350B Loader Control Valve Leaking

[Kaiverol]

My control valve assembly has had a substantial leak for as long as I have owned this machine. So much so that I could not pinpoint where it leaks. I certainly feel that the return side hoses and fittings are also suspect. Therefore I have started the process of disassembly. However, I don’t know how I can/should undo the bottom connections from the steel lines. The fittings are 1 1/8” and 1 1/4” wrench sizes and I have multi angle (including 90 degree) wrench’s. I had a quick look and did not think I could get at them all.

[Kaiverol]

Hopefully I got this photo inserted.

Are these OEM fittings?

[Kaiverol]

[Kaiverol]

Last try.

[original possum]

Chances are your leak is on the low pressure side. You can use hydraulic-compatible hose on that side of the control valve. There is a great temptation to use a close nipple where you have a fitting but you should use the threaded end of a pipe, cut off so that you also have some smooth pipe inside the rubber hose. Then use two clamps if possible, one over the threads, which help keep it in place, and one over the smooth part to prevent leaks. Clamping only over the threads may leak at some point.

[Kaiverol]

Good to know that threaded pipe is ok. I will ensure that I double hose clamp and ensure there is smooth pipe to clamp to. I believe that was already the case, but I have not removed all hoses yet to see.

[LeonardL]

You can access those large lines to the control valve by removing a small sheet metal panel that is located underneath the hydraulic tank and righthand box. One corner of this panel is bolted to the corner of the steering clutch housing and the other end bolts to the seat frame. Remove this panel and you will have a lot better advantage on those two lines.

[Kaiverol]

Sounds good. I had looked to see if anything unbolted, but did not scan all sides very well.

[Kaiverol]

I was able to get the control valve out by undoing the steel lines at all three connections each and sliding them out of the way to get to the rear fittings. Getting a better view of the low pressure pipe fittings explained why I could not stop the leak. The one 1” npt sawed off pipe fitting on the aux valve threaded into a power beyond port fitting but it was so mangled I couldn’t imagine a hose with hose clamp sealing properly. I made a new one and threaded it on with no damage.

Today I was going to reinstall the valve and was cleaning the box before doing so. I pulled on a short hose connected to the three ended fitting that is threaded into the reservoir and the fitting basically was not tightly threaded. This no doubt was another leak location.

The two 1” npt nipples into the three ended fitting are in bad enough shape that I should replace them as well. However, I will need to thread them on after the three ended fitting is in place on the reservoir. Therefore, I will need to cut the hose end of the nipples before installation.

I have two questions:

What is the best way to thread on a pipe (cut off nipple) without damaging it?

I just read that npt fittings shouldn’t really be reused, because they seal when the threads deform on initial installation. I can’t replace the permanent npt connection on the reservoir, so I will rely even more on sealing tape or sealant for a good seal. Am I overly concerned? Is Teflon tape sufficient?

Thanks

[Jim B]

If you use Teflon tape use care and stay back from the first thread, you don't want to get bits of tape in your hydraulic system.

Be sure any sealer you use is rated for oil service. Gasoila, Blue Magic, and Leak Lock are some good sealers.

A pipe wrench or chain wrench with good jaws and adjusted properly to avoid slipping and making burrs, are about the only way to tighten those half nipples.

[jimmydiesel]

If there is room an internal pipe wrench will work.

[Kaiverol]

Thanks guys.

I have plenty of Oatey Megaloc which is rated for fuels and oils.

I do have a good chain wrench which may fit. Otherwise I may shop for an internal pipe wrench. With a socket adapter I could tighten the two nipples from the top and the side easily.