hydraulic oil change on a 312

[JPCobra105]

hi everyone.
im getting ready to do a hydraulic oil change on my 95 cat 312. i have 2 questions. what is the best way to get the fluid out of the system. (hoses and pistons)? im sure that there is several gallons of fluid is a charged system.i dont want to just replace what is in the tank.
and second does anyone know how many gallons of fluid the tank holds. and how many gallons the entire charged system holds? any input on the topic would be greatly appreciated.
thanks for any help.

 

[R Glover]

I have a 1993 CAT312. Mine holds 25.7 gallons for the total system. I will check my book tonight when I get home and see what the tank holds.

Rube

 

[DarrylMueller]

I like the idea of changing as much oil as you can. To get the most oil out open the bucket extend the stick lower the boom. Drain tank and drain the hoses on the cylinders. Be careful that the hydraulic pump has oil on start up. Operate the at slow speed until all the air is out or you could burn a seal. I did one better and bought a filter cart to clean all the oil in the machine. For $1500 it is real cheep and I know that the oil is clean 3 micron clean. It takes 45 minutes to do a 45 gal tank and machine, and you operate the machine to circulate the oil, I still change the oil but not as soon. I feel that even with 1 machine it's cheep insurance. Most dealers have a filter cart it's not 100% but real close.

 

[JPCobra105]

thanks for the imput. i figured that would be the easiest way to get the most out on a change

 

[special tool]

Like Darryl said, be carefull about runnng the pump dry...
Might be best to not obsess over getting ALL the oil and just close all cylnders and dry out the tank.

 

[Cmark]

This kind of links into the thread about oil sampling. Personally, I am a big believer in it.

Granted, a 312 isn't the mother of all HEX's but the same principles apply to this as to a mining shovel. Given time to establish a trend, you might figure out that by spending $200 a year on oil samples, you can make your hydraulic oil go to 4000hrs instead of 2000, or even more. On the other hand you might find it is deteriorating quicker than you expected and you can prevent an expensive failure.

Just my thoughts on the subject....

 

[DarrylMueller]

Not to step on any toes oils samples, they have there place. Remember you filter is only 10 micron. A filter buggy is 3 micron. You can go past the change time in hrs. but there is a point the the (package of supplments in the oil will be depleated the oil sample lab may not tell that they look for contaminats. Be careful. Oil is cheep compaired to a failure. I use 1000 hrs. for change and may go 1500 if the oil looks clean.

 

[Cmark]

Hey Darryl

With respect, I think you're oversimplifying the filter micron issue there. If you put a batch of oil through a 3 micron kidney loop, it doesn't automatically mean that the oil contains no particles >3 micron. No oil in any machine does. Granted, it will be cleaner than before you started, but the filter's beta rating also plays a huge part.

Don't get me wrong, I'm a big fan of kidney looping but without oil analysis you just don't know if your kidney looping has been successful or even if it was necessary in the first place.

Checking additive depletion is exactly what oil sampling labs do. Give them a sample of unused oil to compare with the used oil and ask them.

I know on a 312 with only 100-something liters of oil in the tank, you can argue that the cost of the analysis isn't justified, but I would rather know the condition of my machine. You can't tell if an oil is clean by looking. Without oil sampling, you're just guessing.

I'm not trying to convert you or anything Darryl. If it works for you, then great. Just giving an alternative opinion, you understand.

 

[mowzall]

Why are you changing the hydraulic fluid? It would be interesting to know if your reasons before suggesting how to change it.

 

[JPCobra105]

the machine has about 4500 hours on it. i have put over 1000hrs on it myself and i dont know when the fluid was done last. ive noticed my hydraulics getting a little weaker and just operating different than when i first got the machine. the fluid gets foamy after a good days use and it is much darker than when i first got the machine, 1000hrs ago or so. i figure its about time for a change. its my slow time of the year. time to do service

 

[DarrylMueller]

You can tell with a white paper towel if the oil is dirty. I guess sampling is a lot better than when I used it last. I once bought a machine that had oil sampling as part of the warrenty, I just had false alarm after false alarm. I just do regular service and like you say it's worked out fine. Sorry not dis credit sampling. Anyhow 1000 hrs you need to change the oil in the whole rig, and set up a log then you know what you got. Do change the hydraulic , swing machinery, finals, engine and filters. I don't like that you say it's a little weaker. When did you last change the hydraulic filter? Take a drop of hot hydraulic oil on a white paper towel and look at the edges if it has a black outline, not yellow or brown or tan it's dirty and shoul;d be changed. Thing is you don't know if the oil was changed at 2500 or 3500 and now 4500. Now is the time.