Loss of steering assist

[rollin sorge]

We have an 2007 Cdontessa, At random times, no pattern, when I start a turn the steering locks up ,but only for a second and then resumes normal assist. You never know when it will happen . Anyone expierience anything like it?

[Gerald Farris]

I have never heard of this problem on a coach, but it was fairly common on cars before serpentine belts became standard equipment. The problem is usually caused by a momentary drop in hydraulic pressure. About the only thing that you can check is the level of the hydraulic fluid.

The hydraulic system on your coach operates the engine cooling fan and the power steering systems. If you have not serviced the hydraulic system, it is possable that you have a restricted hydralic filter, but that is just a quess.

Gerald      

[Joel Ashley]

Yup, our 2006 Monterey has done that or something like it every so often since it was new.  You'll be usually in a slow speed turn, often just pulling away from being stopped, and, BAM!  It feels like you hit something except it's almost like someone grabbed your steering wheel and jerked it in the opposite direction.  It's disconcerting because you nearly lose your grip.  Thankfully it is quite brief and momentary and you don't lose control.  It is so rare that I keep forgetting to ask about it when in Bend for annual service.  So I am as mystified as you, I'm afraid, unless Gerald is on to something re the h fluid filter.  But I wouldn't expect that on new rigs.

[chris l meyer]

I have a 06 Montery and it will do the same thing.
With my unit this happens when the tranmison shifts and i am in a turm.
I have changed the filter and checked the fluid.
This happens only in a slow turn and at shift points

[Gerald Farris]

If the problem occurs in a turn only at shift points, it is probably because the engine RPMs drop when the transmisson shifts and therefore the hydraulic pressure drops. This may only happen when the engine cooling fan is also running therefore increasing the hydraulic demand. If this is the problem (original engineering), I do not see an easy correction other than increasing the pump size which can create it's own problem.

The best thing to do is talk to the people at Beaver Coach Sales in Bend to see if they have run accross the problem before and found an acceptable correction.

Gerald

[Mike.Way]

We had this problem with our '98 Marquis.  Adding hydraulic fluid to the reservoir seems to have cured it.

Mike

[Arden Smith]

This is an interesting problem. And I am sure to those it is happening to, quite disconcerting. I taught Industrial hydraulics for many years so I will add my two bits worth. I believe that the problem is a sudden loss of pressure for a moment like Gerald says. This could be caused by the turning on of the hydraulic motor that runs the fan. Most said that the problem occured when at  low speed and when pulling away from a stop. It seems that would be the time when the fan would kick on to full speed to pull away the perculating heat from the engine.  If this be the case the momentary demand for extra volumn of fluid would cause a momentary drop in pressure making the loss of assist in steering seem like a lockup or a reversal. Kind of a long winded answer to what might be the cause.
But a good solution to the momentary demand for extra fluid to prevent that momentary pressure loss would be a hydraulic accumulator which is a pressure vessel much like the accumulator used in the water systems to smooth out the pressure surges from the pump cycling. Hydraulic accumulators are hi pressure vessels or small tanks that have a rubber bladder on the inside that is usually set to about 2/3 system pressure. When the hydraulic system operates the fluid compresses the pressured bladder to a smaller size and when there is a momentary loss of system pressure or demand for extra fluid in the system the bladder pushes fluid under pressure back into the system to support until the system can recover.
Just some ideas.

[Arden Smith]

I forgot to add that the accumulator is not that large and should be added after the pump and before the valving that split the fluid to the steering and the fan or could be put directly in the line to the steering. I believe that a one quart or maybe a 2 quart size would be very adequate.
Arden Smith

[Gary and Judy Doran]

Was a solution ever found for this problem?  I have the steering problem in my 2006 Monterey and had found this link previously but no solution for the steering problem.
Yesterday I met Russ Mann who owns of a 2006 Monterey 400HP cat. He had the same problem with his Monterey he purchased in 2006 from Beaver Coach Sales.
  While still under warrantee Beaver Coach spent a lot of time eliminating a number of things they thought might be causing the problem.
The final diagnosis was that when the exhaust brake was activated the hydraulic cooling fan was also activated, if he was making a turn at the same time the steering wheel would jerk because of loss of steering assist.  It was caused by the dual demand of the cooling fan and steering assist on the hydraulic system under no throttle.
 Beaver Coach took the coach to Cat for reprograming. According to Russ the problem has never occurred since the programing change that eliminated the cooling fan activating when the exhaust brake activated.
  Has anyone heard of this solution or have you found another solution?

[Joel Ashley]

I think your reported cause reflects pretty much Arden's theory.  Except I don't believe my exhaust brake was involved, given I don't use it except on long downgrades.  My incidents like others' were at minimal speeds turning from a stopped condition.  

I think Arden's canister to mitigate sudden pressure loss is still a good idea, like an accumulator tank to smooth out a pump water system.  That said, if reprogramming's no big deal, I may be stopping in at Petersen CAT in Redmond too the next trip to BCS, and at least consult with them.  The problem was infrequent enough that I failed to broach the issue when in Bend last, 2 years ago.  But when it happens it is rather startling;  if my wife was driving the wheel could conceivably hurt her - it did a number on my wrists once or twice.

Thanks for the new information.

Joel

[Gary and Judy Doran]

 I had forgotten about Arden's thought on using a canister.
Last spring I replaced the filter and fluid. I still experienced the steering problem on our travels during the summer, in addition the pressure gage failed. As Joel mentioned when it occurs it can a real abrupt jerk, but for sure it freaks me out.
 Not knowing about the possibility of the programing change, just last week we had the filter bracket changed from the small 3.67" filter to a larger bracket for a 5" filter. ( Worked through this change with Jeff at Bend RV Repair)
The flow on the smaller filter was a rated 24 GPM. The 5" filter is rated at 50 GPM.  We have only driven a few miles with this set up. Because of the infrequent occurrence of the steering problem it will be a while before I can report if this is another solution to the problem.
  Gary

[Joel Ashley]

Don't hesitate to alert us if it occurs again, Gary.

Joel

[Gerald Farris]

Gary,
Since the filter is in the low pressure side (return) of the fluid circuit, I can not see how changing the filter could correct your issue. That being said, I think that the filter change was a good idea on you coach because I have seen two hydraulic cooler failures on the late Monaco era coaches from low side restriction when using AW 46 oil in cold weather.

Gerald  

[Adam Hicklin]

Is a hydraulic filter replacement easy to do?  Is it just a matter of spinning the filter off and spinning the new one on?

[Gerald Farris]

Adam,
Yes, it is that easy to change the hydraulic filter if you have a canister (spin-on) filter. However, there is one thing that makes for an issue when changing the hydraulic filter on some coaches, and that is fluid loss. If your filter is located on the bottom of your hydraulic tank, the hydraulic tank will probably drain about 3 to 4 gallons of oil when the filter is removed, so be prepared for a large fluid loss when removing this filter. Other hydraulic filters will loose varying amounts of oil, so be prepared to catch it and have new oil as a replacement. The latter Monaco design inline filters loose much less fluid.      

Some coaches have a cartridge filter that is located inside of the hydraulic reservoir, so those are a little more work, but there is very little fluid loss when changing them.

Keep in mind that the hydraulic fluid has a change interval just like engine oil, although not as often. I changed my hydraulic system from Dexron III to TranSynd to extend this interval.

Gerald