Caterpillar D6C sticking steering valve

[DoyleX]

I have a 10K PS that has been giving me fits. It looses drive (open clutch) on the left side intermittently, sometimes on the right but mostly left. I have ran it with pressure gages hooked up on the clutch feed elbows and you can see the pressure up to pump pressure meaning the valve is stuck. I have a parts 10k that I swapped the complete steering valve assembly with and it did the same thing. Was thinking of throwing in a set of 4 springs but other than that i'm at a loss. Has anybody ever had this issue?

 

[Bob/Ont]

Check the linkage for jamming, if okay, change and cut open the trans filter. I suspect the trans oil may be contaminated with metal cuttings. They will jam a steering valve and many other valves too. Is torque overheating?
Later Bob

 

[51kw]

Fresh oil, linkage not binding.

 

[51kw]

Plus it seems to always be the left side.

 

[Nige]

As Bob says, the next step would be to replace the transmission filter then cut the old one open and see what sort of particles you can find in it.

 

[tctractors]

The steering control valve is a bit of iron with not much in, I suggest you remove the valve block and strip it out and study why its jambing the spool in, the linkage to it should be free and light to activate, the valves can stick for the stupidest reasons so activate the control links on the valve block with the rectangular plate off and see how little it takes to stick a spool.
tctractors

 

[nicky 68a]

Don't suppose the dreaded cross shaft is starting to lean on the top pinion seals??

 

[DoyleX]

Don't suppose the dreaded cross shaft is starting to lean on the top pinion seals??

I don't know whats possible and not that's why i'm asking.

Previous owner had a fatal transmission failure 1400hr ago. Dealer reman torque, trans and final drives. I put another 150hr on it. I do not think they cleaned out the bevel gear case because the magnet filter was full of big trash and if I work at a extreme angle the magnet will have some chunks again. The filters have been cleaning up so I changed the oil and filters and cleaned up the sticky spots in the valve spools.

I guess I'll just keep cleaning and changing until I get all the crap out. I did pick up a set of springs, after 40+ years and a couple million cycles they might be a bit slacked...

 

[Bob/Ont]

That's your problem, left overs from big failure.
Later Bob

 

[tctractors]

The steering valve block is still worth striping and checking as the spools can stick easily, often this is not on the inner section of the spool? the oil system is filtered so its easy to system check for crap, the pressure filter case needs draining on filter swap, on transmission oil change the 2 plugs should be dropped out of the steering case as well as the tran's drain plug, its not un-common for the steering valves to stick I have had more trouble with the outer section of the spools than contamination within the oil section, you can feel the spool on the steering hand lever if you compare left and right controls, you might be blaming this trouble on the wrong issue,I am no expert but I have done a few.
tctractors

 

[DoyleX]

When I changed oil all the above mentioned was done but the 2 plugs on the steering case. Where are they? Underside next to the trans guard?
The spools in my original valve were worn/scored. I touched up the bores and spools with some 600. They moved better after that. Like Bob said I think i'm fighting the crud from a past failure.

 

[tctractors]

The 2 plugs are directly under the steering clutch position, they have a little sump shape that tends to hold all sorts of gunk, I still think you need to study the spool outer ends some more, but as I said I am no expert, but there is only so much crap you can pump through a system before the transmission pump gives out? what state is the pressure filter and inner case like? have you checked the T/C screen as well as the pump screen, if the machine is so full of floating Scrap something just is not right with the tractor, I don't think its crap sticking your steer valve if the transmission pressure is up to standard, measure this issue at the filter top via the bleed plug is best. tctractors

 

[DoyleX]

Those are the plugs. Thanks

The old oil was burnt and a mix of who knows what. Things would get hot and pressure would fall at the pump. When I changed the oil the pump got replaced with new. Torque screen was clean. My steering pressure is around 315 hot and within pounds of pump pressure.

Every time I take the cover off of the valve you see some tiny flakes in the bottom. Thats where the outer valves rest, at the bottom... Now that you mention I can feel a difference in the resistance in the hand controls between the different valve assemblies ( original/parts). If a outer was sticking you should feel a different pull in the handle.

I'm gonna change the springs, magnet and paper filter again today and take a better look at how the filter canister seals around the filter.

 

[tctractors]

The steering valve block splits in half with a long and a short plunger, long and a short spring with 2 identical valves and slugs, if the slugs are jambing inside the valves I can understand the trash issue, but the usual item to play up is the plungers in the rectangular bit within the block split (I think its held with 5 bolts, if you have junk playing up the steering control the transmission must be giving the same stick, they can take some fine tuning to get the plunger action smooth and constant.
tctractors

 

[DoyleX]

Found the issues. I get Baldwin filters delivered to my door so that's what I used. It's a tin wrapped paper element and don't seal worth a darn on the metal sealing surfaces. The OE cat one has rubber plastic end caps that seal great. Upon suck bucketing out the oil in the filter housing I found the bottom tin sealing surface must have gotten bent and bent back by a hammer mechanic. Thus the bypass of metal into my steering valves... Well shall know in a bit how this plays out.

 

[Nige]

Found the issues. I get Baldwin filters delivered to my door so that's what I used. It's a tin wrapped paper element and don't seal worth a darn on the metal sealing surfaces. The OE cat one has rubber plastic end caps that seal great. Upon suck bucketing out the oil in the filter housing I found the bottom tin sealing surface must have gotten bent and bent back by a hammer mechanic. Thus the bypass of metal into my steering valves... Well shall know in a bit how this plays out.

An interesting story. In the past quite a few posters here on HEF have sworn by Baldwin filters. I still think that oil & filters are the cheapest insurance policy in existence and would take a lot of persuading to use "will fit" elements.

 

[DoyleX]

Nige I too swear by Baldwin and use nothing else except OE cat on some things. This might be one of those circumstances where OE is the only way to go.

I ran the tar out of it for a hour and never felt any slipping so the valves function great now. You can feel the first spring and then the resistance really increases as the second spring comes into play. I'm glad I put in new springs. Thank you everybody for your thoughts on this.

 

[tctractors]

DX, your service method is at fault here, on the bottom of the filter case is a drain plug (3/4" hex) this plug is supposed to be removed at filter change before removal of the filter element, the purge plug on the filter lid should be removed, then the filter case drained, then the filter lid removed, the filter is then removed with the bottom of the filter case being cleaned out, it is hard to catch the oil from the bottom of the filter case, 2 plastic bags 1 inside the other works well, if the suck pump method is used crap can find its way forward of the filter, keep in your mind that any junk in the filter has managed to get there only by going through the pump.
tctractors

 

[DoyleX]

TC the drain bolt head is stripped and it has full screens. Yes I see how when you pull the top cover and the oil is above the clean inlet.

 

[DoyleX]

Well there is something more going on. This is after a couple hours of hard work time and around 6 hours idling around during winter maintenance. I can see some flakes of rust but when you touch them it turns to goo. Clutch facing? Bearing going bad? No chunks. The pan was squeaky clean, now literally a pile of fines out of the filter. Everything works great, no symptoms besides the stuck steering valve when the filter plugged and got some bypassing.