john deere 27 c won't do zero turn

[mg2361]

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.

 

[dmason320]

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!

 

[dmason320]

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

 

[mg2361]

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?

 

[mg2361]

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.

 

[dmason320]

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!!

 

[dmason320]

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

 

[dmason320]

I'm probably going to try to switch two of the hoses from the valve spools on the rotary and retest

 

[John C.]

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.

 

[mg2361]

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.

 

[dmason320]

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.

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.

 

[dmason320]

 

[dmason320]

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

 

[mg2361]

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.

 

[dmason320]

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?

 

[mg2361]

I would drain the tank.

 

[dmason320]

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

 

[dmason320]

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?

 

[mg2361]

Check the pilot line routing? See attachment.

 

[dmason320]

T,hanks will do I am going to check pump pressure also to see if the pumps are following the lines.