Bobcat 632 air in hydraulics

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Sx200

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first post so be kind....... thanks for a grate forum and if anyone could help i would be very grate full i own a old bobcat 632 skid steer just for home, saves me digging, and after changing the rear wheel bearing the hydraulics started tapping. i know the rear wheel bearing has nothing to do with the hydraulics but im trying to give all the information i can....... anyways i carried on regardless (error i know) until eventually the tapping got louder and eventually the hydraulics died. i took the hydraulic motor complete to a (laughs) specialist, labrador hydraulics, who duely ripped me for $800. the guy saying the plates "needed lapping", knowing nothing about engineering or hydraulics i took his word, a week later i picked up the motor installed it but it was exactly the same as b4. i then called bobcat.com.au who sent Ben from Nerang bobcat, a great fella and very helpful. after a couple of hours he changed the pump round as the other guy had it pumping oil out of the hydraulics back to the tank, and got i working, shortly after running it, once again lost hydraulics. Ben tried for a further hour eventually giving up and telling me "its sucking in air from somewhere" he did a great job and told me id be better pulling it apart, getting a seal kit and replacing the seals. so where could it be sucking air in? wheres the best place to start lookin as i dont wanna spend $300 on seals if its something easily fixed... as i mentioned this is my first bobcat and even though im quite mechanicly minded i am a newbie to hydraulics. any info would be a great help ps sorry for the long post but thought it better explaining what happend rather than just "bobcats sucking air in help" pps how do i attach photos?
 

sterlclan

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Welcome to the forum... I own a 630 and I had issues with the port block to pump o rings dried up and brittle do yourself a big favor and get the manual (got mine on ebay for 30 bucks) look for a crack in the supply lines as well usally air in =oil out look for leaks with the machine off good luck Jeff
 

Tazza

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Welcome to the forum... I own a 630 and I had issues with the port block to pump o rings dried up and brittle do yourself a big favor and get the manual (got mine on ebay for 30 bucks) look for a crack in the supply lines as well usally air in =oil out look for leaks with the machine off good luck Jeff
Your best investment is a service manual and a parts manual. I also got mine off a guy on the internet. Postage to Australis is a little pricy, i think i paid 40 USD for air freight but its still cheaper than getting them off clark. If you would like his details just ask. As for sucking in air, the only place i can think of is your line from the oil tank to the port block. All the other lines are at charge pressure or higher so really they shouldn't be able to pull in air. I would have to agree with sterlclan, check the port block seals, where it joins the hydraulic pump. As for seals, i get mine from A & B seals at slacks creek. I take it that your air in the system is affecting only your hydrostatics? and not your hydraulics? they both have seperate pumps but a common oil source.I'm
 

Tazza

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Your best investment is a service manual and a parts manual. I also got mine off a guy on the internet. Postage to Australis is a little pricy, i think i paid 40 USD for air freight but its still cheaper than getting them off clark. If you would like his details just ask. As for sucking in air, the only place i can think of is your line from the oil tank to the port block. All the other lines are at charge pressure or higher so really they shouldn't be able to pull in air. I would have to agree with sterlclan, check the port block seals, where it joins the hydraulic pump. As for seals, i get mine from A & B seals at slacks creek. I take it that your air in the system is affecting only your hydrostatics? and not your hydraulics? they both have seperate pumps but a common oil source.I'm
The pesky thing posted before i finished.
I'm sure the guy from clark who looked at it checked the port block filter, its a bronze filter. When this gets blocked it makes your pupm cavetate and foam up the oil. The machine will make high pitched growling noises and the pump will get hot VERY fast and you will have no power what so ever in your hydrostatics.
 

Sx200

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The pesky thing posted before i finished.
I'm sure the guy from clark who looked at it checked the port block filter, its a bronze filter. When this gets blocked it makes your pupm cavetate and foam up the oil. The machine will make high pitched growling noises and the pump will get hot VERY fast and you will have no power what so ever in your hydrostatics.
thanks for the aspeedy replies i got a service manual when i got the bobcat from the seller its a photocopy of the manual, its not helped me alot, its in black and white so on the hydraulics section i cant tell whats under pressure and which way the oils travelin. i got the o ring seals this morning and installed them one to the large nut, and one either side of the washer on the retaining nut. hasnt made much difference, even though it worked at first. as soon as i reved the engine i lost power and the bobcat wouldnt move, lift still worked though..... what tazza is saying is close as the oil is foamy (is that a word lol) the hydraulic lift works just no travel. the machine does scream and gets hot quick so ill look at the bronze filter now, is there anything else to check thanks
 

sterlclan

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thanks for the aspeedy replies i got a service manual when i got the bobcat from the seller its a photocopy of the manual, its not helped me alot, its in black and white so on the hydraulics section i cant tell whats under pressure and which way the oils travelin. i got the o ring seals this morning and installed them one to the large nut, and one either side of the washer on the retaining nut. hasnt made much difference, even though it worked at first. as soon as i reved the engine i lost power and the bobcat wouldnt move, lift still worked though..... what tazza is saying is close as the oil is foamy (is that a word lol) the hydraulic lift works just no travel. the machine does scream and gets hot quick so ill look at the bronze filter now, is there anything else to check thanks
while youre in there check the cold weather bypass and the neutral bypass they are poppetts and springs make shure that they arent gouged or scored my neutral bypass was actually installed backwards by a previous owner good luck Jeff
 

Tazza

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while youre in there check the cold weather bypass and the neutral bypass they are poppetts and springs make shure that they arent gouged or scored my neutral bypass was actually installed backwards by a previous owner good luck Jeff
Ok, if it is heating up quickly and foaming i would suspect the bronze filter. Have a look see at the port block, the one with that big nut on it that you replaced the O Rings on. If it is the same as mine, its on the left side. There are 3 hoses going into it, the one in the middle is the one you want, it has a larger nut on it than the others. You may need to remove one of the other hoses to get access to it. Remove the hose, then remove the adaptor that is screwed into the port block. There will be a spring behind this that holds the bronze filter in place. Take it out and clean as much muck out of the hole in the port block that you can. You can clean the filter by running degreaser or Kero through it and blowing it out with compressed air. I used some de-greaser and a high pressure cleaner to remove the crap out of it. Then blow air through it. If you are in a rush to dry it, throw it in the oven (just don't let the mrs see you do it). Mine used to start ok, then move a bit then just loose ALL hydrostatic power.
As for the hydraulic/hydrostatic diagrams, don't be too worried, my manual for my 731 is the same, you don't really need to know whats high and low pressure.
Good luck, if you can't follow any of the above information just let me know.
 

Sx200

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Ok, if it is heating up quickly and foaming i would suspect the bronze filter. Have a look see at the port block, the one with that big nut on it that you replaced the O Rings on. If it is the same as mine, its on the left side. There are 3 hoses going into it, the one in the middle is the one you want, it has a larger nut on it than the others. You may need to remove one of the other hoses to get access to it. Remove the hose, then remove the adaptor that is screwed into the port block. There will be a spring behind this that holds the bronze filter in place. Take it out and clean as much muck out of the hole in the port block that you can. You can clean the filter by running degreaser or Kero through it and blowing it out with compressed air. I used some de-greaser and a high pressure cleaner to remove the crap out of it. Then blow air through it. If you are in a rush to dry it, throw it in the oven (just don't let the mrs see you do it). Mine used to start ok, then move a bit then just loose ALL hydrostatic power.
As for the hydraulic/hydrostatic diagrams, don't be too worried, my manual for my 731 is the same, you don't really need to know whats high and low pressure.
Good luck, if you can't follow any of the above information just let me know.
wow thanks guys helped sop much at last im startint to smile a bit, tazza i used to play for camden tigers thats not far from u is it? ok got the bronze filter off, had to take it to a garage as it looked like its never been off before. replaced the 'o'rings. the bronze filter? is that a filter cos mine looks like a solid cone shape? hollow but not a filter as such, is that correct?
 

Tazza

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wow thanks guys helped sop much at last im startint to smile a bit, tazza i used to play for camden tigers thats not far from u is it? ok got the bronze filter off, had to take it to a garage as it looked like its never been off before. replaced the 'o'rings. the bronze filter? is that a filter cos mine looks like a solid cone shape? hollow but not a filter as such, is that correct?
I'm not sure where that is :) i live in sheldon, its out cleveland way.
As for that bronze filter, it is indeed a filter. It looks solid but trust me, it is a filter. You should be able to pour diesel into it and it should drip out (slowly). Mine looked like it was never touched! it had crap everywhere. Like i said, give it a spray with de-greaser and blow it out with a pressure washer if you have access to one then dry it with compressed air and an oven or leave it in the sun.
Worst case, spend the money and buy a new one, they are about 30 bux but there were none available, they had to get it up from Sydney.
Technically you *could* run it without the filter but with the amount of crap that t has caught i wouldn't risk the 5 or so thousand dollar hydrostatic pump.
I'm amazed the service guy that came out didn't pick up on this! when i called about my problem thats the first thing i was told to check. So when anyone had this sort of problem the first thing i ask is have you checked the bronze filter.
When it blocks up it starves the hydrostatic pump of oil, which causes it to cavetate (creates air bubbles) which under pressure implode and cause pitting in metal surfaces (after a bit of time) this is the noise you can hear. Let me know how you go.
 

Sx200

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I'm not sure where that is :) i live in sheldon, its out cleveland way.
As for that bronze filter, it is indeed a filter. It looks solid but trust me, it is a filter. You should be able to pour diesel into it and it should drip out (slowly). Mine looked like it was never touched! it had crap everywhere. Like i said, give it a spray with de-greaser and blow it out with a pressure washer if you have access to one then dry it with compressed air and an oven or leave it in the sun.
Worst case, spend the money and buy a new one, they are about 30 bux but there were none available, they had to get it up from Sydney.
Technically you *could* run it without the filter but with the amount of crap that t has caught i wouldn't risk the 5 or so thousand dollar hydrostatic pump.
I'm amazed the service guy that came out didn't pick up on this! when i called about my problem thats the first thing i was told to check. So when anyone had this sort of problem the first thing i ask is have you checked the bronze filter.
When it blocks up it starves the hydrostatic pump of oil, which causes it to cavetate (creates air bubbles) which under pressure implode and cause pitting in metal surfaces (after a bit of time) this is the noise you can hear. Let me know how you go.
thanks again tazza, i took out the bronze element and it was blocked solid so i let i soak over night, put it in this mornin and everythin seems to be fine, dont wanna get too excited yet but i thinks that was the prob all along....... so much for the experts eh? cost me $250 for bobcat to come out and $800 to the robbing bas**** at labrador hydraulics. whan all it need was $6 in 'o' rings and a bit of degreaser lol suppose you gotta laugh. ill keep you posted as i use it more today and undoubtedly ill be askin for help again when ever anythin else goes wrong.............. THANK YOU VERY MUCH........
 

Sx200

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thanks again tazza, i took out the bronze element and it was blocked solid so i let i soak over night, put it in this mornin and everythin seems to be fine, dont wanna get too excited yet but i thinks that was the prob all along....... so much for the experts eh? cost me $250 for bobcat to come out and $800 to the robbing bas**** at labrador hydraulics. whan all it need was $6 in 'o' rings and a bit of degreaser lol suppose you gotta laugh. ill keep you posted as i use it more today and undoubtedly ill be askin for help again when ever anythin else goes wrong.............. THANK YOU VERY MUCH........
well that sorted out the drive problem and it even stopped the rattle i had in the pump, but i reckon ive not got somethin quite right cos the lift and grab is very weak now, i go to pick up and if ive got any weight in the bucket it hardly lifts, where did i go wrong?
 

Tazza

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well that sorted out the drive problem and it even stopped the rattle i had in the pump, but i reckon ive not got somethin quite right cos the lift and grab is very weak now, i go to pick up and if ive got any weight in the bucket it hardly lifts, where did i go wrong?
The first thing i would check is your relief vavle. With all the work you have done you *may* have let a piece of crap dislodge and get stuck in your relief vavle. This should be located in your control block, it should have some numbers stamped on it. You actually have 2 relief vavles on the control block, one for your main hydraulics and 1 on your lift arm control. I would doubt it is the lift arm relief valve, it should be the main relief valve, it should have something like 2100 or 2200 stamped on it, standing for 2,100 PSI ot 2,200 PSI. Hopefully that is all that is wrong. Have you replaced the hydraulic oil filter? if not, it would be worth replacing they are all of 12 or so bux each. Whenever you do major work on your machine you really should change the filter.
The Relief valve is a simple spring and poppet, so pull out the poppet and spring and claen it out then re-assemble. When you re-assemble it use a bit of thick grease to hold the spring and poppet together for re-installation.
Let me know how you go, if it doesn't work let me know and i will have a closer look at my 731 manual as i am pretty sure these 2 have the same hydraulic/hydrostatic system.
I can't be bothered soing a spelling check, so don't yell at me if i have some terrible spelling.
 

Tazza

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The first thing i would check is your relief vavle. With all the work you have done you *may* have let a piece of crap dislodge and get stuck in your relief vavle. This should be located in your control block, it should have some numbers stamped on it. You actually have 2 relief vavles on the control block, one for your main hydraulics and 1 on your lift arm control. I would doubt it is the lift arm relief valve, it should be the main relief valve, it should have something like 2100 or 2200 stamped on it, standing for 2,100 PSI ot 2,200 PSI. Hopefully that is all that is wrong. Have you replaced the hydraulic oil filter? if not, it would be worth replacing they are all of 12 or so bux each. Whenever you do major work on your machine you really should change the filter.
The Relief valve is a simple spring and poppet, so pull out the poppet and spring and claen it out then re-assemble. When you re-assemble it use a bit of thick grease to hold the spring and poppet together for re-installation.
Let me know how you go, if it doesn't work let me know and i will have a closer look at my 731 manual as i am pretty sure these 2 have the same hydraulic/hydrostatic system.
I can't be bothered soing a spelling check, so don't yell at me if i have some terrible spelling.
I kinda forgot to tell you that you MUST watch the small shims that are between the poppet and spring (they look like thinl washers), these are used to set the relief pressure. If you forget to put them back in your pressure will be lower that it should be.
Good luck
 

Sx200

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The first thing i would check is your relief vavle. With all the work you have done you *may* have let a piece of crap dislodge and get stuck in your relief vavle. This should be located in your control block, it should have some numbers stamped on it. You actually have 2 relief vavles on the control block, one for your main hydraulics and 1 on your lift arm control. I would doubt it is the lift arm relief valve, it should be the main relief valve, it should have something like 2100 or 2200 stamped on it, standing for 2,100 PSI ot 2,200 PSI. Hopefully that is all that is wrong. Have you replaced the hydraulic oil filter? if not, it would be worth replacing they are all of 12 or so bux each. Whenever you do major work on your machine you really should change the filter.
The Relief valve is a simple spring and poppet, so pull out the poppet and spring and claen it out then re-assemble. When you re-assemble it use a bit of thick grease to hold the spring and poppet together for re-installation.
Let me know how you go, if it doesn't work let me know and i will have a closer look at my 731 manual as i am pretty sure these 2 have the same hydraulic/hydrostatic system.
I can't be bothered soing a spelling check, so don't yell at me if i have some terrible spelling.
spot on again tazza, took of the relief valve blew it out and shes now ok, i think i adjusted the allen key as now the pressure is too much. how would i test without a pressure guage?
 

Tazza

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spot on again tazza, took of the relief valve blew it out and shes now ok, i think i adjusted the allen key as now the pressure is too much. how would i test without a pressure guage?
There is no way to know if you don't have a pressure gauge i'm afraid. I am really not sure if you could do any damage if it was a litte higher. A little means just a LITTLE as your hoses will all be rated at around 2,500 PSI and could burst if the pressure exceeds that, they do have a safety factor built in but better to be safe.... Your machine i think only runs 2,200 PSI so a little higher i belive would be ok, don't quote me on that.
I'm going to make an adaptor when i get a change to attach a coupling to a pressure gauge so i can check my pressure. Your machine doesn't use flat faced adaptors does it? if not, when i make it i can always loan it to you so you can set your pressure.
 

Sx200

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There is no way to know if you don't have a pressure gauge i'm afraid. I am really not sure if you could do any damage if it was a litte higher. A little means just a LITTLE as your hoses will all be rated at around 2,500 PSI and could burst if the pressure exceeds that, they do have a safety factor built in but better to be safe.... Your machine i think only runs 2,200 PSI so a little higher i belive would be ok, don't quote me on that.
I'm going to make an adaptor when i get a change to attach a coupling to a pressure gauge so i can check my pressure. Your machine doesn't use flat faced adaptors does it? if not, when i make it i can always loan it to you so you can set your pressure.
thanks tazza i just ordered one from the uk off ebay? hope it works lol.if it does let me know if you wanna borrow it im on the gold coast. i noticed i was losing a bit of oil from that area could that be from the pressure valve?
 

Tazza

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thanks tazza i just ordered one from the uk off ebay? hope it works lol.if it does let me know if you wanna borrow it im on the gold coast. i noticed i was losing a bit of oil from that area could that be from the pressure valve?
I doubt the oil leak would be specifically the relief valve, i would guess it would be your control block. There are no less than 40 O rings inside it, unless it is annoying you i recommend not touching it.

It isn't that hard to repair, but it really is a big job as you have to remove all your tube lines and linkages, its VERY messy. IF you do, remove the block and replace the seals for each section one at a time as to not mix your parts up. Also, note which stage sits where. I get all my seals from a place called A & B Seals at Slacks Creek, they had all of them in stock. ooh, get 90 duro hardness O rings, they handle the high temperatures alot better, and remember to lube all O rings before you install them to prevent pinching when tightening.

I guessed you lived on the Gold Coast, as you dealt with Clark down the coast. I may take you up on the offer of the pressure tester, but i have a long way to go before i would need it. I am still repairing the engine out of the 743. Hopefully the hydraulics/hydrostatics are in good condition....
 
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