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hydraulics

Started by slider, December 31, 2009, 04:42:45 PM

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slider

some advice please,on my boom truck with graffel ,after it gets hot it loses lifting power,the hyd oil gets milky,I have changed oil ,40 gals, 3 times replaced the hyd pump,pumped the contamated oil from the resorvior , can,t remember but I think I changed the canister filter,could be wrong . It is a usa crane 4500 lifting capacity. when I get on the big stuff this happens.any fresh ideas would help thanks,al
al glenn

bill m

Is the oil milky looking when it is cold? If not then the problem could be the pump is getting air somehow.
NH tc55da Metavic 4x4 trailer Stihl and Husky saws

Gary_C

Ya, it sounds like it is sucking air in the pump inlet. Also could be the suction filter is plugged.
Never take life seriously. Nobody gets out alive anyway.

coldnorth

After it cools down and settles, does it still look milky?  I would be concerned that it might be getting moisture somehow.  Also, like others said, make sure suction side of pump has tight fittings and filter is good.
If you want something done correctly, you have to do it yourself.

LorenB

I never figured out for sure how I got water into my sawmill's hydraulic system, but my best guess is that I sprayed it past the breather when I pressure-washed the sawmill.  The oil looked milky, but never cleared up until I changed it. 

Does your oil become clear again after the system sits for a while?  If so, it may be air in the system that bubbles out after a long rest.  I thought that the water in my system would settle out after a long rest, but it didn't. 

As the others have mentioned, check the lines and connections between the reservoir and the hydraulic pump.  That short(?) run is the only part of the system that is pulling a vacuum and is able to draw air into the system.  I would start with all the connections. 

Good luck.

– Loren
Loren
Baker 3667D portable sawmill, Cook's edger, Logrite arches & peaveys.  Husky 272XP chainsaw & two Echos.

Frickman

Sounds like you might have two different things wrong. Like the others have said you may have an air leak on the suction side of the pump or a leak in the pump itself. You also may not be gettin enough fluid to the pump. If there is a constriction in the suction line, too small of a suction line, clogged screen, etc., you may not be getting all the fluid your pump requires. The result would be aeration which is hard on your pump. Aeration can easily destroy a pump.

I have had hydraulic hoses collapse internally while looking fine on the outside. Sometimes they only collapse when you're running the machine so it's real hard to diagnose. When all else fails I start replacing hoses. It's messy, time consuming, and very expensive, but sometimes it is what you have to do.

It suprises me how little water you need in a hydraulic system to make it milky white. I don't think that is your problem though.
If you're not broke down once in a while, you're not working hard enough

I'm not a hillbilly. I'm an "Appalachian American"

Retired  Conventional hand-felling logging operation with cable skidder and forwarder, Frick 01 handset sawmill

Pretend farmer when I have the time

slider

thanks for the response.it will be a few days before I can start back on the problem but I will keep you up dated.The oil cleared up some after it sets a while. At first I thought moisture,now after the third oil change Im thinking air or restriction.The pump is new I,ll recheck the fittings first,the filter is new,don't know about a strainer in the tank but I will replace the suction line and check it first.This has been an on going problem that I've been dealing with.I'm almost sure water is not the culprit .thanks once again for the advice.   al
al glenn

Ironwood

Keep us posted, curious. Ironwood
There is no scarcity of opportunity to make a living at what you love to do, there is only scarcity of resolve to make it happen.- Wayne Dyer

shinnlinger

I might add that whenever you can replace a hose with a pipe, you run cooler and probably save yourself some money.
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

sjfarkas

I don't think the milky oil is a problem.  It could be a week spring on a relief valve.  I have an excavator that lost track power when hot.  It was the swivel.  things expand when warm and seals don't always expand at the same rate causing bypass.  you can use a pressure gauge and start at the furthest part out from the control valve. replace the motor with the gauge and deadhead the system and you'll probably see a drop in pressure.  It helps to know the factory specs.  then drop back to the next component and do the same thing.  if it is a relief or swivel once you isolate out that component you should see the pressure hold.  You should do that test on each component before replacing parts.  Only having problems when hot seems to remind me of the problems we had with the excavator.  I was told that cranes also have some kind of valves that needs pressure to activate for safety reasons. 
Always try it twice, the first time could've been a fluke.

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