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Replacing Hydraulic Fluid Filter (Power Steering)


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Hey Guys, I'm getting ready to replace the filter in my Hydraulic Fluid Reservoir.  Once I remove the bolt, cover, spring and washer, can I simply lift the old filter out of the canister and gently place the new one in its place without removing any of the Dex III fluid?  This is on my 2006 Cayman PBD, 300 ISB.  

Thanks,

Carey

Hyd Res.jpg

Hyd Res Explode.jpg

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Posted (edited)

Yes, its pretty simple to swap out. I did not drain, pull it straight up, have rags handy it will obviously be soaked and dripping.

The large round cap will prob. be stuck on there. I took a small hammer and tapped around the edge to loosen. Prob. had to tap up one bottom lip to pop it off.

Edited by CaymanXL
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Let the engine idle for a few minutes before moving the steering wheel to allow air to be purged. If you move the wheel too soon you could get air into the steering actuator and it will take a while to get it back out.

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1 minute ago, Harvey Babb said:

Let the engine idle for a few minutes before moving the steering wheel to allow air to be purged. If you move the wheel too soon you could get air into the steering actuator and it will take a while to get it back out.

I am assuming you mean after I put the new filter in.  I should start the engine and let it idle for a few minutes to displace any air that might be trapped in the new filter.

Thank you both for your help!

Carey

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2 minutes ago, Idoc57 said:

I am assuming you mean after I put the new filter in.  I should start the engine and let it idle for a few minutes to displace any air that might be trapped in the new filter.

Correct. There will be some air in the filter/housing and it will take a little while for it to purge out. As long as the wheel isn't moved immediately on starting the engine the air will be flushed out without incident. If the wheel is turned too soon the air will be pushed into the steering actuator, making steering "spongy". If this happens it can usually be cleared up by turning the wheel "lock to lock" several times. Not a real problem but since it's easily avoided ....

 

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I get it!  With the price of tires these days, who wants to unnecessarily turn their wheel lock to lock several times and scrub off all of that precious rubber?  😉

Seriously, I understand what you are saying and the reasons why you recommended letting the air purge out.  Thanks again for your advice.

Carey

Now, on to the next question!  

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3 hours ago, Idoc57 said:

Hey Guys, I'm getting ready to replace the filter in my Hydraulic Fluid Reservoir.  Once I remove the bolt, cover, spring and washer, can I simply lift the old filter out of the canister and gently place the new one in its place without removing any of the Dex III fluid?  This is on my 2006 Cayman PBD, 300 ISB.  

Thanks,

Carey

Hyd Res.jpg

Hyd Res Explode.jpg

One word of caution and some info from TRW Tech support.

your steps are correct.  But FIRST.  MAKE SURE WHAT FLUID IS IN THERE.  Monaco, and the old timer, Jim, in Oregon tech support says the manuals are probably wrong.  In that, my 09 manual says Texaco AW 46 HYDRAULIC OIL.  Jim said the lines converted to Automatic Transmission fluid way earlier.  I bought a 5 gal can.  Jim said to drain the reservoir and put in new by cracking a fitting on the bottom.  I had a hand as well as drill pump ready.  Popped the top and took off the clamp.  Opps….RED AUTOMATIC TRANNY FLUID.  OK.  Put it back together.  Called TRW, who made the steering box and the Italian pump company that made the motors for my side radiator fans.  I wanted to use my Texaco.  I was also reluctant to mix.  Both TRW and pump mfg said DO NOT!

TRW told me to drain the reservoir, mine was close to 2 gallons.  On mine, there is a hydraulic, spin on pressure filter.  TRW said.  Change the reservoir element, or NELSON one.  Change the pressure one.  Put in the Allison Transynd or the Mobil Delvac fluid with the TS295 (memory) rating.  TRW will only give truckers or heavy duty applications the extended warranty IF they use the Transynd or the equivalent rated fluid.  He worked for Allison before TRW.  TRW made a warranty decision based on the millions in testing that Allison did to develop Transynd.

Bottom line…verify which fluid and stick with it.  Tractor Supply or NAPA or others sells plain old Hydraulic fluid.  The Delvac is the only one I trust, other than the Allison.  Pull off the top and measure down yo the fluid level with a tape measure….this is your fill line.

Do both filers, pre filling the spin on pressure one.  Pump or siphon out the reservoir.  Replace with new fluid….to the dimension or distance down.

i started mine and let it idle.  I pulled out of my driveway which involves a 2 step maneuver….so I probably went close to lock.  I never had any issues….other than thinking it “felt” better.  I have done this twice.  Once @ 30k and then at 57K.  I figure I am good to go, as I have “turned over” the reservoir twice and gave a high percentage of Transynd in the system.  I doubt I ever do it again.

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15 minutes ago, Tom Cherry said:

   Monaco, and the old timer, Jim, in Oregon tech support says the manuals are probably wrong.  In that, my 09 manual says Texaco AW 46 HYDRAULIC OIL.  Jim said the lines converted to Automatic Transmission fluid way earlier.  

Yeah, I believe that!

My owners, and chassis manuals stated mine was factory filled with Texaco AW-46, fluid, It was light red! Called Monaco tech support to ask about this, and the guy told me "sometimes they added dye."

He sounded to me like he was grasping at straws to try and make sense of it all!

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Tom, that is very interesting.  I think you must have a much larger reservoir than I do.  Mine is about the size of one of those old quart containers (paper & metal top and bottom) that we used to buy motor oil in, back in the "OLDEN DAYS"!  Mine also has a dipstick.  I will definitely take your advice and check what is in there when I pull the top off the reservoir.  

What Ben said makes me uncomfortable in that if I dip up a scoop of red hydraulic fluid, I would just assume that it was ATF.  Why in the world would a manufacturer add red dye to hydraulic fluid, unless they wanted you to think that it was ATF?  After all, my manual specifically says to use Dexron III .  It also specifies Dexron III for the hydraulic unit up front (for the jacks).

The filter that I am changing is the one that is shown in the picture above.  It is a Fleet guard LF634.  The manual also lists a "Filter Assembly" Nelson 91085G.  I don't even have a clue what that is or where it is!

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You, based on your manual, which I pulled, do not have a “Nelson single or triple filter” reservoir.  Now, I say that as most Nelson’s had a band clamp.  Yours has the bolt.  So get the correct filter and compare.  I bought 3 as the “gurus” said every Nelson had 3.  Nope, mine was a REAL Nelson, but smaller and only one filter.

The fluid will be yellowish or Reddish.  The yellow is Hydraulic and the Red is ATF.  Jim, whom I often talked to to get info for members was emphatic that the “folks” that wrote the manuals didn’t come down to the floor much.  As an old Manufacturing Services manager with 20 plus Manufacturing Engineers, I held my tongue from saying, “the folks on the floor ought to follow the prints and instructions and manuals an MILTP… make it like the PRINT…

IF it is RED, EITHER send off a sample or do your own test.  ATF is “thinner” than HD Fluid.  HD is yellow or sometimes blackish and thicker.  If your fluid is red…dip you finger in it and rub your thumb and first finger together.  HD will feel stiffer.  Pull the dipstick out of your car’s tranny.  Feel it….then compare with your reservoir.

I don’t buy the red dye….unless some enterprising supervisor found a few palllets and got really creative.  

You don’t mention an auxiliary hydraulic filter.  I have read that some Monaco’s had none.  From your manual, sounds like you only have the reservoir filter.  You don’t, I believe, have the twin fans like my side draft.  So, yours is simpler.  
 

I would still drain or pump out the reservoir and put in FRESH ATF.  I carry spare Transynd and have had to add a quart when my downshift was rough.  The electronic keypad said OK.  ADDED a quart….still OK.  IT SHFTED, on the downshift, like it should.

So, I would add Transynd or Delvac and keep the remainder for my tranny.  ATF added to HD is way better than adding HD to ATF.  

Just my opinion….others may differ.  I put almost 6K on mine for 10 years when we spent more than 2 months out each year.  So far, nary a hydraulic or transmission or engine issue.  The 15K Monaco number is BS….According to TRW…and if you have a Shepherd steering box, I suspect the same thing.  I did mine twice and am confident it is properly serviced.

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In early April traveling through Texas seals in my hydraulic pump and PTO failed allowing transfer of transmission fluid to over pressurize my Nelson filter assembly causing overflow of the system and loss of transmission fluid.

The only shop that could work in the rig was Robert’s Trucks in Abilene Tx.  
 

Pump and PTO removed and sent out to be rebuilt.  I am not sure why but mechanic used yellow hydraulic fluid, not the Dexron III fluid the manual called for.  Also the three filters were WIX which were reinstalled.  
 
I will be in Eugene Oregon in a week or so and will try to discuss this with Jim or Scott at Source Engineering.  I will post their recommendations whether to drain/flush or keep it as is.

Sorry photos failed to load.  Also not able to delete.

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A work of caution about using AW-46.  Monaco used this hydraulic fluid in a lot of coaches.  Mine came with it from the factory.  The AW-46 sticker matched what Monaco put into my coach from the factory. 

The problem is with the higher viscosity AW-46 in very cold weather conditions (well below freezing), the heat exchangers couldn't take the high viscous oil pressures and the started to fail.  The solution was to move to transmission fluid and that's what Monaco did.

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  • 1 month later...

This is an interesting thread, I purchased a used coach almost a year ago and In talking with the the gentleman that performed the maintenance (Specialty RV in Aurora Or) on the coach before I purchased it, I asked what he used for the hydraulic system in regards to the steering system and cooling system fan, he told me that he used the AW-46 hydraulic fluid when he serviced the system in regards to changing out the filter, I’ve looked at the service records that we were given at the time of the purchase  the owners manual says ATF Dexron III. I wondered about using TranSynd to reduce the different types of fluids to carry on board in case you’d need any on the road. I’m going to suck out some fluid and see what color it is, I’m guessing it’s going to be red, I looked through all of the service records I was given and it appears that the hydraulic fluid has never been changed out, I know the filters have been changed, at least I know the filters have been changed!

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46 minutes ago, Jdw12345 said:

This is an interesting thread, I purchased a used coach almost a year ago and In talking with the the gentleman that performed the maintenance (Specialty RV in Aurora Or) on the coach before I purchased it, I asked what he used for the hydraulic system in regards to the steering system and cooling system fan, he told me that he used the AW-46 hydraulic fluid when he serviced the system in regards to changing out the filter, I’ve looked at the service records that we were given at the time of the purchase  the owners manual says ATF Dexron III. I wondered about using TranSynd to reduce the different types of fluids to carry on board in case you’d need any on the road. I’m going to suck out some fluid and see what color it is, I’m guessing it’s going to be red, I looked through all of the service records I was given and it appears that the hydraulic fluid has never been changed out, I know the filters have been changed, at least I know the filters have been changed!

From someone that spent way too much time on this when I had 5 gallons of AW46 on hand, based on MY manual and three Nelson filters (based on the most common variety of posts....for the OLDER, larger Nelson reservoirs).  TWO OPPS.  Mine was the newer, smaller SINGLE FILTER Nelson....and I did have the RIGHT one....just 2 too many.  RED ALERT.  Mine was definitely ATF.  Manual said AW 46 and I had to chase all over to find the OEM Texaco....

One or two full days of chasing around with Monaco, TRW, the pump and hydraulic motor vendor and also some "revisiting my days in maintenance".  I changed the filter in the Nelson, as well as the Pressure spin on Hydraulic (not ALL Monaco's have them). I siphoned out the old fluid as I did not want to "Crack a line and drain".  I used the Transynd as the recommendation of TRW (I have their Steering box) as TRW had switched to ALLISON Transynd (or TS 295 - MEMORY? of the approved Transynd equivalent) as the ONLY fluid for their "High Mileage Warranty".  The pump and hydraulic vendor said that mixing AW 46 with ATF was a NO-NO....but it had been done in an emergency....and that using Transynd or ATF in an AW 46 System was OK....and eventually, you would get switched over....but DRAINING and refilling with ATF was the recommendation.

As Frank pointed out, we HAVE had failures with the AW46 on super cold mornings. The minute amount of moisture that can "live" in the AW46 caused....MEMORY...at least 10 or so failures.  Typically on startup in the AM when the temps hit ZERO or around that....maybe lower. That was why Monaco supposedly changed circa 2005 tp ATF.  Frank's MH is living proof that Monaco must have found a drum or two and used it up.

Our old buddy, for you oldtimer's, JIM (Monaco Tech Support) told me that they changed to ONLY AFT circa 2005 and that the "tech writers" never got to the floor or knew what was going on.  That is a DIRECT QUOTE....

I vote for Transynd and will probably never change mine again....as I have TWICE and have 67K on it....

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It's been a while since I started this thread.  Thank all of you guys for your input.  I've done quite a bit of reading on fluid compatibility since then.  As I mentioned, my 2006 Manual recommends Dexron III for the power steering fluid.  (as well as hyd. jacks)  The hyd fluid in my PS reservoir has a light yellowish color, with just a tinge of red.  I was under the coach yesterday looking at the draglink and noticed a drop of liquid hanging on the low section of one of the hoses from the steering box.  I dabbed it with my finger and it was red.  My best guess is that originally the PS system was filled with Dexron III, per the manual, but somewhere along the way someone switched it out with AW 46 or possibly even Transynd 295.  I'm not sure about the Transynd 295, but I have read that the newer Transynd 668 is red right out of the jug, but then turns to a light yellow after use.  ( this color change was confirmed by an ex-Allison engineer)   This same engineer said that, without a doubt, Transynd 295 or 668 is totally compatible with Dexron III.  I'm sure a lot of you guys have heard of the 2-step drain & refill on the Allison trannys to convert from Dexron to Transynd.  The way I see it, if you can do that with an Allison tranny, you could surely do the same with a PS system.  So I'm thinking that I will just pump out all of the hyd fluid that I can out of the PS reservoir and replace it with Transynd 668, drive the MH a couple hundred miles, pump it all out again, put the new filter in and fill it with the T 668 and rest easy.  One advantage of doing this (as well as my hyd jack system) is that I will only have to carry one jug of spare fluid for topping off my transmission, power steering and hyd jacks.  Please let me know if you think I'm on the right track or not.

Thanks, 

Carey

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52 minutes ago, Idoc57 said:

It's been a while since I started this thread.  Thank all of you guys for your input.  I've done quite a bit of reading on fluid compatibility since then.  As I mentioned, my 2006 Manual recommends Dexron III for the power steering fluid.  (as well as hyd. jacks)  The hyd fluid in my PS reservoir has a light yellowish color, with just a tinge of red.  I was under the coach yesterday looking at the draglink and noticed a drop of liquid hanging on the low section of one of the hoses from the steering box.  I dabbed it with my finger and it was red.  My best guess is that originally the PS system was filled with Dexron III, per the manual, but somewhere along the way someone switched it out with AW 46 or possibly even Transynd 295.  I'm not sure about the Transynd 295, but I have read that the newer Transynd 668 is red right out of the jug, but then turns to a light yellow after use.  ( this color change was confirmed by an ex-Allison engineer)   This same engineer said that, without a doubt, Transynd 295 or 668 is totally compatible with Dexron III.  I'm sure a lot of you guys have heard of the 2-step drain & refill on the Allison trannys to convert from Dexron to Transynd.  The way I see it, if you can do that with an Allison tranny, you could surely do the same with a PS system.  So I'm thinking that I will just pump out all of the hyd fluid that I can out of the PS reservoir and replace it with Transynd 668, drive the MH a couple hundred miles, pump it all out again, put the new filter in and fill it with the T 668 and rest easy.  One advantage of doing this (as well as my hyd jack system) is that I will only have to carry one jug of spare fluid for topping off my transmission, power steering and hyd jacks.  Please let me know if you think I'm on the right track or not.

Thanks, 

Carey

I was not aware of a new Transynd.  You are making the right choice.  I would call TRW, as I think that you have that….but you can’t tell without knowing.  If you have your build sheets, it might say Dana or TRW for the steering gear.  They can tell you if the original Transynd would be better or the newer one.  TRW a did not do any research, they piggy backed on Allison and said….this stuff is GOOD.

https://www.castrol.com/content/dam/castrol/country-sites/en_us/united-states/home/commercial-vehicle-oils/castrol-transynd-668-brochure.pdf

OK….read the specs.  Since you are going from the ATF with maybe some AW46, I personally would stick with the TES 295 specs.  The Allison guy said that mixing….and draining out a reservoir of AW46 would be OK.  There might, even though the brochure be some seal issues.  So…my call.  The TES 295 is heads and shoulders better than any.  Get the Transynd….but I would also be very comfortable with the Mobil Delvac equivalent.  Some folks prefer the Castrol.  I have run the Delvac in my differential and we have had good reports on it.  
 

Your call….just my opinion.  Some of the super synthetic motor oils did have issues….so, depending on how souped up this 668 is….I would be hesitant….but not on the Transynd 295.  I swear by it.  I have done mine twice….and at 67K, I doubt I’ll do it again.

Thanks for the followup post.  It is always great to hear of a solution and what others are doing.

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Tom, myself and another member of IRV with the same setup, were considering just removing the tank filter and not replacing it. 

I haven't done it yet, and don't know if he did or not. I was hoping he would go first and report back 😀!!

That spin-on filter is 10 micron, and plenty big enough to do the job. Bonus, the head comes with a restriction gauge! 

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4 minutes ago, 96 EVO said:

Tom, myself and another member of IRV with the same setup, were considering just removing the tank filter and not replacing it. 

I haven't done it yet, and don't know if he did or not. I was hoping he would go first and report back 😀!!

That spin-on filter is 10 micron, and plenty big enough to do the job. Bonus, the head comes with a restriction gauge! 

It was a dual design and you probably have the single.  I’d put in a new one to catch any particulates or whatever and not plug up the spin on.  The last time, I on,Yd did the internal.  That’s my take

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Yeah, but the spin-on is far easier to replace 😉!

I understand your trepidation of going rouge like myself, but I'll bet that Nelson filter in the reservoir that you replaced, is just another 10 micron filter!

Of course, you have two more brand new filters to use up 🙂!  

Edited by 96 EVO
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If I have another filter on the power steering system other than the one in the hyd fluid canister in the back of the coach, I am not aware of it.  So, I'm betting that I have the "single" system that Tom referred to above.  By the way, Tom, I apologize for sending you the link to the Transynd 668 spec sheet after you had sent it to me!  Somehow I just missed it in your post 🤔, a case of "couldn't see the forest for the trees".  I am definitely going to put a new filter in the PS reservoir, but not until I do the second drain & refill.

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11 hours ago, 96 EVO said:

Yeah, but the spin-on is far easier to replace 😉!

I understand your trepidation of going rouge like myself, but I'll bet that Nelson filter in the reservoir that you replaced, is just another 10 micron filter!

Of course, you have two more brand new filters to use up 🙂!  

Don't ask me WHY I have the second, much more efficient and useful spinon....it ain't a high end MH....but it has it.  Actually I have only ONE left....and will keep it.

You understand me.  I am an Engineer....and I like to leave things like the "hopefully well educated and informed" folks specified. The Nelson reservoir is SUPPOSED to have a filter.  Here is a copy and past from the Excel spread sheet on the various filters.  The Fleetguard 83804E is what I ordered and it is also known as LF637, whatever that is....the info past the Nelson is what was stamped on the reservoir....and the FG folks did not recognize 91417.... The Zinga was the original OEM filter and I used the HF6777 for it.  YES....double filtration.  I can't find a spec on the internal one.... 

Nelson Fleetguard 83804E Nelson 83804 Stamped - FG 91417
    LF637     Supercedes 83804E
Hydraulic Fleetguard HF6777 Zinga

ZSE-10

 

 

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1 hour ago, Tom Cherry said:

You understand me.  I am an Engineer....and I like to leave things like the "hopefully well educated and informed" folks specified.

           
           
           

X2,

I have the larger reservoir that supplies oil for my side radiator fan motor and steering.

Hydraulics are pretty complicated, lots to take into consideration.  Just throwing this out there but I don't believe my fan motor & power steering circuit have any type of cooler.  So I think the cooler might serve two purposes, cooling and as an expansion tank.  The tank has a dipstick and sight glass which allows for some void at the top of the tank.  It takes ~4 gallons of oil.  This amount of oil does expand quite a bit when it gets hot so the tank allows for this.  My guess is if the tank was replaced with a spin on filter the system could pressurize and seals in the motors could fail.  Not a chance worth taking.  If you don't have a side radiator and only the power steering circuit it might be OK but even still there is usually a small reservoir on most systems. 

I know my manual says to drain only enough oil to expose the last filter by loosening a fitting at the bottom.  But I decided to just go ahead and drain all the oil to get a good look at the tank.  IMHO I believe this is better in that the way the system is designed.  The oil is drawn through the filters via the suction line.  The oil is returned to the reservoir by two return lines located outside of the filter base.  If you only drain enough oil to remove the last filter there is potential for contamination to be disturbed and migrate into the large suction line.  By completely draining the tank this reduces the chance of contamination. 

Thinking back over the years and I can't remember any type of hydraulic system/circuit that did not have some sort of reservoir.  Allowing for expansion due to heat is pretty much standard engineering best practice.  Fluid Dynamics in college has formula's to calculate expansion. 

Edited by jacwjames
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