Hydraulic system works great until the hydraulic system gets hot. About 1 - 1.5 hours of steady use. It doesn't get to panel alarm hot but it gets hot enough where you can't hold your hand on the tank. Everything still functions but weak. It has a rebuilt pump but started this a while after that was done. Pilot filter changed. In tank filter changed. Screen filter changed. Hydraulic fluid has both AW32 & AW68 in it.
How about the oil cooler?
Oil cooler is clean and dirt free. Washed it out as well.
Had the same issue on a 6GK prefix 312 and ended up pulling both the rad and hydraulic cooler and sent them out to a local shop to be properly cleaned. The way both coolers are sandwitched together caused airflow blockage ressulting in hyd temps to spike after running for an hour or so in my situation. Put them back in with some fresh ELC and went back to digging.
I know everyone says their coolers or radiators are clean but realistically, the only way to really clean them, is to take them out and have them tanked. I have a radiator on my Jeep that looks clean, even at the top but I know it’s all scaled up inside.
Have you actually taken the tank temperature with an infra-red gun.? It might pay you to start with some hard numbers for temps. At the same time you could shoot the oil temp into and out of the hydraulic oil cooler. I would imagine no-one can hold their hands on anything much over 70 DegC but a high hydraulic oil temp alarm is probably not going to sound until somewhere around 100 Deg.
Nige said: "Have you actually taken the tank temperature with an infra-red gun.? It might pay you to start with some hard numbers for temps. At the same time you could shoot the oil temp into and out of the hydraulic oil cooler." I'm going to do this weekend or next week when I go out there.
Took some temperature reading today: At start up: TANK TO PUMP LINE - 90F COOLER IN - 90F COOLER OUT - 90F When the machine hydraulics got slow and weak(About 1- 1 1/2 hours): TANK TO PUMP LINE - 191F COOLER IN - 178F COOLER OUT - 161F I slowed the engine speed down to a few clicks off idle and left it for 15 minutes or so. It would cool down enough to start using again.
Do those temps look dangerously high?
I wouldn’t say so, although I would have expected the tank to be at a lower temperature seeing as oil returns to the tank from the cooler, but that's without being able to look at the system setup. With a 17 Deg temp drop across it the cooler appears to be working OK.
Well as far as the tank temp, IMO, it is a metal tank and down here in South Louisiana, we see temps in the mid to upper 90's during the day. When I took that starting reading the other day, it wasn't even noon yet. Just a thought. Would any of those additives help at all? Different fluid?
Has anyone run an additive that helps with the cooling? How about a heavier oil? I think I read that some have run 15W-40 in older machines, such as this. I even read where some have run 0-5W-30 oil. Thoughts?
Excuse me! What do you mean by "Hydraulic fluid has both AW32 & AW68 in it."? Anyway, you can refer to the Caterpillar guide attached.
Yes, there is both AW32 & AW68 in the hydraulic system.
Possibly time for some pressure testing.?
TANK TO PUMP LINE - 191F COOLER IN - 178F COOLER OUT - 161F Something is wrong here! The TANK TO PUMP LINE temperature can sometimes be higher than the COOLER out line, but the TANK TO PUMP LINE temperature must be lower than the COOLER in line temperature. If the temperature you collect is like that, I assume the bypass valve of the cooler is stuck, meaning it does not close the direct oil return line to the tank. If the temperature you collect is like that, I assume the bypass valve of the cooler is stuck, meaning it does not close the oil return line to the tank.
I'm afraid your machine's temperature is higher than the allowed level!
@LACHAU , That temperature you have highlighted is just warm oil temp for testing, not max operating temp. Hydraulic oil isn’t overheated until 220F. Are all of your functions operating properly? Any unusual sounds from the hydraulic system? Does the engine sound loaded at all when all functions are in the hold position? Definitely agree with the cooler, and pressure testing statements.
Can you explain what exactly you expect an additive to do.?
Somehow possibly help with the cooling of the fluid. Not sure if would help or not. The machine works great when the fluid is cooler, but when it gets hot it gets slow and weak.
Sorry it won't. What you need to get your head around, as mentioned by myself and others, is that the hydraulic fluid is not overheated per the actual system temperatures you measured. I would suggest that you go back and carefully read the posts by @LACHAU which contain many useful suggestions of things that you should check. Please read his comment in Posts #16-18 on Page 1 regarding why the temperatures you measured point to something mechanical in the hydraulic system. Note that the 131 +/- 9 DegF hydraulic oil temperature mentioned in the "Operational Test Preparations" is a MINIMUM requirement, so that the testing is not performed with cold oil. As @HeavyMetalRepair pointed out, hydraulic temperature overheat alarms do not normally actuate until the oil temperature exceeds 220 DegF.
Hydraulic oil in most applications, should be running at 160 degrees.
I don’t think any additive will help you. You’re going to have to get some gauges on it and do some troubleshooting.
Thanks for reminding. I was indeed lacking when talking about the hydraulic oil temperature. The exact details are as attached. However, the hydraulic oil temperature of this machine is still higher than the allowable temperature. I also agree with Mr. Nige's opinion that it is necessary to measure the hydraulic pressures: pilot pressure as well as the pressure of the main pump.
There are many cases where the pilot pump is degraded, causing the same phenomenon. When the hydraulic oil temperature increases, the pilot pressure drops ==> not enough pressure to open the spool of the main control valve.