Tilt problem

[Bobpuddy]

I have just bought my first bobcat. It's a 1987 743. My question is, when I raise the boom to around 7 feet, then tilt my bucket all the way down, it will not tilt back up. The only way it will tilt up, is if I lower the boom arms to around 4 feet. Also I have to step on the tilt foot pedal every 20 seconds or less to make the bucket tilt up because it keeps drifting down when the boom is down loaded or empty. What is the most likely cause? Thanks

 

[73Eldo]

Have you checked the fluid level? With all cylinders extended like that (full of fluid) you may be getting low in the tank and getting some air in there, that would make things really mushey. Usually makes the pump(s) whine also.

 

[Tazza]

Have you checked the fluid level? With all cylinders extended like that (full of fluid) you may be getting low in the tank and getting some air in there, that would make things really mushey. Usually makes the pump(s) whine also.

Make sure your right stick isn't stuck in detent. Pull it all the way to the left then let it spring back to centre. When you have your aux hydraulics stuck on, you can get these odd problems.

 

[Bobpuddy]

Make sure your right stick isn't stuck in detent. Pull it all the way to the left then let it spring back to centre. When you have your aux hydraulics stuck on, you can get these odd problems.

I did allready think of the low fluid possibility and found the fluid was all the way up almost to the fill cap. I noticed the sight glass and I assume that it should be half way in the glass. Do I need to siphon some out? Also is it checked with the cylinders withdrawn. I will check the steering arm to be sure it is not stuck in the detent position. I did not think to check for that. Thanks

 

[Tazza]

I did allready think of the low fluid possibility and found the fluid was all the way up almost to the fill cap. I noticed the sight glass and I assume that it should be half way in the glass. Do I need to siphon some out? Also is it checked with the cylinders withdrawn. I will check the steering arm to be sure it is not stuck in the detent position. I did not think to check for that. Thanks

That much fluid may cause a problem, it could spill out up hills or overflow if you work on a cylinder as the oil will foam up and use more space. I would drain a bit off, as you said it should be 1/2 way up the sight glass.

 

[Bobpuddy]

That much fluid may cause a problem, it could spill out up hills or overflow if you work on a cylinder as the oil will foam up and use more space. I would drain a bit off, as you said it should be 1/2 way up the sight glass.

I checked my chain case and it was way low, so I ran a hose from the hyd tank down to the chain case and siphoned them to the correct level. With the tilt problem, I checked the steer arm and it was returning to center as it should. Also I inspected the tilt operation more closely. I noticed that with the boom raised to almost full height, when I tilted the bucket down, it seems to go down with hyd pressure then suddenly swing freely once it reaches straight down position. It acts as though the cylinder extends to far. Is it possible that a stop inside the cylinder has broken? What controls how far the cylinder extends? The bucket swings so far that the fluid line gets pinched between the cylider and the brace under the cylinder.

 

[Tazza]

I checked my chain case and it was way low, so I ran a hose from the hyd tank down to the chain case and siphoned them to the correct level. With the tilt problem, I checked the steer arm and it was returning to center as it should. Also I inspected the tilt operation more closely. I noticed that with the boom raised to almost full height, when I tilted the bucket down, it seems to go down with hyd pressure then suddenly swing freely once it reaches straight down position. It acts as though the cylinder extends to far. Is it possible that a stop inside the cylinder has broken? What controls how far the cylinder extends? The bucket swings so far that the fluid line gets pinched between the cylider and the brace under the cylinder.

I guess the not on the end of the stick internally could be loose. If the gland nut was the correct length you shouldn't have a problem with it over extending, butif someone has fiddled with it, it may be a problem. On some arms they have blocks welded in the inside edge that the bobtach will hit so it will not extend any further and the ram can't keep pushing it around.
The pinched line will be an issue, you can sometimes remove it and hit it on a flat piece of steel to try and open it back up, strike the sides that are puffed out, it will help but won't get t back to normal, but close enough. If its really restricted it will just cause slow operation and heat.
Does it only have a problem moving when its at ether end of the stroke? like fully etended or fully retracted?

 

[Bobpuddy]

I guess the not on the end of the stick internally could be loose. If the gland nut was the correct length you shouldn't have a problem with it over extending, butif someone has fiddled with it, it may be a problem. On some arms they have blocks welded in the inside edge that the bobtach will hit so it will not extend any further and the ram can't keep pushing it around.
The pinched line will be an issue, you can sometimes remove it and hit it on a flat piece of steel to try and open it back up, strike the sides that are puffed out, it will help but won't get t back to normal, but close enough. If its really restricted it will just cause slow operation and heat.
Does it only have a problem moving when its at ether end of the stroke? like fully etended or fully retracted?

There is no problem when retracted other than the drift down problem. Also a friend stopped by today that has owned a 743 a few years ago. He noticed that the tilt pedal seems to operate oppisite. forward on the pedal is rollback and down with your heel dumps. Is this reverse of correct and how is that possible? Thanks

 

[skidsteer.ca]

There is no problem when retracted other than the drift down problem. Also a friend stopped by today that has owned a 743 a few years ago. He noticed that the tilt pedal seems to operate oppisite. forward on the pedal is rollback and down with your heel dumps. Is this reverse of correct and how is that possible? Thanks

Someone reversed the hoses to tilt cylinder to make the pedal work backwards
Ken

 

[Tazza]

Someone reversed the hoses to tilt cylinder to make the pedal work backwards
Ken

Exactly, swap the hoses at the ram, toe should go forward, heal should tilt back wards. Same for the lift, heal is lift toe lets the arms fall.
I would suspect your seals in the ram may be shot, this would cause your bucket to drop. There are load checks that could cause this as well, but usually its only a slow leak. I'm just wondering if the load check poppets could be stuck, i guess it could cause some of the issues you are having..... If you look at your control block, you will notice a bank of 4 spools each spool has 2 lines running out of it and 2 load checks, one for each tube line. They will behind what looks like a bolt next to where the tube line connects in, about 1" hex head. These will have a poppet, spring and a set if seals. Each segment of the spool is separate, they are all linked with the main supply of oil but operate independent. If you find the tilt section you know what 2 load checks you may want to look at.
Remember to keep things clean, dirt in your hydraulic system is a bad thing.
I hope that gives you an idea of where to look.....

 

[Bobpuddy]

Exactly, swap the hoses at the ram, toe should go forward, heal should tilt back wards. Same for the lift, heal is lift toe lets the arms fall.
I would suspect your seals in the ram may be shot, this would cause your bucket to drop. There are load checks that could cause this as well, but usually its only a slow leak. I'm just wondering if the load check poppets could be stuck, i guess it could cause some of the issues you are having..... If you look at your control block, you will notice a bank of 4 spools each spool has 2 lines running out of it and 2 load checks, one for each tube line. They will behind what looks like a bolt next to where the tube line connects in, about 1" hex head. These will have a poppet, spring and a set if seals. Each segment of the spool is separate, they are all linked with the main supply of oil but operate independent. If you find the tilt section you know what 2 load checks you may want to look at.
Remember to keep things clean, dirt in your hydraulic system is a bad thing.
I hope that gives you an idea of where to look.....

OK, switched the hoses. Now what is the best way to access the control block. Under the seat or do I remove the cover between the tires?

 

[Tazza]

OK, switched the hoses. Now what is the best way to access the control block. Under the seat or do I remove the cover between the tires?

Lift the cab, the plate between the wheels only covers the drive motors.
It will be on the right hand side (when sitting in the machine) look next to the hydro pump and you will see a heap of metal tube lines conencting to it.

 

[Centurion]

Lift the cab, the plate between the wheels only covers the drive motors.
It will be on the right hand side (when sitting in the machine) look next to the hydro pump and you will see a heap of metal tube lines conencting to it.

I recently bought a 743 1990/91 vintage. I have the identical situation with the bucket drift and over exetend situation. Let me know if you find the solution

 

[Tazza]

I recently bought a 743 1990/91 vintage. I have the identical situation with the bucket drift and over exetend situation. Let me know if you find the solution

If your arms slowly leak down its most likely the load checks or damaged piston seals in your rams. I replaced the seals in my rams once and the arms still moved, changed the load check seals, was perfect after that.

 

[skidsteer.ca]

If your arms slowly leak down its most likely the load checks or damaged piston seals in your rams. I replaced the seals in my rams once and the arms still moved, changed the load check seals, was perfect after that.

I would think the bucket not wanting to retract could be a lack of hyd pressure issue, or that the stops on the quick attach are letting the bucket dump to fa and the cylinder does not have the leverage left to pull it back up. Especially if the tilt cylinder piston seals are bypassing. The geometery of the cylinder to the QA makes its work harder when the bucket is fully dumped.
Ken

 

[Bobpuddy]

I recently bought a 743 1990/91 vintage. I have the identical situation with the bucket drift and over exetend situation. Let me know if you find the solution

Hey Centurion, have you found the problem yet? I've been busy using mine and haven't had time to work on it.

 

[Centurion]

Hey Centurion, have you found the problem yet? I've been busy using mine and haven't had time to work on it.

No, I have not figured it out yet, but be careful! I put on a 4 in 1 bucket today, accidently over extended, and bent the shaft in the tilt cylinder, I will try to get that fixed, and maybe they will find something inside that is bad. I will let you know what I find. But again, be careful, it could cause problems!

 

[Tazza]

No, I have not figured it out yet, but be careful! I put on a 4 in 1 bucket today, accidently over extended, and bent the shaft in the tilt cylinder, I will try to get that fixed, and maybe they will find something inside that is bad. I will let you know what I find. But again, be careful, it could cause problems!

Thats no good.....
Do you have rectangualr pieces of steel welded to the indise side of the arms, rite at the base? there should be 2 blocks to prevent you from over extending the tilt ram. The bobtach will turn till it hits and stop preventing this exact problem. If its there it may be worn, you may need to fill the worn part with weld to prevent it happening again.

 

[Bobpuddy]

No, I have not figured it out yet, but be careful! I put on a 4 in 1 bucket today, accidently over extended, and bent the shaft in the tilt cylinder, I will try to get that fixed, and maybe they will find something inside that is bad. I will let you know what I find. But again, be careful, it could cause problems!

Thanks for that warning and let me know what they determine is the cause.