Adding fluid to Hynautic steering (48YF)

[silverpaul]

I assume I have Hynautic steering as there is a cylindrical reservoir with a sight glass and pressure gauge. My question is where to add fluid? The bicycle valve is threaded into a large (7/8?) nut but that is all there is on the top. I tried loosening the nut and the valve but both were extremely tight and I stopped before I broke something as I did not have the correct sockets available only adjustable wrenches. The fluid is about half full and the pressure was at 15 psi.

I searched this forum and read a lot about the choice of fluid and was surprised to see in my Hatteras owners manual they advise ATF type A not the hydraulic fluids (Mil spec or Teleflex) that I have used in previous boats.

Paul
FREEWAY
48YF Oxnard CA

 

[bobk]

Usual advice for these situations. Soak a day or two with PB Blaster and use a large socket or box wrench. Or an impact wrench. Sometimes tightening a bit allows it to be loostened. On my 48MY I use the mil spec fluid.

Bobk

 

[Canuck Dennis]

How do you tell what's in there to start with, I doubt you can mix mil spec with ATF A ??

 

[Bugsy]

I think the answer to your question is; "Yes. You're at the right spot. That nut comes off and that is where you fill the reservoir." I suggest that you follow the manual which is express.....do not use ATF --I think it says Detrol for emergency use only.
I think recommended psi is 25-30 but again...check manual.

 

[SKYCHENEY]

That large plug has a rubber seal on the bottom and can be in there very tight. Get long wrench and loosen it. It will break free. The proper fluid is Hynautic fluid or mil spec 5606.

If you have a leak, you need to find it. Don't just keep adding fluid. It will only get worse.

 

[silverpaul]

Thanks for all the info. I was concerned about using WD-40 or some other penetrating oil in case it got in the reservoir - just be careful I guess. The fluid in there appears reddish from the sight glass so I was assuming ATF. I would like to add clear Teleflex fluid that I have - anyone know if mixing is a problem?

Thanks,

Paul

 

[SKYCHENEY]

Thanks for all the info. I was concerned about using WD-40 or some other penetrating oil in case it got in the reservoir - just be careful I guess. The fluid in there appears reddish from the sight glass so I was assuming ATF. I would like to add clear Teleflex fluid that I have - anyone know if mixing is a problem?

Thanks,

Paul

The Texaco Mil Spec 5606 that I have is red as well. Don't assume it it ATF just because it is red.

 

[sgharford]

Anyone ever figure out a simple test to determine if Mil Spec 5606 or ATF? I assumed I had 5606 in mine, so that's I topped it off with.

 

[Persystor]

Do I have to re-pressurize after adding fluid? Why the PSI guage?

 

[racclarkson@gmail.com]

Do I have to re-pressurize after adding fluid? Why the PSI guage?

Yes you do. The pressure forces the fluid into the system. Unless you need to bleed, 15-30 PSI is recommended.

 

[Jammin']

We are getting ready to transport our boat home and my mechanic tells me I must have a hand pump on board to repressurize the Hynautic steering, if necessary, to 20 - 25 lbs.

 

[rsmith]

The reason the system is pressurized is to keep air out of the system not to force fluid anywhere. If you think about it the system is all at a static uniform pressure. This keeps the seals under pressure and sealed. If there is any minor leaks it’s leaking out and not letting air in. Once air gets in the system even the slightest bit the helms get air bound and cavitate.

 

[racclarkson@gmail.com]

The reason the system is pressurized is to keep air out of the system not to force fluid anywhere. If you think about it the system is all at a static uniform pressure. This keeps the seals under pressure and sealed. If there is any minor leaks it’s leaking out and not letting air in. Once air gets in the system even the slightest bit the helms get air bound and cavitate.

And how is this air kept out of the system? It is displaced by fluid from the reservoir that just accumulates there until the added air pressure pushes it into system to displace the air. And, minor leaks do allow air in when reservoir pressure is low allowing fluid to accumulate there.

 

[31FlyCruzr]

If it ain't broke don't fix it!

Do you have a leak, are you loosing pressure? I would pump up to 25 psi and keep going if it is working properly.
Half a reservoir is plenty of fluid.

Pressure is needed to push the fluid up to the helm pumps, it is static head for the three line system to keep air out.

Bill

 

[rsmith]

And how is this air kept out of the system? It is displaced by fluid from the reservoir that just accumulates there until the added air pressure pushes it into system to displace the air. And, minor leaks do allow air in when reservoir pressure is low allowing fluid to accumulate there.

Nooooo the reservoir just maintains pressure on the system. Air can not enter the system as long as there is any pressure. Fluid leaks out until the pressure in the reservoir is 0. Extra pressure in the reservoir doesn’t do squat as long as their are no leaks. RTFM

 

[racclarkson@gmail.com]

Well I have the manual, useful. Regardless of theory, air can find its way into a system that shows no visible leakage when the reservoir air pressure is low. It’s helpful in such situations that Seastar has good technical support. They point out making a system air tight can be more challenging than making it fluid tight. They specifically note that difficulty in very old systems, when not in use and with insufficient air pressure, where fluid tends to drain back to reservoir creating a void. “Nature abhors a vacuum.” Hence, keep the pressure up to force fluid into the system to prevent voids. Their advice.

 

[davidwigler]

The fluid is about half full and the pressure was at 15 psi.

Half full is fine. There should be a fill line below half full. What is the problem?

Don’t fill it. It needs air to pressurize the system.

 

[Pascal]

Air should not enter the system unless there is a leak as hydraulic steering is designed to be sealed. Many smaller boats (single helm) don’t have a reservoir and are simply filled by gravity at the helm pump. Works fine for years without air coming in.

 

[Dan Mapes]

We lost steering in the Bahamas while docking. All along the years we had the boat the gauge indicated 25psi. As it turned out the gauge froze and air got into the helm because there was no pressure. I will suggest an occasional test that cycles the air gauge.

 

[rsmith]

Well I have the manual, useful. Regardless of theory, air can find its way into a system that shows no visible leakage when the reservoir air pressure is low. It’s helpful in such situations that Seastar has good technical support. They point out making a system air tight can be more challenging than making it fluid tight. They specifically note that difficulty in very old systems, when not in use and with insufficient air pressure, where fluid tends to drain back to reservoir creating a void. “Nature abhors a vacuum.” Hence, keep the pressure up to force fluid into the system to prevent voids. Their advice.

Mr Clarkson we’re talking Hynautic not Seastar Sea star is a completely different system that is unpressurized. The reservoir is in the steering head where any air in the system is supposed to collect.