Tilt cylinder wont hold position (853)

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ard

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My tilt cylinder works and has power in both directions. However, the cylinder wont hold its position (both directions) even if not loaded. I would assume the cylinder is leaking internally. Could it be some other fault ? I plan to test as follows: disconnect return (down) line from the cylinder and provide pressure to the up line. In case oil came out, the cylinder is leaking internally, then i will order a new seal kit. Is that the correct way to test ? (I never worked with hydraulics before)
 

Fishfiles

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you will have to plug the hose you take off as oil will shot out when you crank up even with the spool in the netraul position , you can remove both hoses and plug the hoses and the fittings on the cylinder and it should lock the cylinder if there are no internal leaks or you can fab an adaptor cap with an air chuck and apply air to one port of the cylinder and see if air comes out the other port ---------
 
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ard

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you will have to plug the hose you take off as oil will shot out when you crank up even with the spool in the netraul position , you can remove both hoses and plug the hoses and the fittings on the cylinder and it should lock the cylinder if there are no internal leaks or you can fab an adaptor cap with an air chuck and apply air to one port of the cylinder and see if air comes out the other port ---------
Thanks for the hint, removed the cylinder and tried it with air (about 140 psi) and there is a huge internal leak. Will try to open the beast before ordering a new seal kit.
 

Fishfiles

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Thanks for the hint, removed the cylinder and tried it with air (about 140 psi) and there is a huge internal leak. Will try to open the beast before ordering a new seal kit.
Quite a lot , I find when the cylinder leaks down from an internal leak , it is the nut on the end of the rod that came loose letting oil by pass around the threads , you can usually tell before opening it as the rod will go in and out easily just a little bit -------------------another hint while you have it apart would be to put a straight edge on the chrome rod to check for straightness as I see a lot of bent ones , when it gets a bend in it then it will cock the piston in the bore and scrap one side the casing bore , if the marks are not too bad the new piston seal will seal it up
 
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ard

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Quite a lot , I find when the cylinder leaks down from an internal leak , it is the nut on the end of the rod that came loose letting oil by pass around the threads , you can usually tell before opening it as the rod will go in and out easily just a little bit -------------------another hint while you have it apart would be to put a straight edge on the chrome rod to check for straightness as I see a lot of bent ones , when it gets a bend in it then it will cock the piston in the bore and scrap one side the casing bore , if the marks are not too bad the new piston seal will seal it up
Yes, the nut was loose, see pics:
First had to build a wrench to open the cylinder
bobtiltwrench.jpg

it was fairly easy to open the cylinder. The piston main seal is broken (assume part 5), there was no o-ring ? The nut holding the piston was loose, i could remove it by hand.
bobtilt1.jpg

I hope this one will work again when i mount a new seal and o-ring (parts 5 and 6)
bob843tiltcylinder.jpg

This is from a 843, dont know if my 853 has the same cylinder and part numbers. I only have the part list for a 843 and not the one for 853.
 

Fishfiles

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Yes, the nut was loose, see pics:
First had to build a wrench to open the cylinder

it was fairly easy to open the cylinder. The piston main seal is broken (assume part 5), there was no o-ring ? The nut holding the piston was loose, i could remove it by hand.

I hope this one will work again when i mount a new seal and o-ring (parts 5 and 6)

This is from a 843, dont know if my 853 has the same cylinder and part numbers. I only have the part list for a 843 and not the one for 853.
you want to change all the seals and orings not just the piston oring and seal , the whole kit should be around $25 -$40 bucks max , put locktite on the new nut they will give you in the kit even though the nut comes pre loaded with locktite in the threads
 

mrdeere1959

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you want to change all the seals and orings not just the piston oring and seal , the whole kit should be around $25 -$40 bucks max , put locktite on the new nut they will give you in the kit even though the nut comes pre loaded with locktite in the threads
$ 36.84 for 7135551.
 

Tazza

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$ 36.84 for 7135551.
Very good point about replacing the pressure seals in the gland. No point doing half a job.
The piston looks fine, they all have a few marks in them. New seals and it should be good. The main thing that will cause it to not work properly is if there are deep scores in the bore of the tube.
If you didn't know, there have been posts before about how to install new piston seals. You will need to stretch the new piston seal, the yellow one, so it fits over the piston. It will feel loose, so you use cardboard or plastic from a plastic bottle, wrap the piston and use a hose clamp to compress the seal so it shrinks, remove it. Oil it up and install into the cylinder.
Clean the threads and install Loctite, as mentioned earlier, the nuts do loosen up for no good reason without it.
Nice work on the spanner to get the gland off too.
 
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ard

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Very good point about replacing the pressure seals in the gland. No point doing half a job.
The piston looks fine, they all have a few marks in them. New seals and it should be good. The main thing that will cause it to not work properly is if there are deep scores in the bore of the tube.
If you didn't know, there have been posts before about how to install new piston seals. You will need to stretch the new piston seal, the yellow one, so it fits over the piston. It will feel loose, so you use cardboard or plastic from a plastic bottle, wrap the piston and use a hose clamp to compress the seal so it shrinks, remove it. Oil it up and install into the cylinder.
Clean the threads and install Loctite, as mentioned earlier, the nuts do loosen up for no good reason without it.
Nice work on the spanner to get the gland off too.
Hi, no post for a long time but i have made some progress. After ordering the new seal kit for the tilt cylinder, i decided to make it look a little bit better than before, this is how it looked like (i have not made photos before started to dismount)
IMG_1381.JPG

IMG_1382.JPG

There was "a little bit" dirt in the machine, it was a mix of sand, oil, glas, screws, stones, ...
IMG_1383.JPG

IMG_1386.JPG

IMG_1387.JPG

IMG_1390.JPG

IMG_1391.JPG

IMG_1392.JPG

Than i found that selenoid
IMG_1393.JPG

using the electic and hydraulic schematics i found it is the bucket position valve and has no idea what the selenoid is used for. Later i bought a parts manual and saw there is an optional on/off kit. The switch was broken and the +12V was not connected at all. The coil was ok so mounted a new switch, connected +12V and it works.
Repainted the cab
IMG_1395.JPG

and the lift arms
IMG_1398.JPG

IMG_1399.JPG

IMG_1410.JPG

as well as the main frame
IMG_1405.JPG

IMG_1406.JPG

mounted new tires and took it out to respray it
IMG_1413.JPG

IMG_1414.JPG

IMG_1415.JPG

found out there was not enougth oil in the vent gearcase, took it out, dismounted it, checked it, filled new oil in, mounted it again.
and spraying it
IMG_1418.JPG

IMG_1423.JPG

IMG_1424.JPG

for the decals, i found the bobcat logo as eps via google. I drawed the 853 logo and a friend of mine created the decals
IMG_1427.JPG

IMG_1429.JPG

My wokshop is not high enough to mount the cab so used a tree
IMG_1437.JPG

IMG_1439.JPG

IMG_1441.JPG

While trying to mount the tilt cylinder with the new seal kit i found out that the piston was buckled. Took the cylinder to a local hydraulics shop and they repaired it (new piston, new head), was cheeper than the bobcat spare parts.
While initially trying it out i found out that the aux hydraulic does not work. Checked selenoid coils: ok, cables: ok, connected the handle and electically it seems to work. Checked it later after assembling all and it worked. It was the switch in the handle, the right one was defect so i used the left one instead. I found the manufacturer of the switch, it is avaiable from mouser for about 9$ but they want to have 50 bucks (+tax +vat) for sending to germany so i left the switch out. Used a standard switch for horn on the left handle with the original wipe and and an additional spring, works fine.
Found a part that is not in the schematics, what is that ? May be a diode to protect the switches when powering off the coil ?
IMG_1436.JPG

In the meantime i wanted to start the bobcat but i had already mounted the harness in the cab. Have not found the manufacturer of the plugs (was not AMP, may be Delphi) so i build my own remote starter:
IMG_1474.JPG

P><P><IMG border=0 width=1024 src=

And all mounted
IMG_1455.JPG

IMG_1472.JPG

The loader works well, however, there are oil leaks somewhere. Today i cleaned the remaining dirt inside the loader using a power washer, will try to find the leaks next week but it seems to be i have to pull the engine. May be the hydrostatic control block or the punps connected to it.
 

Fishfiles

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Joined
Feb 8, 2007
Messages
1,698
Hi, no post for a long time but i have made some progress. After ordering the new seal kit for the tilt cylinder, i decided to make it look a little bit better than before, this is how it looked like (i have not made photos before started to dismount)


There was "a little bit" dirt in the machine, it was a mix of sand, oil, glas, screws, stones, ...






Than i found that selenoid

using the electic and hydraulic schematics i found it is the bucket position valve and has no idea what the selenoid is used for. Later i bought a parts manual and saw there is an optional on/off kit. The switch was broken and the +12V was not connected at all. The coil was ok so mounted a new switch, connected +12V and it works.
Repainted the cab

and the lift arms



as well as the main frame


mounted new tires and took it out to respray it



found out there was not enougth oil in the vent gearcase, took it out, dismounted it, checked it, filled new oil in, mounted it again.
and spraying it



for the decals, i found the bobcat logo as eps via google. I drawed the 853 logo and a friend of mine created the decals


My wokshop is not high enough to mount the cab so used a tree



While trying to mount the tilt cylinder with the new seal kit i found out that the piston was buckled. Took the cylinder to a local hydraulics shop and they repaired it (new piston, new head), was cheeper than the bobcat spare parts.
While initially trying it out i found out that the aux hydraulic does not work. Checked selenoid coils: ok, cables: ok, connected the handle and electically it seems to work. Checked it later after assembling all and it worked. It was the switch in the handle, the right one was defect so i used the left one instead. I found the manufacturer of the switch, it is avaiable from mouser for about 9$ but they want to have 50 bucks (+tax +vat) for sending to germany so i left the switch out. Used a standard switch for horn on the left handle with the original wipe and and an additional spring, works fine.
Found a part that is not in the schematics, what is that ? May be a diode to protect the switches when powering off the coil ?

In the meantime i wanted to start the bobcat but i had already mounted the harness in the cab. Have not found the manufacturer of the plugs (was not AMP, may be Delphi) so i build my own remote starter:


And all mounted


The loader works well, however, there are oil leaks somewhere. Today i cleaned the remaining dirt inside the loader using a power washer, will try to find the leaks next week but it seems to be i have to pull the engine. May be the hydrostatic control block or the punps connected to it.
Nice job . looking good ------------from the pics it looks like your leak might be controll valve spool seals --------you should have pressure washed the inside before painting , it is really a mess in there
 

Tazza

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Nice job . looking good ------------from the pics it looks like your leak might be controll valve spool seals --------you should have pressure washed the inside before painting , it is really a mess in there
Nice job indeed. I am still in the process of doing this to a 753G, getting there slowly.
I agree that the leak could be the control block, but they can also leak where the steering levers join to the pump. Get it clean, it's much easier to find leaks then.
Yours looked like mine inside, all the oil/dirt. This is where a steam cleaner would really be handy.
 
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ard

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Nice job indeed. I am still in the process of doing this to a 753G, getting there slowly.
I agree that the leak could be the control block, but they can also leak where the steering levers join to the pump. Get it clean, it's much easier to find leaks then.
Yours looked like mine inside, all the oil/dirt. This is where a steam cleaner would really be handy.
Thanks for the answers. I had already cleaned as much as possible before spraying. The power wash was only for the remaining that were not reachable before.
However, in the meantime i found at least one leak, it is the control valve (near part 37/38)
ControlValve853_1.jpg

2 Questions:
For the seals i plan to order the spool seal kit, it is:
6803605 SEAL KIT one spool - Ref. HYDRAULIC CONTROL VALVE(4),
HYDRAULIC CONTROL VALVE(54) & HYDRAULIC
CONTROL VALVE(56) - See S/L 31 Aug. 92 - W
is this the correct one or do i need more that that ?
When i unscrew 56, can i pull the complete spool without loosing any springs or balls ?
Thanks
 

Fishfiles

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Feb 8, 2007
Messages
1,698
Thanks for the answers. I had already cleaned as much as possible before spraying. The power wash was only for the remaining that were not reachable before.
However, in the meantime i found at least one leak, it is the control valve (near part 37/38)

2 Questions:
For the seals i plan to order the spool seal kit, it is:
6803605 SEAL KIT one spool - Ref. HYDRAULIC CONTROL VALVE(4),
HYDRAULIC CONTROL VALVE(54) & HYDRAULIC
CONTROL VALVE(56) - See S/L 31 Aug. 92 - W
is this the correct one or do i need more that that ?
When i unscrew 56, can i pull the complete spool without loosing any springs or balls ?
Thanks
99.9% of the time you really don't need a kit , just spool seals and some new boots , see #37 in the pic , that is the detent cap , don't pull on it from the rear to get the spool out , the springs and balls will fall out , push the spool from the from side
 

Tazza

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99.9% of the time you really don't need a kit , just spool seals and some new boots , see #37 in the pic , that is the detent cap , don't pull on it from the rear to get the spool out , the springs and balls will fall out , push the spool from the from side
If you have a good seal shop close, take the samples in, they should be able to match them for you at a fraction of the price from the dealer.
The rubber boots will be dealer only, the the seals are not
 

7LBSSMALLIE

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Messages
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If you have a good seal shop close, take the samples in, they should be able to match them for you at a fraction of the price from the dealer.
The rubber boots will be dealer only, the the seals are not
ok im blown away OUTSTANDING. gotta ask how many hrs in frame up rebuild and is there a profit or for pernsoal use,
 
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ard

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ok im blown away OUTSTANDING. gotta ask how many hrs in frame up rebuild and is there a profit or for pernsoal use,
thx. I have not counted the hours. It is only for my private use otherwise it would not make sense at all.
Btw, ordered the rubber boots and got new filters, will try to fix the control valve next weekend.
 
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ard

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thx. I have not counted the hours. It is only for my private use otherwise it would not make sense at all.
Btw, ordered the rubber boots and got new filters, will try to fix the control valve next weekend.
sorry, can not post pictures, i dont have a windows pc with office in my workshop. I have removed the cab, the lift arms and hand controls to work on the control valve. I also have a small leak at the point where the steering levers join to the pump (both sides) (as Tazza has already assumed). How do i remove that spool to install new seals (only removing the two bolts at the plate under the sping ?) I will try to post the page from the parts manual tomorrow. Hope this is the last lean but i will see, thx for your help.
 
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ard

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sorry, can not post pictures, i dont have a windows pc with office in my workshop. I have removed the cab, the lift arms and hand controls to work on the control valve. I also have a small leak at the point where the steering levers join to the pump (both sides) (as Tazza has already assumed). How do i remove that spool to install new seals (only removing the two bolts at the plate under the sping ?) I will try to post the page from the parts manual tomorrow. Hope this is the last lean but i will see, thx for your help.
had a few hours today after work so i drained hydarulic fluid, removed the hydraulic tank and removed the spool for the steering levers at the hydrostatic block. I'm wondering that there are no o-rings on the spool:
IMG_1486.JPG

I dont really understand the drawing on pdf page 93 of the parts list.
Should i try to get o-rings ? Two or only one at the top of the spool ?
Sorry for asking so many stupid questions, i simply never worked with hydraulics before.
 

Tazza

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had a few hours today after work so i drained hydarulic fluid, removed the hydraulic tank and removed the spool for the steering levers at the hydrostatic block. I'm wondering that there are no o-rings on the spool:

I dont really understand the drawing on pdf page 93 of the parts list.
Should i try to get o-rings ? Two or only one at the top of the spool ?
Sorry for asking so many stupid questions, i simply never worked with hydraulics before.
The steering setup is different to the other ones i have fiddled with. I'm not exactly sure what needs to be replaced to fix the leak on that. The control block spools i do, just not this one...
It looks to be in good shape, i thought they used to get wear marks on the top where the seal runs, but it looks very tidy.
Hopefully someone can help to tell you what needs to be done that has worked on one before.
Are there any O rings or quad rings in the housing that it came out of?
 

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