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I have a quick question, on my 42 9N, I changed all the fluids when I first got it. Put 90W in the trans/sump/diff. The fluid is clean and not water contaminated, at least that I can tell. I have a 6 ft blade on back for snow removal.

Question: when I first start it up and it is very cold (say below freezing as definition for cold), the pump makes a knocking noise when I operate the lift control, and the lift will not operate. Let the tractor run about 5 minutes and warm up some and the lift starts to slowly work. Once warmed up it works fine, very fast and no hesitation. It does leak down fast so I know I have some bad seals and the pump probably needs rebuilding. But why does it not work when cold? Seems to me the seals being bad should work *better* when cold since the fluid is thicker?

Thanks for any help and understanding what I have going on, Terry.

PS - been getting a work out with all the snow we have been getting here. Received 10 inches on Mon Dec 19, and then 17 inches more on Dec 22-23. So much snow I can no longer push the snow off the side, it moves my tractor sideways. Need some warmer temps and melt off some of this snow!
 

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I'm up here in NW Wisconsin. Not much snow this year but it get's a little "cold" here too. I got an 8Ns but I think the two tractors are close in the hydraulics. The owner's manual calls for a 90 weight mineral oil or a 80 weight mineral oil for cold weather. I am now using the New Holland Multi-G 134 (NH-410B) synthetic fluid. A Little costly. The fluid is thinner (for the cold weather) but there are a few drawbacks. because of the "thinner" fluid, your hydraulics must be in very good shape. The last 8N I got I rebuilt the 3 point lift. I upgraded to the NAA piston and I would recommend this to anyone no matter what the temperature or fluid they use. The rubber seal is SO MUCH better then the steel rings and I get no leaking back at all. Wasn't bad to rebuild either. So if you want to have the extra expense and time rebuilding the pump. I think this will fix your problem. My opinion though. I'm sure there are smarter people here then me.
 

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Ken, as the tractor warms up and the fluid starts moving, the friction causes the fluids to warm. That is why people 30 years ago had to change oil to different weights in the summer and winter (That is in more extreme climates). 40 weight in the summer and change to 20 weight in the winter. That is why they came up with "multi-weight" oils like a 10w-40 or 5w-30. The theory behind this is in the warm weather, it acts like the heaver weight oil and in the cold like the thinner. It doesn't happen as fast behind the engine. But, there is enough heat transfer and friction to warm up the oil. A HA - History lesson!
 

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I understand the engine heating part..I am originally from Illinois..

Ken, as the tractor warms up and the fluid starts moving, the friction causes the fluids to warm. That is why people 30 years ago had to change oil to different weights in the summer and winter (That is in more extreme climates). 40 weight in the summer and change to 20 weight in the winter. That is why they came up with "multi-weight" oils like a 10w-40 or 5w-30. The theory behind this is in the warm weather, it acts like the heaver weight oil and in the cold like the thinner. It doesn't happen as fast behind the engine. But, there is enough heat transfer and friction to warm up the oil. A HA - History lesson!
 

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Switch to 134D if your having trouble in the cold or start it up and let it warm before you start with working it. I think that is what I would do since you say you have some leaks and the heavier oil is good for that.

You could also get a magnetic heater and slap it on the hydraulic sump to help warm the oil if you want to reduve your wait time.
 

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Discussion Starter · #8 ·
Well, I understand the let it warm up a bit part. It helps the engine run better if I let it warm up also. Tractor is outside, so starting up from cold means it is whatever ambient outside temps are, below freezing in many cases since it is primarily used for snow removal.

Is the fluid 90W just too thick and won't flow into the pump why it does not work when cold?

If I switched to the 134 fluid now I would have a lot worse leak down, so I think until I get serious with rebuilding the pump and use the NAA type seals and piston it is best to stick with the 90W.

I use a 10W-40 motor oil and it seems to work fine. Maintains about 40 psi when running and 20 psi hot idle. Not too thick when cold so oil pressure builds quick in the engine.
 

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Is the fluid 90W just too thick and won't flow into the pump why it does not work when cold?
That's what I think any way. The 90W has the consistency of honey and gets quite a bit "thicker" when cold.
If I switched to the 134 fluid now I would have a lot worse leak down, so I think until I get serious with rebuilding the pump and use the NAA type seals and piston it is best to stick with the 90W.
That's what I would do. Wait until you have the time to fix it. Because the 134 fluid is thinner and it will leak much worse. First hand experience on that one.
I use a 10W-40 motor oil and it seems to work fine. Maintains about 40 psi when running and 20 psi hot idle. Not too thick when cold so oil pressure builds quick in the engine.
If that works for you I see no problem. I guess I'm old fashioned, I still use straight 30 weight. Winter and summer.
until I get serious with rebuilding the pump
I rebuilt a few pumps and there is not much to them. The rebuilding of the pump has many posts here and they explain the rebuilding much better then I could. It is a 2 man job to lift off the top cover and you need him back again to replace it. The rebuild itself is very straight forward. And the guys here have a few tricks that make it go real easy. When you are ready to rebuild, let me know and I'll tell you the few tricks I have learned from here and there....Jeff
 

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After Sleeping on it. I think you are doing everything right and I know you need a new lift piston. There could be another problem. The pump itself on the bottom. When you do rebuild the lift piston, you need to clean all the "gunk" from the bottom. This might be clogging the system. OR the worse case would be that the bottom pump needs rebuilt, too. As I said before, you are going in the right direction and the first thing you need to do is rebuild the lift piston and clean the bottom.
 
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