View Full Version : The Dump Truck Shakes

11-19-2007, 07:06 PM
I have the hydraulic cylinder rebuilt for my dump truck and I did the install and removal, the shop told me just reconnect the hoses and run the bed up and down about 10 times and you should get rid of all the air in the lines. Well I think all the "air" is out for it goes up and down no problem except when going up it shakes, kinda bad to. I when back the shop that rebuilt the cylinder and he told me there's still air in the lines and to keep running the bed up and down.

Well itís been up and down about 100 f@#ing times and its still doing the same thing, what else should I do. The bed is power up power down.

11-19-2007, 07:29 PM
It sounds like there's quite a bit more air than the little bit of air the shop thinks is in there. You have to bleed the lines somewhat in order to get most of the air out. i'm no expert in hydraulics but it just sounds like you have too much air in the system.

11-19-2007, 07:52 PM
I'm new, I know, but I'm a hydraulic mechanic. You need two people. One to actuate the lever and one to crack the line going to the cylinder. Be very careful, hydraulics have very high pressure. There are two basic types of cylinders, one only applies pressure in one direction, while the other will provide force in both. Crack the bottom line on the ram furthest away from the resevoir (if more than two rams), actuate the lever and bleed the air. Close the line as soon as fluid flows out while the ram is still extending (not contracting). Repeat for the other ram (if more than one). Check fluid level and check for the shakes.

I'll introduce myself in another thread. Trust me, I'm from the Government, I'm here to help..... :)

11-19-2007, 10:25 PM
They never said anything about opening the lines and actuating the cylinder, I can not loosen the lower line on the cylinder (frozen on to cylinder) for when I had the cylinder at the shop I brought the line with the cylinder. If I attempt to loosen the lines with the cylinder fully extended it going to have catastrophic ending to me, the cylinder in reinstalled on the truck.

Any other ideas?

11-19-2007, 11:16 PM
If I gave you the impression to crack the line with it fully extended I'm sorry, that's not what I meant. If the line at the cylinder is braised to the cylinder you have to crack the line at the flow divider (assuming there is one in that system). Without seeing it first hand it's rather difficult to tell. Exercising it up and down should eventually do the trick but I know it's nerve racking. You could potentially take the line off the other end and fill the hose with hydraulic fluid but that's very messy and difficult to keep the fluid from spilling out while hooking the hose back up. Try cracking the line at a fitting as close to the cylinder as possible. Don't take it all the way off, just a crack, try to lift the bed and hopefully a good amount of the air will be forced out. Then tighten. :dizzy:

11-19-2007, 11:36 PM
I just thought about another possibility. If at some point you feel comfortable that you've gotten all of the air out, the retaining sleeve could very well be too tight. I've seen it happen on forklifts where after the cylinder is rebuilt the retaining sleeve is over tightened and causes the same symptom......just a thought. In the unlikely event you don't know what I mean, where the actuator comes out of the ram there is a retaining sleeve that is threaded into the cylinder. It's either a smooth ring with a allen screw or it's a retaining ring that requires a spanner wrench.

Gravel Rat
11-20-2007, 03:52 AM
Are you sure your hydraulic pump is good ?

If your airating the oil (frothing) you will never get rid of the problem.

11-20-2007, 08:35 AM
That's a good suggestion but I'm not sure that's the problem. If the pump was bad (bad pump, bad pump :nono:) (joking) and it was frothing (mixing air with the fluid) then there would be either a loose line or a crack in the pump. You probably wouldn't notice any fluid leak while it's in operation but there would probably be fluid leaking while it's static. I think you should open the system as close to the ram as possible and fill the line with hydraulic fluid using a paper cup or something that will make it easy to pour a small amount of fluid. That of course is with the bed all the way down. After re-reading one of your earlier posts about this you indicate that you have a dual action ram. Once you fill the bottom line with fluid you should crack the top line then slowly try to lift the bed and bleed the air out of the top of the cylinder. You can do this at no risk to yourself or your equipment so long as you're aware of your fluid level in the tank and you're careful with potential spray from the cracked line.........

11-20-2007, 11:21 AM
CPO,, you know your sh@#,,
I whet out this morning to see if the ram was still shaking and well it finally stopped! I ran the system twice with no hesitation.
If I had been told what CPO told all of us on here I would not have had to run the ram up and down so many damn times. It makes sense, back when I work as a tech if a power steering presser line wasn't bleeding out I would loosen it or try back filling it. I just didn't think that would apply here.


P, S, Gravel Rat, I had the pump checked out before they condemned the ram, Thatís what I originally thought was wrong with the system but they told my just the ram was bad.

11-20-2007, 11:46 AM
Glad to hear it worked out. Now get out there and dump some stuff!!!! :)