Argo Centaur steering problem

[spatind]

Hi, just recently experiencing some nasty steering problems with my centaur. It's operating in a very cold environment (Norway), I started to get trouble with steering for a few weeks ago when it just didn't work at start. (I have hydrostat system). After running the motor for 5min in idle, it was ok. Than it didn't work anymore. After I heated it up at night in my garage (not isolated) with heaters and so on. It again worked fine for a while.

But since last week the steering is totally a mess, it still only works when not driving. to the left normal, to right very slow. But today it was just the otherway around! when not steering the Argo it can just suddenly start to spin. sometimes i got some of the steering back, while driving for like a few seconds, and than gone again. As i said in 0 speed it works for a bit .

Anyway, changed oil, level is being checked every day. Filter is shifted out. No traces of metal pieces in the old oil.

What could this be?

-moisture in the transmission?
-transmission failure?
-hydrostat pump is not operating properly?
Anyone experienced the same?

I hope someone is familiar with this problem

[dirtdobber]

Here are a few things to consider, all of which are general to hydraulic systems. I have never seen a Centaur.
1) if you have the old hydraulic oil filter, cut it open and inspect the folds. See if you can see any metal. If the pump is failing the metal will catch in the filter rather than being obvious in the oil.
2) Check all your steering linkage (if it has any). Make sure all linkage is tight and providing full movement as it should.
3) If your hydraulic system relies on a reservoir that is located away from the pump, check to see that the suction line is good and sturdy and not sucking together and starving the system for fluid.
4) Someone with more knowledge than me will have to give you guidance on the specifics, but you may have a bypass valve that is failing, depending on how the system is made. If you have a failing bypass valve, it will just dump the fluid back into the reservoir rather than delivering pressure to the drive motor(s).
5) Make sure you have the correct fluid. It is not unheard of for incompatible fluids to foam and not do their job. Also, do you have the correct viscosity fluid for your operating temp?
6) Surely you have checked for leaks. If you have one it should be pretty obvious.
7) There should be a way to attach a hose and gauge to the pump to check the pressure it generates. If you aren't producing pressure, or enough pressure, or enough flow, you aren't going to go. This pressure test is also related to the bypass valve i mentioned above. Someone will have to give you the working pressures and instructions on the test procedure.
8)I'm not sure how the hydraulic pump is driven (belt, direct connect) but make sure there is no slippage going on.
9) If there are any electronics that control the hydraulics, that is a whole other can of worms - sensors, calibrations, etc.

Good luck

[spatind]

Thanks for your good answers! hopefully it's just the belt or the hose

[jerseybigfoot]

not familiar with the Centaur but it looks like the hydrostat is directly connected to the steering shaft and spins along with the gear trans and acts on the differential for steering. AKA dual differential tank drive. The belt drive from the trans to the hydrostat would be critical for proper steering as well as the connection from the steering column to the hydrostat. The proper oil viscosity will also play a critical role in the operation.

[jerseybigfoot]

The Centaur manual has a big section on the trans and Sundstrand Hydrostat.
Centuar 8x8 Manuals

[spatind]

Hi, thanx for your answers! the manual i have. It helps a lot for understanding of the system.
These answers helps a lot. I just have to check some of them which i didn't do yet. specially the belt.

[jerseybigfoot]

here is a Youtube vid on how it works. The lower input would be the CVT input and the upper would be the Hydrostat input

https://www.youtube.com/watch?v=FWSYa7b3Vjo

here is another

https://www.youtube.com/watch?v=16EVsBVx4SM

[ARGOJIM]

How cold is your temperature?

[spatind]

It's between -25C and -5C, during at least 2 , 3 months.

Well I had a look today! it seems that the belt is too loose. When running it moves and vibrates to right and left on the sprocket wheel. It's also vissable on the sprocket itself that the position is wrong (clean surface is visable)
I had a little collision a while ago (after the first steering problems started, due to cold). It might have caused the belt to move. because the radiotor was slightly affected by it.
But the newer steering problems at least started a week after this event, so i didn't connected the failure to the collision.

Anyway don't have time to fix it now as i have to work. Will do the adjustment after the weekend. Keep you guys updated. I really hope it's the belt!

[jerseybigfoot]

i would check the cable adjustment from the steering wheel to the stroke control on the hydrostat. if the hydrostat does not center properly it will start turning.

[ARGOJIM]

My thought is an iced cable hanging up, or hanging up control at hydro.

[spatind]

Thanx for your input, good one but I have checked that one already. I changed it some bit to see result, i conclude it was aligned properly. The thing is that the steering failure is completely irregular, sometimes left turnings are bad, but most often right turnings. The belt problem makes sense to me, because it probably doesn't give enough pressure to the hydrostat.

[spatind]

Ok, I've tightened the belt, it was somewhat better afterwards but still not good. It seems that i had another problem: To tighten the belt we had to move the diesel tank. It seemed that after freeing up the space i could pull out the Trunnion shaft (hydrostat) without any force! That should not be. Anyway this looks to cause the problem. After keeping the shaft in its place, the machine worked as before. So i'll try to fix this.

[spatind]

It's a while i posted, but just to provide information to others to finish off this topic:
it seemed it was a problem inside the hydrostatic pump from Danfoss. But i fixed it myself. It was realy easy jobb at the end.
I just opened the pump. it seemed that a splint that holds a flow steering unit inside. (like a little cup) had broken off. Which was easy to replace.
I just ordered a reparation kit from danfoss for like 50$ or so. and shiftet all bearings at the same time as well. Made a new gasket, cut out off gasket paper. Works well.

Be aware of put everything together, proper side of course. Parts ar really alike regarding front and backside, some differences are almost not traceable by the eye. so mark them.
Espacially tricky with the pump ring. If those parts are put back wrong sided, the whole pump doesn't work.

[thejunkman]

If you dont know they do offer a heater made for the centaur transmission it 110 volt to aid in freezing temperatures keeps the oil warm before starting its designed like a block heater for diesel motors I have installed them before.