'64 C-60 with pto driven hydro pump and twin two stage lift cylinders
I blew a hydro line for the dump bed and opted to redo all the lines together given their age. In the process of removing the lines from the lift cylinders, I noticed some crud in the sump of the cylinders so I went ahead and dropped those as well to drain and clean them out. At that point, I took every last fitting and joint off the hydro system except for the reservoir and under-mounted pump itself, figuring I may as well replace everything since im in this deep.
During standard operation, the bed never stays in the raised position, and slowly drops back down whenever raised, but there are no external leaks in the system anywhere. I figured while everything is apart I might as well attend to this problem. Question is though, is it likely to be the cylinders causing this, or the pump? Additionally, assuming I just go ahead and have the cylinders rebuilt (they likely need it), is it worth rebuilding the pump as well?
Curious on your guys input. I haven't gotten a quote yet on the lift cylinders, but I cant imagine that twin stage cylinders are going to be cheap to rebuild.
The control valve should have a check valve built within, that would be my first thought of not holding pressure, the oil could be bypassing internally within the cylinders but the control check or worn valve spool would be more common.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
HFfarms would it stay up before that line blew?? If it did cylinders would seem to be OK. Most of them have metering on the way down and in a spot where a blown hose wouldn't let it fall,because it will bend your frame when it hits. You should be able to let your loaded bed down regroup and spread some more without any danger to your frame. A new to the fleet truck came in the crew got it load locked and when it fell put two sickening puckers in the frame.
HFfarms would it stay up before that line blew?? If it did cylinders would seem to be OK. Most of them have metering on the way down and in a spot where a blown hose wouldn't let it fall,because it will bend your frame when it hits. You should be able to let your loaded bed down regroup and spread some more without any danger to your frame. A new to the fleet truck came in the crew got it load locked and when it fell put two sickening puckers in the frame.
The bed has always done this since I've had the truck. In full upright position, once the PTO is disengaged, the bed slowly drifts back to the down position. It is slow though, taking 10 minutes or so to fully lower. Disengaging the pump allows the bed to return down at normal speed.
Originally Posted by 78buckshot
The control valve should have a check valve built within, that would be my first thought of not holding pressure, the oil could be bypassing internally within the cylinders but the control check or worn valve spool would be more common.
This was my current thought. Any advice on location of this valve? Is it the piston valve attached to the main engagement lever below? If so, I did discover today that the lever extension was contacting the frame and once removed, allowed the piston to close/seat completely as shown in the photo. Before you could still see 1/4" of the piston sticking out. Maybe that was the root of the problem and its just this simple fix? Also discovered a grease zirk I didn't know existed just below this that was obscured by decades of grime.
Neverminded the seemingly leaky pump. Its just leakdown from the main fittings from detaching the hydro lines. The pump itself has never leaked to my knowledge.
I was under the truck tearing down the diff today and took a look at the pump again. Due to the design, it really isn't possible to drop the pump from the truck without cutting off the welds that hold the reservoir to the frame. Although the pump is bolted to the reservoir supports, the fittings between the reservoir and pump are large and in a spot where no wrench can get to them due to the crossmember that the apparatus is mounted directly behind. Seems like a poor design.
The limited experience I have with hydraulic control valves revolves around a Meyer 2 spool snow plow valve from the late 60's and the 2 spool valve on my 1955 IH tractor. The snow plow valve has/had a check valve that would hold the plow in the up position until the manual valve was positioned to lower it, internally it would release the check to let the blade down. I would expect that your hoist valve would be similar, the check would most likely be internal within the valve body. You may have already found the culprit if the valve was unable to fully extend to "HOLD" position.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
HFFarms Sounds like your main piston cups are worn and leaky tipical day with em. Mine will leak off in a few hours but can let it down loaded regroup and spread or dump some more. Only thing more fun...winch truck you'll really learn with those,big ole Tulsa winch !!
I had everything but the pump dropped and I flushed it all. The steel pipe lines and fittings still looked good so I kept them while replacing the hydraulic hoses. I called around to see about getting the cylinders repacked and its currently an 8-12 week lead time minimum which doesn't really work here on my end at this point in time. Thus I flushed and scrubbed them thoroughly before remounting them. I modified the lever on the pump control valve to get better throw and not contact the frame or undermounted toolbox.
After buttoning up the diff I got her pulled from the barn to purge the air from the hydro system and put the bed up. The photos were taken 20 minutes after raising the bed and it still hadn't drifted down an inch. Ill see how it goes with a full load of logs sometime here in the next few weeks.
Sounds like you got a nice fix going on there. If you can, would very much like to see some working pics when hauling logs (or anything else your transporting).
It's a special spot just for showing off your stuff!
Thanks for sharing your progress and pictures.
Dan
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
After talking with Peggy in getting things together for the 'Working Bolts' calendar I realized that I need to get better at snapping photos when she is loaded down and doing work, so I will be sure to do so and start sharing. This old Bolt really does see more miles than my other two farm trucks typically in a year, earning her keep as intended when rolled off the factory floor.
HFfarms Sounds like you've got it sewed up most all hydraulics leak off and unless it hurts your operation I wouldn't worry about it now. Not a cheap fix and they may find some other expensive problem.
Yeah there were some "words" used in the install process. The new lines are significantly thicker than the old which made it tough to fit into that original setup, but I got it. I had flashbacks to replumbing excavators and skid steers while doing it.
