Hydraulic System Operating Temp

[10lemonsk]

I have a 2003 Monaco Signature with the 525 ISX and an Allison 4000. A few months after purchasing this motorhome, I experienced a severe PTO failure that left me stranded, so I've recently replaced both the transmission-driven PTO and the hydraulic pump on the motorhome. I have also drained and replaced the hydraulic fluid with Dexron III (per owner's manual), completed a full servicing on the transmission, and installed a source engineering wax valve kit among other things.

My engine now stays below 205 degrees, and my transmission usually stays in a 200 - 230-degree range. However, after completing the aforementioned servicing and taking the motorhome on a 1-hour test drive in the 100-degree Texas heat, I shot my hydraulic pump & fittings with a laser temp gun and they read around 190 degrees. A quick google search for hydraulic systems in general would lead me to believe this is running wayyy too hot, but can anyone else here with a similar set up shed some light on the normal operating temperatures of their hydraulic systems?

I'm very concerned about a repeat of the PTO and pump failure, so I appreciate any help. Thanks.

[Chad A]

I am following this closely. I have the same coach and just recently had a Pto leak. I also think my transmission runs to hot at the same temperatures yours does. 

[vito.a]

I have not measured the hydraulic fluid temperature, but I know it runs fairly hot.  It has to power the two large engine cooling fans.

I had to rebuild the hydraulic pump and reseal the pump to PTO gasket.  I also had a leak in the PTO lube hose from the transmission.  

The total hydraulic fluid capacity is 50-55 quarts.  Also, there should be a hydraulic fluid cooler in the radiator stack.  

 

[Tom Cherry]

4 hours ago, 10lemonsk said:

I have a 2003 Monaco Signature with the 525 ISX and an Allison 4000. A few months after purchasing this motorhome, I experienced a severe PTO failure that left me stranded, so I've recently replaced both the transmission-driven PTO and the hydraulic pump on the motorhome. I have also drained and replaced the hydraulic fluid with Dexron III (per owner's manual), completed a full servicing on the transmission, and installed a source engineering wax valve kit among other things.

My engine now stays below 205 degrees, and my transmission usually stays in a 200 - 230-degree range. However, after completing the aforementioned servicing and taking the motorhome on a 1-hour test drive in the 100-degree Texas heat, I shot my hydraulic pump & fittings with a laser temp gun and they read around 190 degrees. A quick google search for hydraulic systems in general would lead me to believe this is running wayyy too hot, but can anyone else here with a similar set up shed some light on the normal operating temperatures of their hydraulic systems?

I'm very concerned about a repeat of the PTO and pump failure, so I appreciate any help. Thanks.

There is an alternative that TRW suggested…. They have adopted the Transynd ATF fluid for their “long run” warranty.  This was circa 2012 and I needed to service the hydraulic system.  My manual, GOD FORBID, was wrong,  i bought a 5 gallon pail of Texaco Ranco (memory) HD46 OIL….per the manual.  OPPS….no OIL in my system.  ATF.  I called the pump and fan motor vendor and TRW.  Wanted to mix.  NOPE…not good.  TRW told me to UPGRADE to Transynd….and then keep doing that.  I don’t know the total capacity, but I sucked out the ATF in the reservoir…maybe 2 gallons and replaced the drop in filter.  I have a spin on pressure filter and put in a new one, prefilled with Transynd.

TRW had a bunch of employees that had worked at Allison.  They knew the costs of developing a proprietary ATF…and said…TRW has spent the big bucks.  We won’t and then rewrote their service manuals and warranty to specify TES 295 (memory), but they recommend “OEM Allison Transynd”.  That is good for 250 dF.  

My electronic system keeps my engine and transmission at 195.  So, I have not had to install the Source wax kit…

BUT, if I ever had to service your system, I would replenish, hot wholesale replace, with TES 295…Mobil Delvac or genuine Allison…

My thoughts and what I was told…

[96 EVO]

Allison builds transmissions. They don't make transmission fluid!

They leave that job to select oil companies, that meet their requirements.

Edited August 29, 2023 by 96 EVO

[Tom Cherry]

12 hours ago, 96 EVO said:

Allison builds transmissions. They don't make transmission fluid!

They leave that job to select oil companies, that meet their requirements.

Sort of.  Allison did the testing, with either a lab or in partnership with a company.  Castrol is the only “official Allison Transynd” or Allison “branded” fluid…over 20 years or so.  My comment was about TRW’s decision not to develop a proprietary and recommended ATF when Allison had already done so.  Their logic….it sould impossible, based on the operating and warranty and track record to compete, much less dethrone Allison and that the Allison distributors or certified shops also work on other items, such as TRW products.  Thus, why rediscover America.

Now this is a bit more history that was covered on the Yahoo site.  There are THREE types of TES 295.  

Castrol TES 295 and they are the licensed and OEM Transynd

Allison APPROVED Manufacturers and are listed on the Allison site.  These companies purchase the license…but it is NOT a “rubber stamp”.  They have to submit samples and also, perhaps, random samples or QC verification materials.  Allison runs a tight ship on this…so as not to let a “less than reputable” company cause problems.

Non Licensed or Approved TES 295. The manufacturer obtains independent certification that their product meets the TES 295 specs.  Based on some very credible information from folks in the “oil patch”, the lab certification is much cheaper than going the “Allison Approved & Licensed” pathway.

The term “licensed” is perhaps not correct…but in order to be listed among the names and manufacturers that can use the Allison “seal”, the approval and perhaps annual submission of samples to ensure all parameters are met is somewhat expensive and many TES 295 manufacturers choose not to incur this expense 

Therefore many members chimed in and the discussion was around what to buy and was there significant savings vs the risk.

Mobil Delvac is one that I have confidence in….and they are listed on the approved Allison list.  i use their synthetic gear oil in my differential.

Now you know.  Thanks for the comment as this discussion and past “history” has not come up and we feel it is beneficial for folks to understand the various types or levels of certification….

FWIW to sort of tie up loose ends….there was a major discussion on changing out differential oil and going to a synthetic.  One or two members were almost infomercials on a really popular synthetic gear oil that would do everything but cure the common cold.  But if you read their advertisements and looked at their webpage, no “heavy duty” bus or truck comments.  When pressed, they advised it was for SUV, light truck, high performance, etc….and not recommended for OTR MH or rigs.  That is why the site staff tries to make members aware of the proper specs or grades or types of lubricants, oils, coolant, etc. that the OEM vendors require.  Too many have bought brand name coolants designed for automobiles, but not for our Cummins engines….

[10lemonsk]

Thanks for the help, guys. I found some additional information that may be helpful if someone else is curious. QCC (who distributes the aftermarket Sauer Danfoss CP series hydraulic pumps) says that with the standard seals "the system temperature should not exceed 180° F (82°C) except for short periods to 200° F (93° C)", see attached and CP180_0601512.pdf (qccorp.com). I'm going to look into ways to monitor temperature and pressure for this system to make sure I'm not exceeding these limits. 

Also, Chad, I'm concerned about the transmission temps too. I came across the below post that may be of interest to you. This guy installed an external cooler for his transmission that seems to have helped keep temps down and wasn't terribly expensive. I'm planning on looking into this further soon.

 

[timaz996]

I guess I'm lucky, my engine doesn't bust 195 and the trans 188 even on a long steep climb. I use TES 295 and it holds 5 gal.