hydraulic fluid change questions

   / hydraulic fluid change questions #1  

rownow

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Jan 5, 2009
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My Toolcat is a model C. 2006 190 hours.
1. Hydraulic fluid change interval. The maintenance manual says first fluid change is at 500 hours ***OR EVERY 12 MONTHS***. So even though I have only 190 hours, I have maybe 36 months on the original fluid. So I guess I should change the fluid now, and every 12 months regardless of hours? Does that sound right?

2.Having trouble removing hydraulic fluid drain plug. The plug screws into a brass fitting that is connected to four rubber hoses. The fitting is suspended from the hoses. It is not firmly attached to anything except the hoses. The plug is tight. When I put some torque on the plug, it starts to strain the hoses. I don't want to damage the hoses or pull them loose from the fitting. I tried putting a pair of locking-pliers (vicegrips) on the fitting but is still very hard to avoid twisting the fitting away from the hoses. This seems like a dumb design, I suspect the Bobcat Mechs must have a trick. Would an impact wrench loosen the plug without twisting the fitting? Maybe I should just suck the fluid out of the reservoir and forget about the stuck plug?? Your suggestions?

Thanks.
 
   / hydraulic fluid change questions #2  
My Toolcat is a model C. 2006 190 hours.
1. Hydraulic fluid change interval. The maintenance manual says first fluid change is at 500 hours ***OR EVERY 12 MONTHS***. So even though I have only 190 hours, I have maybe 36 months on the original fluid. So I guess I should change the fluid now, and every 12 months regardless of hours? Does that sound right?

2.Having trouble removing hydraulic fluid drain plug. The plug screws into a brass fitting that is connected to four rubber hoses. The fitting is suspended from the hoses. It is not firmly attached to anything except the hoses. The plug is tight. When I put some torque on the plug, it starts to strain the hoses. I don't want to damage the hoses or pull them loose from the fitting. I tried putting a pair of locking-pliers (vicegrips) on the fitting but is still very hard to avoid twisting the fitting away from the hoses. This seems like a dumb design, I suspect the Bobcat Mechs must have a trick. Would an impact wrench loosen the plug without twisting the fitting? Maybe I should just suck the fluid out of the reservoir and forget about the stuck plug?? Your suggestions?

Thanks.

Right or wrong, I tend to go by hours rather than yearly. However, I think 3 years is on the long side. 2 years is probably my max. Our ag tractors have recommended intervals of 1000 hours for hydraulic oil. I don't have my D series manual in front of me, but I think it said change hydraulic filter at 50 hours then oil and filter at 100 hours.

Your idea for using a impact wrench seems good to me. Support the fitting and hoses with one hand and run the impact with the other hand. I would just give short burst and see what happens. Factorys always seem to put these fittings on too tight IMHO.

My D series has no drain plug on the hydraulic oil reservoir. The manual says siphon it out the top. Personally, I think that is a rediculous way to change oil. I siphoned it the first time. Not again. It took 45 minutes to drain it and I doubt if I got it all. (Although there is a considerable amount of fluid remaining in the system - pumps, hoses, drive motors, cylinders ect.) Next time I will buy a cheap Harbor Freight pump (run by drill or battery) and suck it out that way.

My D series has two filters to change. 1 is the main filter and the other is for the hydraulic fan.
 
   / hydraulic fluid change questions
  • Thread Starter
#3  
Thanks Radman. Nice to get some encouragement.

So the D redesign eliminated the problem fitting, and you use a siphon?
My guess is that the Bobcat mechanics use the siphon on the Model C as well. The "floating fitting" is a self-destructive design... asking for trouble.

Bobcat mechanics probably use a tool similar to this:
JABSCO 3 1/2" Gallon Flat Tank Engine Oil Change System - Plumbing, Accessories & Equipment, Watercraft & Marine Equipment - nuLime.com

I'm leaning towards a siphon. What diameter hose did you use? Obviously I need a very clean hose.

I'm not worried about getting ALL the oil. There is 10 gallons in the whole system and only 3.7 gallons in the reservoir. As I understand it, the approach is to dilute the old fluid with new fluid, and change the fluid often enough that the old fluid never gets funky.

Once I get the fluid out I will have it analyzed at a lab to see where I stand. To explain why I've neglected the fluid change this long... I put 70 hours on this machine since I bought it 8 months ago.
 
   / hydraulic fluid change questions #4  
I used a clear plastic hose with an inside diameter of 7/16 - 1/2. The oil was cool. Would work better if the oil was warm, but I didn't want to mess with hot filters. Just seemed to take long to siphon out. It was about all I do do to create enough suction to get the oil up the tube far to get the siphon to work.

I wouldn't worry too much about the length of time the old oil was in the system. Just refil and enjoy.
 
   / hydraulic fluid change questions
  • Thread Starter
#5  
The siphon approach worked pretty well for me. Though I only removed 2 gallons, which is only 20% of the total fluid in the system. I was able to add more than 2 gallons, so I guess I drained a lot with the filter change.

In the interest of helping (and entertaining) other shade tree mechanics.... here's how I did it. Overall goal is to get the fluid out in a reasonable time with no contamination.

I used about 5 feet of 1/2 PEX tubing, the kind that is used for radiant floor heating. You want clean/new tubing that will not collapse when you put a vacume (suction) on it.

The outlet of the of the tube needs to be lower than the bottom of the fluid resevoir which is about 12" off the ground. I used an oil drain pan which allowed me to get the tube about 5" off the ground. This gave me 7" change in elevation from tube inlet to tube outlet. The greater the change the greater the siphon and the faster the drainage.

Viscosity varies with temperature. My fluid was at about 70d F. Warmer is better.

Be sure to remove the strainer before inserting the tube in the tank.

Starting the siphon is the tricky bit. Do NOT suck on the tube with your mouth. You do not want hydraulic fluid in your mouth.

I put a small funnel in the outlet end of the tube. Hold the end of the tube as low as possible. Gradually bring the end of a wet shop vac closer and closer to the funnel and be careful (lucky) not to get any fluid in the shop vac. Allow plenty of air leakage. Gradually reduce the leakage to gradually increase the vacume. Pull the vac hose away when you see the fluid coming down the tube. Use the minimum amount of suction to keep you shop vac clean.

This might have been a stupid thing to do... as I was wondering whether the oil vapors might ignite/explode from a motor spark in the shop vac?? I put the vac outside as a precaution and there was no explosion ;)

The fluid drained in 5-10 minutes. If you try this at home... you might weight the possibility of an exploding shop vac first ;)

I replaced the breather cap. I'm thinking of drilling a 5/8" hole in the old breather cap for the siphon hose and also a smaller hole where I can jamb the blower attachment from my air compressor. Plan is to pressurize the reservoir tank and force the fluid up the hose to start the siphon. No explosion risk that way ;) I'm only half-joking about the explosion risk.
 
   / hydraulic fluid change questions #6  
Using a shop vac is cheating.;) I used my lungs and a clear hose so I could see the oil. I changed mine on a 40-50F day and it drained slow. My hose may have also smaller diameter. I probably removed about the same amount of oil as you did.
 
   / hydraulic fluid change questions #7  
This is a question to Radman. Do you use the hydraulic oil from the dealership or do you use an equally good oil from a bulk distributor. I'm thinking of using Hyrdrol 50 from Imperial Oil (Ess0) which is a good winter weight for us here in Alberta. There's also a Hydrol 56 that is part synthetic but likely more expensive. Its probably still cheaper than what we have to buy from the dealer.
Hope you get this and can answer right away.
 
 
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