Cat 312C Spool Stuck In Control Valve

[HemlockNW]

Hey Folks, I have a 312c with a stuck spool in the control valve. The spool is for the cylinder that controls the stick. It is jammed in there pretty good, and I need advice on how to get it unstuck? Ive tried light prying upwards, but I can only pry off the spring which just compresses. There is a panel on the right side of the control valve. Can I remove it to gain access to the bore and see whats causing it to bind? Thanks in advance!!!

 

[Per Eriksson]

Most likely a piece of metal is jammed in there somewhere and my first guess would be that it came from the stick cylinder so start by removing the lines going to the cylinder and try looking into the openings.
also remove the line reliefs and do the same thing.
The side cover can also give some more access.

A cheap usb boroscope camera might be worth using to try to find the culprit.

 

[HemlockNW]

Thank you. Would i just remove the one relieif in front of the culprit spool? Also if I open the one side cover no parts or anything will jump out at me? How about removing some of the plugs from around that area? would that be OK?

 

[John C.]

Make sure the weight is off the stick and air is released from the hydraulic tank before you start taking things loose. Take off the hoses that the spool feeds. You will likely have to remove the cover on the other side of the spool and tap the valve a little bit each way to free the particle and the spool.

 

[uffex]

Good day
I don't like to be the bearer of bad news but if the spool is stuck fast there is a great chance that the main block is destroyed, you efforts to remove the spool will not be a means of fixing the machine.Explanation attached.
Kind regards
Uffex

 

[HemlockNW]

Well, I got the spoil unstuck. The Borescope was key!!!!! I do have some concerns moving forward. I have not ran the machine yet..

1.) When I place the spool back in the bore, it moves freely and easily until about the last 2.5", then there is slight resistance sliding it in the rest of the way (see photo). When all the way in, it does appear to function properly and the springs recenter it each time. The interesting thing is, when a slide a neighboring spool into the culprit bore, there is zero resistance. Also, when i slide the culprit spool in the neighboring bore, there is no resistance. Should I try to track down a new spool?

2.) I retrieved a piece of metal from the bore (see photo). I am assuming it came from the associated cylinder judging by its shape. Should I immediately have the cylinder rebuilt before I start and or operate the machine.

Thank you!!

 

[Nige]

Should I try to track down a new spool?

You could try but AFAIK spools are only sold with the control valve and not under a separate Part Number.

I would say definitely tear down and evaluate the stick cylinder before operating the machine. That broken piece is only a part of something and whatever it is the rest of it is still in there somewhere and could disintegrate at any moment.

 

[John C.]

All the spools are lapped to their specific bore so it is unlikely that you would find another. What I have run into in the past was the particle left a knick in the edge of the land inside the bore and the spool now catches on it. On other makes of excavator the spools sit horizontal instead of vertical and I've taken crocus cloth to the lands to get just enough material out of the way that it doesn't stick again. The problem with that is now the function may drift slightly on gravity. The stick was the common problem bore so on a logging shovel it would drift down some while holding a log up in the air. I had lots of Pierce grapple cylinders cause those types of problems as well.

I agree with Nige in having to tear down the cylinder before operation. Blowing something through the tubes and hoses is another thought I've had on those projects.

 

[HemlockNW]

Thank you so much for your input!! I will start working on the cylinder repair Tomorrow!!

 

[Bluox]

Thank you so much for your input!! I will start working on the cylinder repair Tomorrow!!

May I suggest you pull your hydraulic filter and check for swarf before you start taking things apart.
Bob

 

[DEMLONE70]

Whats your serial number ?
You can order spool separate

 

[Nige]

Good info but if a land in the body of the control valve has been damaged by that piece of steel a replacement spool isn’t going to fix the problem IMHO.

Another thought. Does that machine have a high pressure trash screen between the pump(s) and the control valve.? If not then is there a possibility that piece could have come from the pump.?

 

[uffex]

Good day
Considering the root cause must be the way to fix the problem.

Good info but if a land in the body of the control valve has been damaged by that piece of steel a replacement spool isn’t going to fix the problem IMHO.

Another thought. Does that machine have a high pressure trash screen between the pump(s) and the control valve.? If not then is there a possibility that piece could have come from the pump.?

 

[HemlockNW]

Ok. Now I'm getting nervous. The Cylinder is getting torn down at the shop as we speak. I am hoping that we find something in there that is compromised. Most people I have talked too seemed to think that would be the culprit. I guess it makes sense the pump could be the problem. I will see what they say about the cylinder, and then the next steep will be to cut open the filters? What exactly should I be looking for in the filters?

 

[John C.]

Pumps don't usually shed just a piece or two. They usually explode with shards and crumbs getting into every function. The other failure mode on a pump is to just get slow and run hot. Don't sweat it for now.

When you open the return filters look for packing and shiny stuff.

 

[HemlockNW]

Roger that!!!! Shiny stuff.....haha

 

[Nige]

Not a hydraulic filter but it will give you an idea of how to go about it.

I'd suggest have a look in both the case drain & the return filters.

 

[Per Eriksson]

I'm guessing that's a piece of the snubber ring on the piston, you'll for sure find more damage inside cylinder.
Give the spool a once over with some fine grit paper or lapping stone and you'll bre fine.

 

[Cat 312E]

How did you get on with this machine?