My JCB JS220 excavator hydraulics have started overheating. I can idle back down and it cools back to an acceptable temperature in appx 5 minutes, but will quickly overheat again when tracking or working boom, stick and bucket. Hydraulic heat exchange is 30 degrees hotter at the top than at the bottom so I believe it is properly cooling the Hyd oil, but something is causing heat. Any ideas? Also, is there a hydraulic thermostat on these machines? Thanks, Frank
What temp readings were you getting at the cooler? Is it actually overheating, or could it be a sensor?
would shoot the line reliefs with infrared heat gun
Verify that your oil is actually overheating. Senders go bad and end up inaccurate.
Digital readout in cab shows temp steadily increasing from 70 degrees at startup to a high of 200 degrees(takes about 45 minutes of digging/working) which is where I idle down and let it cool back to low 180s. Hyd oil temp idiot light and buzzer activate at 205 degrees. As soon as I start working again it starts increasing toward 200. I have checked temp on pipe at sensor with temp gun and it reads appx 7 degrees higher than the digital readout.
Thanks, I have verified with heat gun….
Thanks, will do that today.
Yep, checked that with heat gun. Thanks
Top of cooler is at same temp as digital readout when hot, bottom of cooler is appx 30 degrees cooler.
Check that the cooler is not clogged with dust, people tend to neglect the corners and only look where the fan blows through
You were saying the readout was 200 Deg in an earlier post, correct.? Is the hydraulic cooler oil-to-air with the flow from the fan blowing over it.? 30 degrees difference between top & bottom sounds very much like a (maybe partially) blocked cooler.
Yessir, whole radiator system is in three adjacent parts. Looks like one big radiator but is actually three. Engine cooling section, Hyd oil cooling section, and fuel cooler section. So far no issues with engine temp or fuel temp.
It sounds like you have a cooling "stack" (exchangers stacked together). If you are not seeing thermal run away with other sections like engine, you could nearly write off the cooling fan, but checking the stack for debris would be wise. What I would do is start chasing around on the machine on cylinders and lines. You did not mention any functional issues, but it sounds like oil is sneaking by somewhere, causing big heating. Swivel for the tracks, a piston seal in a cylinder, or something in the valve block. The pump itself could be causing this too if she is going out and bypassing. Personally, I use a FLIR camera for this stuff. if you don't have one, buy one or go rent one somewhere. Do NOT go the Harbor Freight for some POS. You might think your IR gun is great until you see the entire thermal image. She will glow like a burning VW engine block.
Thanks Fastline, the stack is clean with no debris and engine temp remains fine. Started having Hyd oil overheating issue and then subsequently my Hyd thumb quit working. It was working fine up until one day at startup it just wouldn’t work at all. Tries to move but just will not function. I checked pressure at the cylinder when activating the thumb and had 2800psi, and zero when not activated. I manually locked thumb in open position and have still been using the machine. Since thumb was inactive I didn’t consider it to be a possible heat causing problem as it had zero pressure when not activating the control. Seal kit is ordered cause I like my thumb, but do you think this could be the problem?
Hard to say but possible a valve is stuck and sitting on relief. I'd probably rectify that issue before anything else.
Sounds like a plan. Do you think I can find which valve may be stuck with a temp gun?
Oh yes, if there is enough heat to make the whole hydro system overheat, you could find a hot spot on the valve block. The issue is knowing how oil moves through the valve block. I don't know how your thumb is plumbed but somewhere there is pilot pressure opening the main spool for that circuit. I would start with that pilot valve area. If this has an electric valve, it is very possible it is leaking over, shorted, etc, which would move the main spool, set it on relief, and make the thumb nonfunctional. but when you say the thumb 'stopped working', I don't understand what that means. Stuck and won't move, falls down, etc.
At start up one day it was in the closed position and would barely move toward open. I had to push it into the ground to open fully and it would leak back into the down or closed position in a few seconds. Now it is not moving at all so I locked it open manually which allowed me to continue working. My heat problem started before that thumb failure day though.