2000 RD688

[Ricky Beals]

Got my truck yesterday and going change the Trunnion bushings out at the end of month. In process of moving household down to my birthplace. At this time I’m not getting to work on truck but building cabinets for shop building. 

The parking brake light on left side of truck stays on. What parking brake light is this?  It’s not the one that’s goes off when air pressure hits 70. Anybody got any idea on what to check. I took both wires off the switch on outside of firewall below fuse box, took wires off switch below ignition (key switch) light stayed on. Just taking one problem at a time. 

Edited March 4, 2022 by Ricky Beals
Added

[Ricky Beals]

Ok when that light comes on I should definitely figure out why it’s on. 

[Ricky Beals]

Ok thanks Mark, no coolant in reservoir or near cap on radiator. I’m going put distilled water in and find the leak before adding antifreeze.

[Mark T]

Don't put just water in it. Even if it costs a couple dollars, you're always better off adding the coolant that belongs in it.  Those don't take a lot to make the light come on. You may fill it and be good for a while. 

[Mark T]

I can't really see it in the picture, but it almost looks like someone put a parking brake lens (the red part) in that spot. The shutdown light has a little different graphic with an X and an arrow with a circle.... but I think it's just your water level is low.

[Ricky Beals]

I have no idea what coolant it has in it. Or what it should have in it. I’m going get ALL MAKES ALL MODELS and put it in there for now.

[Ricky Beals]

Good call Mark that turned the light off. I’m guessing when this light comes on you need to respect it and find the problem.

second problem!! Did this gauge come with truck or was it an add on. It’s a psi gauge but not working or i have yet seen gauge move?

its not letting me add the photo and same phone I took the first photo with. I may have to start another thread

[Ricky Beals]

Posted a new photo in the original post with new question. Trying to see if the single psi gauge came standard on this truck or if it was an add on. It hasn’t moved showing any air so not sure what it’s for.

 

this may be  a boost gauge. I read where it doesn’t show boost unless there is a load on truck so may be why I have seen it move. 

 

 

Edited March 4, 2022 by Ricky Beals

[MACKS]

Looks like the boost gauge,should get up to 20 -25 lbs or so under a load..

[JoeH]

+1 on boost gauge. You won't see much activity on that with an empty truck. Throw some weight on there and it should get up to roughly 25 on a hard pull.

[MACKS]

If there’s no fluid leaking out of the cylinder it’s good,no repacking needed,body stays up till u move the lever that opens the valve and lets the fluid drain out and back into the tank..

[doubleclutchinweasel]

The valve probably has a "blocked" position when the lever is in the "hold" position.  Generally, a hydraulic valve has 3 positions.  Applying that common valve thinking to a dump truck, one position would port pressure to the cylinder, the middle position would hold what ya' got, and the third position would dump the fluid in the cylinder back to the tank.

There are variations on this, of course.  Some have an "open" center position instead of a blocked center.  But, anyway, most valves/manifolds have an "A", "B", "Pressure", and "Tank" port.  Shifting the valve connects these in various combinations to accomplish the desired effect.

But, that's just generic hydraulic valve stuff.  If the truck setup is different, I'm sure someone on here will chime in and correct it for me!  If they do, use their info, not mine!

[Onyx610]

There’s a line that goes in the top of the cylinder that pushes the cylinders back down. The same way it goes up. A cylinder will not leak down because of bad seals. 

[doubleclutchinweasel]

6 minutes ago, Onyx610 said:

There’s a line that goes in the top of the cylinder that pushes the cylinders back down. The same way it goes up. A cylinder will not leak down because of bad seals. 

Based on what Onyx said, I would assume that one end of the valve ports pressure to "A" and dumps "B" to tank, and the other end ports pressure to "B" and dumps "A" to tank.  The middle position would be "blocked", so it would stay in place wherever you left it.

The only way it could leak down would be fluid leaking out of the side that is pressurized while lifting the bed...like past the piston.  A leaky rod seal on the other end, as he said, would not allow fluid to escape.  So, it would not cause leak-down.

[terry]

2 hours ago, Onyx610 said:

There’s a line that goes in the top of the cylinder that pushes the cylinders back down. The same way it goes up. A cylinder will not leak down because of bad seals. 

Every dump box i have ever seen is pressure up and gravity down, no two way cylinders on dump truck boxes i have seen, two way cylinder on side dumps and ram eject trailers, and maybe some other applications.   terry

[doubleclutchinweasel]

1 minute ago, terry said:

Every dump box i have ever seen is pressure up and gravity down, no two way cylinders on dump truck boxes i have seen, two way cylinder on side dumps and ram eject trailers, and maybe some other applications.   terry

That's what I was used to seeing, but was not going to argue with someone who knew more about it than I did!  The valve would work essentially the same, though.Would dump "A" to tank but have no pressure going to "B" when lowering.  Thanks, T.

[Onyx610]

13 minutes ago, doubleclutchinweasel said:

That's what I was used to seeing, but was not going to argue with someone who knew more about it than I did!  The valve would work essentially the same, though.Would dump "A" to tank but have no pressure going to "B" when lowering.  Thanks, T.

I stand corrected, I’m not that knowledgeable with hydraulics. 

[doubleclutchinweasel]

8 minutes ago, Onyx610 said:

I stand corrected, I’m not that knowledgeable with hydraulics. 

I'm not all that up on hydraulics used in trucks.  I'm just basing that on what I see in commercial hydraulics...primarily in industrial applications.  That's what I'm more familiar with.  That's why I said I was not about to argue with you guys that know more about it than I do!!!

[terry]

Depends if your pump is separate from control valve or built together, if hoist is staying up and not leaking at the packing on each stage your good to go!

[Onyx610]

19 minutes ago, doubleclutchinweasel said:

I'm not all that up on hydraulics used in trucks.  I'm just basing that on what I see in commercial hydraulics...primarily in industrial applications.  That's what I'm more familiar with.  That's why I said I was not about to argue with you guys that know more about it than I do!!!

Hahaha, after reading what you and terry were saying it makes sense and feel that is pry the correct answer. It doesn’t need to “power” down only up. As for the seals I do know that you can take the seals out of a cylinder and it still won’t drift. Biggest miss conception when a cylinder drifts is it needs new seals. Usually it’s a valve or whatever it may be leaking by.  

Edited March 7, 2022 by Onyx610

[Onyx610]

Here’s a good video for anyone interested. 
 

 

[Mark T]

That's the engine shut down light.  If it's got oil pressure and not overheating, chech the water level

[Ricky Beals]

I got a question about the dump bed part. I was told at dealership the main cylinder needed repacked. We are expecting a lot of rain so I raised the bed. The bed is still up and hadn’t leaked down at all which I felt like it would. Which brings me to another question on how does the bed raise and lower. I understand when I engage the pto it starts the pump which raises the bed thru hydraulic fluid. Does the pump also drain the fluid out of cylinder to lower it? I guess I don’t know what is keeping it up with truck shut off and if the cylinder needs repacked wouldn’t the bed leak down.