743 Noisy Steering Operation

[wilkenstein]

Hello to all. I recently purchased a 743 needing some work to clear some land and do various chores on my property. It runs very well but the steering becomes very noisy as the fluid warms up. It show 1218 hours on the meter which was disconnected from the charge pressure switch. It drives well in both forward and reverse but begins to whine and loose propulsion when turning. I used a remote gauge to monitor charge pressure to the hydrostatic pump. It reads a normal 100psi with the engine running at any speed. The charge pressure will drop to around 50psi when driving straight but will drop to zero when attempting to turn. I removed and disassembled the hydraulic pump and found only some slight scratches in the housing. I went ahead and replaced the pump cartridge, the supply hose to the pump as well as the fluid and filter with no change in performance. What should be my next step. I prefer testing to "guess fixin" but I do not have a hydraulic flow tester. Thanks

 

[Tazza]

Small marks in the vane pump are not an issue, as it wears the vanes just push out a little more.
You said you replaced the hose to the pump, you have the one with a big, about 1.5" hose running to a block on the left of the machine fron the hydraulic pump?

 

[wilkenstein]

Small marks in the vane pump are not an issue, as it wears the vanes just push out a little more.
You said you replaced the hose to the pump, you have the one with a big, about 1.5" hose running to a block on the left of the machine fron the hydraulic pump?

Yes I replaced the 1" ID hose on the left when facing the machine. The old one was very hard and deformed around the clamps. I used a hydraulic grade suction hose.

 

[Tazza]

Yes I replaced the 1" ID hose on the left when facing the machine. The old one was very hard and deformed around the clamps. I used a hydraulic grade suction hose.

Well, that is the newer style pump setup then, no hidden filter.
Not sure what could be the cause, the charge pressure sounds right, so the relief must be in working order. There is always the possibility that it is a worn piston pump. How is it's power in a straight line, can you push up against a tree and get the wheels to spin?
If the hydraulic oil is too thin, when it warms up it by-passes any areas of wear causing power loss.

 

[wilkenstein]

Well, that is the newer style pump setup then, no hidden filter.
Not sure what could be the cause, the charge pressure sounds right, so the relief must be in working order. There is always the possibility that it is a worn piston pump. How is it's power in a straight line, can you push up against a tree and get the wheels to spin?
If the hydraulic oil is too thin, when it warms up it by-passes any areas of wear causing power loss.

Thanks Tazza, I will give it a wheel spin test and give you a report later. It does move foward with maybe a slight drift to the right and it pulls up slight grades fine.

 

[wilkenstein]

Thanks Tazza, I will give it a wheel spin test and give you a report later. It does move foward with maybe a slight drift to the right and it pulls up slight grades fine.

Yeah Tazza it failed the spin test. Initially it spun the tires with cold fluid and good charging pressure. As the fluid heated up the charge pressure dropped so did the power to the wheels. Makes sense the fluid is flowing thought the excessive clearances in the piston pumps faster than the hydraulic pump can supply it. Your thoughts?

 

[Tazza]

Yeah Tazza it failed the spin test. Initially it spun the tires with cold fluid and good charging pressure. As the fluid heated up the charge pressure dropped so did the power to the wheels. Makes sense the fluid is flowing thought the excessive clearances in the piston pumps faster than the hydraulic pump can supply it. Your thoughts?

Do you know what weight oil you are running? It should be fairly heavy, 10W30, 15W40, 20W50. The older vickers pumps worked well with engine grade oil. Some talk about the fact they have additives, but it's all i have ever run, so it's your choice as to how you go.
Another thing.... How is the oil cooler? are the fins free of dirt? Just wondering if when it gets warm, its getting too hot and allowing the oil to thin out too much.
If none of that fixes the problem, you may need to look at touching up your pump. There are two wear plates that get scores in them that will lower the pressure to the drive motors.
If you can get your hands on a IR temperature meter, check the pump temperature, at a guess, it should be under 80c, the lower the better. There is a point where the oil starts to break down, i just can't remember what it was.

 

[wilkenstein]

Do you know what weight oil you are running? It should be fairly heavy, 10W30, 15W40, 20W50. The older vickers pumps worked well with engine grade oil. Some talk about the fact they have additives, but it's all i have ever run, so it's your choice as to how you go.
Another thing.... How is the oil cooler? are the fins free of dirt? Just wondering if when it gets warm, its getting too hot and allowing the oil to thin out too much.
If none of that fixes the problem, you may need to look at touching up your pump. There are two wear plates that get scores in them that will lower the pressure to the drive motors.
If you can get your hands on a IR temperature meter, check the pump temperature, at a guess, it should be under 80c, the lower the better. There is a point where the oil starts to break down, i just can't remember what it was.

I changed the hydraulic fluid and used the Bobcat brand fluid which I think is a10W30 weight oil. Well I checked the pump operating temperatures and found the fluid to be relatively cool at around 120 degrees F when the whining and loss of power begins to occur. I talked to Flint Hydraulics, the local Eaton/Vickers distributor and service center here in Memphis. Nice folks and they have all the parts on hand to service these TA1919 hydrostatic pumps. He did give me a tip and say that the pumps should not bypass more than 1/2 gallon per min of fluid. They have a test stand that they will performance test the pump for $75. Looks like I will be pulling the pump. I am going to take your advice from another post Tazza and pull the motor in conjunction with the pump. It needs a good service anyway. I will keep you posted.

 

[Tazza]

I changed the hydraulic fluid and used the Bobcat brand fluid which I think is a10W30 weight oil. Well I checked the pump operating temperatures and found the fluid to be relatively cool at around 120 degrees F when the whining and loss of power begins to occur. I talked to Flint Hydraulics, the local Eaton/Vickers distributor and service center here in Memphis. Nice folks and they have all the parts on hand to service these TA1919 hydrostatic pumps. He did give me a tip and say that the pumps should not bypass more than 1/2 gallon per min of fluid. They have a test stand that they will performance test the pump for $75. Looks like I will be pulling the pump. I am going to take your advice from another post Tazza and pull the motor in conjunction with the pump. It needs a good service anyway. I will keep you posted.

If you need parts, i have details for a place to get them pretty cheap, send me an e-mail if you want to go that way.
Hopefully it's something pretty simple and cheap to repair.

 

[diggerman]

If you need parts, i have details for a place to get them pretty cheap, send me an e-mail if you want to go that way.
Hopefully it's something pretty simple and cheap to repair.

Just registered, have been reading forum for last couple years with great info being posted. Have a late 80's 743 that I've had for 3 years but have only used for about 2 months because of problems - fuel problems,rebuild bobtach and arm pivots,electrical,etc. I finally got it back together and ran it for 30 minutes and the u-joint let loose and bent the input on the hydro pump. Contacted Vickers and they told me this was a priority part and they could not sell me parts. Tazza, you say you have a source for these? Also, I have the back of the hydro with the shaft apart, what should I be looking at and are there any specs and clearances I shoulod be checking. There are different size spacers shown in the parts manual.

 

[Tazza]

Just registered, have been reading forum for last couple years with great info being posted. Have a late 80's 743 that I've had for 3 years but have only used for about 2 months because of problems - fuel problems,rebuild bobtach and arm pivots,electrical,etc. I finally got it back together and ran it for 30 minutes and the u-joint let loose and bent the input on the hydro pump. Contacted Vickers and they told me this was a priority part and they could not sell me parts. Tazza, you say you have a source for these? Also, I have the back of the hydro with the shaft apart, what should I be looking at and are there any specs and clearances I shoulod be checking. There are different size spacers shown in the parts manual.

diggerman - look up my profile and send me an e-mail, i'll look up the details for you with the people to try and contact.
Have you removed the swash plates? The parts that the steering levers connect to. These are set with shims, if you haven't touched them, leave them alone.
With the pumps apart, check for wear on the valve plates, they have a brass surface that the rotating groups run on. Ensure these are flat, no scores. If there are socres, get a sheet of glass and a few sheets of wet and dry. Use the glass for a flat surface and rub the valve plate on the sand paper to get it flat. Keep moveing the plate around, this will prevent you working more on one spot than another. The spring in the rotating group will take up the small amount you will remove when doing this. There really is nothing else that you need to look at in there that i can think of.
As the shaft is bent, you will need a new shaft seal though, it can be replaced while in the machine, but easier on the bench.

 

[mahans7]

diggerman - look up my profile and send me an e-mail, i'll look up the details for you with the people to try and contact.
Have you removed the swash plates? The parts that the steering levers connect to. These are set with shims, if you haven't touched them, leave them alone.
With the pumps apart, check for wear on the valve plates, they have a brass surface that the rotating groups run on. Ensure these are flat, no scores. If there are socres, get a sheet of glass and a few sheets of wet and dry. Use the glass for a flat surface and rub the valve plate on the sand paper to get it flat. Keep moveing the plate around, this will prevent you working more on one spot than another. The spring in the rotating group will take up the small amount you will remove when doing this. There really is nothing else that you need to look at in there that i can think of.
As the shaft is bent, you will need a new shaft seal though, it can be replaced while in the machine, but easier on the bench.

What grit wet dry sandpaper would you use?

 

[Tazza]

What grit wet dry sandpaper would you use?

It depends on how bad the scoring is. If it's only light, 600/800 should do for the initial pass. Then finish with about 1200. I have used rougher on really bad ones then work my way up to really fine to finish off. I also use WD40 on the paper to lubricate it a little, if it's a good or bad thing, i have no idea, all i know is it works for me
As for the scoring, if you can feel the scratches with a fingernail, they are too worn and need rubbing back. I have images on my pc at home, but the power lines are being worked on, so i won't have access to the files for a day or so. They are from a different brand pump, but the plates look pretty buch the same. If you e-mail me to remind me to send them to you, i can when time allows.

 

[wilkenstein]

It depends on how bad the scoring is. If it's only light, 600/800 should do for the initial pass. Then finish with about 1200. I have used rougher on really bad ones then work my way up to really fine to finish off. I also use WD40 on the paper to lubricate it a little, if it's a good or bad thing, i have no idea, all i know is it works for me
As for the scoring, if you can feel the scratches with a fingernail, they are too worn and need rubbing back. I have images on my pc at home, but the power lines are being worked on, so i won't have access to the files for a day or so. They are from a different brand pump, but the plates look pretty buch the same. If you e-mail me to remind me to send them to you, i can when time allows.

I got my hydrostatic pump out and apart. There was no bringing those wafer plates back. Some of the wear groves had to be .003" deep. I pulled the motor which made getting the pump out much easier. This exposed the root cause for the failures on this machine. Apparently there was a fuel leak at the return hose from the injectors to the tank. This leak would only occur when the engine ran so no one bother to fix it. Consequently this mixed with limestone gravel dust to for a waxy mortar consistency material inside the fan shroud that completely stopped up the oil cooler and partially the radiator. I am certain the oil overheated on numerous times but no one would notice as the temp sensor was unplugged. The oil had a slight burned aroma when I changed it. In addition to the wafer plates I also replaced the rotating groups had excessive wear in the swivel joints for the pistons. Max end play spec is .003" and these had at least .005-.006". Good thing I pulled the motor as one of the coupling joints was disintegrating. More later.

 

[Tazza]

I got my hydrostatic pump out and apart. There was no bringing those wafer plates back. Some of the wear groves had to be .003" deep. I pulled the motor which made getting the pump out much easier. This exposed the root cause for the failures on this machine. Apparently there was a fuel leak at the return hose from the injectors to the tank. This leak would only occur when the engine ran so no one bother to fix it. Consequently this mixed with limestone gravel dust to for a waxy mortar consistency material inside the fan shroud that completely stopped up the oil cooler and partially the radiator. I am certain the oil overheated on numerous times but no one would notice as the temp sensor was unplugged. The oil had a slight burned aroma when I changed it. In addition to the wafer plates I also replaced the rotating groups had excessive wear in the swivel joints for the pistons. Max end play spec is .003" and these had at least .005-.006". Good thing I pulled the motor as one of the coupling joints was disintegrating. More later.

Over heating oil sure will do that. I have seen a rotating group that one of the piston holes was so worn that the piston would just wobble around, had to be 1/4" of play in there.
At least you found the cause of the problem, just not too cheap to repair.

 

[mahans7]

It depends on how bad the scoring is. If it's only light, 600/800 should do for the initial pass. Then finish with about 1200. I have used rougher on really bad ones then work my way up to really fine to finish off. I also use WD40 on the paper to lubricate it a little, if it's a good or bad thing, i have no idea, all i know is it works for me
As for the scoring, if you can feel the scratches with a fingernail, they are too worn and need rubbing back. I have images on my pc at home, but the power lines are being worked on, so i won't have access to the files for a day or so. They are from a different brand pump, but the plates look pretty buch the same. If you e-mail me to remind me to send them to you, i can when time allows.

Here's Tazza's Hydrostatic pump vane sanding pics

"It shows before and after. Different pump, but the valve/wear plates look pretty close. Note the marks, these are what you want to remove. Flatter is better."

 

[Tazza]

Here's Tazza's Hydrostatic pump vane sanding pics

"It shows before and after. Different pump, but the valve/wear plates look pretty close. Note the marks, these are what you want to remove. Flatter is better."

That is a 'sunstrand' pump used in the later model machines. The innards are pretty much the same as the vickers TA1919 pump in the 743 machines. The biggest difference you can see is the housing.