kennyd
Advertiser
Good news! Out with that Salami:laughing:
Thumb Valve Leak Mystery
- Thread starter mmranch
- Start date
- Views: 8281
Good news! Out with that Salami:laughing:
OP
mmranch
Gold Member
Sigh... the saga continues.
The Prince valve has worked great with no leaking since it was installed... until yesterday (it's less than a year old). I was using the backhoe yesterday (had only used the thumb a couple of times yesterday) when I noticed that the Prince thumb valve was leaking. The valve body has a protruding thing that I think is some kind of pressure relief valve. The hydraulic fluid is leaking from the tip of this pressure relief valve (see attached photo) which seems to have some kind of adjusting locknut.
The tractor's hydraulic system is 10.4 GPM and about 2200 PSI (the PSI is not listed in my specs but the dealer has mentioned this PSI in the past). I know that my dealer probably got me a valve that exceeds this PSI but it seems to me that sometimes there must be a spike in the PSI that is much greater and this is causing the replacement Prince valve to leak from the pressure relief valve (and was probably causing the Salami valves to blow the O-rings from the piston originally).
So my questions are:
1. Is this little locknut on the pressure relief valve adjustable in some way?
2. Can the pressure relief valve portion be replaced with one that will only blow at a higher PSI?
3. Am I doing something wrong that is causing this pressure relief valve to blow? I can't imagine what it is as I am simply using the backhoe (and occasionally the thumb). Now I am torqueing the **** out of the backhoe as I frequently reach the limits and it simply won't lift or dig the big rock or tree stump out, but it's not like I sit there holding the levers continually after I see it won't budge... I simply attack from another angle until it eventually does! (We're at 10000ft in the Rocky Mountains so I'm dreaming of a giant track hoe!).
Thanks for any ideas!
The Prince valve has worked great with no leaking since it was installed... until yesterday (it's less than a year old). I was using the backhoe yesterday (had only used the thumb a couple of times yesterday) when I noticed that the Prince thumb valve was leaking. The valve body has a protruding thing that I think is some kind of pressure relief valve. The hydraulic fluid is leaking from the tip of this pressure relief valve (see attached photo) which seems to have some kind of adjusting locknut.
The tractor's hydraulic system is 10.4 GPM and about 2200 PSI (the PSI is not listed in my specs but the dealer has mentioned this PSI in the past). I know that my dealer probably got me a valve that exceeds this PSI but it seems to me that sometimes there must be a spike in the PSI that is much greater and this is causing the replacement Prince valve to leak from the pressure relief valve (and was probably causing the Salami valves to blow the O-rings from the piston originally).
So my questions are:
1. Is this little locknut on the pressure relief valve adjustable in some way?
2. Can the pressure relief valve portion be replaced with one that will only blow at a higher PSI?
3. Am I doing something wrong that is causing this pressure relief valve to blow? I can't imagine what it is as I am simply using the backhoe (and occasionally the thumb). Now I am torqueing the **** out of the backhoe as I frequently reach the limits and it simply won't lift or dig the big rock or tree stump out, but it's not like I sit there holding the levers continually after I see it won't budge... I simply attack from another angle until it eventually does! (We're at 10000ft in the Rocky Mountains so I'm dreaming of a giant track hoe!).
Thanks for any ideas!
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kennyd
Advertiser
1. Yes-that is a PRV, and it is adjustable-but you will need a gauge to do it.
2. No need to replace-take it apart and fix it (probably just a o-ring) and then set it to just below the tractor's PSI level (you can determine that also when you get a gauge).
3. Thumbs take a lot of abuse-mostly because the bucket pushes on them so hard and the pressure built up in the cylinder has to go somewhere or the rod/thumb/dipper bends or breaks. The use of a crossover releif valve/cushion can help protect everything. Search the terms "crv" and "x-over" for some reading-mostly about snowplows but it works the same on thumbs.
OP
mmranch
Gold Member
kennyd,
Thanks very much for the info!
So I need a pressure gauge that will plug into my QD to see the pressure. Is this a standard something I can buy (any recommendations for places to buy?).
So after I have a gauge and can see the pressure, would I simply be turning the screw and locking the locknut to set a new pressure setting?
Assuming for the moment I DON'T change the pressure setting but just want to get leak-free again, are you saying I need to remove the PRV and replace a damaged O-Ring to get this to not leak?
Thanks again!
Thanks very much for the info!
So I need a pressure gauge that will plug into my QD to see the pressure. Is this a standard something I can buy (any recommendations for places to buy?).
So after I have a gauge and can see the pressure, would I simply be turning the screw and locking the locknut to set a new pressure setting?
Assuming for the moment I DON'T change the pressure setting but just want to get leak-free again, are you saying I need to remove the PRV and replace a damaged O-Ring to get this to not leak?
Thanks again!
kennyd
Advertiser
Gauges are cheap. TSC sells them, and so does the Surplus Center. Add a short hose, a coupler and a QD nipple and you have a setup for about $30.
Yup-plug it in-then operate the valve to send pressure to that port. The PRV setup will be displayed. Do something on the tract first (like the FEL) so you know where the main PRV is set at.
The damaged o-ring is/was a guess. But if you take it apart to check you will need a gauge to set it anyway...
Yup-plug it in-then operate the valve to send pressure to that port. The PRV setup will be displayed. Do something on the tract first (like the FEL) so you know where the main PRV is set at.
The damaged o-ring is/was a guess. But if you take it apart to check you will need a gauge to set it anyway...
OP
mmranch
Gold Member
kennyd,
Sorry to be so thick about this but I want to understand before I start ordering parts.
I have 3 sets of hydraulic QD remotes on the back of the tractor. There are two hoses going from two of the remotes to the backhoe valve block (which is hard to get to, inside the backhoe control tower). The thumb valve is bolted to the outside of the control tower with hoses going into the control tower and into the backhoe valve block. So none of the hoses/valves are easy to get to and I'd like to avoid going there if possible. The PRV on the thumb valve IS accessible.
So for the pressure gauge... would I be creating a short hose with a T and gauge in the middle and QD connectors on each end? (male on one end and female on the other). And then I would plug this in between one of the backhoe hoses and it's remote on the back of the tractor?
If so then I understand the concept of how to hook this inline and see the pressure. Now I would just need to order the appropriate parts:
gauge (1/4" fitting)
T fitting (1/2" on ends/1/4" in middle)
2 short hoses w/ 1/2 male ends
2 QD connectors (1/2" ball type male/female)
Am I understanding this correctly?
So in theory...
Once I have the gauge setup, how do I see the pressure of the tractor (by the FEL trying to lift something it can't? What do I see on the gauge? The pressure goes up to 2200 psi and then stops? (So in theory, the tractor pressure is 2200 psi).
Then I go to use the thumb and make it press against the bucket until it stops and the gauge shows 1800 psi. Now I want to set the PRV to be 2000 psi... do I just turn the screw a bit and then pressure test again to see if I'm now at 2000 psi?
Sounds like I probably need to get the exact model # of the Prince valve to see what it's specs are.
Thanks again!
Sorry to be so thick about this but I want to understand before I start ordering parts.
I have 3 sets of hydraulic QD remotes on the back of the tractor. There are two hoses going from two of the remotes to the backhoe valve block (which is hard to get to, inside the backhoe control tower). The thumb valve is bolted to the outside of the control tower with hoses going into the control tower and into the backhoe valve block. So none of the hoses/valves are easy to get to and I'd like to avoid going there if possible. The PRV on the thumb valve IS accessible.
So for the pressure gauge... would I be creating a short hose with a T and gauge in the middle and QD connectors on each end? (male on one end and female on the other). And then I would plug this in between one of the backhoe hoses and it's remote on the back of the tractor?
If so then I understand the concept of how to hook this inline and see the pressure. Now I would just need to order the appropriate parts:
gauge (1/4" fitting)
T fitting (1/2" on ends/1/4" in middle)
2 short hoses w/ 1/2 male ends
2 QD connectors (1/2" ball type male/female)
Am I understanding this correctly?
So in theory...
Once I have the gauge setup, how do I see the pressure of the tractor (by the FEL trying to lift something it can't? What do I see on the gauge? The pressure goes up to 2200 psi and then stops? (So in theory, the tractor pressure is 2200 psi).
Then I go to use the thumb and make it press against the bucket until it stops and the gauge shows 1800 psi. Now I want to set the PRV to be 2000 psi... do I just turn the screw a bit and then pressure test again to see if I'm now at 2000 psi?
Sounds like I probably need to get the exact model # of the Prince valve to see what it's specs are.
Thanks again!
kennyd
Advertiser
Mike, you do not need a Tee. The gauge can be plugged into the QD-when you activate the control the system will go into relief and the pressure will be displayed on the gauge. look at the picture of mine below.
Basically you are "deadheading" the system into the gauge, does that clear things up for you a bit?
Basically you are "deadheading" the system into the gauge, does that clear things up for you a bit?
Attachments
OP
mmranch
Gold Member
kennyd,
Thanks for that photo. Yes I understand how that should work regarding plugging into one of the remotes and getting the pressure from the tractor.
But what about when checking the pressure that the thumb valve is getting? Do I need to attach the gauge directly to the thumb valve for that or the thumb cylinder? If so, then I'll need to get some additional fittings since I don't have any QDs right in any of those places.
Thanks again... getting more comfortable with this.
Thanks for that photo. Yes I understand how that should work regarding plugging into one of the remotes and getting the pressure from the tractor.
But what about when checking the pressure that the thumb valve is getting? Do I need to attach the gauge directly to the thumb valve for that or the thumb cylinder? If so, then I'll need to get some additional fittings since I don't have any QDs right in any of those places.
Thanks again... getting more comfortable with this.
kennyd
Advertiser
Just to clarify: you are not going to check the pressure the valve is getting. That will be set by the main PRV on the tractor that you will have already tested. The gauge would need to be hooked the the "work ports" (the ports going to the thumb cylinder). Then you will do as before and "deadhead" into the gauge OR you can add the Tee there, and operate the thumb till it stops moving then read the gauge.
OP
mmranch
Gold Member
Thanks again kennyd!
I think I understand now. I just checked the backhoe and it turns out that I DO have QD couplers right at the thumb cylinder (not quite sure which one to connect to). But they appear smaller than my 1/2" QD couplers on the remotes (guessing they are 3/8" size). So I will need to be able to make my gauge do both sizes.
Hmmm... maybe a T in the middle with the gauge and 1/2" on one end and 3/8" on the other?
Thanks again!
I think I understand now. I just checked the backhoe and it turns out that I DO have QD couplers right at the thumb cylinder (not quite sure which one to connect to). But they appear smaller than my 1/2" QD couplers on the remotes (guessing they are 3/8" size). So I will need to be able to make my gauge do both sizes.
Hmmm... maybe a T in the middle with the gauge and 1/2" on one end and 3/8" on the other?
Thanks again!
