
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
Perry
First you need to check your pressure the setting may be fine. Hook your guage to the quick couplers on the front of the machine and activate the aux hyd flow in the intermittant mode for operating cylinders.
Run the machine for 20 minutes or so to warm the oil then put the presuure to your guage using the thumb switch at see what the reading is.
I check the book, pressure should be 2700 to 2750 psi
Adjusting screw is on the operators right rear of the main hyd control valve. Believe a 9/16“ wrench fits the locknut, remove it and turning the stud that nut was threaded over clockwise will raise the pressure.
Low pressure at a idle is a sign of a pump thats getting a little worn. If you get max press at idle your pump is excellent.
Its common for the spring in the main relief valve to get a little weak over time and the pressure to get a few hundred pounds low.
However sometimes people crank the pressure up to get more power. The least pressure you can put up with and still have a functioning machine will provide the longest component life.
Example
My 553 calls for 1600 psi, When I got it it would nearly stall when it hit the end of a cylinder, checking the pressure revealed someone had miss adjusted it to 3000psi, Its a wonder the pump did not split. No wonder the engine was lugging down
I spoke with a local Bobcat tech and they set theirs 400 over the book at 2000 psi to get a little more power. The motor handles the 2000 psi setting much better. Bit bobcat likely tested and found the pumps lasted better at 1600 psi
Often people will reset the pressure do to a low reading, then in 100 hrs or so they find that no longer is helping. The pump is the real culprit, was all along,its just worn worse now. So they install a new pump and the pressure skyrockets because they never back the relieve valve setting back out. Now they have a split new pump or other damage.
Just food for though
Ken
 

perry

Well-known member
Joined
Aug 22, 2006
Messages
869
Perry
First you need to check your pressure the setting may be fine. Hook your guage to the quick couplers on the front of the machine and activate the aux hyd flow in the intermittant mode for operating cylinders.
Run the machine for 20 minutes or so to warm the oil then put the presuure to your guage using the thumb switch at see what the reading is.
I check the book, pressure should be 2700 to 2750 psi
Adjusting screw is on the operators right rear of the main hyd control valve. Believe a 9/16“ wrench fits the locknut, remove it and turning the stud that nut was threaded over clockwise will raise the pressure.
Low pressure at a idle is a sign of a pump thats getting a little worn. If you get max press at idle your pump is excellent.
Its common for the spring in the main relief valve to get a little weak over time and the pressure to get a few hundred pounds low.
However sometimes people crank the pressure up to get more power. The least pressure you can put up with and still have a functioning machine will provide the longest component life.
Example
My 553 calls for 1600 psi, When I got it it would nearly stall when it hit the end of a cylinder, checking the pressure revealed someone had miss adjusted it to 3000psi, Its a wonder the pump did not split. No wonder the engine was lugging down
I spoke with a local Bobcat tech and they set theirs 400 over the book at 2000 psi to get a little more power. The motor handles the 2000 psi setting much better. Bit bobcat likely tested and found the pumps lasted better at 1600 psi
Often people will reset the pressure do to a low reading, then in 100 hrs or so they find that no longer is helping. The pump is the real culprit, was all along,its just worn worse now. So they install a new pump and the pressure skyrockets because they never back the relieve valve setting back out. Now they have a split new pump or other damage.
Just food for though
Ken
Thanks ken, I thought the pump would need to be under pressure such as tilting the bucket and holding it there to get max pressure?. so your saying just hook up the gauge and check pressure under normal operating speed and not having pump under pressure by raising arms or tilting bucket?.

Thanks
 

farmboy55

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Joined
Aug 16, 2006
Messages
324
Thanks ken, I thought the pump would need to be under pressure such as tilting the bucket and holding it there to get max pressure?. so your saying just hook up the gauge and check pressure under normal operating speed and not having pump under pressure by raising arms or tilting bucket?.

Thanks
Hey Perry When you hookup your gauge to the hyd line it will be like a load it cannot move. It will put all the pressure it can produce against the valve. dennis
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
Thanks ken, I thought the pump would need to be under pressure such as tilting the bucket and holding it there to get max pressure?. so your saying just hook up the gauge and check pressure under normal operating speed and not having pump under pressure by raising arms or tilting bucket?.

Thanks
What your saying will work to, but if you have any quick couplers for your 3rd valve/ aux hydraulics, Just snap the guage onto one of the front couplers and activate the aux hydraulics.
Its the same “main relief” as the boom and bucket uses, its just simpler to tie in at the couplers.
When you activate the thumb switch, the oil dead ends into the guage and press will come up to “relief pressure” near instantly.
If you don't have any couplers you can T into any one of the cylinder lines, if you run that side of the cylinder to the end of its travel you will get your pressure reading.
Ken
 

Fishfiles

Well-known member
Joined
Feb 8, 2007
Messages
1,698
Perry
First you need to check your pressure the setting may be fine. Hook your guage to the quick couplers on the front of the machine and activate the aux hyd flow in the intermittant mode for operating cylinders.
Run the machine for 20 minutes or so to warm the oil then put the presuure to your guage using the thumb switch at see what the reading is.
I check the book, pressure should be 2700 to 2750 psi
Adjusting screw is on the operators right rear of the main hyd control valve. Believe a 9/16“ wrench fits the locknut, remove it and turning the stud that nut was threaded over clockwise will raise the pressure.
Low pressure at a idle is a sign of a pump thats getting a little worn. If you get max press at idle your pump is excellent.
Its common for the spring in the main relief valve to get a little weak over time and the pressure to get a few hundred pounds low.
However sometimes people crank the pressure up to get more power. The least pressure you can put up with and still have a functioning machine will provide the longest component life.
Example
My 553 calls for 1600 psi, When I got it it would nearly stall when it hit the end of a cylinder, checking the pressure revealed someone had miss adjusted it to 3000psi, Its a wonder the pump did not split. No wonder the engine was lugging down
I spoke with a local Bobcat tech and they set theirs 400 over the book at 2000 psi to get a little more power. The motor handles the 2000 psi setting much better. Bit bobcat likely tested and found the pumps lasted better at 1600 psi
Often people will reset the pressure do to a low reading, then in 100 hrs or so they find that no longer is helping. The pump is the real culprit, was all along,its just worn worse now. So they install a new pump and the pressure skyrockets because they never back the relieve valve setting back out. Now they have a split new pump or other damage.
Just food for though
Ken
When I read the 1600 psi I thought that couldn't be right as it is pretty low , but I got the tech service guide in my hand and find that there are three different settings for 553 depending on serial number ,one which doesn't state a serial number break is 1575 psi , man that is low 516311001 up = 2000 psi , 520311001 up =3000 psi , are you sure your in the right bracket
 

perry

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Joined
Aug 22, 2006
Messages
869
When I read the 1600 psi I thought that couldn't be right as it is pretty low , but I got the tech service guide in my hand and find that there are three different settings for 553 depending on serial number ,one which doesn't state a serial number break is 1575 psi , man that is low 516311001 up = 2000 psi , 520311001 up =3000 psi , are you sure your in the right bracket
Appreciate the feedback fella's, I noticed when I'm at idle the arms will not move but, when I rev it up to almost operating speed the arms raise normally?. I hope it's the relief valve, should know in a while.
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
Appreciate the feedback fella's, I noticed when I'm at idle the arms will not move but, when I rev it up to almost operating speed the arms raise normally?. I hope it's the relief valve, should know in a while.
Hate to say it Perry but that sounds like 1 symtom for a worn out pump. Do you notice it get weaker as the oil warms up?
If setting the relief brings you pressure up and the loader maintains it as the hyd oil gets fully warmed up, thats good, but then check it in 50 and 100 hours to see if its staying up. If the pump is good it should stay right there.
Why did you back the relief pressure down.
The 553 is a c model, I'd have to check the serial #, but 3000 psi was more then the engine could handle. At 2000 it has all the lift power it needs.
Ken
 

perry

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Joined
Aug 22, 2006
Messages
869
Usually if the main belt is loose, you will notice the wheel speed are slow or stop under heavy loads. Or here the belt squeal when climbing a hill.
Ken
Ken, it was a new pressure relief valve and wasn't sure if it was pre-set, so I backed it out until I knew how much pressure it needed. The belt tension is correct and no obvious operating issues so far.
I mentioned a while back there is a guy selling BC hyd. pumps on ebay, just curious if anyone has bought from him?, he has a good feedback rating and I will probably purchase from him if I ever need a pump. this is his listing #........ 120092206367
Thanks
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
Ken, it was a new pressure relief valve and wasn't sure if it was pre-set, so I backed it out until I knew how much pressure it needed. The belt tension is correct and no obvious operating issues so far.
I mentioned a while back there is a guy selling BC hyd. pumps on ebay, just curious if anyone has bought from him?, he has a good feedback rating and I will probably purchase from him if I ever need a pump. this is his listing #........ 120092206367
Thanks
Do you think your pump is worn out?
If you loose 200 to 300 psi at a idle and it come to the relief setting pressure at 500 rpm higher, I'd say use it for awhile yet. If the pressure keeps dropping from cold to warmed up the its likely time for a new pump. (first 1/2 hour of operation)
I would not be afraid to buy one from ebay, they are the same pump, just not reboxed for bobcat. Just be sure its new and ask about warranty and his exchange return policy.
Ken
 

perry

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Joined
Aug 22, 2006
Messages
869
Do you think your pump is worn out?
If you loose 200 to 300 psi at a idle and it come to the relief setting pressure at 500 rpm higher, I'd say use it for awhile yet. If the pressure keeps dropping from cold to warmed up the its likely time for a new pump. (first 1/2 hour of operation)
I would not be afraid to buy one from ebay, they are the same pump, just not reboxed for bobcat. Just be sure its new and ask about warranty and his exchange return policy.
Ken
Ken, I don't believe the pump is worn out, I'll know within a few hours when I set the pressure relief.. I'll also be changing out the hand control assy. for a foot control today.

Thanks
 

skidsteer.ca

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Jan 20, 2006
Messages
3,853
Ken, I don't believe the pump is worn out, I'll know within a few hours when I set the pressure relief.. I'll also be changing out the hand control assy. for a foot control today.

Thanks
Perry
Pump is likely fine. Just set the relief where you want it but try to warm the hyd oil up b4 hand.
I'd check where you have the pressure now and check again after you warm the oil to see if they read the same.
Put a piece of cardboard over the oil cooler to block the air flow, run one of the hyd functions to the end so the oil goes “over the relief” and hold it on for a few minute to warm it up to 120 to 140 degrees.
Then adjust your pressure to where you want. After 50 hrs or so and check it again.
Relief valve springs may soften slightly after some use, you don't have to double check, but if you do and the press is staying put, then you know all is well.
The hand controls on your machine, are they cables that hook the handles to the valves or are they electric over hyd?
Regards
Ken
 

perry

Well-known member
Joined
Aug 22, 2006
Messages
869
Perry
Pump is likely fine. Just set the relief where you want it but try to warm the hyd oil up b4 hand.
I'd check where you have the pressure now and check again after you warm the oil to see if they read the same.
Put a piece of cardboard over the oil cooler to block the air flow, run one of the hyd functions to the end so the oil goes “over the relief” and hold it on for a few minute to warm it up to 120 to 140 degrees.
Then adjust your pressure to where you want. After 50 hrs or so and check it again.
Relief valve springs may soften slightly after some use, you don't have to double check, but if you do and the press is staying put, then you know all is well.
The hand controls on your machine, are they cables that hook the handles to the valves or are they electric over hyd?
Regards
Ken
Ken my hand controls are cable control, pulled it yesterday and hopefully have the foot control assy, installed today. Removing the unit wasn't all that bad, I should have disconnected the drive cable from the hydrostat, much easier than reaching under arms assy. to remove the nuts.
 

perry

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Joined
Aug 22, 2006
Messages
869
Ken my hand controls are cable control, pulled it yesterday and hopefully have the foot control assy, installed today. Removing the unit wasn't all that bad, I should have disconnected the drive cable from the hydrostat, much easier than reaching under arms assy. to remove the nuts.
I did learn one thing that will save some aggravation. place a large towel or cloth under where your working, when you drop a nut, bolt or screw it won't fall into the abyss.
 
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