Hydraulic Fluid Type Change

[lonestarace]

We have a 98 Newmar DutchStar on Spartan chassis w/side radiator and C8.3. Its hydraulic system is a 9 qt Verst w/Vickers V20 vane pump.

Last summer we had overheating problems on long multi-mile climbs in 90+ degree heat. So, I'm thinking about changing the type of hydraulic fluid in the fan motor/power steering.system. I'm currently using ATF which is 10w. I think the overheating was caused by too low a viscosity, which resulted in the fan not spinning fast enough to keep things cool. We were below gross wt. and weren't towing anything. I can't remember if I tried to keep the engine rpm high or low. I now know to keep it high. I'm thinking about switching to a higher multi-viscosity oil like Rotella T 15-40w, which is what I use in the engine.

I've read the pump manufacture recommendations
http://hydraulics.eaton.com/products/pdfs/E-FDGN-TB001-E.pdf

Now we would appreciate your recommendations?

Thanks
Don, Lisa, and Alexa

[jimkate]

I don't know if the oil viscosity has anything to do with your overheating. Also, I think that ATF has a viscosity of 8W. Somebody else may know better.

I think that a multi-viscosity oil makes more sense. In mild weather, a 15W40 oil would work well. In really cold weather, possibly a 5W30. And certainly, if your hydraulic system is running hot, an oil capable of maintaining a higher viscosity makes a lot of sense to me.

I think motor oils have become quite sophisticated. The hydraulic valve lifter used in all modern engines is as precise a mechanism as any hydraulic component. For a hydraulic valve lifter to function properly, the oil must be able to maintain it's viscosity, cold and hot, not foam when churned and heated. Personally, I suspect that today's motor oils are a good choice to use in our power steering/hydraulic systems.

Jim Sanderson
Canada, eh?

[RV Wizard]

You need to find out what hydraulic fluid the system was designed for. My 99 Spartan chassis uses AW-46 hydraulic fluid; NOT ATF. You need to get the right fluid in the system. Have you cleaned the fins on the radiator? Has the coolant system been maintained properly? Has the transmission been maintained properly? Has the engine actually overheated; or has the gage shown it to be running hot?

[jimkate]

There's a fairly broad range of acceptable oils for the Vickers V20 hydraulic pump. I think your website link covers it pretty accurately. We don't use AW46 oil where I live, because it's just too thick on our cold mornings, causing pump cavitation damage and blown seals.

The AW (Anti Wear) oils are available in different viscosities, down to AW10 I believe. But again, using AW10 brings us back to the same problem as using ATF. OK cold, but possibly much too thin when hot. The fact that some manufacturers are using a 46W oil could indicate that the hydraulic pump needs a heavier weight oil when hot.

I still think a multi-viscosity oil is worth considering. I haven't seen it available in anything other than engine oil.

Jim Sanderson
Canada, eh?

[Cruzer]

Our '04 Bus with a side radiator/400 ISL Freightliner chassis ran very hot on mountain grades. FL had a number of service campaigns regarding this and one of them was to replace the Dexron III with 15W-40. The reasoning was that the Dexron II thinned out too much, but the real issue was an undersized radiator at 1,050 sq in of area. This band-aid fix didn't do anything. In fact they started blowing oil coolers because the cooler couldn't take the pressure from the thicker oil. So, the next campaign was to replace the oil coolers with heavier ones.

Our '07 Bus with a side radiator/400 ISL Spartan chassis never overheats. But then it has a 1,326 sq in radiator that is vertically stacked rather than in-series like the Freightliner. It comes with AW46 hydraulic oil. I run it in all temperatures and have never had any issues with it being too thick, and it gets plenty cold up in Wisconsin. The hydraulics aren't a high wear situation like an engine and by the time you use them things are reasonably warmed up.

We use AW hydraulic oil in our construction equipment. Dexron works for some applications but even our Cat loaders that do snow removal use AW46 oil. The AW stands for "Anti Wear" and is designed for hydraulic systems. Dexron works too but it is thin and won't adequately protect the system if it gets good and hot. Both Dexron and AW oils are design for hydraulics and have anti-foaming features. 15W-40 is engine oil and is designed to clean engines so it has higher detergent ability. For that reason alone I would shy away from using engine oils in a hydraulic system. They can foam too easily in that application and foam contains air, which doesn't do a very good job of lubricating.

[lonestarace]

Thanks for the input

We live in hot TX, and we go skiing in Colorado too, so we need a fluid that can get the job done in both worlds(multi-viscosity). I'm also considering 100% synthetic Amsoil motoroil(SSO 10-30w) like we run in our daily drivers.

We've owned our 98 DSDP for 18 mths and don't know its full history. We've put 22,000 100% reliable fun filled miles on it. The odometer currently reads 73K miles. I drained and replenished the antifreeze shortly after we bought it, and the water filter gets changed every 6,000 miles. The trans fluid(Mercon) a filters(from Allison) were changed early last summer as were the 2 engine thermostats(180 degree). I don't let the engine overheat, but it tries to. A buzzer starts sounding at 215 degrees The tranny temp follows the engine temp. The tranny has a heat exchanger plumbed around the outlet side of the radiator. We've had the hyd cooler and CAC off from in front of the radiator and we cleaned everything.

Last summer Spartan sent us the DTS hyd. system training manual. They said my coach originally came with Mercon ATF but some owners have switched to #AW32. When we changed the hyd fluid and filter last summer, red ATF is what came out of it, and is what we put back in it. Spartan said hyd fluid#AW32 is also equivalent to Mercon ATF. The owner of a local hyd shop told us that #AW32 & Mercon ATF is equivilent to 10w, and #AW46 to 20w. He said most folks around here use #AW46.

We realize that there are many things that could be causing the engine to try to overheat on long hot multi-mile climbs in the western USA and locally in hot stop & go traffic. We like to start with inexpensive DIY fixes for first.

Even our Spartan chassis manual it states that our situation might occur.
In the end it may be that the radiator is too small for the extreme conditions? but well try to find a cure.

Don, Lisa, and Alexa

[jcthorne]

You are talking hydralic fluids here. Going to a motor oil and a heavier viscosity at that will make your problem WORSE. The thicker oil will have higher pumping and plumbing system losses and result in a less efficient hydraulic system. You want the thinest oil that will do the job of protection and lubrication you can use. Likely what was originlly in there MERCON ATF is about as good as you will get for this application.

You have a cooling problem, not a hydraulics one. You either need more air flow or more surface area to increase cooling. If this only happens on long hill climbs, my recomendation is that if the system is all in top notch working order, leave it alone and slow down a bit.

[DAN L]

Quote:

Originally Posted by lonestarace Thanks for the input We live in hot TX, and we go skiing in Colorado too, so we need a fluid that can get the job done in both worlds(multi-viscosity). I'm also considering 100% synthetic Amsoil motoroil(SSO 10-30w) like we run in our daily drivers. We've owned our 98 DSDP for 18 mths and don't know its full history. We've put 22,000 100% reliable fun filled miles on it. The odometer currently reads 73K miles. I drained and replenished the antifreeze shortly after we bought it, and the water filter gets changed every 6,000 miles. The trans fluid(Mercon) a filters(from Allison) were changed early last summer as were the 2 engine thermostats(180 degree). I don't let the engine overheat, but it tries to. A buzzer starts sounding at 215 degrees The tranny temp follows the engine temp. The tranny has a heat exchanger plumbed around the outlet side of the radiator. We've had the hyd cooler and CAC off from in front of the radiator and we cleaned everything. Last summer Spartan sent us the DTS hyd. system training manual. They said my coach originally came with Mercon ATF but some owners have switched to #AW32. When we changed the hyd fluid and filter last summer, red ATF is what came out of it, and is what we put back in it. Spartan said hyd fluid#AW32 is also equivalent to Mercon ATF. The owner of a local hyd shop told us that #AW32 & Mercon ATF is equivilent to 10w, and #AW46 to 20w. He said most folks around here use #AW46. We realize that there are many things that could be causing the engine to try to overheat on long hot multi-mile climbs in the western USA and locally in hot stop & go traffic. We like to start with inexpensive DIY fixes for first. Even our Spartan chassis manual it states that our situation might occur. In the end it may be that the radiator is too small for the extreme conditions? but well try to find a cure. Don, Lisa, and Alexa

i suggest you try amsoil hydraulic fluid.
https://www.amsoil.com/a/Synthetic-Hydraulic-Oil

[lonestarace]

I hadn't seen the Amsoil hydraulic multi-grade 5-30w before.
We'll give it a try
Thanks

[lonestarace]

Our other MHs hydraulic system holds 12 gals. This one 3 gals.

Wrong fluid type for the conditions, too little quanity, and too small of a hydraulic cooler are my guesses as to what the problems are.

We'll start by switching to a better fluid, Amsoil Synthetic Hyd 5-30w. If that doesn't work, then a bigger cooler.