Split hydraulic motor

[Iceni John]

This afternoon I took my bus out for its first real test-drive after completely replacing its entire cooling system, but after a few miles I heard a faint pop or snap noise and felt a brief surge of power while doing about 45 MPH.   Almost immediately smoke filled up the bus and billowed out from the back, so I pulled onto the shoulder and turned off the engine.   The entire engine compartment was dripping with hydraulic oil which had also sprayed onto the exhaust pipes to make the smoke.   WTF?   On closer examination I saw my brand-new Webster YC hydraulic motor for the radiator fan had cracked apart near its inlet.   The brand-new Multi-Wing fan is OK, so obviously nothing got caught in its blades  -  if something had, all its blades would have sheared off or been damaged.   When I tried to turn the fan by hand, it rotates only a few degrees before hitting a solid obstruction inside the motor.   Evidently something catastrophic happened inside the motor to lock it up solid, and then the hydraulic fluid had nowhere to go so it over-pressured the motor and split its casing apart.   No bueno.

Has anyone here ever had anything like this happen to them?   I'm using the same make and models of fan motor and hydraulic/PS pump as before, and I even reused the priority flow divider valve assembly from the old pump onto the new pump.   I checked the shuttle inside the divider valve and it moves freely, but I didn't touch the poppet pressure valve which is only for the power steering circuit anyway.

Good Sam came to the rescue, after waiting three hours on Pacific Coast Highway for the tow truck  -  it was a month-old Peterbilt triple-axle wrecker with all the bells and whistles, half a million dollars' worth according to its driver (Victor from Anaheim Fullerton Towing, a consummate professional who I would happily recommend to anyone).   Unfortunately the RV storage yard where I keep my bus closes at 5.00 PM on weekends, so we left the bus in the adjacent Home Depot parking lot until tomorrow morning when we'll move it the last few hundred yards into the RV yard.   Nobody can easily steal the bus because we left its front wheels up on blocks, ready for the wrecker tomorrow!

I'll have to buy a new axle seal because the old one ripped when Victor pulled out the axle, but ABC Bus just down the road should, I hope, have them  -  I'll buy one or two spare ones "just in case . . ."   Victor also suggested attaching towing eyes or loops under the front of the bus for the safety chains to be attached to if I ever need a tow in the future, so that's another project for whenever.

What bugs me most about this whole dabacle is that I now have to completely remove the brand-new radiator again  -  it's sodding heavy for one guy to move by hand!   Once the radiator's out, it's plain sailing to pull the fan off the motor and swap out the motor.   I'll call Quality Control Corp. on Monday to have them replace the motor:  it was custom-built by them, so I can't just buy an off-the-shelf replacement.   Damn.   Everything else I've done works perfectly, except for this motor  -  no leaks or drips anywhere (at least, until it split apart!), and I hope no more over-heating issues.

John   

[Oonrahnjay]

     I have a pretty severe case of heat against that hydraulic motor builder.  But if I guess if they make it right, you only wasted an afternoon then a few days of work on their blunder (and a few score of $$$ of fluid).
     Sorry that that happened to you, John.  Here's hoping it gets fixed as soon and as right as it can. 

[Tom Y]

Sorry for your problems. I would remove before calling. Any chance something was left in lines or system? Has the fan run before? Or is this first time it came up to temp? Mine will spin slow and when needed come on strong or I can turn it on with a switch. Good luck

[Iceni John]

Sorry for your problems. I would remove before calling. Any chance something was left in lines or system? Has the fan run before? Or is this first time it came up to temp? Mine will spin slow and when needed come on strong or I can turn it on with a switch. Good luck

I really don't think anything was left inside the lines  -  I capped off the open ends of the hoses and made sure no dirt could get in them.   I've also installed a new Baldwin hydraulic filter just before the reservoir that would catch any contaminants.   Because this happened after at least ten minutes of driving, I think any possible contaminants would have already flushed through long before the seizure.   The motor feels like it has a solid blockage inside  - the fan does not turn at all beyond the few degrees of free movement it now has.   My guess is that one or both of the gears inside has jammed against the gear housing, but I don't know why.   The fan has run before at idle and fast idle, at both slow and fast speeds, and it was turning well  -  it wasn't making noises or getting hot, so it seemed OK then.

John   

[HB of CJ]

Was this your Crown that blew up that hydraulic motor?

[Lee Bradley]

Most hydraulic systems have a pressure relief  valve to prevent this problem.

[Iceni John]

Was this your Crown that blew up that hydraulic motor?

Yup.

[Iceni John]

Most hydraulic systems have a pressure relief  valve to prevent this problem.

The only pressure relief valve is for the steering  -  that's the one incorporated into the priority flow divider valve assembly on the back of the pump.   The other circuit for the fan motor has no relief valve.   I'm thinking now of adding one to prevent any recurrence in the future.   However I'm curious what caused the motor's casing to split  - was it a mechanical failure within the motor itself that increased its drag, and hence the pressure upstream of it, or something else?   The previous pump and motor had worked well for 26 years and 277,000 miles, and the new ones are exactly the same models and capacities as before.   If anything, the new motor has less load than before because I now have an efficient plastic fan instead of the heavy old metal fan:  the new fan is less than half the weight.

Let's see what the manufacturer says after they've done a post-mortem on it.

John

[Brassman]

Off hand, it would seem to be over pressure.  If you want to find out why the motor failed you would need to do a disassembly, but that could nix the warranty.

[luvrbus]

One of vanes likely broke since it will not rotate they use a compensating valve to control the flow under all pressure I think the Webster is around +or-3000 psi max I don't recall a pressure relief valve on the fan systems   

[eagle19952]

is this a vaned motor ?
axial piston ?
sounds like a relief problem, are any quick coupled hoses involved ?

[luvrbus]

is this a vaned motor ?
axial piston ?
sounds like a relief problem, are any quick coupled hoses involved ?

Lol there is a lot that go wrong in bent/axial motor,it is a very popular hyd motor but I stay away from one if all possible 

[Iceni John]

The Webster YC is a gear motor, not a vane or piston type.   Is it the best motor  -  of course not, but it's the only one that will fit!   However, the old motor worked for 26 years and 277,000 miles without bursting apart, so I guess it's adequate for the intended task.   I have only about 2 inches between the back of the motor and the exhaust down pipe, and that space is occupied by the heat shield there.   There's nothing made by Parker or Eaton that will fit.   Quality Control Corporation, the manufacturer of it, has just replied to my email saying that they will look into it, so who knows what they'll do?

I had an idea last night in the shower (all my best ideas are when I'm in the shower!) if QCC doesn't warranty it, to instead use a more commonly-available and longer-depth motor with a more-common clockwise rotation (the new Webster motor is CCW), and connect it to the fan by a simple gear drive that would reverse the rotation to match my new CCW fan.   This way the motor would be beside the exhaust pipe and not directly ahead of it, so its depth would not matter, and if it's a common CW rotation then I can get one anywhere for not too much.   It would also be a heck of a lot easier to replace if needed, instead of having to remove the whole darn radiator now to get to the fan and motor.   That's my Plan B if QCC doesn't warranty it, but why wouldn't they?   I would have thought that a hose would have burst before the motor split if it was a simple case of too much pressure  -  I think a mechanical failure inside the motor locked it up solid, and the split was then a result of that.   We'll see.

This is SO frustrating.   I've worked so hard over the last six months to completely replace my entire cooling system, and all my work has performed flawlessly except for this one thing.   I suppose that's what test-drives are for.

John

[luvrbus]

I agree with you it would have burst a hose or blew the seal in the pump with too much pressure I think something came loose .I have had the aluminum body pumps and motors split before because of too much pressure fwiw  

[Iceni John]

I just got off the phone with a Gary from QCC.   He is saying that an over-pressure protection failed.   Because the motor only drives a fan which would never stall, unlike a mechanical load that could possibly stall the motor and hence raise the pressure beyond the motor's burst strength, there is only a small Danfoss 7WA110-2 flow diversion valve cartridge that is used to vary the fan speed from half to full depending on coolant temperature.   This cartridge valve sends excess flow, such as when in half-speed, back into the return hose and thus back to the reservoir.   The cartridge has worked just fine for the last quarter century  -  why would it not work right the moment I install a new motor?   I still do not follow Gary's thinking  -  if the pressure protection failed, surely a fan would simply speed faster than intended, and the faster it runs the lower the pressure for any given flow rate.   The pump can only produce so much flow, so in my mind the system is self-correcting  -  increase flow, fan speeds up, pressure then drops to equilibrium to maintain new speed.   How can pressure therefore exceed the motor's burst strength?   Also, because it was cool on Saturday the fan never even reached full-speed, so this proves the Danfoss valve was working  -  I can hear when the fan goes to full-speed because it sounds like a big vacuum cleaner.   My coolant never exceeded about 180 degrees on Saturday, and the fan only goes to full-speed at 195 degrees.   If the motor failed at half-speed, that's not a good sign.

Gary at QCC says they will give me a return authorization number to return the motor to them, but after listening to him I'm not optimistic that they'll do anything to help me.   If I spend almost $700 on a motor, why would I do something to harm it?   I guess what rankles me most is that he automatically assumes it's not QCC's fault without even seeing it.   He should defer judgment until he knows what happened, not just try to wriggle out of any responsibility.   At this point QCC's customer service is not shaping up too well.

So, it looks like my Plan B may be the route I'll have to go.   Maybe I should email this thread to one of QCC's senior managers or executives?

John, more than a little disappointed.