Case DH4B Trencher/Backhoe Won't Spin Trenching Chain

[oldnslo]

R8
Can you post some pictures of the pump in question. Reason for asking is that some piston pumps have a geroler style charge pump.

Another question, how many hoses are connected to the pump in question?

 

[Doaaj50]

A picture of the name tag would be super helpful, if available.

 

[r8f1k]

(DH4B) - CASE TRENCHER (1/79-12/91) (8-206) - ATTACHMENT DRIVE PUMP - H672705 Case Constructuion

spare.avspart.com

99% sure it is this pump

 

[r8f1k]

Not sure if this photo is coming up.....

 

[oldnslo]

(DH4B) - CASE TRENCHER (1/79-12/91) (8-206) - ATTACHMENT DRIVE PUMP - H672705 Case Constructuion

spare.avspart.com

99% sure it is this pump

That parts diagram is a closed loop (hydrostat) pump with a geroler style charge pump. The only components that could be generic are seals and bearings. None of the internal oil moving components will be generic.

Has this unit ever worked or did you buy it in this condition?

I would suggest performing some pressure tests before condemning that pump.

Is charge pump getting flow and building pressure?

how is the pump driven? Is something slipping or wore out in the drive couplings, splines, etc. ?

 

[r8f1k]

I bought the machine dead. Did not run, didn't even crank over. From the dates written on the filters, late 2009 was the last oil change. I'm betting it was last really used sometime after that, say 2010-2011. It has 3 total pumps, 1 drives the propulsion, the other 2 operate the backhoe and the trencher. I am going to pull the pump out, and take a good look.

I will check to make sure that the pump is getting a full flow of fluid, but I'm betting that there is something more involved going on. I drained as much fluid as I could prior to the initial startup to prevent any old debris from getting recirculated in the system.

This pump is driven off of a drive plate with 3 splined holes. Each hole has internal splines and drives one of the pumps. This pump is all the way over to the right, although labeled as the LH pump. It could have worn out splines or something like that. I think the only way to really find out is to pull it out and take a look. Even if I don't take the pump apart, I should probably take a look at the drive splines. I will check the fluid flow going to it, but I am betting there is plenty of fluid, although the line could be plugged???? Worth a check before pulling it.

 

[oldnslo]

Do the spline couplings run in an oil bath or dry? If dry couplings have been known to fail due to fretting. Slipping splines could cause the chatter you are hearing while attempting to operate in either direction..

 

[r8f1k]

I am not sure......I can see some RTV where someone was in between the engine and the drive plate. Maybe it had an issue already. Lets just say the splines are worn, if they are worn off of the input shaft of the pump, what should/can be done? If they are the splines on in the inside that are worn, what then? I am guessing that a pump input shaft is easier to repair where a machine shop can index new splines.

 

[Doaaj50]

So what you have on that machine is an old Sauer-Sundstrand 18 Series pump. The model number is 18-2081. For Sundstrand/Danfoss, anytime you see a "R" at the end of a model number, it indicates that it has been remanufactured.

The "LH" indicates that it is a Left Hand rotation pump (counter-clockwise). If the pump was sitting in front of you with its input shaft facing you, the shaft would need to rotate to the left, or counterclockwise.

Since we know that it is an 18 Series pump, we also now know that it is a closed circuit system. Oldnslo had already mentioned that based on the exploded view diagram.

Based on what you have described so far, my first thought would be to check for charge pressure. I believe oldnslo has also mentioned that in one of his posts. The problem with a direct displacement pump, is that you can force it into stroke without charge pressure. Without any charge flow, there is no oil in the circuit to send from the pump's rotating kit to the motor and thus no trencher chain movement.

The noise that you are hearing from the pump could be the charge pump running without any oil. If that has been going on for a while, then you may have an issue because those parts rely on an oil film to keep them from damage.

I would first start by making sure you have oil getting to the inlet of that pump. The inlet of that pump can be found on the diagram that is attached.

I would crack that hose fitting at the pump and see if oil is reaching the pump. If not, you will need to backtrack it to figure out where the obstruction lies. There may be a suction filter or screen that is plugged.

If you have oil at the inlet, then get a 500psi gauge and plumb it into the charge pressure gauge port and see what pressure, if any, the pump has when the engine is running. It should be at least ~100 psi. Some of the 18 series pumps ran fairly low relief settings so don't be surprised if it is at that level. It may be higher, but it shouldn't be lower than that.

In case you are not familiar with a closed circuit system, here is a system that should be similar to the one that is on your trencher.

Keep us posted on how your investigation goes. We can help direct you based on your findings.

 

[r8f1k]

Ok, I can see if there is oil heading down to that part of the pump. HOWEVER, right now I have no oil in the machine at all. I am swapping the excavator controls for a 2 joystick control and there was a lot of water in the system. I am opening all the lines I can find at the lowest points to drain out any water, old fluid. It looks like it had ATF and everything is PINK in the system, so my bet is there was plenty of water in the system and all the fluid is/was contaminated. I have all new filters and new fluid, but I also want to pull the hydraulic tank out and give it a rinse in my solvent tank to get any trash that might be in it. Since there are so many lines on this thing, any advice for purging out old oil without wasting a bunch of new? I thought about putting an air line on it and blowing the system out. The lowest lines have been dripping for days and have rendered about 5 gallons of oil/slime/water.

It is a distinct possibility that the oil tank is full of trash and the line is plugged going to the pump. I ran the pump in one direction or the other for not more than 10 seconds. Each time I tried an separate occasions (4 times), the chain would barely move.

The only thing I have no real experience with is getting a pressure gauge in line. Any recommendations on what to buy and where from?

 

[r8f1k]

Any thoughts on where to get a seal kit for my leaking cylinder? Below is the link to a kit, but no one has it in stock. I'm betting that most of the seals are generic, but any guidance on getting a kit would be ideal.

Manufactured by - CASE

H122234 Machine Parts from CASE 2-Year Warranty - SEAL KIT CYLINDER H

www.radwell.com

 

[laurencen]

for most of my rebuild kits I use HW partstore, had several times the Deere dealer price was 6 times what HW could supply, never had a issue with the quality or fit

Quality Construction Equipment Seal Kits & Repair Parts

HW Part Store is an organized and easy to navigate online store for Aftermarket Hydraulic Seal Kits & Replacement Parts for Case, Caterpillar, & John Deere Industrial Construction Equipment at Discount Prices.

hwpartstore.com

 

[Doaaj50]

Here are a couple of options for you:
Northern Tool
Discount Hydraulics

I would go with a 0-600 psi gauge for charge pressure. That would work for measuring it on your propel system as well. You can have a test hose made up at a local NAPA or you can even just buy one online at Discount Hydraulics. Don’t forget about the fitting that you will need to install into the pump. The size of the port was on the diagram on my previous post.

You also mentioned that there was water in the system. Another action I would take is disconnect the case drain hoses from all your pumps and motors. This way you can get that contaminated oil out of those components. I would also do the same on the system hoses.

After you do that, make sure you follow a good startup procedure. Here is one you can follow to ensure you have success.

Startup Procedure

I know it is a pain to do all that work, however it is worth getting that bad oil out and good oil in. Otherwise it can lead to continued issues in the hydraulic system.

 

[r8f1k]

Ok, I'm usually pretty good at tracking down odd parts, I can't find this seal kit anywhere. I have most of the measurements available through AVSPARE.com, I have crossed a lot of the parts, but for things I can't find, am I able to measure them and look up by size on HW Part Store.

 

[laurencen]

R18 in all my cases I simply give them the machine info as you do with dealers they look up the part number in there system, usually I buy the seal kits not individual seals

 

[r8f1k]

A little bit of progress today, pulled the hydraulic tank off, gave it a good cleaning, some debris, not too bad. That gave me access to the pump, pulled the two 1/2 bolts out that hold it against the drive plate and I wiggled it back to see if there was any issue with the splines. Splines look GOOD! Pushed it back in and pulled a couple lines off, drained more pink fluid and I noticed an inline check valve on the intake side. It seems to me something is wrong with the placement. It also seems very tight. I can see the same check valve in the diagrams from Case, but wouldn't it restrict the all of the fluid from going into the pump? The fluid would have to be fed by gravity and I don't know how it would overcome the check valve. The other side of the check valve is a 'T' and that comes from the oil cooling system. What am I missing?

 

[oldnslo]

Which port is that check calve connected to? The case drain or charge pump inlet?

Looking at diagram I suspect case drain but not certain that is correct.

 

[r8f1k]

Pretty sure it is the pump inlet

 

[Doaaj50]

Would you mind double checking based on this diagram?

If it is on the charge pump inlet, I can’t think of any reason why it would be there. It would only lead to more pressure drop that makes it more difficult to get oil into the inlet of the charge pump.

The only place that a check valve would make sense is on the case drain. If it is on the case drain port then it wouldn't let oil flow from the tank to the pump case. I have seen that if there are case pressure spikes from another component and they are trying to isolate the pump case from those events.

If it is on the charge pump inlet line, I would remove it. If it is on the case drain line, I would make sure it is working properly and the oil can flow from the pump to the tank. It should not take much force to open it. If it does, I would be concerned about it causing high case pressure in the pump.

 

[r8f1k]

Here is where it is