AP Ram Hydraulic Fluid

[kev_rm]

My ram calls for some very expensive and hard to find oil, which I have dutifully obtained, ($25/quart)

but I am wondering, in a pinch, I'm leaking, and I have several quarts of ATF on board.. would ATF work?

[tkeithlu]

I'll bet that it will, and yes, I'd try it in that situation. Within my limited experience, cleanliness is critical in an autopilot hydraulic system, given those tiny spring-loaded valves. But then, my Simrad AP has been running on the ordinary tractor-level hydraulic oil that I feed to my leaky steering for the last six years without complaint. The system is not particularly high pressure or high heat.

There may be someone on the forum with more technical expertise than mine on this topic. I think I hear a "OMG HOW COULD YOU" somewhere in the background noise.

[rslifkin]

CHF 11S is thinner than most ATF if I'm remembering correctly, so that could be a concern. Not sure if there would be any seal compatibility issues.



I know at least some European cars (BMW, for example) use CHF 11S in hydraulic suspensions and power steering. Supposedly bad things will happen if you use ATF in that application, although the non hydraulic suspension versions of the same cars use ATF in the power steering.



Because of the automotive applications, it shouldn't be as hard as you might expect to find the stuff if you're ever in need. Anywhere that sells parts for European cars is likely to have it.

[fred1]

This reply is not a direct response to your problem but I wanted to put it online as an FYI for boaters in my situation. My upper helm station steering wheel became unresponsive, just turned freely and not moving the rudder or rudder indicator. The lower station was still working but the wheel was turning to freely. Both stations are on one hydraulic loop. So in checking the fluid level (directly in front of the upper helm steering wheel in my boat) it was low. The hydraulic steering system is a Lecomble & Schmitt (French) and calls for "Dexron or ATF" with a viscosity of 22.

At West Marine none of the ATFs showed their viscosity on the labels so I went with Startex hydraulic fluid......and it mixed with with the current lubricant fine and steering is great. I just filled it very slowly as I turned the rudder back and forth slowly from post to post.

[tkeithlu]

Your experience parallels mine, Fred. My system leaked for six years. I finally found and solved the problem recently, but until then I fed a bunch of tractor-level hydraulic fluid into my Lecomble & Schmitt helm pump, Simrad AP, and Surplus Center double acting steering cylinder. Back and forth the wheel does go... I did once have the AP complain about a dog hair in a tiny spring loaded valve, which I flushed out, but never any problem with being fed cheap stuff, despite the French helm pump.

[Chotu]

Here you go! Straight from the manual, which I just got.

[RaymondR]

Automatic transmission oil appears to work quiet well as well.

[Chotu]

I’m even more impressed that in an extreme emergency, ANYTHING works. Gallon of milk, gallon of water. Not a bad plan for an extreme emergency.

I got the SeaStar hydraulic steering fluid of course, but I was quite surprised when reading the manual.