Control Valve Leak- Test?

[coreya3212]

I have a 825 with a leak in the control valve. I thought it was the o rings on hte spool covers so i changed those. Valve in, engine back in, still leaks. Engine out, vlave out, split apart and replace all theo rings between the valves. Back in, engine back in, still leaks. i dont know what else it can be. Also, I f I hook the aux hyd from another bobcat to my control valve and run pressure to them, obviously a pressure line and the return line, and just put oil through, will the open ports on the spool valves spray oil??

 

[coreya3212]

I guess to be clear on my above post, I am looking to see where it is leaking, as the oil comes out from underneath the control valve. Then it would be nice to test it off the aux hyd before putting it back in. I figure as long as I dont actuate the spool valves, no flow should come through the ports, correct? The machine starts leaking hyd oil with out working spool valves if this helps.

 

[coreya3212]

I guess to be clear on my above post, I am looking to see where it is leaking, as the oil comes out from underneath the control valve. Then it would be nice to test it off the aux hyd before putting it back in. I figure as long as I dont actuate the spool valves, no flow should come through the ports, correct? The machine starts leaking hyd oil with out working spool valves if this helps.

I hooked the control valve to aux hyd on my neighbours machine and it works to test for the leak. we could easily see oil coming from between the the inlet cover and the first spool section. Changed the o rings in this section 2 more times and the leak remains. Gonna have to take it to a hyd shop to see if they can reseal it. I cant see why it is still leaking.

 

[Fishfiles]

I hooked the control valve to aux hyd on my neighbours machine and it works to test for the leak. we could easily see oil coming from between the the inlet cover and the first spool section. Changed the o rings in this section 2 more times and the leak remains. Gonna have to take it to a hyd shop to see if they can reseal it. I cant see why it is still leaking.

I see your having a one man thread , let me jump in with some ideas , I don't know the 825 as I have never seen them around here but they are similiar I am sure to every other model , and I have had some do-zees to find ----------orings on fittings that screw into the valve , aux hydraulic spool cover orings , spool seals put in backwards , orings on relief , cavation valve or such , rusted out metal on the sides of the reliefs vavles , possibly even a crack in the valve bank ----------get it very clean and dry , pressure wash thourolly, degrease and wash off again and blow with air , get lights under valve in position before starting it up , use mirrors , fire it up and see if you can find the source

 

[coreya3212]

I see your having a one man thread , let me jump in with some ideas , I don't know the 825 as I have never seen them around here but they are similiar I am sure to every other model , and I have had some do-zees to find ----------orings on fittings that screw into the valve , aux hydraulic spool cover orings , spool seals put in backwards , orings on relief , cavation valve or such , rusted out metal on the sides of the reliefs vavles , possibly even a crack in the valve bank ----------get it very clean and dry , pressure wash thourolly, degrease and wash off again and blow with air , get lights under valve in position before starting it up , use mirrors , fire it up and see if you can find the source

thanks Fish. I was starting to think I stunk... I can see the leak now, witht he above mentioned test method. Much easier than putting it back in the machine. it is a 3 spool greyson valve bank. the oil comes out the bottom between the inlet/outlet section and the first valve. I replaced all the o rings between all the valves and covers and the other 3 sections seal ok but the oil comes out the same spot each time. I havent switched the 1st and 3rd valve for each other yet to see if its the valve side or the cap side yet only because it doesnt do me much good. I am gonna take to a hyd shop and get them to have a look. A crack that I cant see is kinda what I am expecting.

 

[coreya3212]

thanks Fish. I was starting to think I stunk... I can see the leak now, witht he above mentioned test method. Much easier than putting it back in the machine. it is a 3 spool greyson valve bank. the oil comes out the bottom between the inlet/outlet section and the first valve. I replaced all the o rings between all the valves and covers and the other 3 sections seal ok but the oil comes out the same spot each time. I havent switched the 1st and 3rd valve for each other yet to see if its the valve side or the cap side yet only because it doesnt do me much good. I am gonna take to a hyd shop and get them to have a look. A crack that I cant see is kinda what I am expecting.

Well, they hyd shop resealed my valve with proper orings, bench tested and said no more leak. I get it home, in the machine, put the engine in and she leaks just like before. I phone the hyd shop and raise the roof. 2 hours and I have to guys here from the shop trying to figure this out. They put a pressure guage on the outlet side of the valve bank and it reads 50 PSI. They claim this is way to high and feel that the back pressure is what is cause the orings to fail in the valve.We isolate the oil cooler, 50 psi still. We isolate the return filter, basically just pump the oil through the valve and back into the hyd fill tube, and the pressure is basically no pressure. After studying this a while, there are 2 filters prior to the oil returning to the hyd reservoir, with 2 separate check or relief valves. One is set at 65 psi and the other is a 2 psi relief. he figures the 2 psi relief is stuck or something and that will likely be the culprit.

Is back pressure on the outlet side of the valve supposed to be less than 20 psi?

Anyone in the know believe the backpressure would blow the oring?

I dont know much about hyd so any advice would help. My current plan is to pull the 2 psi relief valve and test it with air, if it holds too much pressure I will replace and retest the back pressure on my system before I replace the o rings in the valve bank again.

 

[Fishfiles]

Well, they hyd shop resealed my valve with proper orings, bench tested and said no more leak. I get it home, in the machine, put the engine in and she leaks just like before. I phone the hyd shop and raise the roof. 2 hours and I have to guys here from the shop trying to figure this out. They put a pressure guage on the outlet side of the valve bank and it reads 50 PSI. They claim this is way to high and feel that the back pressure is what is cause the orings to fail in the valve.We isolate the oil cooler, 50 psi still. We isolate the return filter, basically just pump the oil through the valve and back into the hyd fill tube, and the pressure is basically no pressure. After studying this a while, there are 2 filters prior to the oil returning to the hyd reservoir, with 2 separate check or relief valves. One is set at 65 psi and the other is a 2 psi relief. he figures the 2 psi relief is stuck or something and that will likely be the culprit.

Is back pressure on the outlet side of the valve supposed to be less than 20 psi?

Anyone in the know believe the backpressure would blow the oring?

I dont know much about hyd so any advice would help. My current plan is to pull the 2 psi relief valve and test it with air, if it holds too much pressure I will replace and retest the back pressure on my system before I replace the o rings in the valve bank again.

I ain't buying into to 50 psi back pressure is too much , are you absolutely sure you are putting the correct spool seals in there and are you putting them in facing the right way , there is quite a few different style spool seals out there , I never see any 825's around here so I don't know what style they use , the black quad rings can be installed facing either way but all the other style only go in one way , and the orange colored one require a special tool to not cut them while sliding over the spool , it can been done with out the tool

 

[coreya3212]

I ain't buying into to 50 psi back pressure is too much , are you absolutely sure you are putting the correct spool seals in there and are you putting them in facing the right way , there is quite a few different style spool seals out there , I never see any 825's around here so I don't know what style they use , the black quad rings can be installed facing either way but all the other style only go in one way , and the orange colored one require a special tool to not cut them while sliding over the spool , it can been done with out the tool

I should have posted some more info about the valve itself I suppose. It is a 3 valve grayson bank. The leak occurs between the inlet section and the first valve section, when the machine is running without moving any of the spool valves. So when the machine is idling, and should just be pumping fluid through the intake and outlet of the valve bank without diverting flow to the spools, it leaks between the first valve and the inlet side. they hyd chart in my service manual shows this as hi pressure to the valve, but low pressure exiting the valve in the neutral position. they claim that 50 psi for the low pressure side is abnormal? The entire valve bank is basically sealed with a bunch of orings. 3 between sections each, and the spools have a o ring on each end with a back up plsatic seal . I dont think they can be reversed as long as they are in the right order, being oring to the inside of the spool and back up seal to the outside with a retaining washer to keep them in place.
Thanks Fishfiles.

 

[Tazza]

I should have posted some more info about the valve itself I suppose. It is a 3 valve grayson bank. The leak occurs between the inlet section and the first valve section, when the machine is running without moving any of the spool valves. So when the machine is idling, and should just be pumping fluid through the intake and outlet of the valve bank without diverting flow to the spools, it leaks between the first valve and the inlet side. they hyd chart in my service manual shows this as hi pressure to the valve, but low pressure exiting the valve in the neutral position. they claim that 50 psi for the low pressure side is abnormal? The entire valve bank is basically sealed with a bunch of orings. 3 between sections each, and the spools have a o ring on each end with a back up plsatic seal . I dont think they can be reversed as long as they are in the right order, being oring to the inside of the spool and back up seal to the outside with a retaining washer to keep them in place.
Thanks Fishfiles.

I too don't believe a word of the 50psi limit.
Is it leaking between segments or out of the actual spool?
If the seals were correct between segments there is NO way it would leak, even with 3,000 PSI behind it. I re-sealed my 731 years ago, they had a really snug fit, if the correct O rings were used it ain't gonna leak!
I'm pretty sure charge pressure is generated with back pressure to the valve. So the 50 PSI is required for the drive pump. The newer machines run 120 PSI and they don't leak.
I even had a 753 that someone repaired incorrectly, its charge pressure was 400 PSI! did the control block leak? not a drop.

 

[Fishfiles]

I too don't believe a word of the 50psi limit.
Is it leaking between segments or out of the actual spool?
If the seals were correct between segments there is NO way it would leak, even with 3,000 PSI behind it. I re-sealed my 731 years ago, they had a really snug fit, if the correct O rings were used it ain't gonna leak!
I'm pretty sure charge pressure is generated with back pressure to the valve. So the 50 PSI is required for the drive pump. The newer machines run 120 PSI and they don't leak.
I even had a 753 that someone repaired incorrectly, its charge pressure was 400 PSI! did the control block leak? not a drop.

I can't picture what you got in my head , but I am pretty sure I seen something like it before , some ideas for you : could it be there were some poppets or springs and balls that went between the sections and nybe they got lost during disassembling ----could it be the vavle is a "compensated " valve in which there is a spring on a spool which holds pressure in the valve which could be sticking ----could it be a problem with the centering spring not centering the spool -----------could it be the wrong sized micron element hydraulic filter causing the back pressure , did you change the filter lately and use a cross over referenced filter ---------can you take a picture of your machine and valve and post it

 

[coreya3212]

I can't picture what you got in my head , but I am pretty sure I seen something like it before , some ideas for you : could it be there were some poppets or springs and balls that went between the sections and nybe they got lost during disassembling ----could it be the vavle is a "compensated " valve in which there is a spring on a spool which holds pressure in the valve which could be sticking ----could it be a problem with the centering spring not centering the spool -----------could it be the wrong sized micron element hydraulic filter causing the back pressure , did you change the filter lately and use a cross over referenced filter ---------can you take a picture of your machine and valve and post it

It is leaking between segments. Between the inlet and the first valve segment. I dont know what a compensated valve is, so I dont know if I have one. Sorry Fish. Everything functions properly, just that it leaks and doesnt seem to be cured with new o rings. The shop looked up the valve bank and say they put the proper o rings in. To day i bypassed one of the external filters and the 20 PSI, ( not 2 psi) like the hyd guy said, relief and my pressure was actually higher at around 65 psi. I did this to try to reduce the back pressure, but I went through my manual and everything is plumbed to spec, same control as in the manual. i believe this is intended to run with some pressure and those guys are full of crap. I will scan my manual with the hyd schematic and the page with the breakdown of the control valve and try to post. Thanks guys.

 

[coreya3212]

It is leaking between segments. Between the inlet and the first valve segment. I dont know what a compensated valve is, so I dont know if I have one. Sorry Fish. Everything functions properly, just that it leaks and doesnt seem to be cured with new o rings. The shop looked up the valve bank and say they put the proper o rings in. To day i bypassed one of the external filters and the 20 PSI, ( not 2 psi) like the hyd guy said, relief and my pressure was actually higher at around 65 psi. I did this to try to reduce the back pressure, but I went through my manual and everything is plumbed to spec, same control as in the manual. i believe this is intended to run with some pressure and those guys are full of crap. I will scan my manual with the hyd schematic and the page with the breakdown of the control valve and try to post. Thanks guys.

Uploaded Hyd schematic, and a page that shows the valve itself. In the media section in the photo album titled Corey Shop Build. Last 3 downloads,

 

[Tazza]

Uploaded Hyd schematic, and a page that shows the valve itself. In the media section in the photo album titled Corey Shop Build. Last 3 downloads,

If its leaking there they have done something wrong. I have worked on gresson valves before. Tere is no reason for it to leak between segments. The only other possibility is a hair line crack allowing it to leak.
Fishfiles - They are pretty simple. There is a top and bottom 'cap' you can then stack one, two or as many segments in between as you like. There are 3 or 4 O rings that have faces machined into each segment for the O rings to sit in to seal between segments. Install the correct length bolt to hold the top cap to the bottom and you're set. Its the same style as most excivator attachments have fitted to them.
I did my 731 and i did my excivator attachment, neither leaked.

 

[coreya3212]

If its leaking there they have done something wrong. I have worked on gresson valves before. Tere is no reason for it to leak between segments. The only other possibility is a hair line crack allowing it to leak.
Fishfiles - They are pretty simple. There is a top and bottom 'cap' you can then stack one, two or as many segments in between as you like. There are 3 or 4 O rings that have faces machined into each segment for the O rings to sit in to seal between segments. Install the correct length bolt to hold the top cap to the bottom and you're set. Its the same style as most excivator attachments have fitted to them.
I did my 731 and i did my excivator attachment, neither leaked.

Sooooo...from everything that has transpired thus far, i should assume they used the wrong o rings.

 

[Fishfiles]

Sooooo...from everything that has transpired thus far, i should assume they used the wrong o rings.

I know having done this seal job so many times has got to be frustrating for you -------- I looked at the three seals in the picture in the galley and they are as I tried to explain , what gets me is I would think that one of the three would be all that is needed and not all three , the black one is a quad ring and can be installed in either direction , and third green one is only right when the cup side is facing the oil pressure and it comes in different colors which some have different diameters for different sized spools , some different colors are just from them using different materials over the years , the orange colored one looks like the old style cup seal that requires a tool to make not cutting it while sliding it over the spool easier , those three different seals are interchangeable in different situatuions , like they use to use the black one then went to the orange one and now use the green one , but what gets me is that all three are in there , it seems to me that it should be one of the three and not all three , also you say it is leaking from between the banks (sections) , could it be that you put to many seals into the bore and caused a problem , ------------ orings between the sections should be a good quailty oring and not a oring out of a cheap oring kit , the rubber orings don't hold up well to pressure, -------could you give me a serial number and I will call my dealer and see what they would give to seal the spools , I am really thinking that you have too many seals on the spool and possibly could have cracked the housing when tightening it up , it is hard enough to trouble shoot a problem when you are not there to see whats going on -- I think I can picture a gressen valve now , flat on the bottom , rounded on the top and has three thru bolts not 4 --hang in there you will get it figured out

 

[coreya3212]

I know having done this seal job so many times has got to be frustrating for you -------- I looked at the three seals in the picture in the galley and they are as I tried to explain , what gets me is I would think that one of the three would be all that is needed and not all three , the black one is a quad ring and can be installed in either direction , and third green one is only right when the cup side is facing the oil pressure and it comes in different colors which some have different diameters for different sized spools , some different colors are just from them using different materials over the years , the orange colored one looks like the old style cup seal that requires a tool to make not cutting it while sliding it over the spool easier , those three different seals are interchangeable in different situatuions , like they use to use the black one then went to the orange one and now use the green one , but what gets me is that all three are in there , it seems to me that it should be one of the three and not all three , also you say it is leaking from between the banks (sections) , could it be that you put to many seals into the bore and caused a problem , ------------ orings between the sections should be a good quailty oring and not a oring out of a cheap oring kit , the rubber orings don't hold up well to pressure, -------could you give me a serial number and I will call my dealer and see what they would give to seal the spools , I am really thinking that you have too many seals on the spool and possibly could have cracked the housing when tightening it up , it is hard enough to trouble shoot a problem when you are not there to see whats going on -- I think I can picture a gressen valve now , flat on the bottom , rounded on the top and has three thru bolts not 4 --hang in there you will get it figured out

I have a feeling you are looking at pictures other than mine. What gallery were you looking in and I will see if thats the same as mine. The pictures I uploaed were black and white out of the manual so you wouldnt have seen colors of the seals. This leak does not have anything to do with the spools, or bores or too many seals etc. It is definately coming between sections. I have narrrowed it down to one of the valves. the leak always occurs in the same spot, between the inlet and first valve section. I reversed the 1st and 3rd valve, as they are the same, and the leak moves to between the middle and 3rd section, so I know it is that piece causing the problem. I just cant see why. No defect evident. What are thoguhts on lapping that face a bit? Should this be attempted? Thanks Fish and Tazz. I am getting close to starting a fire...

 

[Tazza]

I have a feeling you are looking at pictures other than mine. What gallery were you looking in and I will see if thats the same as mine. The pictures I uploaed were black and white out of the manual so you wouldnt have seen colors of the seals. This leak does not have anything to do with the spools, or bores or too many seals etc. It is definately coming between sections. I have narrrowed it down to one of the valves. the leak always occurs in the same spot, between the inlet and first valve section. I reversed the 1st and 3rd valve, as they are the same, and the leak moves to between the middle and 3rd section, so I know it is that piece causing the problem. I just cant see why. No defect evident. What are thoguhts on lapping that face a bit? Should this be attempted? Thanks Fish and Tazz. I am getting close to starting a fire...

I did run my sections over a piece of sand paper and glass to flatten them, there was not an issue with flatness, but i did ti anyway. Its worth checking it for flatness with a steel ruler, see if it is indeed warped.

 

[Fishfiles]

I have a feeling you are looking at pictures other than mine. What gallery were you looking in and I will see if thats the same as mine. The pictures I uploaed were black and white out of the manual so you wouldnt have seen colors of the seals. This leak does not have anything to do with the spools, or bores or too many seals etc. It is definately coming between sections. I have narrrowed it down to one of the valves. the leak always occurs in the same spot, between the inlet and first valve section. I reversed the 1st and 3rd valve, as they are the same, and the leak moves to between the middle and 3rd section, so I know it is that piece causing the problem. I just cant see why. No defect evident. What are thoguhts on lapping that face a bit? Should this be attempted? Thanks Fish and Tazz. I am getting close to starting a fire...

http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=0&path=valve%20seals I went to the media /photos and on the 3rd page the last pictures was the ones above , so I thought that had to be you , I looked again and never did find anything that could seem to fit your app. ----------- it could be warped and possibly straightened out , as Tazza said use a good straight end and a feeler gauge to see if you can see any low spots , if so then lap it flat , also a crack is possible , a machine shop could possiblly magnaflux it for you , or you can do it your self , I use to have to do it to crane block hooks all the time , you spray cleaner , then a penetranting dye and then a over coat that if there is a crack it will bleed thru the white stuff and show up , only thing is it might be cracked in a spot that you can't see internally ,have seen a few 7 series Bobcats crack the vavle internally and not leak externally but give you fits trying to troubleshot problems from internal pressure going to the wrong place , the three cans of magnaflux are expensive though ------------- did you check to see if the bank ( section) is available and how much it cost

 

[coreya3212]

http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=0&path=valve%20seals I went to the media /photos and on the 3rd page the last pictures was the ones above , so I thought that had to be you , I looked again and never did find anything that could seem to fit your app. ----------- it could be warped and possibly straightened out , as Tazza said use a good straight end and a feeler gauge to see if you can see any low spots , if so then lap it flat , also a crack is possible , a machine shop could possiblly magnaflux it for you , or you can do it your self , I use to have to do it to crane block hooks all the time , you spray cleaner , then a penetranting dye and then a over coat that if there is a crack it will bleed thru the white stuff and show up , only thing is it might be cracked in a spot that you can't see internally ,have seen a few 7 series Bobcats crack the vavle internally and not leak externally but give you fits trying to troubleshot problems from internal pressure going to the wrong place , the three cans of magnaflux are expensive though ------------- did you check to see if the bank ( section) is available and how much it cost

Thanks Fellas. Those pics are not mine Fish. Mine are in the folder " Corey Shop Build" last 3 pics. Nothin to see really, just the diagram of the valve from the service manual. I think I gonna try lapping the bad side to see any deformity. I have inspected it under a magnifying lamp and cant see any cracks so lapping it is about all I can try at this point. i havent priced out a new one yet....too scared,
Would I be able to just get one new valve section or do these banks have to come in one piece, as in , all 3 valves and new covers?