Webster Hydraulic Fan Motor

[davidbrady]

Judging from the schematic I think so Tommy; a failed Webster Relief Valve could prevent the fan from getting pressure; although, I don't know the internal workings of the relief valve. Also it took time to pump all the hoses full of hydraullic fluid when the engine was first started. This along with moving the steering wheel may have allowed the pump to survive for the duration you mentioned.

Tommy, it'd still be very interesting to take a close look at the failed 8V92 PTO splines. I'd like to see if the failure looks like a sudden fracture or a gradual wearing away. This will tell us if the two failures are related to the same cause.

[davidbrady]

Incidentally Tommy, the Webster Pressure Relief Valve is one of the reasons that 8V92's get slightly poorer fuel mileage than the other birds. A while back Leroy and DonB reported that their 8V's got the same mileage regardless of the fan override being on or off; whereas, my S60 get's 0.5 mpg difference under these scenarios. The difference is that on the S60 when the fan is off pressure is relieved in the hydraulic system; that is, no work is done and the pump simply freewheels. The Webster Pressure Relief valve always maintains pressure in the 8V systems whether the fan is on or off, or whether the power steering is calling for pressure or not. IOW's the pressure relief valve only dumps pressure in excess of some amount, say 3500 psi. It needs to do this because the system is shared by both the fan and the power steering. The relief valve pressurizes the system by default so the power steering can work. All this adds up to work being done even though neither the fan nor the power steering is using it. The result: a constant fuel mileage hit!

[davidbrady]

Tommy,

I pulled this pic out of your previous Hydraulic Pump Thread:

Although it's not quite a close-up of the sheared splines, it does show a lack of fretting or long term grinding wear on the intact splines. This is more evidence that the damaged splines were catastrophically fractured which leads me to believe that we're on the right track - the two failures are probably due to the same cause and if you threw a new pump at it you'd probably damage that one too!

[cmillsap]

(09-22-2013 00:23)davidbrady Wrote:  Tommy,

There is a Webster Relief Valve in your hydraulic circuit. When neither the power steering nor the hydraulic fan is calling for pressure the relief valve redirects fluid back to the reservoir. I'd look closely at this valve. If it's failing to open pressures could build to excessive and damaging levels. Here's a schematic of your system. In the drawing item number 37 is the Webster Relief Valve:



My theory is that the pump worked fine as long as you were moving the steering wheel, when you stopped the pressure built and the shaft failed. When you stopped, the pressure had no where to go most likely due to a faulty Webster relief valve.

David,

Is Item #34 the solenoid valve? It appears that is the only item in the fan circuit with wires. If it is and is somehow blocking the flow of oil to the relief valve, the pump (being a positive displacement pump) will dead head at it before the relief valve and cause the system to be over pressurized and blow the pump shaft.

We have no idea how that solenoid valve is designed. We don’t know if it is possible for it to completely block the fluid flow by the position of the spool. I think we need to know more about that solenoid valve and how it works.

Chuck

[davidbrady]

Chuck,

I should have included the document where the drawing came from. It's out of our Library and it's the 1990 Wanderlodge Wide Body Chassis Parts Catalog, page 118. Item number 34 is a high pressure filter with a wired dash indicator. Item number 37 is the Webster relief valve with an integrated fan solenoid valve - wires are also visible on this part. We don't know what portion of this valve has failed and likely never will. The good news is that both pump drive failures look like they have the same cause and that's excessive a damaging downstream head pressures. It's my hope that Tommy will benefit by not subjecting a third pump to the same environment without first rectifying the root cause.

Trying to fulfill WaGu's mission of "answering every question and on occasion even correctly". No guarantee that this one of those rare occasions...

[cmillsap]

(09-22-2013 20:23)davidbrady Wrote:  Chuck,

I should have included the document where the drawing came from. It's out of our Library and it's the 1990 Wanderlodge Wide Body Chassis Parts Catalog, page 118. Item number 34 is a high pressure filter with a wired dash indicator. Item number 37 is the Webster relief valve with an integrated fan solenoid valve - wires are also visible on this part. We don't know what portion of this valve has failed and likely never will. The good news is that both pump drive failures look like they have the same cause and that's excessive a damaging downstream head pressures. It's my hope that Tommy will benefit by not subjecting a third pump to the same environment without first rectifying the root cause.

Trying to fulfill WaGu's mission of "answering every question and on occasion even correctly". No guarantee that this one of those rare occasions...

That makes more sense, David, as there is only the one dump line back to the tank showing in the system. Tommy said the solenoid valve is no longer available. If it is an integral part of the relief valve; I’m wondering if a new relief valve would include the fan speed solenoid valve with it… Again, the relief valve which is probably internally piloted may be working properly and the solenoid valve spool may be blocking the flow.

A schematic or diagram of the internal flow pattern of that relief/solenoid valve would be a big help.

Chuck

[pgchin]

David and Chuck,
Great brainstorming...... after looking at the schematic, I agree with your "assessment". The only other thing I could add is if that filter is original or deteriorated and blocking the fan side....... that and the two valves are the only other items left to try and eliminate. Leroy knows about that solenoid valve in great detail. Alas he is an OTR trucker so I am not sure of his ability to surf the forums while he is working.........
Tommy, can you get more "specific" about what your shop did to the solenoid valve to modify it?
Another suggestion for them to "evaluate". How about getting a length of 5000PSI hose and fittings and bypassing the two valves and filter for a "test"........... show them the schematic and let them "call the ball"....given you cannot find that valve, I do not know of any other way to try and eliminate those 3 items as root cause unless David or Chuck has a better idea. As David cautions, this is extremely high pressure so if a "bypass" test is to be utilized, it MUST be with qualified parts suitable to sustain the pressures of the system.......hose, fittings, connectors, etc..... a good hydraulics shop can handle this as long as you tell them the max PSI the system runs............ FWIW the old lines have the max pressure ratings on them if you can read them.

Chuck, I am going on memory here of over 6 years since I read Leroy's post so I am going to SWAG based on how the 95-97 s60 system works and his old post as the the 95-97's only have 2 speeds, high and low like the 8v's.....that said I "believe" that valve and relief valve works in tandem with a "constant pressure" at all times to spin the fan at low speed (partially open always). When you hit the AC switch OR the temp cooling system sensor trips due to a "certain temp" ( I think Leroy said 190 and he changed it to 180) the valve opens wide open to allow full pressure and high fan speed. In low speed, the fan circuit utilizes the return line for excess pressure....... Again, Tommy, this is a SWAG........let your shop "call the ball".......maybe these tips might trigger some thought or direction for them to utilize. I do remember Leroy wanting that valve ALWAYS open, hence he went with a lower temp "trigger" to make sure it always is full on at regular operating temperature and the fan only spun at low speed while the engine was getting up to operating temp.

[cmillsap]

David, Pete,

I think we all agree that Tommy should make sure that relief/solenoid valve is working properly before trying another pump. The odds of two pumps being bad are pretty low. They have checked all the hoses and lines for blockage so unless he has some sheared metal off the shaft gear that is getting into the pump; the only other things that could cause the problem is that the flow is blocked at that filter or at the relief/solenoid valve.

Chuck

[RetDA]

(09-23-2013 14:19)cmillsap Wrote:  David, Pete,

I think we all agree that Tommy should make sure that relief/solenoid valve is working properly before trying another pump. The odds of two pumps being bad are pretty low. They have checked all the hoses and lines for blockage so unless he has some sheared metal off the shaft gear that is getting into the pump; the only other things that could cause the problem is that the flow is blocked at that filter or at the relief/solenoid valve.

Chuck

Information received from Webster today is that the new hydraulic pump failed apparently from defective internal assembly, locked up causing the torsion separation of the shaft. Subject to a "final autopsy, it appears they are going to send me a new one (Unless they want to blame it on me). John Boy Hughes at CoachCraft advises that the relief valve was tested at the last session, this past Thursday and it is in good working order. Also, using the mechanic's equivalent of a colonoscopy "snake" the power end of the DDEC II all is well and the gears are without damage.

With regards to the old Danfoss hydraulic solenoid, replacements being non existant, we will by-pass it. The fan will run at a constant 1800 RPM, which it has done anyway since I have owned the coach.

We've also removed the Parker filter. Its just somehing else in the line that BB engineered as a redundancy. The hydraulic reservoir contains three staged filters anyway.

Now, the diagnosis of the first secondary gear in OEM hydraulic pump can be attributed to improper installation. When installed, there was a 1/4 " gasket with a thick layer of black silicone that diminished the distance between the top of the gear and the pump shaft, thus seriously diminishing the amount of contact with the cylindrical secondary gear. Eventually the teeth were worn down of the first secondary gear. The old pump has been checked and is in good servicable condition, which I will keep as a spare.

New fan motor, new hoses, new fittings should put me back on the road, hopefully, I might add.

Thanks for everybody's help and advice.

[davidbrady]

Thanks for the thorough write-up Tommy. Arcticdude was right (post #7), you're in good hands with John Boy Hughes and the staff at CoachCraft. There was clearly no way of knowing this past weekend that the Webster relief valve was given a thorough testing. Again this thread illustrates the great difficulty involved in diagnosing a problem over the web; nonetheless, I know in this process I learned a lot about Wide Body fan and power steering hydraulic systems; I had fun and I think the other contributors did too! That's what it's all about, helping each other, learning, and having fun! Good luck Tommy!