Hello I just bought a jd 27c zts and each track will move forward and back but if i try to go forward with one and back with the other it does nothing. It doesn't even make a sound like its trying too. This was a rental machine and I'm wondering if this action was disabled somehow? Any help would be appreciated!
Good day The machine should counter rotate unless it has wide track pads on a sticky surface, maybe get the pressures checked. Kind regards Uffex
pressures seem good. I did however find a pressure sensor broken off on the bottom of the propel linkage control box. there are two of them, one on each side, When I look up the number it is linked to the travel alarm electrical harness. would this be the reason it does not counter rotate?
Check pressures then rotatory swivel
Pressure switches in the travel pilot circuit only affect the travel alarm and "two speed" operation, not power.
can I test the pressure right at the auxillary ports on the dipper?
I think you need to test at pumps as I believe each travel motor runs off a seperate section of the pumps
Check at the pumps like bmckenzie said. Checking at the couplers creates to much opportunity for errors (control valve, circuit relief valves, etc). There should be a plug on the fittings for the high pressure hoses that can be used for testing pressures. Picture is of a 35C. 27C is the same.
Thanks this is great info! I am going to order a pressure meter off the internet and going to get a hose and fitting made up to fit on my machine and I'll get back to this post. by the way I can't find the main relief valve does anyone have an idea where it is?
Here are the locations.
When at the hose making place get the test tee's in the 2-3 sizes that fit your machine and the gauge on a 8 foot long hose so you can see pressures as you run and work the machine, helps with the diagnosis of problems.
I just received the gauge and am going to get a hose made up this week! I was just going to take the plugs out of the tees on the 3 pumps one at a time and run the propel forward and back and then counter rotate. Does that sound like a good plan and can anyone tell me what pressure I should be looking for and if each drive is run by a different pump? Thanks!!
Make sure to relief hydraulic tank pressure before removing test port plugs. Hydraulic Pumps 1, 2, and 3 System Relief Valve—27C ZTS 1. Install pins or round bar stock between the sprockets and track frame to stall propel motors. 2. Engine at fast idle and oil at operating temperature. 3. Slowly actuate the left propel to load hydraulic pump 1, right propel to load hydraulic pump 2 or blade to load hydraulic pump 4. Record the pressure readings. Hydraulic Oil Temperature 45—55 °C (110—130 °F) Engine Speed Fast Idle Hydraulic Pump 1, 2, and 3 System Relief Valve Pressure 20 600—22 600 kPa (206—226 bar) (2990—3280 psi)
Correction. End of step 3 above should read blade to load hydraulic pump 3.
Thank You mg2361 for all your help!
Update: I tested the blade pump pressure. I raised it till it stopped and it was 3400 psi. i should also say that he machine is up on blocks with the tracks off because I am doing the rollers. Then switched to the right propel pump. Well I do not want to put a metal bar into those sprockets so i put 2 x 4s and it snaps them like tooth picks. I have not figured how to "stall" the sprocket drives yet. tomorrow I'm going to cut an old tire and see if that will jam the drive.
That wont stop it you need to put tracks on ans put a big pin in sprocket
Dave is correct, a tire won't work. A big pin between the sprocket and the frame will work to save on installing the tracks.
I took the ball off one of my reese hitches and that fit in and worked perfectly the left pressure was 3250 psi and the right was 3400 psi. what does that tell you? could it be a relief valve not working?
You need the manufacturers specification to know. If the machine has piston pumps that sounds low. But you need the spec to be sure.
Did you test the pressures in both forward and reverse? Need to do that. Make sure the oil is warmed up as well (specs post #13). Post results.
I plan on retesting because I didn't have the idle at full, so i'll record both forward and back pressures hopefully within a few days Thanks!
Ok, i warmed the machine up for 20 minutes and tested pumps 5 and 6. I thought that each pump would operate the drives forward and back on the same side , but backwards was the other side. here were the readings at full throttle: pump 5, right side propel forward was 3600psi left side propel back was 3600 also. Pump 6, left side propel forward was 3300 and right side propel back was 3300
Hydraulic pump 1 supplies oil to the left propel forward and reverse. Pump two would supply oil to right travel forward and reverse. You have your gauges connected as in the attachment?
Has there been repairs to this machine? Hoses replaced and connected to the wrong ports? Someone has turned pump 1 relief way up also. Top of spec is 3280 psi. You may have to check that the hoses from the control valve to the rotary manifold are correct as well as from the rotary manifold out to the drive motors. Also the pilot hoses that stroke the spools may have been installed incorrectly if one or more of them has been replaced. I attached a diagram of the propel main line connections, but do not have one for the pilot line connections.
I bought this excavator from a rental company, it has 3805 hours. I have all the sides off and top plate off over the rotary. there is not a cover at the bottom of the rotary and it is brownish red in color. This makes me think that it has been replaced at some point. I have one hose with a meter attached to it, so I tested one pump at a time. When I did not get a reading in reverse on the drive I was testing, I pinned the other drive and got a reading. That also made me think that something was probably connected wrong. The lines to the spools look like no one has messed with them. So next I'm going to look at the rotary lines. At this point I'm glad that the machine is up on blocks and I've cleaned out the drive motors, because I'll be on my back under the machine. Life is good! Thanks mg2361 you are very big help!!
i've checked the bottom of the rotary and it seems like just in the schematic. there are 4 lines from each drive a small one, a medium size one and two larger ones the small and medium ones are different sizes and couldn't be switched because of the different size fittings. the two larger ones have angled fittings and seem to be where the are supposed to be. see photo. I just can't figure out why the pumps work properly in forward but switch sides in reverse
I'm probably going to try to switch two of the hoses from the valve spools on the rotary and retest
Before you switch hoses maybe you could answer a question first. Are you saying that in going forward one pump has pressure and when you run the same track in reverse the other pump is feeding it? The relief valves for the travel circuits are in the travel motors and not in the main control valve. Forward travel is one relief and reverse travel is the other relief in the same motor.
Looking at the picture it is not likely they are switched at the bottom of the rotary since the length of the hoses would most likely prevent that. On top of the rotary the hoses may have been switched but more likely they could be mismatched on top of the control valve with one hose for left motor and one hose from the right motor connected to each spool section. Another possibility is the pilot lines at the spool sections being mixed in the same scenario.
Yes pump 1 runs left forward and right in reverse, pump 2 runs right forward and left in reverse. It makes sense to me now that it doesn't counter rotate because the same pump is trying to go forward on one side and reverse on the other instead of both pumps working together.
On the side of the rotary the 4 lines that go to the control box I took this pic. I ran the engine and went forward and reverse while holding each line and feeling for a pulse this is what I think the lines are at his time. from left to right: bottom line = right forward, top = left forward, bottom line = right reverse, top = left reverse. So since pump 1 runs left propel and forward was right and reverse was supplied by pump 2, i believe that the line bottom line on the left and the top line right are supplied by pump 1 so the bottom line with the red stripe should go up and the that line should go down to that spot
That red striped hose is not original so maybe whoever put it on got two mixed up? If you can reach it, try swapping them.
i can reach better from the bottom. They all seem to be 7/8 fittings I'm going to have to remove half of the side on the bottom fittings and get some plugs for those lines before i can get right at them. Last time I did this on my bobcat I cut a smaller wrench short and then took a grinder to it to get 4 of the sides of the nut to fit tight. a7/8 crow wrench would probably be helpful too. maybe I should drain the hydraulic tank down too?
I would drain the tank.
While the tank is drained I'm going to clean it and replace the suction filter and o-ring. It took some help but I changed around the two reverse lines at the rotary when my parts come in later this week I'll fire it up and post the results! now on to my travel switch problem
Well got the tank filled back up and ran it forward. Same as before but when I ran the drives backward the right control now runs the left in reverse and the left control runs the right drive in reverse. I only changed the reverse lines so I guess they were probably right. Also the main problem is still not fixed, it still will not counter rotate! I'm totally confused now. If the forward was running on one pump and the reverse was running on another, would't it as least counter rotate at this point or does that point to the drives being mixed up at the propel levers somehow?
Check the pilot line routing? See attachment.
T,hanks will do I am going to check pump pressure also to see if the pumps are following the lines.
Are you sure that pump 1 runs left forward and reverse? I'm just looking at the diagram and pump 1 is in front, and on the left side of pump 1 is left forward (3a) on the right is right reverse (4a). The same for pump 2 (3b and 4b) Or is the control valve (3a and 3b) run only by pump 1, and 4a and 4b by pump 2 ?
100%. Pump 1 supplies left propel 3A and 3B. Pump 2 supplies right propel 4A and 4B (see attached hydraulic control valve schematic).
Thanks Mg2361 you are a huge help! I don't know what I would do without this forum. I felt for lines pulsing as I ran the drives forward and back but didn't get what I needed so I drained the tank again and am in the process of switching the lines back on the rotary so I know where I was at that point
Can you elaborate on the relief valves and how they work? I switched two lines on the rotary that I thought were the problem (right reverse and left reverse) but the drives just worked on the opposite lever than they were supposed to.
If you pull the covers off on the inside of the track frames behind the sprockets you will see the travel motors. The reliefs are two cartridge valves with adjustable screws held from turning with lock nuts. You check the pressures for each direction by putting a pin in an tooth groove and turning the final until it locks against the track frame. With a gauge plumbed into a fitting between the pump and the main control valve you can check the relief pressure for that direction. Then reverse direction and put the pin in the opposite way to lock the track the other direction and check pressure. They should be nearly the same. If one side is lower than the other you can swap the cartridges and check again. If the pressures switch sides you can just adjust the cartridge up to the same as the opposite side. If the pressures don't switch sides you likely have a swivel seal issue or a pump problem. Swivels are cheaper to reseal than pumps are to fix and reseal so that would likely be your next step. Good Luck!
I'm starting from scratch like in the shematic, I don't read a lot of these and could use some advice because it could be read two different ways. Left forward and left reverse are the bottom two lines that run into the rotary. I have added a side view of that. I don't know if LR is in port D or above LF in C
Try these.
Thanks MG your the best!
I reversed the propel lines at the track motors all it did was reverse the direction of the motor. there were no cartridge valves that I could see, the lines when right into the fittings attached to the drive motor. i guess all I can do now is pull the rotary and rebuild it. There are 4 bolts on the bottom that seem fairly straight forward to remove. I'm concerned with these two rusty bolts on top. they seem to attach to a bracket coming from the top on one side of the rotary. I don't know if this bracket is attached to the rotary or not, the pictures don't show it.
Usually that is a bracket that makes the top half of the swivel turn with the house while the bottom half stays put in the carbody. On most of the machines that I've worked on, that bracket has a boss and a pin that attaches to the swivel housing. There has to be some flexibility in the connection so tops are not bolted down hard in place.
UPDATE: I pulled the rotary to rebuild it with a new seal kit. The very bottom seal was gone so it would have began to leak anyway at some point. The other seals seemed intact so I don't think my problem came from any of those. I did realize that 3 of the lines going to the rotary were in the wrong ports, right reverse was the only one in the right place. I compared the schematic to the rotary with air pressure in each port and I am confident that the schematic is correct so I will switch the three lines from the pumps to the correct ports on the rotary. I guess that is not where my problem ends. The three propel lines that go to the pumps need switched also. Don't you agree? I also called the previous owner and they eluded that some young guy did repairs to this machine and probably did not have access to any material for guidance. For anyone doing this repair this is what I did: rotate machine 90 degrees left for access to the rotary fittings Drain hydraulic tank mark bottom lines that go to propel motors with zip ties and remove wrapped with wire and tie back out of the way with blade lines. mark and remove the four lines form the pumps on the starboard side and remove the small line on the bottom of the port side. All those lines are accessible with normal 3/4 and 7/8 wrenches however the last two fittings on the port side rotate horizontally so I made two sized wrenches from two large crow foot wrenches that i would never use. A 7/8 for those and 3/4 for the last two lines on the top. See photo. Now its time to put it all back together!
Let me know how you make out when you get your hose routing straightened out. Just in case I attached a pilot system schematic for you in case you need it in the future.
Thanks MG!
Success! problem solved, I switched the three lines that where coming from the pumps to the bulkhead that connect to the propel pedals twice and got it right. Thanks for all the help!!
I want to turn down the relief pressure on pump 1, Also I may add a hydraulic thumb and want to also make sure the relief on the auxiliary is set lower than the bucket curl so I don't damage the thumb. Can you point me in the right direction on how to do this?
Do you ever plan on running a breaker?
No just a two way hydraulic cylinder for the thumb
As far as the pump 1 pressures all the info you need are in posts #8, 10 13 and 14. As for your thumb see attachment.
Thanks for the help MG!