L4740 power steering issue

[lynrob]

Friday I took delivery of a root grapple from Everything Attachments and also got my tractor back from the dealer who installed the factory third function valve kit. I connected the grapple and I was pleased to find that everything worked!! It was late so I waited until Saturday before doing any work with it.

I used it for about 4 hours yesterday and for another 2 today and everything about the grapple and third function valve seem fine. The problem is that the power steering seems to randomly stop working at full capacity. While in this impaired mode, it makes a sound like a car does when you crank the steering wheel into the stops when I move the steering wheel. The PS behavior varies from hardly noticable (except for the different sound) to almost no power assist at all.

The first time it happened, I thought that maybe I was low on hydraulic fluid. Even though I had checked prior to starting the tractor, I checked again and the level was still OK. Nothing else seems to be affected, the HST and all loader functions including the 3rd function work great.

I brought the tractor up to the house and consulted the owner's manual. (This tractor has 312 hours on it but I bought several weeks ago when it had 300 hours on it. It is nearly perfect shape, before I bought it, it was used at the local community college in the tractor safety course. I don't think the loader had ever been in the dirt before I bought it.) I found nothing in the manual and so went back outside and started the tractor back up and the problem was gone and did not return the rest of the day.

Today, I had issues from the get go but, as with yesterday, it would get better after stopping and restarting the engine... sometimes. Other times stopping and restarting didn't help. I am not totally famiiar with this tractor yet but I think it has a dedicated pump for power steering and that both that pump and the main hydraulic pump use the same fluid reservoir. It seems to me like maybe there is an obstruction in one of the lines leading to the PS pump and that when I turn off the engine, it settles for a while but then causes problems later when it gets stirred up again. Or maybe there is air in the line. Do these systems need to have air bled from them once they are opened up?

I had a PS leak in my truck once and when it was low on fluid, it acted the same as the tractor... OK on the road but very hard to steer when going slow or when at a stop.

Does this ring a bell with anyone? I am a novice when it comes to hydraulics and I am not sure what to do. The tractor is under warranty so any big problems should be covered but I am hoping it is something simple. Any help is certainly appreciated. Thanks!! BTW, thanks for this forum I have learned a lot just by lurking about reading about other people's issues and victories.

 

[art]

Sounds like a relief valve on the steering system.

 

[Happyman]

My steering (L3940) will act in a similar manner as yours, but only when I have a HUGE load on the FEL. If I max out the FEL capacity with a load and have to run the RPM's up to about 2700 in order to get the FEL to lift, the steering will cut in and out. It only happens when the FEL is maxed out and never happens otherwise. It's like there is such a large load on the front axle that the capacity of the steering hydraulics to turn the wheels just isn't there.
This is a normal situation, at least for my tractor.

 

[lynrob]

I called the dealer today and he had a mechanic onsite about two hours later. Wow!! The mechanic quickly diagnosed the problem as a part in the power steering/PTO priority valve that not been reassembled correctly during the recent installation of my third function valve. I think Art was definitely on the right track when he suggested that the problem was a relief valve.

While he was there, I told the mechanic that the new solenoid valve in for the third function tended to stick open from time to time. He dissassembled and reassembled it several times and could not determine the exact problem so he is going to order and install an new valve.

I am very impressed with the dealership (Linn-Benton Tractor, Tangent, OR) and I am glad I am dealing with a company that will stand behind their work and products. Those on this forum who have advised that a major part of a tractor purchase decision is the integrity of the dealership are right on the money.

For anyone who is interested, the mechanic told me that the Grand L40 series HST models have a single hydraulic pump that is divided internally into two separate pumps. One supplies the HST, loader and, in my case, the third function valve. The other pump supplies the power steering and the PTO. I surmise from what he said that the job of the priority valve that caused this problem problem is to ensure that there is always enough pressure to operate the power steering regardless of the needs of the PTO.

What a relief (no pun intended) it is to have my tractor back in working order. I was concerned that with an intermittent problem it might be difficult to pinpoint the root cause. As it turned out it only took about 15 minutes to find and fix.

 

[Happyman]

I called the dealer today and he had a mechanic onsite about two hours later. Wow!! The mechanic quickly diagnosed the problem as a part in the power steering/PTO priority valve that not been reassembled correctly during the recent installation of my third function valve. I think Art was definitely on the right track when he suggested that the problem was a relief valve.

While he was there, I told the mechanic that the new solenoid valve in for the third function tended to stick open from time to time. He dissassembled and reassembled it several times and could not determine the exact problem so he is going to order and install an new valve.

I am very impressed with the dealership (Linn-Benton Tractor, Tangent, OR) and I am glad I am dealing with a company that will stand behind their work and products. Those on this forum who have advised that a major part of a tractor purchase decision is the integrity of the dealership are right on the money.

For anyone who is interested, the mechanic told me that the Grand L40 series HST models have a single hydraulic pump that is divided internally into two separate pumps. One supplies the HST, loader and, in my case, the third function valve. The other pump supplies the power steering and the PTO. I surmise from what he said that the job of the priority valve that caused this problem problem is to ensure that there is always enough pressure to operate the power steering regardless of the needs of the PTO.

What a relief (no pun intended) it is to have my tractor back in working order. I was concerned that with an intermittent problem it might be difficult to pinpoint the root cause. As it turned out it only took about 15 minutes to find and fix.

That's great news :thumbsup:
And you are so right about the integrity of the dealer. I also have an outstanding dealer, Cavalier International, Ashland, VA.
Glad you are back in the saddle again :cool2::cool2: