Guidance to avoid damaging hydraulics in very cold weather...

[tjacobson01]

I have a nice older Bobcat 742B with low hours, and live in a northern area where we sometimes get temps down to -20F or even -30F in the morning during Jan and Feb. Wondering if there is guidance/wisdom regarding starting up and operating at very cold temps? I would assume one plugs in the block heater the night before, and starts up and lets the engine warm up for perhaps 10 mins, in hopes that some of the heat will migrate to the Vickers drive pumps... and that the movement of hydraulic fluid at those temps will also slowly warm things up.. ? I would assume moving the machine without warmup at such a cold temp would be a very bad idea, as the hydraulic fluid is probably like goo at those temps and really needs to warm up a bit in order to lubricate and even flow....? Or, should one just not use the machine when temps are below say -10F or so..? The cost to damaging the pump rotating groups etc. might make it better to just stay inside by the fire and wait.. but then sometimes one needs to get out of the driveway for some more hot chocolate... and needs to plow the snow.... I suppose one could wrap the Vickers pump(s) in heater tape with blankets on top for some hours? Thanks for any advice, or experience from those who have operated their machines at low temps. Thomas.

 

[jerry]

I have seen it advocated and done it myself when starting in sub zero temp that you hold the tilt cyl bottomed out in the up position to force the oil over the relief valve to warm it. Oil that is restricted will heat quickly. You could always run synthetic hyd oil of course. I do use rotella t6 in the engine and always have. Just take it slow at first and don't overload anything. I have seen 2 and 1/2 inch cyl rods snapped off by loggers by overstressing when it is bitter cold/ .

 

[reaperman]

I've always been curious how warm hydro fluid gets in cold weather, now I have a better idea. We have a new bobcat at work that has a fancy computer that displays the actual temp of hydro oil. I was surprised to see the oil rarely gets over 100 degrees is cold weather operation, mostly its somewhere in the 90's. I suspected it would have been warmer. Plus that machine is stored in a headed shop. Which tells me machines like my own that aren't in a heated shop probably struggle to warm up hydraulics.

 

[Bobcatdan]

I've always been curious how warm hydro fluid gets in cold weather, now I have a better idea. We have a new bobcat at work that has a fancy computer that displays the actual temp of hydro oil. I was surprised to see the oil rarely gets over 100 degrees is cold weather operation, mostly its somewhere in the 90's. I suspected it would have been warmer. Plus that machine is stored in a headed shop. Which tells me machines like my own that aren't in a heated shop probably struggle to warm up hydraulics.

Generally speaking, let the machine idle for 10 minutes at start up. Then at 1/4 to 1/2 throttle, work the machine lightly until the hydraulics feel normal. I don't know if I like deadheading the system to warm it up. It's putting max load on the system as well as a cold engine.

 

[Bobcatdan]

Generally speaking, let the machine idle for 10 minutes at start up. Then at 1/4 to 1/2 throttle, work the machine lightly until the hydraulics feel normal. I don't know if I like deadheading the system to warm it up. It's putting max load on the system as well as a cold engine.

Also to add, Bobcat hydraulic fluid actually flows pretty good when cold. As someone who has had to change blown hydraulic hoses in -20° and fill the system with stone cold hydraulic fluid, it wasn't much thicker then normal. Compared to cold engine oil, I could see extreme cold being one thing bad with running 10w30. If extreme cold starts are one of your concern, look for fluid that is good in cold.

 

[mmsllc]

Also to add, Bobcat hydraulic fluid actually flows pretty good when cold. As someone who has had to change blown hydraulic hoses in -20° and fill the system with stone cold hydraulic fluid, it wasn't much thicker then normal. Compared to cold engine oil, I could see extreme cold being one thing bad with running 10w30. If extreme cold starts are one of your concern, look for fluid that is good in cold.

DON'T LAUGH, but I've seen some boat owners use HEAT LAMPS to help keep their bilges warm & dry. Those guys are just trying to keep the temperature above freezing, but that is still +32 degrees, instead of -30! I wonder if that might be something that might help out a bit. If you put a similar lamp (or even a halogen lamp or a incandescent drop light) under the cab & closed it up tight for the night. Obviously, a engine block heater might help, too, or even thinner engine oil; like 5W30 versus 10W30, would speed up the flow of fluids in that extreme of a climate.

 

[mmsllc]

DON'T LAUGH, but I've seen some boat owners use HEAT LAMPS to help keep their bilges warm & dry. Those guys are just trying to keep the temperature above freezing, but that is still +32 degrees, instead of -30! I wonder if that might be something that might help out a bit. If you put a similar lamp (or even a halogen lamp or a incandescent drop light) under the cab & closed it up tight for the night. Obviously, a engine block heater might help, too, or even thinner engine oil; like 5W30 versus 10W30, would speed up the flow of fluids in that extreme of a climate.

I've also been told that you can thin out the thick / cold hydraulic fluid is by adding a little bit of diesel to the hyd. system. It is a way to thin out the system in order to preserve the pumps from pumping something too thick that it can not be pumped. after the severe cold weather, the system can be drained & filled with fresh fluid. I would not use more than 10% diesel to the system capacity. Another idea might be to use a small heat exchanger / cooler (like what is found on CAT 931 loaders) that could be hooked up to the hydraulic system that would use warm coolant to warm the hydraulic system faster. Then have a ball valve turn water flow off to the cooler during use in warmer weather.