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View Full Version : Hydraulic dump trailer hydraulic question/help needed.



Mr Fixit
10-04-2014, 09:34 PM
Hello Group,
I am using my family dual axle single cilinder hydraulic dump trailer to regravel the driveway and parking pads. I think I have maxed out the hydraulic sytem with a heavy load. The pump works fine, the bed lifts and lowers fine, but there is some hydraulic fluid that has deposited inside the pump box that was not there when first used. The resevoir is full in the down position or just below the fill cap. What it looks like is in lifting or lowering with a 1/2 full or more load it may have vented out the fill cap.
So after that long discription my question is, how do you tell when the system is full, in the full down or full up position?
As I say it all still works, just concerned that something isn't right and don't want to break it. Jobs not quite done yet, still 3-4yrds left to dumpin the trailer.

Tx for answering, hope someone can help a OK home mechanic figure this out.

Mr fixit for the family
Chris :)

1-800miner
10-04-2014, 10:04 PM
Check the oil with the rams retracted.

George Seal
10-04-2014, 11:20 PM
Oil probably heated up due to heavy use expanded more than tank can hold

Black Forest
10-05-2014, 01:35 AM
The filler cap should act as a vent also. Maybe you lowered the dump bed quite fast and the oil from the cylinder returned to the tank under quite a lot of pressure and splashed out the vent. So as long as there is enough oil for the cylinder to extend fully and not empty the reservoir then you are OK I would say.

Mr Fixit
10-05-2014, 12:13 PM
Thank You Guys,
Exactly what I needed. The fast drop theroy makes very good sense as that did happen. I will add what was lost in the down retracted ram position and think I will be good as new. ;)

TX Mr fixit for the family
Chris :)

Mr Fixit
10-07-2014, 11:33 AM
Hello Group,
Got some hydraulic fluid at work for mowers, AW-46 b,y NAPA Auto says its for high speed pumps and such. Can l use it for a top off in the trailer hydraulic ram pump?
If not what do l need for a single cylinder ram on the trailer?

Tx Mr fixit for the family
Chris :)

Black Forest
10-07-2014, 01:06 PM
how big is the reservoir? Just change it out for the oil that you brought from work. It is probably the same grade but it is not a good idea to mix oils of different grades in anything.

Willy
10-07-2014, 02:02 PM
Check the oil with the rams retracted.


Oil probably heated up due to heavy use expanded more than tank can hold

This would be my thought as well. The reservoir should be checked with the dump bed in the down position and the oil level should be low enough to allow for expansion when it comes up to operating temperature. It's always amazing how much fluids will expand when heated.
The level it as at now, after it puked out the excess oil, is probably the level that it should operate at.

Nothing at all wrong with the oil you picked up at NAPA but as BF mentioned try to stay with the same type and weight oil you have in there now or at least make it all the same. When changing oil on a hydraulic system I try to change all of the system rather than just the reservoir. Sometimes the rest of the system holds almost as much oil as the reservoir.

Mr Fixit
10-07-2014, 04:27 PM
Thanks for the responses. The reservoir is about 1gallon. How would you empty the lines and ram if any is in them to not mix oils?

Tx Mr fixit for the family
Chris :)

Willy
10-08-2014, 12:54 AM
It's not imperative or critical that you get out every last drop. Just retract the cylinder, drain the hoses and the reservoir.
That should take care of all but a few drops on a small system like the one you're dealing with. You don't have to get anal with it, as long as the major portion of the fluid is changed you'll be fine.

Good luck with the driveway!

Lu47Dan
10-08-2014, 10:46 AM
Before you change the oil out, find out who manufactured the hydraulic unit. I had one here to diagnose that would not lift the bed when cold,40F, but worked fine when it was above that. I found who built the pump and they said it should run 5w motor oil not AW46 hydraulic oil. As the owner was using it to haul firewood in the winter lifting the bed when cold was the priority to him.
I drained the system and filled it with Royal Purple 5w - 20w synthetic motor oil and it has been working fine ever since.
Most power units have a range of acceptable oils that can be used in them. But that one was designed to use 5w motor oil.
Dan.