Hydraulic Steering Observation- What Do you Think?

[Jim Allen]

The Problem:
I have a small Ford tractor with hydraulic power steering. It specifies plain hydraulic fluid and I have changed it as well as changed the filter as part of normal maintenance. The tractor is commonly used with a loader (front mounted) and when the loader is on and the tractor is warmed up, the extra weight up front makes the steering heavy unless the rpm is bumped up by a few hundred revs. With the loader off, there is no problem. This performance has been consistent in the five years I have owned the tractor, even after rebuilding the steering box (for leaks) and replacing one hydraulic cylinder (for external damage), so have come to regard it as "normal."

The Observation:
I noticed that when the tractor is cold, the steering is not so heavy, even when the loader is on. For the first 10 minutes of operation (or so) the steering feels "normal"... like the loader is not attached.

Ideas: I'm still researching the oil I use (a Mystic product) as to the exact viscosity and other properties, but it seems to me that:
1) The viscosity is higher before the oil warms up, so;
2) Hydraulic assist is better with higher viscosity oil, so;
3) Either this is a fluid issue, or;
4) Perhaps the pump is weak and the higher viscosity fluid pumps a little better and masks the weak pump,or;
5) It really is normal, but:
6) Perhaps a higher viscosity fluid would help operation with the loader on, which is most of the time.

I will pressure test the pump, flow rate it if I can. Anyway, not a critical problem but any observations and thoughts appreciated.

 

[bruce381]

higher vis oils like a 68 or 100 will offer much higher
Efficiency the trend is to use a very high VI shear stable oil that acts like a 46 cold but a 100 hot, anyway for now go to a 68 or 100 and see how it feels.
bruce

 

[bruce381]

Jim check this site for more info on MEHF Fluids:

Maximum Efficiency Hydraulic Fluids (MEHF) - a new performance level for hydraulic fluids that provides increased power, efficiency and performance.

www.mehf.com

 

[Jim Allen]

Bruce381: The oil that's in there is ISO 46, so there you are! That might be the root of all the trouble because the manual (it's a 1989 tractor) specs Ford M2C-41-B and M2C-159-A, or M2C-159-B. These last two are multi-use 10w30 oils that can be used in engines, transmissions or hydraulics. Do you think I could just dump the Mystik and pour in Rotella 10w30? It's a simple system.. a pump, spool valve and two rams and it's separate from the rest of the tractor hydraulic system. I'm using 10w30 RT in the tractor engine now so that would be VERY convenient! Maybe I could even use the same 5W30 GTX I use in the Honda?

The MystikISO 46 is spec'ed at 6.7cSt @ 100C and 46.5 cSt @ 40C (thinnish 20 wt).
The M2C-41-B is cSt 9.0 @ 100C and 45 @ 40C (almost 30 wt).
My RT 10w30 is cSt 11.9 @ 100C and 83 @ 40C. (well into 30 wt)

 

[bruce381]

yeah would be worth a try
bruce

 

[onion]

Generally speaking, there are no compatibility problems when switching from hydraulic oil to motor oil in a hydraulic system. I've seen motor oil used as a hydraulic oil as the OEM reccomended fill in both Case and Deere equipment- and I'm sure others do it. Matter of fact, Deere's latest line of skidsteers reccomends either hydraulic oil or 15w40 depending on temperature range. Case uses 10W30 in their skidsteers- used 10W40 years ago.

About your pump- I've never done much work on the smaller Ford tractors, but it's a safe bet that you have an open center hydraulic system of some sort for the power steering. Does the power steering have its own pump, or (more likely) does the steering run off the main hydraulic system?

Making adequate pressure at higher RPM's but not at idle is a pretty good indication that the pump is worn. A flow meter test and the specs to compare are the only way to say 100%... but it's pretty likely your problem. A thicker oil might bandaide the problem, though... definitely worth a try.

 

[Jim Allen]

Onion: Your question seems to show you did not fully read the previous posts, but that's OK... I'm happy to recap!

The power steering has it's own pump and is seperate from the rest of the tractor hydraulics. I Have been mistakenly using an ISO 46 oil. It specs an ISO 68 or even 100 plus (the 10w30). My problem only occurs with the loader attached and when the fluid is warm. I have also had some recurring trouble with seepage at the steering box (a spool valve on the steering shaft... it's basically mechanical steering with a spool valve and two rams). I'll be changing it today and trying it (I have to chop a bunch of weeds prior to plowing) so we'll see. I have plenty of RT 10w30 soe that's what I'll use. Thanks for your input!

 

[Steve S]

Quote:

---

Jim check this site for more info on MEHF Fluids:

Maximum Efficiency Hydraulic Fluids (MEHF) - a new performance level for hydraulic fluids that provides increased power, efficiency and performance.

www.mehf.com

---

Bruce this is a multi visc. hyd. fluid? Seems that hydraulic fluid heats up to operating temps pretty quick unless the problem is in freezing weather? If the temps are that cold wouldn't/shouldn't there be fluid heaters?

 

[bruce381]

just an interesting read on using the HI VI multi type oils as to increase in work output and efficiency.
bruce

 

[Jim Allen]

FYI Report- I changed the fluid, though it was hard to get it all out without making a big mess. Because I needed that tractor yesterday, I did it "quick-n-dirty" and probably did about an 80 percent change. I also used some Castrol GTX 5w30 I had left over rather than the Rotella, figuring I would change it again. Bottom line: No appreciable change. I'll change out more when I do a pressure test this fall during its normal maintenance period. Thanks for the useful input Bruce and Onion!

 

[widman]

you could probably try 10W-40 to give it more viscosity when it heats up, as long as the viscosity doesn't become the heat source.

 

[Jim Allen]

Wanted to update this thread. The bottom line of my problem turned out the be the steering box. It had started leaking not long after I bought it, five years hence. I had the NH dealer reseal the box at the time because we were building a house. Now I wish I had done it m'self. Four years later, I was having the problems noted above and more leaks. Now that I have the time to do it mysel, I did and found some very major problems in the box that probebly existed when it was "rebuilt" before. I won't detail them here but the parts cost to fix the box almost equalled the cost of a complete new box... which itself was obscenely, knock you on your keister, expensive. In the end, I found a used, low-time box for less than half of the new, installed it and, voila, no more leaks and much improved power assist at low speeds with the loader attached. And with the ISO 46 oil, even! I had two gallons of it and decided to flush the system with it... but it worked so well, I just decided to keep using it. BTW, did a pressure test of the PS pump (it has a separate system from the tractor hydraulics) and it was right at spec, 730 psi.

 

[MolaKule]

I am glad it wasn't the PS pump, but I would rec. an ISO68 hydraulic oil, specifically a semisynthetic for your cold Ohio winters.