Td15b blade dropping, poor lift power

[DanielLesley]

Hi everyone, I have a TD15b dozer I just bought and the hydraulics worked great until today. Now the blade lowers on its own fairly quickly- about 10 seconds from top to bottom, and also it lack lift power (wont pick up the machine any more) or pop stumps well. It seems it at a large bypass somewhere, has anyone ran into this before and can help?

 

[Fritz Maurer]

Blown packing in at least one cylinder, or look to see oil pouring from the belly pan.

 

[Janicholson]

Hi everyone, I have a TD15b dozer I just bought and the hydraulics worked great until today. Now the blade lowers on its own fairly quickly- about 10 seconds from top to bottom, and also it lack lift power (wont pick up the machine any more) or pop stumps well. It seems it at a large bypass somewhere, has anyone ran into this before and can help?

Welcome to YT !! If the cylinder pistons (even just one) looses its seal it will do that. Flow rating the hydraulics would be great, but probably not happening. Jim

 

[DanielLesley]

I wondered about internally bypassing cylinder or control valve. How do I determine which one?

 

[DanielLesley]

No external hydraulic leaks and fluid level is good. How do I isolate the problem?

 

[Fritz Maurer]

Take one apart… you have 50/50 chance of getting the right one. Should repack both anyway… soon as you fix one the other one will let go. Maybe in an hour, maybe in a month, but right when you need it the most.

 

[used red MN]

Hello Daniel, welcome to YT! Very likely the cylinders are double acting, so there would be no external leak in that case with a ram piston packing failure. Not sure how complex the hose connections are on that dozer but here is what you can do if it is common pipe thread or can be adapted to it. Get a valve the appropriate size. Place it into to the lift circuit for one of the cylinders. Raise the blade and close the valve, sounds like you will need an assistant if the valve can’t be reached from the platform. Shut off the engine and move the tractor valve to lower the blade. If you have placed the valve to block fluid flow out of the good cylinder it will hold, if it is on the bad one the blade will drop.

 

[Fritz Maurer]

I wondered about internally bypassing cylinder or control valve. How do I determine which one?

I’m sorry I misunderstood your question. Did you mean which one, meaning the valve vs. the cylinders? The cylinders are a way safer bet because they have a lot more parts, are down in the dirt, and absorb all the shock loads. The valve on the other hand has basically one moving part , and no seals. For the valve to bypass at the rate you describe, there would have to be large pieces of metal going through it, and would take considerable force at the control to cut a gouge that deep.
Another reason to start with the cylinders is they are cheaper to fix and easier to get at.

 

[DURTFANN]

A easy way that can tell you a lot if you don't have access to test equipment & fittings needed for proper testing is a cylinder with blown piston seals will usually generate a lot of heat from the bypassing oil , so if you have one cylinder cool & the other hotter then a two dollar pistol that's your culprit

 

[used red MN]

I’m sorry I misunderstood your question. Did you mean which one, meaning the valve vs. the cylinders? The cylinders are a way safer bet because they have a lot more parts, are down in the dirt, and absorb all the shock loads. The valve on the other hand has basically one moving part , and no seals. For the valve to bypass at the rate you describe, there would have to be large pieces of metal going through it, and would take considerable force at the control to cut a gouge that deep.
Another reason to start with the cylinders is they are cheaper to fix and easier to get at.

My reply does only determine which cylinder may be the culprit. If I was doing the diagnosis I would still approach it this same way, because as Fritz mentions the prospects of it being the valve. Had I not chosen to place the valve in the failed cylinder’s line I might continue this way. If the connections required to place the valve in the line before the tee to the cylinders was the same I would probably go ahead and test with the valve there to assure the problem was not in the valve. In other words the valve would not allow fluid to flow back through the machine remote valve if it was leaking by. Do you have manuals for your machine if not let me know, I think I can point you to access to some.

 

[DanielLesley]

Hi again, little update, I took apart both cylinders, and the packing didn’t show a smoking gun as far as I can tells. Thinking it’s the valve. Also I ran it with the lift line off one cylinder and had lots of oil coming from the line with the valve not pressed but also out the other end of where the line attaches, even with valve not pressed which was why I checked the packing.

 

[DanielLesley]

Hi again, little update, I took apart both cylinders, and the packing didn’t show a smoking gun as far as I can tells. Thinking it’s the valve. Also I ran it with the lift line off one cylinder and had lots of oil coming from the line with the valve not pressed but also out the other end of where the line attaches, even with valve not pressed which was why I checked the packing.

I attached a picture of the packing, what’s you thoughts on it?

 

[DanielLesley]

Also, Is the lift valve rebuildable? Thanks again everyone!

 

[used red MN]

Not much of a dozer guy, I assume you pulled the ram and piston out but the barrel was left on the machine? If it is off I would find a way to block off the lift port. Then prop it on its end pour a couple quarts of oil in it then set a skid loader or tractor loader bucket on it and see if it leaks by. Judging by the gland it probably is not just a pipe thread connection to make the test I suggests in my other reply. Although this side of the packing looks in reasonably okay condition I can’t see the other side to say it’s perfect put it back in. There is probably no way someone can tell you if that packing will leak or not by a picture, maybe not even looking at it in person.

 

[Jim.ME]

Also, Is the lift valve rebuildable? Thanks again everyone!

The packing shows wear. The lips are worn and there are chips and scratches in the wear rings. It is apart, personally I would replace the packing (that includes all the wear parts, not just the vee packings). What is the internal condition of the cylinder barrels?

Very few valves are rebuildable as the spools are fitted to the bores. Generally, the best you can do is replace an external O-ring or seal at the spool ends. Sometimes the centering spring/mechanism has broken or loosened letting the spool rest out of center.

 

[Fritz Maurer]

There is nothing in the valve that is repairable other than seals for external leakage.
The problem with the packing shown is the fiber rings have failed and are climbing up over Teflon ring and holding it away from the cylinder wall. The Teflon should be the highest of that whole stack of components. There is a rubber ring under the Teflon to hold it out.
You need to check the cylinder bores before buying any parts because the piston shown has evidence of loose pieces in the hydraulic system, and may have put a gash in the cylinder wall, in which case a re-tube is necessary. Check your filters and the magnetic strainer (if you have one) for steel fragments.

 

[moresmoke]

As the others have said, it looks like there have been big chunks in that hydraulic system. Beyond that, it appears to me that the seals are not installed correctly on that piston. Both of the v rings look to be facing the barrel of the cylinder. I would expect that one would face each direction.

Also remember that only one of the cylinders need to be bypassing for the blade to drop. It doesn’t look as though that cylinder would cause a rapid drop, but what does the other one look like?

 

[Janicholson]

The seals on the piston are in my opinion bad enough to cause your issue. Replacing them in both cylinders is reasonable at this point why not!!! Jim

 

[DanielLesley]

Both cylinders look the same, if anything the other side looks better. Bores look ok, but I will check more closely to be sure. I do plan on replacing them both regardless and will go from there and update you as I go. Thanks for the help!