UFO FCA Old vs. New Style Details

[gbs2320]

As we all know the UFO problems with the Fan Clutch Assembly causing premature water pump failure has been vexing and the long promised recall by Workhorse cannot come soon enough.

I got my FCA and water pump replaced with the new design in Santa Fe during my recent trip and was able to get part numbers from the old and new ones as well as the manufacturer name. Also I used the Scan Gauge II to note my mileage and water temps on the long trip from Va out to Arizona and New Mex and back (mostly on I81 and I40). So I have info how the old design vs. new design performed and thought you might be interested and have comments to share.

Old Design FCA:
Manufacturer: Visctronic (TM) by Borgwarner
# W0010697, Other number on FCA: 4c02HI
My average MPG: 6.2-6.5
Water Temps:
Normal running 60 -70 mph including small hills almost always 198 F and up to 229 F going up long big hills when FCA went full on and kicked it back to 196 - 198. (note the thermostat is a 195 F which means is starts to open at 195 and is fully opened at 212 F (at least that was the full opened spec degree for my v8 Jeep)

Old Water Pump: GM casting number: 2558830

New Design FCA:
Manufacturer: Visctronic (TM) by Borgwarner
#W0012138, other number on FCA: 4H25J1
My average MPG: 6.9 to 7.2 (one day of 7.5!)
Water Temps: normal running 60-70 mph including small hills it varied from 202 to 207 (sometimes 215 or so on medium hills) and then on long (2 or more miles) and steep hills it went up to 229 when the FCA came full on and knocked it down to 196 -198 while still going up the hill.

New water pump: Ac Delco GM #8901773

I am not sure whether the new water pump is a more robust version than the old one. Perhaps others can figure this out based on the normal applications for which these pumps are used.

Visctronic FCA operating methodology:

This is a electro viscous FCA which is operated by the engine PCM. The PCM controlls fan speed (partial or full) based on info from engine sensors re temp and based on fan speed info from the FCA. The PCM controls fan speed by opening a valve in the FCA to allow viscous fluid from the storage chamber to go into the operating chamber where it causes the fan clutch to engage at a speed dictated by the amount of fluid in the operating chamber. See how does a vistronic fan clutch work and how do ... - JustAnswer and Powered by Google Docs

Many other vehicles of recent vintage including my 08 Ford Expedition have these type of fans. I have heard that some of the newer desiel pushers also have them. I believe the old non elec thermal FCAs were either full on or off and depended on hot air off the radiator to hit the front of the FCA and trigger the thermal switch. Of course that probably would not work on our rear engine UFOs since the air is blowing away from the FCA and then out through the radiator to the rear of the vehicle.

My speculation based on the above is that the old FCA either had a defective control valve or was overfilled with fluid so that excess fluid remained in the operating chamber. Whatever the cause I believe the severity of the probem varies with each old design FCA thus causing some of us to have worse mpg and worn out water pump bearings at much lower mileage than others.

Unfortuantely, based on my research it appears the engine computer only throws a trouble code if the fan is too slow not too fast. The default situation if the fan loses communication with the pcm is to go to full on which is not our situation.

Monitoring the water temp on my Scan Guage II is the only way for me to monitor the FCA since I can not hear it when partially engaged and in fact cannot hear it when fully engaged at the back of coach. The temperature gauge on my dash is worthless for this purpose since it can not tell me such fine tunned info. In fact at 198 the pointer is a hair on the left side of the center point and when at 229 it is only a hair on the right side of the center point. That guage would give me not enough warning of a leak etc. It may be possible to code the Scan guage to read the real time fan speed signal from the FCA that the PCM is seeing but I have no clue where to get that info to do the coding. Perhaps OEMY or Brazels knows?

I hope this info was helpful and welcome any corrections or comments.

Greg

[DriVer]

√ Thank you!

[gresults]

Thanks for the information, I just had mine replaced but truthfully never had issues with orginals.

But will hook up my scan gauge and monitor..

[-Gramps-]

Thanks for the great info.

I have not had my FCA replaced and since I have a quiet engine, 7.5 mpg going up and down the Blue Ridge mountains with a toad on Route 89 above Mt Airy NC (and that is a bit of a climb!) I am not planning on replacing it anytime soon.

[gg]

Greg,

A excellent post, Data is King when trying to solving a complex problem.

Another plug for a scanguage to read the coachs systems while on the go.
I hope scanguage will get the Allison 6sp temp data code broken , so it can be added to the xguage.

gg