Farmall 806 MCV Problems

[moore60.purdue]

Good Morning,
My Dad?s has a Farmall 806 that I am having trouble getting the MCV pump to take a prime.

Where it all started:

The tractor stopped moving with a loud bang, coming from the speed transmission while cutting weeds. It still had power steering and brakes.

What has been done in chronological order that they were done:

We pulled all the transmission covers and couldn?t find anything wrong. We decided since the TA had been slipping in low or high (I can?t remember which) to replace it since we assumed it was the TA.

I split the tractor over the winter, and replaced the TA. The one way clutch came out with a handful of teeth and pieces. While I was in there I replaced the reverse driven gear because it was missing a couple teeth from the parking brake paw. I drilled a 1/2? hole in each side of the differential housing to the axle housing to let the oil circulate and maintain the proper level. (I read that it was an upgrade to the later models.) I also wiped down the inner housing and looked for any other metal shavings.

Put a new MCV pump in it (9 gpm used the same gear from the old one), new o-ring between the transmission housings around the metal ring on the brake side, new o-rings on the TA supply tubes, on the pump, new o-ring on the power steering supply line under the mcv, new check valve and spring, then put it all back together. We put a new detent bushings on it, and replaced a broken shifting mechanism with grooves in it that the detents ride in (I can?t remember what they are called and this one had a broken piece on the end). Then put new hy-tran fluid in it.

Had very little (and stiff) power steering and no brakes, but the TA would shift and it moved well after a quick adjustment of the shift linkages.

Pulled the 5/8 plug on the back of the MCV, had a trickle of oil and if I put my thumb on it, I could feel suction. We over filled it by 5 gallons of hy-tran thinking maybe the o-ring between the housing was leaking air, no help. We pressurized the fill hole with compressed air, no help.

I replaced the filter and cleaned the filter screen and housing, replaced the priority valve behind the battery, cleaned and rebuilt the MCV with all new springs, seals, o-rings and gaskets this last weekend. The rebuild kit came with diagrams for each spring and o-ring. I double checked the check valve and spring, to make sure they were installed correctly.
I pulled the 5/8 bleed plug again with no change in pressure. Finally with compressed air and the engine running it took prime and pressurized (and sprayed oil for about 10 seconds before I got the engine shut off). Put the plug back in and restarted the engine, still no brakes and very hard power steering. I did not drive it to check the TA. I cracked a line on the steering hand pump and spun the wheel to try and bleed the air out. I noticed the wheel turns easier to the left than to the right. It is almost impossible to turn to the right with the engine running.

I cracked the oil supply line at the brake pedals and have very low flow.

I cracked the line at each brake to try and bleed the air out and worked the pedal, I get air bubbles out, but never get fluid.
I loosened (not removed) the 5/8 plug again and get oil to trickle. I then loosened the plug on the top of the divider valve and get oil and air. Since I don?t have gauges, I do not know the pressure

I have a book coming (GSS-1343d) but it hasn?t arrived yet.

The pump sounds like it is caveating, but I don?t know where it is sucking air from. I am almost ready to take it to CIH to fix it??

This weekend I am planning on putting the old pump back on since it worked before I took it apart. The only thing I can think of is maybe the pump is sucking air around the shaft seal, or it is sucking air past one of the o-rings on the pump.
I have searched the forums and tried about everything that has been suggested so far. I am at a loss on where to look now, any suggestions would be greatly appreciated. Thank you.

 

[the tractor vet]

Oki so you installed a spring kit in the MCV , but did you put all new gskts and O/Rings in the MCV?? did you replace the sump check plug , Did you put a new key in the new MCV pump ?? did you PRIME the new MCV pump before you just stuffed it in .. Now that you have installed the new spring kit you will need to check pressure once you get it to suck prime up . As you may have to trim the pressure reg . spring , you want around 235-245 on a 806 . Did you set end play on the new T/A ?? . While you were replacing the rev. driven gear did you look at the hyd oil pick up tube to see if it had any cracks around the mounting tab ?? did ti fit tight and the seal good on it while you were in there. Did you install a new Hyd Filter and use a new gskt and make sure the Square cut o/ring behind the hyd. filter was in place is the bypass screen inplace in the end of the filter ?? Try removing the 9/16th headed plug on the back side of the MCV not the 5/8ths one.

 

[moore60.purdue]

Hi Tractor Vet,
Thank you for the response. I put all new O-rings and gaskets in the MCV when I rebuilt it.

I put a new sump check plug and spring in it.

I reused the gear and key from the original pump, they both looked like new, I also put lock-tight the nut to be sure. I can tear it back apart to look at it again.

I feel stupid, but I was not aware I had to prime the pump before installing it since it was supposed to be a "self-priming" gear pump. How is this done?

I did set the end play on the TA. It was a hair under .010" and spec was .005 to .015"

I did not see any cracks in the pick up tube when I wiped out the differential housing. but I was not looking for one either.

The Filter and Gasket I installed was new, but I reused the o-ring in the bottom of the filter holder because it looked ok. The pump for the lift arms work, so I sure the filter is sealing ok.


I will get a gauge to set the pressure regulator. Is this the pressure relief valve in the bottom that looks like it has a screw in it, and comes out as a unit? If so that is the only one that I did not change because it didn't come with the kit. I did notice that the inner spring of the pressure regulator was missing when I rebuilt it. I reassembled it with both springs.

I may have forgotten to mention that everything worked before we took it apart, and I only rebuilt the MCV and changed the filter after it would not prime the first time after it was put back together the first time.

I will try the 9/16 bolt this weekend when I get time to work on it. Is there any place I can dump oil into to try and get it to prime?

Thank you again for info.

 

[the tractor vet]

I always wet the gears of a new pump before i install them , now does it help ?? don't know it is something i do . The pressure reg spring is up on top . the valve in the bottom is the steering pressure valve and you are NOT going to change the setting as it is factory swedged . You need a fitting to go in that port to check the system pressure . No there is no place that i can think of to wet the pump once installed . I have had a few that were hard to get to prime and the way i do it MOST of the time is to run the engine at around 1500-2000 RPM and turn the steering wheel to the left and keep on turning it . IF you do not get prime in five min then it is plan B , and that is pulling the dip stick and sticking a blow gun down the fill tube and place a rag around it to seal and run the engine at about the same speed and start putting air to it . Now this practice will take some time to build pressure to force the oil up the tube and to the MCV . IF and when you pick up prime DO NOT JUST PULL THE BLOW GUN OUT AND REMOVE THE RAG. If you do it will be raining HY TRAN and make old faithful look wimpy . Let the pressure off slowly. DON"T ASK how i know this because it rained HY TRAN for two weeks in the shop . NOW IF and WHEN you do get prime up and checking the pressure you want to check pressure at operating temp of the oil and set at operating temp . IF your to high then for each coil on the inner spring you remove by grinding it off you drop about 10 pounds .

 

[cjd12000]

I had a similar problem. Hard steering poor brakes on a 706 once but the key was sheared in the hitch pump and it had no remotes or three point. Not sure how there related in the system.

 

[moore60.purdue]

Hi TV,

Thank you again for the info. I will push it outside and give that a try this weekend. I should be able to borrow a set of gauges from work. If I can't get it to prime I will put the old pump back on it and try again. I have 3 gaskets .015" gaskets left, so I can take it apart 3 more times. It worked before I had replaced the TA, but while we had it apart we wanted to replace it since we had trouble with steering and moving when it was cold (<15F outside). I guess the say is true, If it ain't broke don't fix it. Thanks again.

 

[the tractor vet]

Well I do not know of one of any hyd. steering that is NOT stiff when cold . some worse then others . The way the steering system is designed you could have moisture built up in the lines that is frozen , it's hard to get all that out of the steering unless ya take it apart and clean it since for the most part what is in the lines just moves back and forth . and once you get moisture in the system you have one heck of a time getting the whole system moisture free . Even the 806 i have now is stiff when it is cold out and of all the 706's and 806's i have had over the years this ugly rag that i have now has the best steering of any I H that i have been around as it steers like a John Deere , yea i did say that when it is warm , now why it steers so easy i have not a clue as i have never taken it apart to see why . And until the day comes that i have to take it apart to fix it i just run it . I bought this one off and auctioneer friend of mine over in the hills of eastern W.Va over the phone sight unseen till i went over to pick it up as i needed a tractor and could not find anything at any of the sales at the time that i could afford and i needed a tractor to farm with , Old Ed told me she was UGLY but ran good and everything worked . Well he did not lie to me and it does run good as a matter of fact it runs vary well to the point that it impresses me to this day and the only thing i have done to it was put one clutch in it and the IDPTO shaft in it and rebuilt the wiring harness at the same time . Now i have to put a new hitch pump in it and a seal on the 540 shaft on the PTo and a new unlatching valve in the one remote as it is leaking . Now if you were close i would just come by and have a look and see what is going on . plus everything i need to work on a I H tractor is in the truck .

 

[moore60.purdue]

I appreciate the offer, but I have to have it done by this weekend. We are getting close to needing it, and if I don't have it done we will need to look for a replacement. Which I would hate to see it go because of all the work I just put in it, and the new seat we got Dad for Christmas. Still looking for a nice set of the square top fenders with the two lights in them and a wide front end but every place we find those parts, they are way more than we want to pay. I will work on it this weekend and let you know what I find. Thank you again for the help.

 

[moore60.purdue]

Hi tractor vet.

I worked on the 806 all day today. I am still having the same problems as before, but I was mistaken about some of the symptoms. I bought a clear hose and a nipple to screw into various places of the MCV and tube it back to the fill neck. It turns out I am getting fluid low through to the brakes. But I don't think the pressure is very high. If I reconnect the brakes and disconnect any of the 3 lines FROM the brake pedal assembly, I get nothing.

Now for the steering. I disconnect one high pressure line to the steering I get flow there. I didn't check the other one yet. I noticed I can only turn the wheel right when the tractor is off. If I pull the wheels by hand to the right and start the tractor, the steering wheel will now slowly rotated to the left and the front wheels turn to the left. In fact if I hold the wheel and steer it to the left myself, it feels almost norma . If I go to the right, the steering gets very stiff and I can only turn it about2/3 of a turn before I can't turn it any more due to fighting the back pressure.

And I am still waiting for my manual. It SHOULD have been here last Friday. Anyway if anyone has any idea where I should check next, I would appreciate it. Thanks

 

[moore60.purdue]

We finally got the 806 fixed. There was a series of problems and the way they were worked on caused other problems. The first problem was air in the steering lines. It was misdiagnosed as a bad steering valve. The steering valve was replaced with a different one which was bad. This gave us different problems. Still no brakes, still no steering but we had T/A. The original steering valve was put back on, and the front of the tractor was jacked up off the ground. We moved the wheels left and right while dumping oil down into the steering valve. After that we had steering and T/A. A new (used) brake assembly was ordered, a fitting was damaged in shipping, when dad took the fitting off the old unit he saw the orifice inside was completely blocked. It was packed so bad he couldn?t get it cleaned out. Put the new brake assembly on and everything works perfect now. The book I ordered finally came in and once we had the schematics and a detailed functional description it was easier to know what ports in the MCV when to what.

Thanks so much for all the information.