743 Tilt cylinder rebuild post by Tazza

Bobpuddy · Nov 21, 2008

I read there is a How-to post by Tazza on a 743 tilt cylinder rebuild. Can someone tell me how to find it? I tried the search option but had no luck.

mllud · Nov 21, 2008

Tazza

Joined: 08 Dec 2004

Total Posts: 3382

Re: Rebuilding 743 front bucket tilt cylinder question
Posted: 12 Oct 2005 06:58 AM

You are more than welcome.
Now, the tilt cylinder, this is really quite easy and NO you do not need the service manual for this. Sorry, but this will be quite a long post, you have been warned

First, remove the cylinder from the lift amrs and the bobtach (not always an easy job). Remove the 2 hoses and mark and cap them! yo don't want it to work backwards (yes, i have done this before....)
Drain the cylinder of oil by pushing the chrome bar all the way in, then all the way back out. Mount the cylinder in a vice from the bottom so you can see the aloy gland nut where the chrome bar comes out of. You really should use a propper spanner to remove this gland nut, a pair of stillsons (not sure if you call them the same over there) or a large wrench will also work, but will mark the aloy but will not damage it.
When removed, pull the chrome bar up and out, this will have a piston attached to the bottom. Remove the outer of the cylinder from the vice. Put the chrome bar in the vice on the end where it joins to the bobtach. Be VERY carefull not to damage the chrome bar at ANY time. Remove the nut that holds the piston on to the chrome bar. Remove the piston from the bar and also remove the gland nut (aloy bit with 2 seals inside it).
Now, to remove the seals and O rings, you really need an O ring pick for this, first remove the outer O rings, there is one behind the shoulder at the end of the thread, then there will be 1 O ring and 1 backup ring on the part that sits inside the cylinder. Now for the inside ones.
There is a wiper seal and a pressure seal remove the wiper first, this is where the chrome bar comes out of, stick the O ring pick in and twist it out, do the same with the pressure seal, this one is a little harder as it is a fair way in, you are best to attach this one from the end where the nut enters the cylinder. Please be very carefull not to stab your hand doing this, the picks are really quite sharp!
When you remove the seals, take note of the direction they were installed. The pressure seal sits with *lips* facing the pressure side or the cylinder and the wiper sits with the lips facing outwards. Oil the seals up before installing them, don't be worried, but you will need to really flex the seals to get them in. Once they are both in, install the backup ring and the O ring, then install the O ring that sits behind the nut after the thread.
Oil the chrome bar up and the gland nut and carefully re-install it on to the chrome bar. There should be an O ring sitting where the piston was, remove this and replace it.
Now to re-seal the piston. Get a sharp knife and cut the pressure seal and remove it, then remove the energising ring (looks like an O ring), install the new energising ring. Use a hair drier to warm up the pressure seal, installing this ring is really quite hard...... when its warm, pull at it to stretch it a little, then you have to try and get it on with an O ring pick or small screw driver. When it is on, it will slowly shrink back, you can use a cable tie to help it shrink. Oil the O ring on the chrome bar and install the piston, tighten the nut.
Oil the piston up and the bore of the cylinder then carefully push the piston into the cylinder, it will be quite tight, but take it slow, as you need to get the piston seal to close up and if you force it too hard it can get pinched and shear it in half. But it will need a bit of force to do. once in, oil the O rings on the gland nut then screw it in and tighten up. Make sure you have the O ring then backup ring in that order, NOT backup then O ring.
If anything is un-clear e-mail me tazza_ at tpg.com.au with the at being @ of course

I can scan in pictures of all of this if required, it really is easier than it seems. Its a good thing to learn, as once you have done one, you can do ALL the rams on your SSL.
The only tricky part is the pressure and wiper seal orientations. NEVER replace wiper/pressure seals and not the piston seal, never do half a job, you will regret it. This should prevent your tilt cylinder falling under its own weight as most do (mine does) i need to get time to do it, i am currently repairing 2 lift cylinders that broke the chrome bar. I need to finish making 2 new pistons and 2 new gland nuts (almost finished).
Again, sorry for the long post, but it should help anyone that wants to re-seal any hydraulic cylinder.
Sorry for the many spelling mistakes too

Bobcat 743, 751, 763.

Fishfiles · Nov 21, 2008

mllud said:
Tazza

Joined: 08 Dec 2004

Total Posts: 3382

Re: Rebuilding 743 front bucket tilt cylinder question
Posted: 12 Oct 2005 06:58 AM

You are more than welcome.
Now, the tilt cylinder, this is really quite easy and NO you do not need the service manual for this. Sorry, but this will be quite a long post, you have been warned
First, remove the cylinder from the lift amrs and the bobtach (not always an easy job). Remove the 2 hoses and mark and cap them! yo don't want it to work backwards (yes, i have done this before....)
Drain the cylinder of oil by pushing the chrome bar all the way in, then all the way back out. Mount the cylinder in a vice from the bottom so you can see the aloy gland nut where the chrome bar comes out of. You really should use a propper spanner to remove this gland nut, a pair of stillsons (not sure if you call them the same over there) or a large wrench will also work, but will mark the aloy but will not damage it.
When removed, pull the chrome bar up and out, this will have a piston attached to the bottom. Remove the outer of the cylinder from the vice. Put the chrome bar in the vice on the end where it joins to the bobtach. Be VERY carefull not to damage the chrome bar at ANY time. Remove the nut that holds the piston on to the chrome bar. Remove the piston from the bar and also remove the gland nut (aloy bit with 2 seals inside it).
Now, to remove the seals and O rings, you really need an O ring pick for this, first remove the outer O rings, there is one behind the shoulder at the end of the thread, then there will be 1 O ring and 1 backup ring on the part that sits inside the cylinder. Now for the inside ones.
There is a wiper seal and a pressure seal remove the wiper first, this is where the chrome bar comes out of, stick the O ring pick in and twist it out, do the same with the pressure seal, this one is a little harder as it is a fair way in, you are best to attach this one from the end where the nut enters the cylinder. Please be very carefull not to stab your hand doing this, the picks are really quite sharp!
When you remove the seals, take note of the direction they were installed. The pressure seal sits with *lips* facing the pressure side or the cylinder and the wiper sits with the lips facing outwards. Oil the seals up before installing them, don't be worried, but you will need to really flex the seals to get them in. Once they are both in, install the backup ring and the O ring, then install the O ring that sits behind the nut after the thread.
Oil the chrome bar up and the gland nut and carefully re-install it on to the chrome bar. There should be an O ring sitting where the piston was, remove this and replace it.
Now to re-seal the piston. Get a sharp knife and cut the pressure seal and remove it, then remove the energising ring (looks like an O ring), install the new energising ring. Use a hair drier to warm up the pressure seal, installing this ring is really quite hard...... when its warm, pull at it to stretch it a little, then you have to try and get it on with an O ring pick or small screw driver. When it is on, it will slowly shrink back, you can use a cable tie to help it shrink. Oil the O ring on the chrome bar and install the piston, tighten the nut.
Oil the piston up and the bore of the cylinder then carefully push the piston into the cylinder, it will be quite tight, but take it slow, as you need to get the piston seal to close up and if you force it too hard it can get pinched and shear it in half. But it will need a bit of force to do. once in, oil the O rings on the gland nut then screw it in and tighten up. Make sure you have the O ring then backup ring in that order, NOT backup then O ring.
If anything is un-clear e-mail me tazza_ at tpg.com.au with the at being @ of course
I can scan in pictures of all of this if required, it really is easier than it seems. Its a good thing to learn, as once you have done one, you can do ALL the rams on your SSL.
The only tricky part is the pressure and wiper seal orientations. NEVER replace wiper/pressure seals and not the piston seal, never do half a job, you will regret it. This should prevent your tilt cylinder falling under its own weight as most do (mine does) i need to get time to do it, i am currently repairing 2 lift cylinders that broke the chrome bar. I need to finish making 2 new pistons and 2 new gland nuts (almost finished).
Again, sorry for the long post, but it should help anyone that wants to re-seal any hydraulic cylinder.
Sorry for the many spelling mistakes too

Bobcat 743, 751, 763.

I do it a little different , I don't take the cylinder casing off the machine , leave the casing attached it's less work and it acts as a vise to hold the casing from turning , loosen the hose the goes to the tube (or base end ) so that pressure and vacuum( when pulling it out and pushing it back in ) will be released , have the boom up enough so that the bobtach will be at a comfortable working height ,usually I will have the bucket off and rest the bobtach on the lip of the bucket and stand in the bucket to work.
Remove the pin holding the chrome rod end , if you don't have the tool which removes the gland nut (head) by grabbing the two holes in it , you can use a pair of large channel lock pliers ( water pump pliers) and usually that will work , sometimes it can be frozen up and could require a little heat around the end of the casing to break the rust but that is rare.
After unscrewing the head you can pull the shaft out the casing , remember loosing the base end hose if not there will be a suction and you will have a hard time pulling it out , another trick is the yellow raw hide piston ring , I stretch it over the piston with a pick as I turn the piston and get it into place then put a ring compressor tool over the piston for a couple of minutes to get it to reshape and fit tight into the piston.
I did a 743 tilt cylinder this Tuesday that bent the rod and pulled all the threads off the aluminum head and there are 4 different cylinders that are possibly on that 743 machine , the serial number alone is not always a sure fire way to ensure the right parts as it could have been replaced alone the way before , I was burned and given the wrong parts , it is best to describe the casing to the parts guy.
The factors which distinguish different ones are the way the base end is made and the length from the head end of the casing to the fitting welded to the casing and if the tubing to the rear fitting is removable or welded on are ways to distinguish the different types , if all goes well it's a 45 minute job

Fishfiles · Nov 21, 2008

Fishfiles said:
I do it a little different , I don't take the cylinder casing off the machine , leave the casing attached it's less work and it acts as a vise to hold the casing from turning , loosen the hose the goes to the tube (or base end ) so that pressure and vacuum( when pulling it out and pushing it back in ) will be released , have the boom up enough so that the bobtach will be at a comfortable working height ,usually I will have the bucket off and rest the bobtach on the lip of the bucket and stand in the bucket to work.
Remove the pin holding the chrome rod end , if you don't have the tool which removes the gland nut (head) by grabbing the two holes in it , you can use a pair of large channel lock pliers ( water pump pliers) and usually that will work , sometimes it can be frozen up and could require a little heat around the end of the casing to break the rust but that is rare.
After unscrewing the head you can pull the shaft out the casing , remember loosing the base end hose if not there will be a suction and you will have a hard time pulling it out , another trick is the yellow raw hide piston ring , I stretch it over the piston with a pick as I turn the piston and get it into place then put a ring compressor tool over the piston for a couple of minutes to get it to reshape and fit tight into the piston.
I did a 743 tilt cylinder this Tuesday that bent the rod and pulled all the threads off the aluminum head and there are 4 different cylinders that are possibly on that 743 machine , the serial number alone is not always a sure fire way to ensure the right parts as it could have been replaced alone the way before , I was burned and given the wrong parts , it is best to describe the casing to the parts guy.
The factors which distinguish different ones are the way the base end is made and the length from the head end of the casing to the fitting welded to the casing and if the tubing to the rear fitting is removable or welded on are ways to distinguish the different types , if all goes well it's a 45 minute job

You know Tazza spelling is a (bear) as you would put it on this forum , for some reason letters skip , there seems to be a jump every now and then in the system which causes the skip , have you ever noticed that

Tazza · Nov 22, 2008

Fishfiles said:
You know Tazza spelling is a (bear) as you would put it on this forum , for some reason letters skip , there seems to be a jump every now and then in the system which causes the skip , have you ever noticed that

I haven't really noticed it, my spelling has always been shocking. I love IE spell, it makes it appear i can actually spell 90% of the time when i know for a fact i can't.
The piston ring compressor works a treat, i install a few sheets of paper between the piston and ring compressor to prevent marking the ring where it overlaps.

Bobpuddy · Nov 24, 2008

Tazza said:
I haven't really noticed it, my spelling has always been shocking. I love IE spell, it makes it appear i can actually spell 90% of the time when i know for a fact i can't.
The piston ring compressor works a treat, i install a few sheets of paper between the piston and ring compressor to prevent marking the ring where it overlaps.

Thanks for the info. My bucket drifts down slowly even empty.

mllud · Nov 24, 2008

Bobpuddy said:
Thanks for the info. My bucket drifts down slowly even empty.

Since your asking about kits for the cyls. you must have fluid leaking out of the cyls.. If not it could be in the load checks in the control valve. Mike

Bobpuddy · Nov 25, 2008

mllud said:
Since your asking about kits for the cyls. you must have fluid leaking out of the cyls.. If not it could be in the load checks in the control valve. Mike

no leaks, just assumed it is the cylinder. Is there a easy way to determine if the problem is the cylinder or the load checks?

mllud · Nov 25, 2008

Bobpuddy said:
no leaks, just assumed it is the cylinder. Is there a easy way to determine if the problem is the cylinder or the load checks?

If you dont see fluid leakung in the cyl.s or the hoses it is probably an internal leak in the valve.
The load checks hold the position of the load on a cylinder, The reason I suspect load checks is unluss both cylinders are leaking one cylinder would hold a empty boom up. You will se fluid if the seals in the cylinders are leaking.
Tazza and ken and steerclan are very familiar with where the load checks are located on the Bobcat control valve.I own a N/H. I believe its a fairly easy fix without removing the control valve. External axcess. Mike

skidsteer.ca · Nov 25, 2008

mllud said:
If you dont see fluid leakung in the cyl.s or the hoses it is probably an internal leak in the valve.
The load checks hold the position of the load on a cylinder, The reason I suspect load checks is unluss both cylinders are leaking one cylinder would hold a empty boom up. You will se fluid if the seals in the cylinders are leaking.
Tazza and ken and steerclan are very familiar with where the load checks are located on the Bobcat control valve.I own a N/H. I believe its a fairly easy fix without removing the control valve. External axcess. Mike

Cylinder bypassing the piston internally?
The test, unhook the hoses, push the rod in and out to remove most of the oil. Plug the port on the barrel end of the cylinder, and take the pin out of the rod end, hook your air compressor to the port on the rod end and pressurize it. If the packings are good the rod will retract into the cylinder and STAY there. If the cylinder is bypassing, the rod will retract then begin to extend itself.
As the air bypasses the piston it moves from the rod side that has a smaller piston area to the backside, since the piston has more area on the back side (becasue the chrome rod is eating up the usuaable area) and the back port is plugged the pressure equalizes on both sides of the piston but the back has more area so the rod extends out of the barrel
If the cylinder passes this test then its your load check (unless you have a external leak)
Ken

Bobpuddy · Nov 25, 2008

skidsteer.ca said:
Cylinder bypassing the piston internally?
The test, unhook the hoses, push the rod in and out to remove most of the oil. Plug the port on the barrel end of the cylinder, and take the pin out of the rod end, hook your air compressor to the port on the rod end and pressurize it. If the packings are good the rod will retract into the cylinder and STAY there. If the cylinder is bypassing, the rod will retract then begin to extend itself.
As the air bypasses the piston it moves from the rod side that has a smaller piston area to the backside, since the piston has more area on the back side (becasue the chrome rod is eating up the usuaable area) and the back port is plugged the pressure equalizes on both sides of the piston but the back has more area so the rod extends out of the barrel
If the cylinder passes this test then its your load check (unless you have a external leak)
Ken

The only external leak I have is from the fuel filter. I have tried several times to stop that. I will try the air test on the tilt cylinder. If it passes the test, how difficult is it to repair the load checks? Thanks

Tazza · Nov 25, 2008

Bobpuddy said:
The only external leak I have is from the fuel filter. I have tried several times to stop that. I will try the air test on the tilt cylinder. If it passes the test, how difficult is it to repair the load checks? Thanks

Load check seals are easy, gaining access isn't so easy though as you have metal tube lines that are sorta in the way. If you lift the cab and look at the control block, where the tube lines attach you should see like 1" head, these are the load checks.

cmb97 · Feb 4, 2009

Tazza said:
Load check seals are easy, gaining access isn't so easy though as you have metal tube lines that are sorta in the way. If you lift the cab and look at the control block, where the tube lines attach you should see like 1" head, these are the load checks.

Does any one have pictures of this control block

Tazza · Feb 5, 2009

cmb97 said:
Does any one have pictures of this control block

I would have to re-scan it in, but that won't be till Monday

Send me a reminder e-mail "taz38sup at yahoo.com.au" at = @ naturally!
Tell me exactly what control block you want an image of, 743 or the newer 753/763 style.

cmb97 · Feb 5, 2009

Tazza said:
I would have to re-scan it in, but that won't be till Monday
Send me a reminder e-mail "taz38sup at yahoo.com.au" at = @ naturally!
Tell me exactly what control block you want an image of, 743 or the newer 753/763 style.

I have a 7753 which i think would be the same setup just wondering is it the block that is under the seat on the passenger side close to the front where all the controls lead to. That is where i have a pretty large leak but I am not sure where it is coming from.there are some what look like dust boots on the front of it and they are very wet so wondering if there are seals in there that need to be replaced.

Tazza · Feb 5, 2009

cmb97 said:
I have a 7753 which i think would be the same setup just wondering is it the block that is under the seat on the passenger side close to the front where all the controls lead to. That is where i have a pretty large leak but I am not sure where it is coming from.there are some what look like dust boots on the front of it and they are very wet so wondering if there are seals in there that need to be replaced.

Its different to the 743 one, does it have a bunch of steel lines going into it? and a few coils connected to your wiring harness? if so, that is your control block. There may also be a bucket positioning valve, it could be that as it sits further forward on the right.

cmb97 · Mar 12, 2009

Tazza said:
Its different to the 743 one, does it have a bunch of steel lines going into it? and a few coils connected to your wiring harness? if so, that is your control block. There may also be a bucket positioning valve, it could be that as it sits further forward on the right.

Got my cylinder fixed Thanks for the posting Tazza Now on to the Hydrolic control valve for the 7753 has any one replaced the seals and is it hard or just time.it looks like there are alot of seals

coreya3212 · Apr 8, 2009

cmb97 said:
Got my cylinder fixed Thanks for the posting Tazza Now on to the Hydrolic control valve for the 7753 has any one replaced the seals and is it hard or just time.it looks like there are alot of seals

Just refreshing this one, dont know how to post a link to it.

skidsteer.ca · Apr 8, 2009

coreya3212 said:
Just refreshing this one, dont know how to post a link to it.

Just type the link in, but be sure to leave a extra space at each end of the link or put it on its own line like this.
www.skidsteer.ca
It will turn blue and undeline automatically after you type a space at the end.
Ken

743 Tilt cylinder rebuild post by Tazza

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