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Stiff steering on 706


W6tractor

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Replaced MCV and all springs and o rings in MCV. Brakeswork, TA works(TA has had handle removed and is locked in direct.) steering is very stiff. I can hear the pump whining. Tried all solutions listed on other posts. Possible bad pump? Think not since brakes work. TA starts in low and it takes a while before it changes to direct (oil light stays on until TA changes to direct-remember it’s locked in direct). TA was behaving this way before the change of pump-main reason for change. Any suggestions welcomed. Thanks in advance. 

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Make sure you have Hy Tran oil no aftermarket stuff . You need to set your psi up on your steering relief valve . It's in the bottom right rear corner of the MCV valve . Set a drain pan under the valve remove the plug , turn the motor over and it will blow the valve out . Clap it in the vise with a rag around the capsule ( don't damage ) get a good flat blade screwdriver and turn the screw in until you can see two treads in the capsule . Take a center punch and put a set punch lining up with the screw , this will keep the screw from backing out . Make sure the oring on the capsule is ok and put it back in the valve .

if this don't take care of it there are two more things I will have you do , jack up the frontend and unhook the steering lines at the ta housing . Make sure the tractor has been in the shop and is warm so if there is water in the front bolster is not ice . Have the lines unhooked with some short hoses hooked to them into a oil pan , then slam the front wheels from side to side . This will get the water out of the front bolster . Hook the lines back up and start the tractor turning from side to side filling the front bolster with oil . Shut it down and repeats until you have clean oil coming out of the steering lines , you  might have to do this a few times . Most people don't reliese that the moisture collects in the wet bolster up front and cold weather don't like each other ?

Let  me know if this don't take care of it , Danny 

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  • 5 weeks later...

Well I'm back after the cold weather and a bout with the flu. Bled the MCV at the rear port, unhooked lines to front bolster and moved wheels back and forth, added air to reservoir, pulled Relief valve-cleaned replaced o ring and reinstalled. No joy. Pulled the MCV again yesterday looking for torn gaskets, missing/torn o rings etc. Nothing obvious. . I checked the plastic control valve in the frame and it appears good. The parts diagram show an o ring that goes with it. Where does it go? Could that be the problem?  Leaning toward a bad replacement pump as I can hear it whining while the tractor is running. If I can get gauges to check pressures, where exactly do they attach? Thanks in advance for your help.

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The o-ring that is shown with the plastic sump check valve goes in the recess in housing. It is the pressure port o-ring .  It does not go in with the check valve at all.  There is a replacable seat  the check valve seats on and you should always test to make sure that check valve seats good. Any leak there will effect all regulated circuits but not power steering because the flow to that area comes after steering is satisfied.

  I would want to know the pressure that the system is operating under when steering is in neutral .  It should be regulated pressure plus maybe 200 psi max. In other words, not over about 450 psi. .  If it is running 7 or 800 psi or more you have a restriction of the power steering flow which will effect all other functions.  There is a  check valve in the steering pilot valve that fails or gets junk in it when things are taken apart and can cause you problems. A recent poster on here had tons of problems until he found that check valve had failed and was partially blocking oil flow. 

If you have made sure the o-ring is good on the steering relief valve you should be ok there.  The squealing makes me think you have back pressure and that is why I would want to know neutral pressure.   I never adjust relief valve over specs as it can cause blown gaskets in MCV.  

It all comes down to having gauges and knowing steering pressure, regulated pressure and lube pressure.  If an experienced guy was with the tractor he may be able to determine problem without gauges by checking several different ways the system is acting,  but from the keyboard here ,  I can not. 

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Was your replacement pump a 9 or 12 GPM unit? I'm probably one of the few who use and prefer the 9 gallon pump on all but the 86 series tractors. I have a 12 gallon pump in my 756 and it always whines. It's coming back out someday. I was advised by Allied Precision to drill the flow control orifice out to 9/64" when using the 12 gpm pump on 06, 56 and 66 series tractors. 

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Thanks Pete23. Looks like I need to get gauges. Which ports do I connect to and what pressures should I expect? Also is the steering pilot valve the one mounted on the center housing above the MCV?

farmerfixemup it’s a 9gpm pump. Looks like a direct replacement for the one I took off. St least that’s what I ordered. 

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You need a 3000psi gauge for steering and connect it right in that plug with the 5/8th head on rear of mcv.   A 600 psi gauge into the lower rear plug, (where steering relief valve is located) for regulated pressure of around 240 to 270 psi, and a 60 psi gauge hooked into port the lube red light sender is in and should read about 18 to 22 psi at moderate engine speed.   I have in recent years found pretty good reasonable priced liquid filled gauges at the local truck shop.  

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  • 2 weeks later...

Thanks to all for your comments. Slowly, maybe not so surely. Putting the MCV back together-again. Trying to cover all my bases. My replacement pump came with o rings already installed. There is a place for an o ring in the MCV itself that matches to one of the ports on the pump, are there two o rings that go in that spot? One on the pump and on on the MCV? Are the o rings on the CIH parts diagram numbered 13 and 14 the only ones that go between the MCV and the pump? Hope this makes sense.

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