# Central Hydraulic Freeze Up



## bnbilott (Dec 16, 2011)

Hello,

Just bought my first truck with central hydraulics (PTO hydraulic pump runs tenco bed and spreader, as well as 9' western plow). Its a 2011 F550. I've got a nice commercial contract this year for it. 

I went to start it the other day when it was 15 degrees out to see how it would start. The truck started fine, but I believe there was ice in the hydraulic fluid. I'm going to change the fluid, but would like to know what fluid to use. It looks like regular old fluid, but I'm wondering if I need to use something else since it runs the plow as well. Anybody out there have experience with this?

PS - looked at the hydraulic tanks, valves, etc, and did not see a manufacturer, and the truck did not come with a manual for the accessories.


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## Aerospace Eng (Mar 3, 2015)

A mineral based hydraulic fluid is almost always used unless it is something esoteric. The trick is to get the right viscosity, which unfortunately depends a great deal on temperature of the fluid while operating. If you use your spreader continuously, you will need a higher viscosity than if you use it intermittently (or you need a cooler). However, in that case you may need to put a pan heater on your hydraulic tank so you don't harm the pump on startup.

Your system may have been built for cold weather from the start and may be designed to use UDT/ATF or something else.

Pump manufacturers will give you a viscosity range for optimum life, as well as maximum viscosity for starting when cold, etc. Depending on how hard the fluid is working, you will need a different ISO viscosity to get the proper viscosity while operating.

Bosch/Rexroth for example has this guidance....

http://www.boschrexroth-us.com/coun...vice_documentation/a_downloads/9535233456.pdf

Note that the viscosity ranges are different for different types of pumps (vane/gear/piston).

Eaton/Vickers has other guidance.

Most of the equipment I have uses ISO 32 or ISO 46.

I would start by figuring our who made the pump and go from there.


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## Mark Oomkes (Dec 10, 2000)

Aerospace Eng;2068695 said:


> A mineral based hydraulic fluid is almost always used unless it is something esoteric. The trick is to get the right viscosity, which unfortunately depends a great deal on temperature of the fluid while operating. If you use your spreader continuously, you will need a higher viscosity than if you use it intermittently (or you need a cooler). However, in that case you may need to put a pan heater on your hydraulic tank so you don't harm the pump on startup.
> 
> Your system may have been built for cold weather from the start and may be designed to use UDT/ATF or something else.
> 
> ...


This is plowsite, not readabooksite.

AW32

Was it milky? Pretty easy to tell when hydro oil is contaminated.


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## SnoFarmer (Oct 15, 2004)

UTF
Universal tractor fluid 

Aw-32 

And be sure to drain and purge your lines.

Good luck.

Some of the smaller systems also used atf.


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## Aerospace Eng (Mar 3, 2015)

For a geek like me, I thought I was being restrained by only giving a link to the book.

To the OP....Since you are in Pittsburgh, although you can go to Tractor Supply or equivalent for their store brand, I would probably get some from Purvis Bros. I personally like Shell Tellus S3V, but I generally have to order it. They have other fluid in stock.


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## Superior L & L (Oct 6, 2006)

General tractor fluid is all we've ever used. Typically flush the system ever other year. Sometimes when it's real cold out I'll turn the system on to get the fluid flowing and warmed up when we warm the trucks up


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## bnbilott (Dec 16, 2011)

Thanks for all the quick responses. i guess I was just concerned because I'm so used to buying "snowplow" fluid for my electric/hyd plow. I'll stick with the aw 32 and change the fluid. 

"Read a book site"- Funny. ( but still very much appreciated aerospace eng!)


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## Randall Ave (Oct 29, 2014)

Is this a new install, or did you buy the truck used, and it was already installed? There should be a filter in the return line, no one ever changes them. Drain the tank, replace the filter, use the fluid Mooks suggested.


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## Aerospace Eng (Mar 3, 2015)

Amazing -- everyone is actually agreeing!

I also found the "readabooksite" versus "plowsite" funny. It was even better that it came from "Einstein." 

I figure most people will just skip most of my posts, but then the info is out there for anyone that wants to go a little deeper.

AW 32 is the designation for "Anti Wear" ISO 32 hydraulic fluid, and you have to look hard to find ISO 32 fluid that does not have the "AW" additives (jack oil, large stationary plants)

Basic UTF is generally an ISO 68 (about the same as a 20W motor oil). "Premium" UTF, such as Kubota UDT is typically about a 10W-20, so an ISO 32 when cold and an ISO 68 when warm. If you have some, great. It will work. If you have to go buy something, I would buy hydraulic fluid over UTF as UTF is designed to work as a transmission fluid, hydraulic fluid, gearbox fluid, differential and axle fluid. As a result, it is a jack of all trades, but perfect for none, since some additives you might like in hydraulic fluid would not be good for a transmission, and vice versa. In a tractor it makes perfect sense, since it simplifies maintenance, and the ability to use more and better filtration and temperature control of a single fluid outweights the slight compromises of the fluid itself.

For the same reason, I buy separate hydraulic fluid for my heavy equipment, even though it allows 15W-40 diesel engine oil to be used as hydraulic fluid.

Cleanliness of fluid in hydraulic systems is probably the most important variable for long life of the equipment, and I absolutely agree with changing the return filter. 

On most systems, if hydraulic fluid looks the least bit dirty, it is way part time to change it.


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## Mark Oomkes (Dec 10, 2000)

Zzzzzzzzzzzz


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## SnoFarmer (Oct 15, 2004)

Diesel oil is a very poor choice.
10W-40 automotive engine oil may be used, providing it _does not contain degertant additives_, and these additives used in_ engine oil can cause corrosion and cavitation._ This occurs because the detergents can cause water that has condensed into the system to emulsify, preventing it from being separated from the oil.
It is recommended however, that a proper hydraulic fluid be used, and chosen based on its ISO grade. These fluids do not contain harmful additives that can cause damage to components, and are designed to work within a specific temperature range.

UTF is a high quality, specially designed lubricant containing anti-rust, anti-foam and oxidation inhibitors, along with other additives necessary for the wide range of applications recommended by various tractor manufacturers. The product is an "all-seasonal" type of oil that resists thickening in cold weather and thinning in the heat of the summer.
Operators, especially farmers, will appreciate the multipurpose application for transmissions, final drives, _and hydraulic systems_ of tractors thereby eliminating the need for additional oil products.
Also a Low pour point to provide mobility and prompt lubrication at low ambient temperatures.Excellent anti-wear package to Prevent scoring and gear wear.

UTF (Universal Tractor Fluid) is a multi application lubricant used to lubricate the moving parts of off-highway mobile equipment. These fluids are used to lubricate the transmissions, differentials, final drive planetary gears, wet brakes and hydraulic systems of farm tractors and construction equipment that have a common fluid reservoir calling for a combination lubricant and power transmission fluid. The properties of these products provide unique characteristics since the same fluid must lubricate the transmission as well as the final drive, actuate hydraulic type disc brakes which are submerged in oil, _and serve as a hydraulic fluid to operate power steering units, power take-offs, implements and attachments._

its not rocket science.


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## 1olddogtwo (Aug 6, 2007)

Komatsu used to spec 15-40 weight oil, they still may.


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## SnoFarmer (Oct 15, 2004)

I'm sure they do in their engines.....
I never added it to the hydro tank on the one Komatsu dozer I operated.
and nether should you they do make their own hydro fluid...
First you never want to use a detergent oil in a hydraulic system - it can cause anything from foaming in the oil which will cause cavitation in the hydraulic pump and result in premature pump failure, to it picking up waste/contaminants in the oil and depositing it as sludge throughout the hydraulic system.

Komatsu America, they DO NOT recommend a detergent oil in the hydraulic system...What is supposed to be in the hydraulic system is either a 10W or a 30W non detergent oil or their own hydro fluid.
There were a few exceptions, like the one in the fine print of the Operation and Maintenance Manual that recommended the use of Tractor Hydraulic Fluid in wheel loader, as per Komatsu America.

http://www.komatsu.com/CompanyInfo/profile/report/pdf/163-E-07.pdf

I believe you ran in to some advertising/recommendation from Texaco?
where they recommended the wrong fluid.

now, I'm sure someone will come back with but Sno, they make a detergent hdro fluid,
yes, yes they do...
DIN 51524; HLPD fluids are a class of hydraulic fluids which contain detersive and dispersive additives. The use of these fluids is approved by most major hydraulic component manufacturers and can be advantageous in many applications, including mobile, to prevent build-up of sludge and varnish deposits, which can lead to valve stiction and other reliability problems. The main caution with these fluids is that they have excellent water emulsifying ability, which means that if present, water is not separated out of the fluid. Emulsified water reduces lubricity and filterability, can cause corrosion and cavitation and reduces the life of the oil. These problems can be avoided by maintaining water content below 0.1% - which is not a low water content target for any high-performance hydraulic system. A hydraulic fluid that has the ability to emulsify small amounts of water can be beneficial in mobile applications.


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## Aerospace Eng (Mar 3, 2015)

Didn't say I used it as hydraulic fluid, just that it was acceptable for certain machines. 

Volvo, Cat and Moxy off road trucks all allow 15W40 diesel engine oil as hydraulic fluid. I wouldn't use it because the additives you ened to make it a good engine oil don't help with being a good hydraulic fluid.

My point was that for a hydraulic system, I would use hydraulic fluid before UTF.

In my L35 I use Kubota super UDT, but if it had a separate hydraulic system I would use Shell S3V.


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## Mark Oomkes (Dec 10, 2000)

Zzzzzzzzzzzz


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## SnoFarmer (Oct 15, 2004)

Water-glycol.


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## Superior L & L (Oct 6, 2006)

Back to my original comment. Use simple tractor hydro fluid. While I don't know much, putting engine oil in sounds crazy to me. 

Use the k.i.s.s method


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## Aerospace Eng (Mar 3, 2015)

Superior L & L;2069324 said:


> Back to my original comment. Use simple tractor hydro fluid. While I don't know much, putting engine oil in sounds crazy to me.
> 
> Use the k.i.s.s method


No-one advocated using engine oil.

I think the consensus in the absence of any manufacturer's info is to use an AW 32 fluid.

But just to show the variety, here's a cut and paste (sorry for the low res) from an MT-30 articulated truck, the generation after mine. Everything from engine oil to ATF to hydraulic fluid is acceptable, with different temperature limitations. "AW" is the same as "HV" in this chart.


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## LON (Aug 20, 2006)

ISO/AW15 period in a clutch pump system. Have been using for 20+ years in all our clutch pump builds after AW32 was showing to be too heavy for customers with unheated garages. Don't use hy-trans or ATF as it's not really designed for a clutch pump system. I've seen a lot of different stuff used in my 37 years of doing municipal type builds.


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## beanz27 (Dec 22, 2012)

Both Deere and Cat say engine oil can be used in hydro. Systems, both also say there are better options. Reason for engine oil is so large outfits-think open pit mines- can lower operating costs by stocking one fluid. Means the new guy can't put in the wrong oil if they only use one kind. For something as simple as a pto on a truck, just put AW32, and move on with your life.


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## bnbilott (Dec 16, 2011)

*replaced with AW32*

Thanks for all your help guys. Drained the system, changed filter, replaced with AW32. It doesn't freeze up anymore, although the PTO is very loud on cold mornings, the system still works.


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## Mark Oomkes (Dec 10, 2000)

LON;2099378 said:


> ISO/AW15 period in a clutch pump system. Have been using for 20+ years in all our clutch pump builds after AW32 was showing to be too heavy for customers with unheated garages. Don't use hy-trans or ATF as it's not really designed for a clutch pump system. I've seen a lot of different stuff used in my 37 years of doing municipal type builds.


Define cold temps.


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## Mark Oomkes (Dec 10, 2000)

bnbilott;2099398 said:


> Thanks for all your help guys. Drained the system, changed filter, replaced with AW32. It doesn't freeze up anymore, although the PTO is very loud on cold mornings, the system still works.


Good to hear, so are mine. I have a couple trucks per night that sit ootside with central hydros that have AW32 that whine for a bit. One is over 20 years old.

Upfitter by us that builds municipal trucks uses AW32 on everything as well.


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## leolkfrm (Mar 11, 2010)

put some dry gas in it, the type without the skull and crossbones on it


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## LON (Aug 20, 2006)

bnbilott;2099398 said:


> Thanks for all your help guys. Drained the system, changed filter, replaced with AW32. It doesn't freeze up anymore, although the PTO is very loud on cold mornings, the system still works.


That loud noise is pump starvation as it is running dry until it picks prime back up. Don't have that with ISO/AW15


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## LON (Aug 20, 2006)

Mark Oomkes;2099400 said:


> Define cold temps.


Anything in the teens and below whether it's ambient or 20's plus wind chill. Ask member whitegardens how dramatic his truck changed when he went from 32 to 15 in hydraulic oil.


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## LON (Aug 20, 2006)

Mark Oomkes;2099404 said:


> Good to hear, so are mine. I have a couple trucks per night that sit ootside with central hydros that have AW32 that whine for a bit. One is over 20 years old.
> 
> Upfitter by us that builds municipal trucks uses AW32 on everything as well.


Used 32 until 93 when we changed to ISO/AW10 blended by then Minuteman Lubricants (now Agip). When they stop producing it we went to the 15. 
Now all of our tandem gear pumps on IH, Freightliner or Pete's we use AW46 that is custom blended by Agip as their engineers worked with our pump manufacturer to develope it.


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## Mark Oomkes (Dec 10, 2000)

LON;2099660 said:


> That loud noise is pump starvation as it is running dry until it picks prime back up. Don't have that with ISO/AW15


No it isnt.

Oil weight has nothing to do with whether one loses prime or not.

A properly sealed hydro system never loses prime whether it's +100 or -100 AMBIENT air temp.


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## Mark Oomkes (Dec 10, 2000)

LON;2099662 said:


> Anything in the teens and below whether it's ambient or 20's plus wind chill. Ask member whitegardens how dramatic his truck changed when he went from 32 to 15 in hydraulic oil.


This shows that you are clueless. Wind chill has absolutely nothing, zero, zip, nada to do with the temperature of anything other than what it feels like on exposed skin.

Nothing gets below ambient air temperature or actual pavement temperature. Nothing. You can have your truck at the top of Mt Washington with an ambient air temp of -10 and a wind chill of -100 and the oil temp will be -10. All the time, every time. 15 or AW32 are both going to be -10.


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## johnhenry1933 (Feb 11, 2013)

LON;2099662 said:


> plus wind chill





Mark Oomkes;2099792 said:


> This shows that you are clueless. Wind chill has absolutely nothing, zero, zip, nada to do with the temperature of anything other than what it feels like on exposed skin.


Thank you Mark. You beat me to it.

Actually, a clarification: Windchill has no effect on inanimate objects, _except_ to shorten the time that object reaches the ambient temperature.


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## Mark Oomkes (Dec 10, 2000)

johnhenry1933;2099797 said:


> Thank you Mark. You beat me to it.
> 
> Actually, a clarification: Windchill has no effect on inanimate objects, _except_ to shorten the time that object reaches the ambient temperature.


Thumbs UpThumbs UpThumbs Up

Thanks for the clarification.


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## Mark Oomkes (Dec 10, 2000)

Mark Oomkes;2099790 said:


> No it isnt.
> 
> Oil weight has nothing to do with whether one loses prime or not.
> 
> A properly sealed hydro system never loses prime whether it's +100 or -100 AMBIENT air temp.


I also need to add one thing to the last sentence:

A properly DESIGNED and sealed hydro system..................


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## LON (Aug 20, 2006)

Mark Oomkes;2099792 said:


> This shows that you are clueless. Wind chill has absolutely nothing, zero, zip, nada to do with the temperature of anything other than what it feels like on exposed skin.
> 
> Nothing gets below ambient air temperature or actual pavement temperature. Nothing. You can have your truck at the top of Mt Washington with an ambient air temp of -10 and a wind chill of -100 and the oil temp will be -10. All the time, every time. 15 or AW32 are both going to be -10.


I guess I'll be happily clueless and still building the same great municipal trucks that we have been for 46 years now.


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## 1olddogtwo (Aug 6, 2007)

Since I'm among many mad scientist let me ask a scientific question.

Which will melted out quicker, a 5oz ice cube froze at 30F and a identical one froze at -30. Both place in room at 70?


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## johnhenry1933 (Feb 11, 2013)

LON;2099824 said:


> I guess I'll be happily clueless and still building the same great municipal trucks that we have been for 46 years now.


I'll agree with you on one issue you've stated: that a lighter fluid will flow more easily (more viscous) in cold temps.

I've run aw32 in central hydraulics and my loader for years and it works fine. In single digits or subzero the tools move a bit slower, and the pump whines initially...until it warms.

I've never damaged a pump, or any part of the hydraulic systems in my equipment using aw32 in single digits...or even subzero temperatures.


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## Mark Oomkes (Dec 10, 2000)

1olddogtwo;2099828 said:


> Since I'm among many mad scientist let me ask a scientific question.
> 
> Which will melted out quicker, a 5oz ice cube froze at 30F and a identical one froze at -30. Both place in room at 70?


What is the heat index?


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## Mark Oomkes (Dec 10, 2000)

LON;2099824 said:


> I guess I'll be happily clueless and still building the same great municipal trucks that we have been for 46 years now.


Doesn't matter how long you've been building trucks, you're wrong aboot wind chill and wrong aboot heavier weight oil resulting in a hydraulic pump losing it's prime.



johnhenry1933;2099839 said:


> I'll agree with you on one issue you've stated: that a lighter fluid will flow more easily (more viscous) in cold temps.
> 
> I've run aw32 in central hydraulics and my loader for years and it works fine. In single digits or subzero the tools move a bit slower, and the pump whines initially...until it warms.
> 
> I've never damaged a pump, or any part of the hydraulic systems in my equipment using aw32 in single digits...or even subzero temperatures.


I've never disagreed that lighter weight oil will flow better at colder temps......but it will also potentially result in cavitation at higher temps because it becomes too thin.

I've been running central hydros since 1990, never damaged a pump or system by using AW32 in cold temps either.

And we have another guy here from North Dakota using AW32. Pretty sure it gets colder there than Pennsyltucky or Michigan. So far LON is the only one saying everyone else is wrong. Pretty sure we aren't.


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## leigh (Jan 2, 2009)

Mark Oomkes;2099792 said:


> This shows that you are clueless. Wind chill has absolutely nothing, zero, zip, nada to do with the temperature of anything other than what it feels like on exposed skin.
> 
> Nothing gets below ambient air temperature or actual pavement temperature. Nothing. You can have your truck at the top of Mt Washington with an ambient air temp of -10 and a wind chill of -100 and the oil temp will be -10. All the time, every time. 15 or AW32 are both going to be -10.


zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz..........

:salute:


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## SnoFarmer (Oct 15, 2004)

johnhenry1933;2099797 said:


> Thank you Mark. You beat me to it.
> 
> Actually, a clarification: Windchill has no effect on inanimate objects, _except_ to shorten the time that object reaches the ambient temperature.


Bingo......Thumbs Up


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## SnoFarmer (Oct 15, 2004)

1olddogtwo;2099828 said:


> Since I'm among many mad scientist let me ask a scientific question.
> 
> Which will melted out quicker, a 5oz ice cube froze at 30F and a identical one froze at -30. Both place in room at 70?


The one at 30f as it has less energy to absorb.
This takes time.

Just becuse water frees at 32
Doesn't mean it can't get colder.

Wind would only speed up the process.

Then, low humidity and just wind will cause sublmation
Even at -30.


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