Case 350 - hydraulics drop from full height in less than 1 minute

[Godhungry777]

Hi guys, I'm a newbie to forums.

I've got a Case 350b with 4in1. My hydraulics are not holding at all. Most noticeable is the drop on the front arms. It will go from full height to ground in less than a minute. All systems have similar symptoms (i.e. the rear ripper will drop over an hour or so, the jaws won't hold onto an object for more than a few seconds). From others with similar issues it would seem that mine is pretty severe.
I've had a hydraulics guy come and have a look. He started trying to test the rams and was reasonably convinced that they weren't the issue.

My thinking has been that the problem is in the spool valve assembly/control valves (not sure if I've got the terms right there). The hydraulic guy did pull out the main relief valve and said it looked alright as well. He ran out of time and is still to come back.

The hydraulic guy has spent a bit of time on it which I am thankful for (took me quite a while to find someone who was willing to even come and have a look at something so old) but being so old and not a machine that he is familiar with, he is sort of fumbling his way through.

Is there a part that is more likely to be at fault than another on the Case 350b?
I'm assuming there's not going to be a simple fix to it, but do you have any suggestions on what I should do or where I should point the guy when he returns?

Thanks in advance for your help.
Paul

 

[oldnslo]

If there are no external leaks it is either your cylinders or valve spools.

Can you tell if the spools are spring returning to center properly? Could be with age they are dirty and binding some.

Try raising the loader and releasing the lever. Now very slowly start pulling on the lever like you are raising the load. How much do you have to move the lever before the loader quits dropping?

Raise the loader again. Now slowly start pushing on the lever like you are lowering the loader. How much do you have to move the lever before the drop speed changes?

These two distances should be very similar if the spool is centering properly.

Without breaking into the hydraulic lines it is sometimes very difficult to isolate a leak path.

Roy

 

[J_J]

Each valve has it's own neutral position, and in that position, the cyl are supposed to be blocked.

If the lift ares are falling down while in neutral, the trouble could very well be the spools are not centered as oldnslo said..

If the valves are cable operated, check for worn cables

You could take the bottom cap off the spools and see if the centering springs are broken or perhaps weak.

Same with the 3pt, in neutral, the cyl is blocked and should hold, again, check for neutral position.

You can test your loader lift cyl by installing a needle valve in the cyl circuit. If you raise the lift arms and shutoff the needle valve, the lift arms should stay up. If they drop down, the cyl seals are worn and leaking.

Install a hyd gage and test the hyd pressure on all valves.

 

[Godhungry777]

Thanks J_J and oldnslo,
I'll do some testing this arv and let you know what I find. Thanks for your help.

 

[Godhungry777]

OK so I did the centering test you mentioned oldnslo and the distances from center are about the same. So I guess that's working ok. I have to be at half revs or more to be able to produce any lift, so it is working overtime.

The levers are all linkage (not cable) and located directly on the spool valve assembly.

I'll have to wait till I can get the hydraulic guy back out to do the testing that requires test equipment.

 

[boggen]

for online part diagrams / part lists. granted it is not a "shop manual" that would most likely give description of things. but might help ya.

Parts | Case Construction

click on "parts catalog"
type in 350B and then search

click plus sign " + " beside 350B crawler dozer. to see a list of parts.

144 to 228 goes over hydraulic doings.

 

[Godhungry777]

Thanks bogged. That's a great online resource I hadn't seen. I do actually have a hardcopy of the full shop manual including parts lists and diagrams that came with the machine, but I don't have any of the hydraulic testing equipment that is probably needed (e.g. hand pump, gauges, etc.). I should say that I'm not a mechanic but have a basic understanding of mechanical things from maintaining and repairing the motorbikes, cars and tractors we've owned over the last 20 years. This is however the start of my 'education' in hydraulics And this is my first crawler loader which I bought from a friend in January 2012.

While not absolutely confident that the rams aren't the problem, the hydraulic guy did go around isolating each of the rams one at a time and it made now difference to the symptoms. He even went as far as disassembling two of the rams for inspection and said they were good.

If the problem is in the equipment control assembly, does anyone have an idea of which would be the more likely cause of my problem - a spool valve, main relief valve, one of the secondary relief valves or something else?
Is a visual inspection of each of the above the best way to find the problem or is it going to need special testing or equipment?
If I was to pull any one of the above out to check it, what would I be looking for in terms of wear/damage?

Thanks again for your input.

 

[J_J]

If as you say that the rams are good, then something in the valve is not working or broken, or stuck.

After you raise the loader, the spools are supposed to block any fluid movement. You can determine id the rams are leaking by installing a needle valve in the loader cyl hose and when you raise the loader and shut off the needle valve, if they stay up, then the cyl are good.

If the levers on the valve can cause the relief to activate, that probably means that the spools are good and can put max pressure to the rams.

The relief only activates when you exceed the pressure setting, and when you release the levers, the spools are supposed to block any fluid.

Most valves have load check valves that prevent the load shifting when you move the levers.

If they are bad, fluid will leak past them.

Remove the load checks and inspect, clean and re-install. If they are rusty, you may need new load checks.

 

[Godhungry777]

Thanks J_J. I'm on to it.

 

[boggen]

you have multi 0-rings, seals, within the valve body. and it could be any one seal or 0-ring, or could be a combination of them. no way to really tell which is which without tearing it apart.

with age of tractor. and notation of other hydrualics on dozer. it might be worth, spending some cash on new set of seals / o-rings for the valve. i mean ya asking what specific seal or o-ring, or check valve or spring, went out within the valve/levers that control the loader. ya testing would most likely narrow it down. but you are talking any were from 50 cents to couple bucks per seal or o-ring.

if me, i would just get a couple end caps for hoses connecting to valve. and put the end caps on hoses so nothing gets into the end of them. (rag and tape could work as well vs end caps) while you pull the valve off of tractor, and tear it apart, clean it all up. and put a new set of seals / 0-rings on it. if you see something clearly broken, or bent. then ya get replacement part.

if you were talking tearing apart a cylinder. and putting new seals in. i am like you with fixing stuff. but i do not have tools to properly tear apart a cylinder and put it back together. on other hand, i have screw drivers, socket wrenches, a torque wrench. a bowel to put parts in along with some cleaner to clean the parts up. and a used old tooth brush to help clean parts up. to dismantal a valve.

just make sure you keep things in order as you tear things apart and put back together. and keep a reference picture of parts manual or shop manual on hand to double check against.