Guys, hope someone can educate me on this one. The issue is with a CAT 941B. I've been using it on the weekends to clear some land and about two weeks ago I noticed that the hydraulic tank on the side of the seat was very hot to the touch. I checked the sight glass and could not see the fluid level, which had normally been about half way up the sight glass. Thinking maybe I was low on fluid I decided to let it cool and add fluid, that was two weeks ago. Yesterday I planned on adding fluid since it had been sitting and was cool. Still could not see the fluid level in the sight glass. Cracked the cap and first a lot of air hissed out then the fluid came bubbling out, with some force behind it. After pumping a substantial amount of fluid down the side of the machine it settled and showed about 1/3 on the sight glass. Used the machine for a few hours and same thing occurred, tank got very hot and could not see any fluid in the sight glass, i.e. could not make out the level. Any ideas?
The vent in your cap must be plugged .
The tank's pressurized on that machine to assist with suction into the implement pump. The cap needs to seal tight.
OK Thanks, I'll check that
Thanks. I'll double check the cap, but is it normal for the tank/fluid to get hot?
Do you have access to an infra-red temp gun that you can use to determine that exact temperature ..? What is "hot" to one person might be totally normal in terms of machine operation. Generally a hydraulic system will run at somewhere around 175-195 DegF, that's pretty hot to put your hand on the tank.
Thanks Nige. I'll ask around for a temp gun and see if I can get an exact temperature. I didn't realize the system runs at that temperature.
The working temp still doesn't explain why your oil disappears from the sight glass when the machine gets up to temperature. The pressure generated in the tank by the temperature of the oil when the machine gets hot should not change the level of the oil in the sight glass by any perceptible amount.
Hmmm...yes, in the past I would check the glass after using the machine and there no difference from when I started. Could a plugged vent in the cap, as suggested, be the culprit?
It sounds like he's making fluid to me. Empty or over full site glass looks the same and he puked fluid.
There is no vent in the cap of that tank, it is designed to have an air-tight seal once it's tightened down. Otherwise pressure could not be generated in the tank when the oil warms up.
It did indeed look the same, I couldn't tell if it was below the sight glass or above it. Apparently it was above and once it puked the fluid I was able to see the level in the sight glass. How would it "make fluid"
Hot to the touch isn't too hot for a hydraulic tank and the reason fluid comes out of the tank is the stand pipe to prevent over filling. I think everything is okay. Later Bob
I agree with Bob. Here is a quote from the manual, it may help clarify things - "Traxcavator must be on level ground, bucket flat on ground, hydraulic controls in HOLD, engine stopped and oil cold. Maintain the oil level between the ADD and FULL marks of the sight glass." So you should not really open the cap when the oil in the tank is anything other than cold, and even the open is slowly and carefully just in case there is any residual pressure in there. Your oil level may well change when the machine is working and the oil is hot. The possibility exists that your tank maybe slightly over-full.
Thanks Bob.
Thanks for all the info, you've been a big help putting me at ease. Being new to this whole heavy equipment arena I appreciate the sage advice.