Hydraulic System Pressure

[HollemanA]

I have searched the Forum but not found this problem discussed. So please forgive me if I missed finding the discussion.  My 08 Marquis with 600 Cat has experienced 3 failed hydraulic radiators and one spin on hydraulic filter failure in the 5 years and 53,000 miles I have driven. Two of the radiators failed at welded seams badly enough for fluid to flow freely and one had a tube blow open. The spin on filter sprang 2 leaks about 1" apart and large enough to squirt fluid several feet.  I just had a 2006 Marquis with same engine and hydraulic system park next to me and he is on his 3rd hydraulic radiator, so maybe it is not just my bad luck.
My hydraulic pump was a Sauer Danfoss but after this last radiator failure I replaced it with a QCC, which is an exact replacement.  The pump is driven off the Alison 4,000 transmission. I have never had an engine heating problem or any issues with the power steering except when I experienced the failures.
Has anyone else experienced these failures or does anyone know of a solution?
Thank you,
Art Holleman
08 Marquis

[Gerald Farris]

Art,
The only issues that I am aware of with hydraulic cooler failures is related to the AW 46 oil that is used in the hydraulic system. It is too viscus (thick) for use in the system in cold weather and causes excessive pressure in the return side (cooler and filter). I think that Monaco cautioned about this problem in your owner's manual and suggested changing to a lighter weight oil in cold weather.

Gerald

[Dave Atherton]

Art, the problem does not sound like thick oil, but what it sounds like a restriction on the return
oil. You indicate oil cooler failures and a spin on filter but did not mention what system pressure.
Possible pump relief valve stuck or set for incorrect pressure. What you are saying high pressure
has caused failure 3 times and damage. My suggestion connecting up a hydraulic flow meter into hydraulic system at hydraulic shop or Cat shop, check for hydraulic flow, system pressure and
system back pressure. Your system back pressure cannot exceed 25% of system pressure, that
would be likely cause of your problem. How far are you from Quartzsite,Az if you are anyway
near Quartzsite I do have a flow meter that can check your hydraulic system.
Dave Atherton Retired Cat Mechanic

[Larry Dedrick]

Art:
       While I can not help you with your hydraulic concern, I would like to exchange any experiences we have with our coaches since we both have a 2008 Beaver Marquis with a C-15. If there have been problems you have experienced, I certainly would like to hear about them and I would certainly share my experiences also.
       Feel free to contact me at any time.

               Larry Dedrick

[HollemanA]

Thank you for the responses! First of all my RV avoids cold weather like the plague. All my failures have occurred in warm to Very Hot weather. The last 2 were in 90+ temps in AZ.
I do not know the pressure my system is running at but I have followed the hydraulic hoses and  I do not have any kinks or sharp bends in the hoses. There are 90 degree fittings but I don't think this is unusual in a hydraulic system. I replaced the pump with the last radiator failure hoping that there was an internal problem with it.  I am currently in Moab for the rest of Oct. and headed toward Napa,CA. for Nov.
It is encouraging that none of respondents have had this problem!
Art Holleman
08 Marquis

[Dave Atherton]

Art, reading you responds and failure happened in warm weather. You mention pump replacement
which is leading to replacement pump has wrong value ( pumping to much flow which will increase
pressure within the hydraulic system ). Hydraulic pump looks the same from the outside but inside
Volume or flow can be changed very easy and even looks like kind, it is different. The tag on pump
info will relate gallons per minute and at max pressure and what rpm. Again is everything spec out
pump for system in motorhome than there is a restriction in flow ( hydraulic valve spool sticking or
too much back pressure in system. Have ran into hydraulic problems before everything looked all ok
but cannot tell by this. Would suggest looking deeper into the hydraulic pump and sticking hydraulic
spool of which can cause back pressure. one thing you can check as you are heading west, stop
a feel you hydraulic filter after running see how warm hydraulic filter is. This will tell a real lot about
what is going on. Dave Atherton Retired Cat mechanic

[Jim Edwards]

Hi Dave, Have been having hydraulic filter problems as well. Filter gasket failed ( leaving 2 gals of dextron all over my toad). Replaced filter and reset indicator. 1500 miles later I noticed the filter change indicator popped up again. What will filter temp tell me? It is warm to the touch. Thanks .

[HollemanA]

Hi Dave, The tag on the pump has a date code of 25 AUG 16 and Type CPC-1047. That is all the information on the tag on pump. The bill for the pump has that info and a description of CPC050R2AEBC.
I use a laser temp Gage to check tires and hubs  when I stop. What temp should the hydraulic spin on filter be reading?
Thanks,
Art Holleman
08 Marquis

[Dave Atherton]

Jim and Art, the temperature for hydraulic system 145 - 165 DEG F. If  temperature
gets to 177 - 180 DEG F that is when damage will start with seals and o-rings etc.
Your hydraulic pump system pressure should run 1,050 psi to 1,250 psi driving a hydraulic
motor. Your hydraulic hose should be a 2 ply hose with burst point at 2,650 psi. Another
Question into the problem, vent on your hydraulic system is it big enough to handle the
return fluid back to tank and is any fluid coming from vent or wet around tank vent. Note:
as I was saying earlier backpressure on the return oil or flow to hydraulic tank. If for some
reason the vent is too small opening or plugged the hydraulic pump returning fluid back
To tank will build pressure if air cannot escape enough to match the return fluid. Yes this
would cause the damage you have experienced. Dave Atherton Retired Cat Mechanic

[HollemanA]

Dave, the only vent for the hydraulic system I am aware of is the dip stick cap on the tank reservoir.  On my last repair I overfilled the system and fluid would blow out the fill hole when I removed the cap. The first time it blew all over me and higher up the engine compartment--so it was under a good deal of pressure. After I got the fluid down to correct level it did not blow out and has been OK since.
My question is---doesn't the system have to be under pressure to work? My understanding from the hydraulic shop that I bought the new pump from was that the pump had a pressure by-pass built in.
On the issue of temperature----I pulled the radiator almost immediately after it failed and did not notice elevated temps from either the oil or hose connections. I then bypassed the radiator and drove 80 miles and the temps were high enough to melt the plastic on ice bags I placed on the hose hoping to keep it cool  in the first 20 minutes of driving. So it can get very hot.
Art Holleman
08 Marquis
 

[Dave Atherton]

Art, we are getting restriction on return fluid or possible vent is too small for hydraulic flow
returning back to hydraulic tank. Next thing making a heater from your hydraulic system,
Looking at your hydraulic fittings coming off hydraulic pump and off the motor driving fan.
Where I'm going, connecting into new replacement hydraulic pump possible add on fittings
to connect up present hoses. Possible the ID. of hose fitting is smaller. Pushing hydraulic fluid
under pressure and pump has more volume than pump that failed ( now comes the back pressure )
and heat on return to tank. Relief valve that dumps pressure could not set up to correct pressure
and set to high. I am asking lot of questions but feel problem is, too much flow into fittings
that have smaller openings, too small hydraulic hose to handle present flow creating back pressure
In return back to tank. What you told me today extreme heat is being generated and above
is what is causing extreme heat. One thing, readjust relief valve which is part of this problem remove
castle nut on relief valve and turn outward 3 turns CCW and lock back down. The heat should be
cooler. In troubleshooting problem the use of a pressure gauge will not pickup on problem,
where a hydraulic flow meter will read hydraulic gallons per minute, hydraulic back pressure and
Fluid temperature. What your going find is a restriction in your system. Ran into this kind of
Problem several times with hydraulics. Last question is your hyd fan motor condition, a person
can tell if motor problems by removing the 3rd hose on motor body ( this is called motor case drain,
And you have stream of oil coming from this point you have a problem with fan motor. )
Dave Atherton Retired Cat Mechanic

[HollemanA]

Hi Dave, thanks for the info and guidance. It is beyond my ability to check out. Do you know of a facility in the west that could check out the hydraulic system? One other question, since the pump runs off a PTO in the Alison Transmission, could it(the transmission) play any part in this?
Thanks,
Art Holleman
08 Marquis

[Dave Atherton]

Art, yes that could be the problem, the rpm off Allison transmission is set. The hydraulic
pump is rated to provide flow of X amount gallons at X amount of pressure at certain rpm.
What could be happening the hydraulic pump is turning faster because it is not matched
to allison transmission and basic over driving the hydraulic pump. This in return is providing
excess flow that relief valve if completely backed offsetting will restrict flow making hydraulic
oil heat up. This where Dave keeps coming back to the term back pressure in hydraulic system
Creating excess heat. Have seen hydraulic pumps on engines over driving rpms because of
pulley for belt incorrect size and again creating excess heat in system. I would suggest going
to a Cat dealer where they understand use of a flow meter and connect into you system,
Than also builder of hydraulic pump on your MH get spec's gallons per minute at rated rpm.
Looking at tag on PTO on Allison will tell rpms in that area.The hydraulic motor tag will
also provide what flow and rpm it needs to run at. This is where your problem located and
Results you have experience now with heat and excess pressure in hydraulic system.
Dave Atherton Retired Cat Mechanic

[Joel Ashley]

There are several Wheeler facilities in your area, Art, but I note especially this one:

WHEELER MACHINERY CO.
1831 N. HIGHWAY 191
MOAB UTAH, 84532-0000
2.4 Miles
Driving Directions
Phone Numbers
1 435 259-1077 - GENERAL INFO
1 435 259-1087 - GENERAL INFO (FAX)
E-Mails:
MCHAPPELL@WMCCAT.COM


http://wheelercat.com/?_ga=1.200314222.1909667465.1476413258

They seem to be more into construction equipment, though.  Whether they'd work on On Highway engines, or are familiar with the process Dave suggests, I'm not sure.  They might send you east to Grand Junction Peterbilt.

I've also had good service at Warner Truck Center in West Valley, Utah, just west of Salt Lake;  they are a Freightliner facility, not a CAT dealer, but a CAT authorized service center.  I believe Dave has pointed out there is a difference. Nevertheless, I found them knowledgeable re. my engine, and they may be quite up to the use of the flow meter.

-Joel

[Dave Atherton]

Art , Wheeler Cat earthmoving can handle your problem and are a very good Cat Dealer. One
thing would not suggest Moab, Ut because is a small store that field service operates service
out of with mobile service on heavy equipment. Wagner Cat on I-70 to Grand Junction, Co which
Is 70 miles to northeast right on 1-70 west side. Than Wheeler Cat ( there main store in Salt
Lake, UT. on I-15 south and on west side of I-15 ). The Cat heavy equipment dealer will be
The best working with hydraulic problems because all the off road equipment is heavy hydraulic
useage is why Dave has related your problem as such. Thanks Joel for bringing Wheeler Cat
up for Art. Also K/W truck in Grand Junction is on same service road about one short block from
Wagner Cat along I-70. Dave Atherton Retired Cat Mechanic