As our 300's are getting older, the viscous fan is failing more and more. This is becoming a common cause of increased engine temperatures, especially during extended idling. The reason for failure seems to be loss of the oil in the hub. This is how to bring your hub back to life. First remove the hub - remove the 4 bolts from the front of the plastic fan using a 10 mm socket with short extension, the the 4 nuts that secure the hub with a 10 mm ring spanner. Next, carefully drill and tap 2 holes in the front of the hub. Try to minimise the amount of filings that have a chance to fall into the hub. Optionally, this is a good opportunity to invert the hub and allow it to drain the old oil for a couple of days - it's very thick and will take that long. This may also carry any filings out with it. The local hobby shop will stock Silicone Shock and Diff Oil. There are many weights available. I chose 7000 which seemed very thick and about right, but perhaps a slightly thinner one would be adequate say about 3000 - 4000. I'd like to say fill the hub but I emptied the bottle into the hub and it didn't fill it, but still with a good result. Finally, insert screws to seal the holes. Refit the hub in reverse order
Thanks. Indicators, the fan works - actually starts pumping air when it gets hot. Engine temp no longer goes up with extended idling. That said however, it may be working to well. There's more fan noise than I'd expect so I think it might be too stiff. I've got another to play with so I'll let you know how it goes.
as one has come to expect from "burpin'garry", nothing but technical excellence ... thanks for this top tech tip ..as ever ... ..and to the Mods ..one for the tech section ..?? ... please ...
Do you think it's a loss of oil or the oil breaking down over time? I'd be tending towards the latter, I've never seen a fan hub leak. Good write up though
The problem with the failing hubs is not actually the oil. It is the temperature switch that fails. The coiled up bit of steel reacts to the heat and makes a mechanical switch inside the hub. That way, when the engine bay is cold (no heat coming off the radiator) the hub "slips" and doesn't drive the fan. When the engine bay is hot the fluid drive is engaged and the forces air through the radiator. BlueZ's modification makes the hub drive all the time. I have heard of people putting grease in the hab to achive the same result.
Whats the case then with a cold engine. If the fans spinning upon start up? Is it the centrifugal force that is spinning it? But allowing a certain amount of slipping until the coil reacts to the heat and locks the hub up? And the best i can understand, should the hub not be leaking, the silicone has aged and lost its viscosity allowing hub to not lock up and spin the fan enough, prompting the higher engine temps? If thats the case, then replacing the silicone, per this instructional thread, should at least give the hub some form of normality - when new for eg. Providing you dont get a silicone oil thats too high in viscosity... Or something like that... If thats the case then what BlueZ has done shouldn't have permanently locked the hub up - providing the silicone oil isnt too high in viscosity.
There is some drag when the engine is cold but with a fully funtioning fan clutch you can hold the fan with a flexible plastic ruler and start the engine without the fan spinning. When you try to start the engine with the engine hot you should not be able to stop the fan with the plastic ruler. fan cluct ruler test "How does a thermal clutch fan work?" A thermal clutch fan operates using silicon fluid as a viscous coupling medium. When the clutch is cool and disengaged, most of the silicon fluid is stored in the reservoir allowing your fan clutch to slip relative to your water pump shaft thereby spinning at a lower RPM than the water pump. This saves you money because the horsepower from your engine is not wasted driving a clutch fan when it's not needed. As your engine heats up, the thermal spring on the front of the clutch expands, which opens a valve allowing the silicon fluid to drive your clutch at an increased RPM. This provides more air flow through your radiator, preventing your car from overheating.
I thought this "rebuild" was fairly common knowlege...... obviously wrong Available from most Toyota dealerships over the counter Hate to say it but yota's actually got it right, their hubs are rebuildable without having to drill anything. Unbolt, wash out, add new medium & Oring, reassemble, refit to engine. & nissan ...... mutter mutter mutter mutter
combination of 2 things..... oil breaking down over time contamination via wear..... you'll see this when you pull a non working unit apart, the medium is more a paste than oil and its usually grey in color ( a finely ground alloy contamination color ) Grease works .... sort of also done 2 hubs on the rallycar over the years..... a tekscrew through the guts is a faster and easyier fix to get us going again
