M6800SDT 4WD CAB - Engine oil Problem

Ok, here we go......
I got new pump.
Disassembled pump mount to clean and check idler gear and bearing, all is ok. I had some metal between pump and mounting base from shaft shearing. All was cleaned and reassembled. Flushed entire suction line incase any metal from gears in pump fell down. The original pump was bad when I put it on. I could turn the shaft fairly easily, unlike the new pump that has quite some resistance.
I reinstalled new pump with all new orings (suction and delivery). I start the tractor and check pressure at rear accessory port. At idle, 500-600 RPMS ,
I get 2400 psi. The front loader moves up and down great, however I limited the range and use of loader until I test it.
All seems well.
Here's where it gets interesting. I pulled the relief valve, however there is no jamb nut or adjust, as shows in diagram below. It is just a solid plug. It has a cylindrical shaft with an oring and backup seal at the end of it. It is not what is in the diagram no adjustment or internal parts at all. I called Messicks Service line and gave them my serial numbers, and they claim it should be what's in the diagram.
I put the gauge on my lift side outlet port. If I start the tractor and just bump the lift lever it pegs my gauge past 5000psi.
I can take more pictures if nessessary.
Am I testing properly?
How could a setup like this work for 700 hrs?
I will remove the relief valve under the return line and take some good pictures, it is definitely not what is in the diagram.


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Here is what is in relief valve location.

Is this possibly a bypass plug of some sort?

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rbargeron said:

My guess would be that the component might be a special fitting used for temporarily defeating the relief valve as part of a testing procedure, or as part of the installatiion of another optional hydraulic function where relief valve function normally at this location is intentionally moved further downstream beyond the point where normal relief might cause nuisance pressure fluctuations under momentary loads. Howver all of that is a RANK GUESS - which, given the service history of this machine is an irresponsible way to approach it. What does Messick's say about this well-worn but obviously non-original looking part?

At some point, what starts as legitimate curiosity and do-it-yourself guessing has to give way to getting higher-level help that considers multiple unknowns simultaneously. This machine has suffered from outright inexperience and or outrageous indifference. Unfortunately there are now so many fingerprints on so much of it, so many incomplete answers, you may never be able to know who did what, causing the first damage and setting off the chain of nasty events.

You ask if you are testing properly. I think you are definitely NOT testing properly if you just connect it all together, start the engine and watch it pin a 5ksi pressure gauge! You are courting more wreckage, but no one can help if you just forge ahead without a map. Every new question suffers from an increasing backlog of incompletely posed and unanswered questions from before. Pretty difficult to have a clue at this point.

Click to expand...

Hello Dick B.,

I appreciate your responses and Understand your frustration. I am not quite sure what is going un-answered, The only step Backward I took was trying the pump with only replacing shaft seal 2 weeks ago. I had the shaft seal already and had to wait for the rebuild kits for the pump about 7-10 days. So I decided to see if the original seal was defective since the pump was only on a very short time (less than 20 hrs). I realize there was a risk to this, but at my expense I wanted the question answered, (Did I have a faulty seal or a catastrophic failure)? It is obvious to me now since the pump did not pump hydraulic oil, it was a catastrophic failure originally, probably caused by overpressure (since as we discussed a few post back, the seal was blown outward toward the engine).
As for the installation of the new pump, Guess I should have elaborated instead of saying "checked the idler gear", I should have said, I X Rayed the Idler gear and the bearings along with the Pump mount and cover. Fortunately, I have access to this equipment where I work, We use this to find stress fractures in precision mold parts. While I could not visibly see any Stress cracks in the Idler gear I wanted to be sure. The Pump Shaft is completely inserted in the female spline in center of idler gear. To me it looks like it is designed for the pump shaft to be the weakest point in the event of pump failure. Since there was no fluid being pumped the failed internal gears stayed right at the pump. I also, split the suction line and removed it completely to make sure there were no metal gear teeth in the suction line directly beneath the pump.
I have been very thorough throughout this process. I have purchased both shop manuals for the loader and the tractor. I have read and studied diagrams and procedures for every aspect of this hydraulic system.

As for testing pressures, The loader service manual only discusses the other control valve assembly for earlier version serial numbers. However it states that you should test and set pressure by letting engine idle to warm up, and disconnecting the loader Lift or dump quick connect and connecting a gauge directly to it then activate lift or dump port which ever you connect it to and take reading.Max pressure should be 2700 PSI. This is the procedure I followed, but again this is for a variable safety relief valve. I was putting it out there to see if anyone with knowledge of these M6800Specials with LA1002 68C loader could maybe explain how this particular control valve works.

The rear PTO relief valve is set at 2500 PSI and works fine, I checked this according to book procedure as well.
Again the loader is working fine, up and down real smooth and steady, I exercise the loader to just just before hard stops at end of cylinder. This is when I expect a relief valve would kick in. So until I figure out what is going on with this control valve, i will not use it.

My goal is to try and find out what caused over pressure to cause original pump failure.

As for the Messicks service Tech, He told me that my particular control valve should have an adjustment on relief and it should be set to slightly less than PTO relief. As for what the Plug/bypass I referenced above is, He was not sure. However, He stated that maybe someone had set it up to relief with the PTO valve, which by the way is a big no no. He also mentioned that the relief valve for earlier version control valve assembly was not adjustable. However, he was not sure if that is what I had since he did not have one in stock and couldn't look at it. He then told me to to check the pressure and see what I am getting, So that's what I proceeded to do.

I will continue to research and update as gain knowledge of this particular loader and why it is setup this way.

Thank you again for help and input.

Jason

Thank You Wolfman! I Appreciate that information, based on what you said. I have some questions to be clear.

I have a LA1002-68C loader, see serial pic below. My hose hookup from tractor is like below. It is my understanding that the pressure in is forward hose and PB is rear hose or if looking at it from right side of tractor, the pressure in is closest to the pump on right side of online block and PB is second from pump or left side of block.
Is this a correct statement?

If so, my PB and Pressure in hoses are opposite of the 68C hookup below.

Should I swap them?

Was it common to put a 68R/6R1 control valve on a 68C loader or is this something someone has done after factory?

I am currently building my tee to hookup gauge.

Thanks again
Jason



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Mine are currently opposite, not sure how or when that happened,
I replaced hoses 1 at a time.
The return is correct, but in and out are backwards.


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So, I have installed a gauge in line with Loader lift.

I checked Pressure at rear PTO 2500PSI
Loader gauge reads about 1000 PSI lifting empty bucket at idle.
I moved bucket up and down along with rolling the dump back and forth each of these movements I was careful not to bottom out cylinder. Loader pressure stayed around 1000-1200 PSI for lift, and dropped out for lowering.

After Cycling for air removal a few minutes, I raised the loader to the Fully lifted position. If I extend out cylinders until they stop the PSI Pegs my 5000 PSI gauge. I only bump it at this position and returned pressure to 0. I assume the same thing is happening with Dump at each end of the roll. This would explain why the pump and hoses are blowing up, there is no relief if the loader is over extended or under significant load.

With regards to the In and OUT based on discussion above. My hoses are definitely opposite. I tried to switch them but the loader doesn't move, It acts like it is over pressured at the control body and loader controls seem inverted push forward to raise and pull back to go down. I say this because the loader attempts to move but then doesn't. I did not want to do damage until I gt some other opinions.

Regardless of how the IN(Pressure) and OUT(PB) are hooked up, I get 2500 PSI at rear accessory.

Currently, Loader and tractor working and running fine with the exception of no Over pressure relief when loader is maxed out at top of travel.

I guess I'm relieved to find out why the Pump Failed, But Now to figure out how fix it.

Jason

The Moment we have all been waiting for.... In Short, The Control Valve I have on my Loader belongs on a LA1002-68R and will not work on My M6800 SDT W/CAB and LA1002-68C loader.
I will explain why along with Diagrams. Please bare with me its been a long night of research, but I believe I can say with confidence, this mystery is solved.

I will start with a section from WSM for LA1002 Loaders. Please look at the snap shot from my manual.



The only Model the LA1002-68R is compatible with is M6800S (No CAB)
The LA1002-68C is for Cab type.
Now why is this a problem?
Well, the 68C Pump and Power Beyond Lines are inline right after pump.
Prior to any relief valve, That is why the 68C has a relief valve
See illustrations


View attachment 29657

Now the LA1002-68R is only compatible with M6800S- NO CAB.
Therefore, the control valve is mounted on the loader and the Pump and Power beyond hydraulic lines are supplied from the accessory mounting arm connected directly to the 3PT Cylinder AFTER THE RELIEF VALVE.
See M6800S no cab below



As for why my loader does not work when I hook the Pump and PB lines up correctly. I will explain in a second post Shortly.

JbirdM6800 said:

The Moment we have all been waiting for.... In Short, The Control Valve I have on my Loader belongs on a LA1002-68R and will not work on My M6800 SDT W/CAB and LA1002-68C loader.
I will explain why along with Diagrams. Please bare with me its been a long night of research, but I believe I can say with confidence, this mystery is solved.

I will start with a section from WSM for LA1002 Loaders. Please look at the snap shot from my manual.
View attachment 29650


The only Model the LA1002-68R is compatible with is M6800S (No CAB)
The LA1002-68C is for Cab type.
Now why is this a problem?
Well, the 68C Pump and Power Beyond Lines are inline right after pump.
Prior to any relief valve, That is why the 68C has a relief valve
See illustrations
View attachment 29653
View attachment 29654
View attachment 29657

Now the LA1002-68R is only compatible with M6800S- NO CAB.
Therefore, the control valve is mounted on the loader and the Pump and Power beyond hydraulic lines are supplied from the accessory mounting arm connected directly to the 3PT Cylinder AFTER THE RELIEF VALVE.
See M6800S no cab below
View attachment 29658
View attachment 29659

As for why my loader does not work when I hook the Pump and PB lines up correctly. I will explain in a second post Shortly.

Click to expand...

For whatever Reason, the Lift(yellow) and Curl(Red) Lines are swapped on the 68R vs the 68C in regards to position they are hooked up on Control valve. I am assuming the Internals are slightly different because the 68R is operated with lever mounted directly to it and the 68C has lines running from the CAB. The Pump, PB, and Return lines are the same. I would have to get the internal schematics to find out why 68R works on mine when I have the Pump, and PB lines inverted. I bet if I swapped the loader lines and the Pump and PB lines the loader will work, however still with no relief.



Looks Like someone put some thought into this setup to get it to work. Obviously, with disregard to the fact that it would not have relief. I suppose the gentleman I bought it from could have used it for years with out ever maxing the pressure long enough to blow anything, but I doubt it. I used it an hour and blew 3 hoses and a pump. I will ask him tomorrow at work.

I think for myself I may just go ahead and order the proper Control Valve assembly, Get myself some new fittings and quick couplers to go along with all my new hoses and put this hydraulic lesson in the books.

I appreciate all the help and support.
Maybe this thread will help some others on down the road.

Jason

Bowfan,

Yes, it was an unusual problem. The loader and tractor have worked fine since the new control valve. I did end up selling the yw234.

Jason

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