mg2361
Senior Member
I'm curious, are the Dp sensor readings delayed now when you stroke the levers? If yes, does the angle sensor readings respond immediately?
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EX120-2 system base pressure too low
- Thread starter Jason Klassen
- Start date
Jason Klassen
Well-Known Member
I'm curious too! The diagnostic connector has been giving me trouble lately. It was connecting with Dr.Zx intermittently and now it won't connect at all. When I probe the 4 pin connector I seem to be missing one of the 5V signals.
Lock tab up I get:
top left 0.20V
top right 0.13V
bottom left 0.13V
bottom right 5.13V
The top left should be 5V also.
The last time I had this issue I lost both 5V signals and that was due to the new china dp sensor being internally shorted and stealing the 5V signal. Putting the old dp sensor in brought back the 5V signals and communication. Unplugging the dp sensor this time did not help.
Wiggling the harness does not help. All 4 pins go directly back to the pvc. I tested their continuity last time and all the wires were good.
I don't know if this china pvc is failing or not. I have not even dug a hole with this machine yet.
I tried poking around the other sensors looking for some sort of short but did not find anything conclusive.
Lock tab up I get:
top left 0.20V
top right 0.13V
bottom left 0.13V
bottom right 5.13V
The top left should be 5V also.
The last time I had this issue I lost both 5V signals and that was due to the new china dp sensor being internally shorted and stealing the 5V signal. Putting the old dp sensor in brought back the 5V signals and communication. Unplugging the dp sensor this time did not help.
Wiggling the harness does not help. All 4 pins go directly back to the pvc. I tested their continuity last time and all the wires were good.
I don't know if this china pvc is failing or not. I have not even dug a hole with this machine yet.
I tried poking around the other sensors looking for some sort of short but did not find anything conclusive.
mg2361
Senior Member
Yep, those dash 2 and 3 machines have always been full of gremlins
.
.Jason Klassen
Well-Known Member
If only I knew that before buying, but I probably would have said "how hard could it be". I feel like that is the only way to get things done, if you don't try you will never get anything done!Ok, so today I put my gauge on the output of the pilot pump, and then checked the operational performance test section of the manual.
For pilot primary pressure the spec is 52 +10 -0 kg/cm2. That works out to a range of 740-880 psi.
The performance tests are supposed to be done in "P" or power mode.
idle: 640 psi P mode: 690 psi
I then added a 2mm thick washer to the stack of shims that were already in the pilot pressure regulator.
idle: 720 psi P mode: 790 psi
I decided to leave it there. Elsewhere in the manual I have seen a spec of 711 psi being called for.
The next section in the performance tests that caught my attention was called "Main Pump Delivery Pressure" (in neutral)
The spec is 31 +10 -3 kg/cm2 which works out to 440 + 140 - 40 psi, giving a range of 400-580 psi.
Using the same gauge that I just measured the pilot pressure with, I hooked it up to the output on the pump.
idle: 0 psi P mode: 0 psi The needle did not even move on the gauge!
Do springs like the one in the unloading valve wear out and loose tension? Causing it to open early and bleed off pressure too soon.
Since Dr.Zx is not working right now I back probed the differential pressure and angle sensors.
idle: DP 2.92V P mode: DP 2.73V (higher voltage means bigger difference in pressure)
I was expecting the voltage to go up when going from idle to P mode. In neutral there is supposed to be no load sense on the dp sensor. Only the pump pressure being regulated by the unloading valve should be acting on the dp.
idle: A 3.14V P mode: A 3.64V (higher voltage means more pump angle)
The bucket, boom, arm, and swing controls seem to respond fairly quickly (but I don't know what normal is lol). The tracks on the other hand... I can pull the levers and count to 5 while watching the pressure gauge. Then the needle starts to move and it takes another 3-4 seconds for it to reach almost 4000 psi in P mode. It only reaches the 4000 psi when using one track to turn and it stops moving.
Jason Klassen
Well-Known Member
So I was reading this thread https://www.heavyequipmentforums.com/threads/hitachi-ex100-3-overheating.69884/ In there Knivens894 talked about an overheating issue that turned out to be the result of low pilot pressure caused by the spring in the pilot relief valve becoming weak due to heat.
This made me wonder if my unloading valve spring could have become week. I took the unloading valve out today to have a look at it. The end of the spool where the spring goes looks like it has gotten hot or has been heat treated. You can see the blue color it has turned in the pictures. Why would the end of the spool need to be heat treated?
Now I also tried to find out if the spring was actually weak by testing it.
Here goes my maths lol!
From the manual the unloading valve opens from a pressure of 284 psi
I measured the bottom of the unloading valve spool and it comes out as 0.552 inches in diameter.
Then apply the area of a circle formula (A=pie(r)2) lol and arrive at an area for the oil to push on the bottom of the spool of 0.239 inches
So if it takes 284 psi to move the spool but the area for the pressure to work on is only ~ 0.25inches, that means that it should take 1136 lbs of force to compress the spring.
Next I put the spring in my hydraulic press with a bathroom scale underneath it. When I got to the point where the spring was almost coil bound the reading on the scale was only 309 lbs.
The oil pushes on the bottom of the spool after going through a tiny hole. I don't know if that would have an effect on my calculations.
Any ideas?
This made me wonder if my unloading valve spring could have become week. I took the unloading valve out today to have a look at it. The end of the spool where the spring goes looks like it has gotten hot or has been heat treated. You can see the blue color it has turned in the pictures. Why would the end of the spool need to be heat treated?
Now I also tried to find out if the spring was actually weak by testing it.
Here goes my maths lol!
From the manual the unloading valve opens from a pressure of 284 psi
I measured the bottom of the unloading valve spool and it comes out as 0.552 inches in diameter.
Then apply the area of a circle formula (A=pie(r)2) lol and arrive at an area for the oil to push on the bottom of the spool of 0.239 inches
So if it takes 284 psi to move the spool but the area for the pressure to work on is only ~ 0.25inches, that means that it should take 1136 lbs of force to compress the spring.
Next I put the spring in my hydraulic press with a bathroom scale underneath it. When I got to the point where the spring was almost coil bound the reading on the scale was only 309 lbs.
The oil pushes on the bottom of the spool after going through a tiny hole. I don't know if that would have an effect on my calculations.
Any ideas?
John C.
Senior Member
I've only done a limited amount of work on old Hitachi excavators but can make some observations about what you show in the photo.
My first thought is that it would take over 700 degrees to actually affect the temper of the spring. The spring in the photo appears to have the same amount of space between all the coils so I doubt very much that there is anything wrong there. The blue color is what I'm used to seeing on a component like this. I'm guessing that the spring fits over the raw end of the spool and the oil pressure acts against the machined end of the spool. I can also see the half moon groove in the middle land which tells me the spool is a regulating spool. I'm also wondering if there is a cap that is supposed to sit on the free end of the spring. Usually that cap with have a mark for an adjusting screw to seat into.
I don't see any smoking gun to say something is wrong there.
My first thought is that it would take over 700 degrees to actually affect the temper of the spring. The spring in the photo appears to have the same amount of space between all the coils so I doubt very much that there is anything wrong there. The blue color is what I'm used to seeing on a component like this. I'm guessing that the spring fits over the raw end of the spool and the oil pressure acts against the machined end of the spool. I can also see the half moon groove in the middle land which tells me the spool is a regulating spool. I'm also wondering if there is a cap that is supposed to sit on the free end of the spring. Usually that cap with have a mark for an adjusting screw to seat into.
I don't see any smoking gun to say something is wrong there.
Jason Klassen
Well-Known Member
Hi John, here is a picture of the rest of it...
There is no adjusting screw on the top. This entire control valve is from a 120-3 even though my machine is a 120-2. The parts guy at my local Hitachi dealer told me that this is most likely a gray market machine and when they arrive in containers the guys just put them together with the parts that are in there, not necessarily the specific ones that belong to each individual machine.
On the 120-3s the regulator was replaced with the plug that you see here. The relief on the bottom of the control valve became the new system relief.
Some interesting results this evening. I decided the only way to rule out the spring for sure was to eliminate it as a factor. I cut a piece of pipe to the same length as the spring and installed it in the springs place.
I figured it could not hurt the machine since when someone is operating the controls load sense oil is supposed to fill the cavity where the spring is and help hold the unload valve down in the closed position. Then the main relief valve comes into play and is supposed to open at 5000 psi.
The "Main Pump Delivery Pressure" (in neutral) (in P mode) is supposed to be 400-580 psi. Previously I stated that the needle on my gauge did not even move. Turns out there is a marking for 100 psi literally right on the needle stop so there might have been some pressure but nothing significant at idle or in P mode.
This time with the pipe in place of the spring there was still nothing significant at idle but when put into P mode I got 250 psi. Nowhere near the 400-580 psi that I was looking for but its something. Not sure if that means the spring is bad or not, but I'm leaning towards its fine.
I can still hear a hissing at idle even with the pipe in place which tells me that some valve is still bleeding off pressure. Right?
Another weird thing, I tried to use the thumb which has not been working properly since I refreshed all the circuit relief valves. I pushed the rocker switch to close the thumb and about 3800 psi was built, but when I went to open the thumb it did not move and no pressure was built. Only when I let off the rocker switch was there a momentary spike in pressure to about 4000 psi.
I know the pressure is high for a thumb but I still have all the reliefs cranked. I am waiting to find the actual problem before trying to set them properly.
Thoughts?
There is no adjusting screw on the top. This entire control valve is from a 120-3 even though my machine is a 120-2. The parts guy at my local Hitachi dealer told me that this is most likely a gray market machine and when they arrive in containers the guys just put them together with the parts that are in there, not necessarily the specific ones that belong to each individual machine.
On the 120-3s the regulator was replaced with the plug that you see here. The relief on the bottom of the control valve became the new system relief.
Some interesting results this evening. I decided the only way to rule out the spring for sure was to eliminate it as a factor. I cut a piece of pipe to the same length as the spring and installed it in the springs place.
I figured it could not hurt the machine since when someone is operating the controls load sense oil is supposed to fill the cavity where the spring is and help hold the unload valve down in the closed position. Then the main relief valve comes into play and is supposed to open at 5000 psi.
The "Main Pump Delivery Pressure" (in neutral) (in P mode) is supposed to be 400-580 psi. Previously I stated that the needle on my gauge did not even move. Turns out there is a marking for 100 psi literally right on the needle stop so there might have been some pressure but nothing significant at idle or in P mode.
This time with the pipe in place of the spring there was still nothing significant at idle but when put into P mode I got 250 psi. Nowhere near the 400-580 psi that I was looking for but its something. Not sure if that means the spring is bad or not, but I'm leaning towards its fine.
I can still hear a hissing at idle even with the pipe in place which tells me that some valve is still bleeding off pressure. Right?
Another weird thing, I tried to use the thumb which has not been working properly since I refreshed all the circuit relief valves. I pushed the rocker switch to close the thumb and about 3800 psi was built, but when I went to open the thumb it did not move and no pressure was built. Only when I let off the rocker switch was there a momentary spike in pressure to about 4000 psi.
I know the pressure is high for a thumb but I still have all the reliefs cranked. I am waiting to find the actual problem before trying to set them properly.
Thoughts?
John C.
Senior Member
The only thing I can remember on a similar situation and I can't remember the model of machine was where the bore for the servo piston inside the pump was worn and there was enough leakage in that bore that the pump would not reach full system pressure. I don't remember how I figured that out but you might try to find out where that hissing noise is coming from.
No way to know when you machine came into the country but back in the nineties when the big rush was on, the bulk of those machines came in whole and not in containers. I used to see rows and rows of them on the docks waiting for trucks to pick them up to deliver to washing stations or to leave the Ports in Seattle and Tacoma.
No way to know when you machine came into the country but back in the nineties when the big rush was on, the bulk of those machines came in whole and not in containers. I used to see rows and rows of them on the docks waiting for trucks to pick them up to deliver to washing stations or to leave the Ports in Seattle and Tacoma.
Jason Klassen
Well-Known Member
Hey John, that sounds like it would be tricky to figure out. The pump on my machine was rebuilt about 40 hours of use before I bought it. I have had it apart because I did not totally believe them, turns out they weren't lying and the pump is all new. That includes the head on the pump where the servo piston lives.
Is there a good way to figure out where the hissing is coming from? Tips or tricks?
Just by listening I can tell it is coming from the main control valve but it is very difficult to pinpoint. I can hear it the best when the machine is idling but if I rev it up it becomes almost impossible.
I have tried a mechanics stethoscope with no luck, the cast iron of the main control valve is just too thick.
Would a thermal imaging camera/gun work? They have gotten a lot cheaper lately. I was thinking of just letting it run at idle with the hissing going on and then start looking for a warm spot on the main control valve. Where the oil is blowing by it should be warmer?
Should there be no hissing if it is all working properly?
I have put in a new main relief from Hitachi but there are also 8 more circuit reliefs. Two for each of the bucket, boom, arm, and thumb. I don't want to replace them all if I don't have to. I am trying hard not to be one of those throw parts at it mechanics lol!
That would have been quite a sight to see on the docks. Were any of the 120s ever not considered gray market?
Is there a good way to figure out where the hissing is coming from? Tips or tricks?
Just by listening I can tell it is coming from the main control valve but it is very difficult to pinpoint. I can hear it the best when the machine is idling but if I rev it up it becomes almost impossible.
I have tried a mechanics stethoscope with no luck, the cast iron of the main control valve is just too thick.
Would a thermal imaging camera/gun work? They have gotten a lot cheaper lately. I was thinking of just letting it run at idle with the hissing going on and then start looking for a warm spot on the main control valve. Where the oil is blowing by it should be warmer?
Should there be no hissing if it is all working properly?
I have put in a new main relief from Hitachi but there are also 8 more circuit reliefs. Two for each of the bucket, boom, arm, and thumb. I don't want to replace them all if I don't have to. I am trying hard not to be one of those throw parts at it mechanics lol!
That would have been quite a sight to see on the docks. Were any of the 120s ever not considered gray market?
John C.
Senior Member
That machine was done in 1996 as I recall. It was a warranty claim on a used machine that had less than a month of work when problems started. What I seem to recall was that the machine just wouldn’t perform. All the pressures were OK.
I haven’t had much luck with stethoscopes either. I would be interested in listening to someone who has experienced success with an infrared camera. Most of the time I have had to use some twisted thought process to make a theory and then prove or disprove it.
I’ll try some thoughts. If your system is load sensing, then the main relief shouldn’t be opening at all. The pumps will de-stroke before the pressure gets that high. The circuit reliefs can be a mixed bag. Some machines have them set low to release before the mains. Others are set higher than the mains. Their purpose is to release pressure shocks from outside the machine hydraulics. Say a tree limb falls across the boom or a big rock off a high bank crashes down. The exception to that is the thumb. The cylinders for that were never intended for machine system pressure. My gut kind of says something on the main valve is stuck or hooked up wrong. Does the hiss go away when you use something?
I haven’t had much luck with stethoscopes either. I would be interested in listening to someone who has experienced success with an infrared camera. Most of the time I have had to use some twisted thought process to make a theory and then prove or disprove it.
I’ll try some thoughts. If your system is load sensing, then the main relief shouldn’t be opening at all. The pumps will de-stroke before the pressure gets that high. The circuit reliefs can be a mixed bag. Some machines have them set low to release before the mains. Others are set higher than the mains. Their purpose is to release pressure shocks from outside the machine hydraulics. Say a tree limb falls across the boom or a big rock off a high bank crashes down. The exception to that is the thumb. The cylinders for that were never intended for machine system pressure. My gut kind of says something on the main valve is stuck or hooked up wrong. Does the hiss go away when you use something?
Jason Klassen
Well-Known Member
The manuals only help so much, the twisted thought processes are what really fixes a machine lol!
Today I went back to the problem with the thumb. It would close but not open. It started after I had all the relief valves out and apart for cleaning and re-oringing. I didn't think it could be the relief since I had just looked at them and everything was good. So I checked that the spool moved freely, checked the pilot pressure and checked for internal leakage on the hydraulic cylinder. Everything was fine! It had to be the relief valve so today I swapped it with the arm relief beside it. Wouldn't you know it, the thumb would now open like before. The arm also turned into a bit of a pendulum so I know something is wrong with that relief because the problem followed it.
I will have to check if the hiss goes away when I use a function, I was just happy that the thumb moved again today.
According to the relief valve setting procedure I got from mg2361 the main relief is set to 5000 psi and the circuits are set to 5250 psi.
Before I tried setting the the pressures I noticed that the thumb reliefs were backed off a lot more than the others. This makes sense since it would be nice for the bucket to be able to overcome the thumb while holding something, like a log. That way you could curl the bucket without having to try and match the speed of the bucket with the thumb and still hang onto the log. The bucket would just push through the thumb relief.
I am a little confused though. I can't seem to find it right now but mg2361 sent me some info a while back. The info was from john deere and it mentioned that if any of the circuit reliefs were set to a lower pressure than the main relief, that circuit relief would turn into a main relief.
Thumbs are usually set quite a bit lower than the main relief. It seems to contradict the info from john deere???
I am starting to think I have multiple questionable relief valves in the main control valve.
Today I went back to the problem with the thumb. It would close but not open. It started after I had all the relief valves out and apart for cleaning and re-oringing. I didn't think it could be the relief since I had just looked at them and everything was good. So I checked that the spool moved freely, checked the pilot pressure and checked for internal leakage on the hydraulic cylinder. Everything was fine! It had to be the relief valve so today I swapped it with the arm relief beside it. Wouldn't you know it, the thumb would now open like before. The arm also turned into a bit of a pendulum so I know something is wrong with that relief because the problem followed it.
I will have to check if the hiss goes away when I use a function, I was just happy that the thumb moved again today.
According to the relief valve setting procedure I got from mg2361 the main relief is set to 5000 psi and the circuits are set to 5250 psi.
Before I tried setting the the pressures I noticed that the thumb reliefs were backed off a lot more than the others. This makes sense since it would be nice for the bucket to be able to overcome the thumb while holding something, like a log. That way you could curl the bucket without having to try and match the speed of the bucket with the thumb and still hang onto the log. The bucket would just push through the thumb relief.
I am a little confused though. I can't seem to find it right now but mg2361 sent me some info a while back. The info was from john deere and it mentioned that if any of the circuit reliefs were set to a lower pressure than the main relief, that circuit relief would turn into a main relief.
Thumbs are usually set quite a bit lower than the main relief. It seems to contradict the info from john deere???
I am starting to think I have multiple questionable relief valves in the main control valve.
mg2361
Senior Member
They will only turn into the main relief when that function is activated (if they are set lower than the system relief). With the spool for that function in neutral, the relief for that function is out of the equation.
The thumb circuit relief is lower because the thumb cylinder must collapse with the bucket cylinder or you will be bending rods.
Jason Klassen
Well-Known Member
So I listened more closely today. The hissing is there at idle (in neutral) and is still there as I raise the rpm.
I checked the thumb operation and it is working in both directions.
I then lifted the boom off the ground and tried to move the arm. I can move the arm out away from the cab like normal. I brought the arm back to a vertical position and then tried to move it towards the cab. It moved about 2 feet towards the cab slowly and then world move no further. I had the control lever pulled all the way back. There was a pronounced hissing coming from the control valve.
When I let go of the control lever the arm would swing back to the vertical position instead of holding the position that I had left it in.
This is exactly how the thumb was behaving before I swapped the reliefs. The problem definitely followed the the relief to its new position in the arm circuit. Its really strange, that relief must have something wrong with it's poppet or spring because when I have pulled it out it looked closed and I could move the little pistons with a pick tool and they would spring shut. Once it is installed in circuit it is opening for some reason.
Just to clarify this in my head... If I were to have the thumb set at 2100 psi like John C suggests. When I go to use the thumb will the thumb reliefs turn into a main relief because 2100 psi is so much lower than 5000 psi? If I were using another function at the same time would it be limited to the 2100 psi the thumb is set at? I feel like the thumb pressure setting should have no effect on the other functions because that would not be very productive.
I attached some pictures of the control valve from the manual. Can you guys make better sense of it than me? It looks like the variable pressure compensators might be involved in this low pressure mess. There is another problem where if I move the boom and arm together slowly its fine but if I pull on both control levers fully, the arm will move first while the boom remains stationary and then the boom will move once the arm is done moving.
I checked the thumb operation and it is working in both directions.
I then lifted the boom off the ground and tried to move the arm. I can move the arm out away from the cab like normal. I brought the arm back to a vertical position and then tried to move it towards the cab. It moved about 2 feet towards the cab slowly and then world move no further. I had the control lever pulled all the way back. There was a pronounced hissing coming from the control valve.
When I let go of the control lever the arm would swing back to the vertical position instead of holding the position that I had left it in.
This is exactly how the thumb was behaving before I swapped the reliefs. The problem definitely followed the the relief to its new position in the arm circuit. Its really strange, that relief must have something wrong with it's poppet or spring because when I have pulled it out it looked closed and I could move the little pistons with a pick tool and they would spring shut. Once it is installed in circuit it is opening for some reason.
Just to clarify this in my head... If I were to have the thumb set at 2100 psi like John C suggests. When I go to use the thumb will the thumb reliefs turn into a main relief because 2100 psi is so much lower than 5000 psi? If I were using another function at the same time would it be limited to the 2100 psi the thumb is set at? I feel like the thumb pressure setting should have no effect on the other functions because that would not be very productive.
I attached some pictures of the control valve from the manual. Can you guys make better sense of it than me? It looks like the variable pressure compensators might be involved in this low pressure mess. There is another problem where if I move the boom and arm together slowly its fine but if I pull on both control levers fully, the arm will move first while the boom remains stationary and then the boom will move once the arm is done moving.
John C.
Senior Member
The compensators appear to be in the motor circuits and not the cylinder circuits. Is there anyway that the spools got put in the wrong holes?
The circuit relief is always a circuit relief. The main relief is installed between the pump and the main control valve. The circuit relief is installed between the main control valve and the function that is being operated.
The circuit relief is always a circuit relief. The main relief is installed between the pump and the main control valve. The circuit relief is installed between the main control valve and the function that is being operated.
mg2361
Senior Member
Compensators are in every circuit.
Don't get hung up on this. Thumb circuits have to be set to 2500 psi or less to protect the thumb cylinder and will not affect the rest of the machine. You obviously have an issue with the relief you swapped, so fix that.
Jason Klassen
Well-Known Member
Thanks for the replies gentlemen, I have been sick the last couple of days but feeling better now so I will pull that relief soon to check it out.
Jason Klassen
Well-Known Member
Ok, got the problem relief valve out and there is a little carnage lol! I remember now that when I had all the reliefs out to service them there was one that sounded a little funny when I was screwing it back together. Turns out that funny noise was the spring perch on the poppet crumbling to bits and the poppet getting pushed down into the spring itself. None of the others made any funny noises while going back together.
Thumbs are not installed from the factory so the relief locations for the auxiliary spool are just plugged normally. When someone installed this thumb they would have had to buy relief valves for it. I wish I knew what kind they were so I could know if this was a oem relief or a aftermarket one that failed. Guess I will never know.
All of the relief valves are turned all the way up right now except for the new main relief that I got from Hitachi. That I left because it was supposed to come pre set. I was planning on waiting until the real cause of the low pressure was found and then I could back them down to their proper settings.
I turned them up all the way because I didnlt know if one of them had a weak spring or what was going on. Probably should have just stopped turning after one full turn made no difference to any of them. Live and learn
Thumbs are not installed from the factory so the relief locations for the auxiliary spool are just plugged normally. When someone installed this thumb they would have had to buy relief valves for it. I wish I knew what kind they were so I could know if this was a oem relief or a aftermarket one that failed. Guess I will never know.
All of the relief valves are turned all the way up right now except for the new main relief that I got from Hitachi. That I left because it was supposed to come pre set. I was planning on waiting until the real cause of the low pressure was found and then I could back them down to their proper settings.
I turned them up all the way because I didnlt know if one of them had a weak spring or what was going on. Probably should have just stopped turning after one full turn made no difference to any of them. Live and learn
Jason Klassen
Well-Known Member
Ok, I have my old main relief valve taking the place of the broken one right now and the machine is back to being as broken as it was before thumb stopped working. I will probably swap over the poppet and seat from the old main relief into the thumb relief that failed. I can't leave the old main relief in the machine because it does not have the anti-cavitation feature that the circuit reliefs are supposed to have.
Yesterday I received the thermal imaging camera that I ordered. It is a Hikmicro B10. I decided that my first test would be to start the excavator and just let it run with all the controls in neutral. I know that there is a low pressure problem in neutral so might as well start there.
The pilot system warmed up first which was expected but then after about 10 minutes I noticed something funny with the travel pressure hoses that run to the center joint. One of them was warmer than the others. With all the controls in neutral they should have all been the same temperature since no hydraulic oil should be flowing.
The hose that is getting warm is coming from the bottom of the right hand travel spool. Could this be the internal leak that is causing the low pressure?
Here are some thermal pics of the center joint.
Yesterday I received the thermal imaging camera that I ordered. It is a Hikmicro B10. I decided that my first test would be to start the excavator and just let it run with all the controls in neutral. I know that there is a low pressure problem in neutral so might as well start there.
The pilot system warmed up first which was expected but then after about 10 minutes I noticed something funny with the travel pressure hoses that run to the center joint. One of them was warmer than the others. With all the controls in neutral they should have all been the same temperature since no hydraulic oil should be flowing.
The hose that is getting warm is coming from the bottom of the right hand travel spool. Could this be the internal leak that is causing the low pressure?
Here are some thermal pics of the center joint.
Jason Klassen
Well-Known Member
Is there a method/procedure for figuring out if the main control valve itself is worn? When I had the control valve out I was able to polish out the small vertical scratches in the spools with wet sandpaper dipped in hydraulic oil. I did not do anything to the bores that the spools ride in though.