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patmax61

MCV PUMPS

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So I've done all the fixes for my 856 mcv pump except change the o ring on the rear split. I've put in a rebuilt MC valve, new pump, new seals on the rear suction tube and main frame pump, made sure to have clean oil, new filter and gasket and double checked filter gasket to keep air out, but the pump still cavitates on start-up. It used to happen only in cold weather but it's gotten worse. Now it might not start on a 60 degree day. I just bleed the little 5/8 wrench o ring plug on the side of the mcv and everything works perfectly after that. I'm skeptical that the o ring on the rear split for the pump suction line could go bad sandwiched in there like that. Has anyone actually seen one of these gone bad? Also, has anyone tried air testing this line? I'm thinking of having a helper brace a rubber cork in the filter housing suction port while I apply a few pounds of air to the pump oil supply port under the mcv. If the o ring leaks from suction even a small amount of air pressure should leak from the o ring and we should hear a hiss from the top of the rear split, right? 

Any thoughts out there?

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Put a new pump in my 560 and it did the same thing ... then it locked up . Made in India pump. Got the USA pump no problems. 

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I would see if your case ih dealer would stand behind the bad one. I use all AG Parts LTD  parts they also work well.

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BTW, I air tested the suction line between the filter housing and the mcv valve pump intake port and it seemed fine. Plugged the filter housing port with a rubber cork, Mcgivered an adapter on the pump port, then juiced the line with a rubber tipped air gun. No signs or sounds of an air leak, and a big back flow whoosh when I pulled back the rubber tip.

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On 11/5/2017 at 2:22 PM, patmax61 said:

So I've done all the fixes for my 856 mcv pump except change the o ring on the rear split. I've put in a rebuilt MC valve, new pump, new seals on the rear suction tube and main frame pump, made sure to have clean oil, new filter and gasket and double checked filter gasket to keep air out, but the pump still cavitates on start-up. It used to happen only in cold weather but it's gotten worse. Now it might not start on a 60 degree day. I just bleed the little 5/8 wrench o ring plug on the side of the mcv and everything works perfectly after that. I'm skeptical that the o ring on the rear split for the pump suction line could go bad sandwiched in there like that. Has anyone actually seen one of these gone bad? Also, has anyone tried air testing this line? I'm thinking of having a helper brace a rubber cork in the filter housing suction port while I apply a few pounds of air to the pump oil supply port under the mcv. If the o ring leaks from suction even a small amount of air pressure should leak from the o ring and we should hear a hiss from the top of the rear split, right? 

Any thoughts out there?

Do you have the 856 style hyd filter cover or newer one with wing nuts?

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whatbwould the wing nut cover effect?  I ask.....because I just bought an 856 with a 1066 style wing nut cover on it, and previous owner says the pump looses its prime if it sets. 

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If you over tighten wing nuts to many times it warps cover. Making it hard to seal and leaking suction on cover. Making hard to prime. My dad used to be very irate if you changed filter through wing nuts once it was sealed leave it go and take bolts off like old tractor and replace gaskets. You can tell right away if filter is leaking air when using hydraulics on baler should lift doors smooth and fast if jerky on hyd pump your steering ta pump is affected even more so. Seen it to many times on a lot of tractors even older ones with bolt cover. Bolt holes must be smooth and gasket good. Dad would have fits if you took wing nut off and he had good reason for it. The oring on center section is surrounded by a gasket also not saying it can't cause problems but more than likely something else causing it. If you go through front to back seals and new mcv pump they usually work good for a while. p.s any hydraulic engineers on here and from the 1950s to 2000 . The whole bunch should have been whipped with barb wire. So many makes of tractors want to suck oil uphill to pumps. Your hydraulic oil needs to be above pump fo positive feed on suction solves all your problems. Every tractor designer  hydraulic engineer was smoking dope and drinking to much for years

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I grew up changing 4-5 of those filters a year, for over 25 years (still do)  knock on wood, I've never had a problem with either style cover leaking. 

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I used to think no problem spinning those wing nuts off either doing it the easy way. 2 episodes taught me that I wasn't as smart as I thought first one is dads 966 it can be a bugger to seal the cover. That is the one dad would get mad at you if you took cover off. He learned this from previous tractors he had. You can always tell when it is sucking air hydraulics would be jerky on longer acting cylinders. 2nd one was neighbors 1456 farmall. I put a clutch and pp in it splines stripped he used it on Hesston hay stacker.I changed hydraulic filter just to do it. This is the old style bolt on cover. Gasket seemed to be good so I wiped it off put filter in. Adjusting clutch before I ran it back home to him a mile away. Steering was real jerky and tractor  would move stop and be real jumpy. Dad came out wondering what was happening. Told him piece of crap was shot needed ta or pump. Dad said fix the filter like I told you before and it will work. I thought you don't know anything. He even went and did it himself changed gasket hammers holes even in cover. Tractor worked like new then. After that I pay attention to any ih tractor you can tell immediately on hydraulics if filter is sucking air. Over 50 % of them are sucking air on filter housing even if you think they are good like I said before if they won't lift a long cylinder smoothly they are leaking. I used to be young and stupid also but you pick up on stuff when someone schools you. Now I am older and still not so bright. I will post some pictures if I have time how much oil you actually have to add to cover intake pipes and pumps on a ihc.

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Went out and took picture to give you idea of oil needed to cover steering pump in oil.picture is of 966. Full line is about equal to top of filter. The camera angle is off not filter housing. Top of filter. Adding five gallons which from experience is dipstick bottom to full mark will get you almost over top of filter cover. You need a little more than 5 gals about 8 to cover filter suction completely. To cover steering or ta pump you would need over 12 or 13,gals to cover shaft seal or pump completely to stop air inclusion. As you put more oil in tran you get into the longer part so takes more oil to raise level. These are close approximate of what you need not exact measures. This is also the cover that is warped a bit that needs attention sealing it

IMG_1763.JPG

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A lot of those covers with the  wing nuts do not fit properly from the factory.  With a new , oiled 0-ring, there should be considerable resistance to pop cover on.  Some seem to have too deep a groove for o-ring and others the cover just too sloppy a fit.  Using the old 0-ring is asking for trouble.   I agree that making that mcv pump pull oil up hill and then down is stupid.  Way too many problems with aeration that could have been avoided with a little engineering. 

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50 minutes ago, pete23 said:

A lot of those covers with the  wing nuts do not fit properly from the factory.  With a new , oiled 0-ring, there should be considerable resistance to pop cover on.  Some seem to have too deep a groove for o-ring and others the cover just too sloppy a fit.  Using the old 0-ring is asking for trouble.   I agree that making that mcv pump pull oil up hill and then down is stupid.  Way too many problems with aeration that could have been avoided with a little engineering. 

It seems certain tractors do it worse. Dads 966 and he had a1466 would give trouble.

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