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Topic: Hydraulic Tank and Fluid Replacement (Read 617 times) previous topic - next topic

Hydraulic Tank and Fluid Replacement

hydraulic0.jpg When we purchased this coach we noted there was a small dent in the face of the hydraulic tank, about the size of a golf ball. The inspector felt that it was likely caused by the engine door hitting it or hitting/pinching the hose from an aggressive slam. There is not much room between the tank and the door so any out of adjustment may have caused an issue, and it was just cosmetic.

The tank had other cosmetic issues, flaking paint and rust on both the cover clamp and the mounting clamps. It also looked like someone may have applied Ospho or similar and then did nothing. Anyway this is something we wanted to clean up.

Going through the service records there was no mention of the hydraulic fluid or filters having been changed. Granted it is a sealed system, but with potentially 25 years, it is enough service life.  We decided it was time to do its oil/filter change and while doing that clean up all the cosmetic issues as best we could.

Drain the Oil
hydraulic1.jpg To empty the reservoir we purchased an inexpensive ($8) Harbor Freight Multi-Use Transfer Pump. That worked fine but its an arm workout pumping out the 4 or so gallons of oil. Once empty I decided to fully remove the tank, so it could be given a proper spa treatment and paint job. Here is a Full Hydraulic Oil and Filter Change Walk Through that will guide you through the steps.

Sourcing replacement filters could be a challenging. The original P/N is a Nelson 84101B (10 Micron), and the only cross ref I could come up with (that was available) was Main Filter MF0066241.  There are (3) filters stacked on top of one another.  They are held down with a cone washer / spring / wing nut combination.

Tank Removal
hydraulic2.jpg hydraulic3.jpgThe hydraulic hoses loosen without much fuss, but you will need some large combination wrenches or a large adjustable knuckle buster.  Once removed, the end of the hose ends were covered and then secured up high so they would not drain.

hydraulic4.jpg hydraulic8.jpgWith the tank on the ground, and the filters removed we noticed another problem. Looking inside the tank you could see the lower end bell seam was "pooched" away from the side of the tank. In that same area on the outside there was a ~1.5" gash running vertically that was nearly through the tank, just an onion skin of metal remained.  Extrapolating the obvious, it was an immovable object that someone had backed into that caused the dent. Looking further, the two "Z" brackets that go between the tank mounting and the rear wall were deformed, pushed over and back.

The tank was likely recoverable with a weld patch etc., but always good to check the internet for what is available and at what cost. Ebay came though with a NOS Nelson 16 Quart Hydraulic Reservoir Tank $100. We purchased that, and it was exactly what was in there and included site glass, dipstick, cable, etc ... Just supply your own fittings or salvage and reuse.

Fittings
hydraulic5.jpg The most difficult items with installing the fittings are
A) Getting a grip on the tank
B) Aligning the fittings so they point in the correct direction.
I made myself a hillbilly pipe wrench using a 4x4 and one of the tanks mounting clamps. This held the tank secure (added a rubber slab to help) and the 4x4 clamped into my bench vise. With that I could apply the needed grunt.  For sealing the pipe threads I used a tape and dope combination, you will need all the help you can get to tighten those large fittings and have them oriented correctly.  You can love or hate doing that, DWMYH

Tank Installation
hydraulic6.jpg The bent "Z" brackets were precision formed back to dimensional accuracy with a bench vise and engineer hammer, wack wack wack, looks good now ... wack. The brackets, engine wall, etc. got the POR15 treatment.

hydraulic7.jpg Putting it back you just reverse the process. Bolt in the Z brackets, attach the retaining rings, tank and hoses.

giphy2.gif Before filling it up with oil, in our case 15W-40 SAE 400 Plus. I decided it was a good time to change the air filter and the vacuator (duckbill) valve on the air canister. Remember what I said about someone hitting an immovable object? The air filter canister had a good bit of damage, but that's yet another adventure.
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: Hydraulic Fluid Tank Replacement

Reply #1 –
For all things pumpable having a couple of inexpensive Drill-pumps for one-use transfers helps.  Then discard pump, rather than clean it out or deal with dissimilar liquids.

Re: Hydraulic Fluid Tank Replacement

Reply #2 –
Nice job!

I hate changing the oil in that thing .
I've tried several ways and keep on thinking of putting a no spill or similar drain on it.
Frank & Daisy
NO LONGER  "looking for the perfect Foretravel
36' or less non slide preferred."  She has been found and is ours.
2003 U320 36' non slide  Unit 6103
Cummins ISM 450
Allison 4000MH

Re: Hydraulic Fluid Tank Replacement

Reply #3 –
I replaced the pump for that thing last summer and well, the retired road mechanic that helps with my service told me, he had seen  worse oil.  And I had changed it a few years back.  So.... I said how often should I change it. He said every other engine change.
  Wonder if that contributed to the pump seal going out ?
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Hydraulic Fluid Tank Replacement

Reply #4 –
Quote from: Lt403 –
Nice job!

I hate changing the oil in that thing .
I've tried several ways and keep on thinking of putting a no spill or similar drain on it.

I just siphon it out-- a 5' piece of hose works fine.

And, as a caution to those who have not changed their hydraulic filters yet, be sure to drain the tank (even if the fluid looks clean and you will reuse it) BEFORE removing the filters. If you remove the filters with oil in the reservoir, you mix unfiltered oil with filtered oil.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Hydraulic Tank and Fluid Replacement

Reply #5 –
I did super scientific research and analysis (joking) several years ago when I changed my steering and fan oil. I installed regular hydraulic fluid that is used on heavy equipment. Because it's made for hydraulic systems, instead of engines. Perhaps I gained 0.00000302mpg and moar HPerzzz. Feels like my steering is smoother too, especially after I take that placebo pill.
1998 U270 34'

Re: Hydraulic Tank and Fluid Replacement

Reply #6 –
And do not drop the wingnut as it could fall into one of the bottom hoses.
How about keeping several inexpensive drill pumps around to drain hydraulic tank, use them one-time and discard to not deal with cleaning or different liquids.

Re: Hydraulic Tank and Fluid Replacement

Reply #7 –
Quote from: Barry & Cindy –
do not drop the wingnut as it could fall into one of the bottom hoses
Good point, easy to loose your grip on that since you are also keeping the spring compressed while trying to add/remove the wingnut.
Quote from: Barry & Cindy –
keeping several inexpensive drill pumps around to drain hydraulic tank,
Looks like you get those for around $20 ... if that works it would certainly be easier than the armstrong model.  I saw some smaller hand level pump models but those only moved 2oz per pump.


For the fittings, mine were as follows (shown as connection size, check what YOU have) and cost ~$30 from the local hydraulic place. About the same price that you can find them online, for example at Hose Warehouse | Industrial & Hydraulic Hoses

  • (1) 90° Elbow, 37° 1/4" JIC Flare x 3/8" MPT (upper hose) 2024-6-4S
  • (1) 1-1/4" MPT x 3/4" FPT Hex Reducer Bushing (bottom center port) 2081-20-12S
  • (1) 90° Elbow, 37° 3/4 JIC Flare x 3/4 MPT (for bushing) / 2024-12-12S
  • (1) 90° Elbow, 37° 1-1/4 JIC Flare x 1-1/4 MPT (bottom outside port) / 2024-20-20S
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"