Viscous Fan

[Maniac]

I recently replaced the clutch and on the viscous fan because it did not want to ever stop once it had come on. The fan now still does te same thing.

When cold, the fan is definiately off, but as soon as the temp guage reaches the "running" mark, at about 11 o'clock on the guage, the fan kicks in and the fan will then stay on while driving.

IMHO the fan should be coming on and off when needed? It will only switch off when the car has been stationary for quite a while.
To test, I permanently engaged the two electric fans in the front, to try and see if the car was running hot, but to no effect.

Is this normal? What could be the problem? The heat guage never goes any higher, even when 48 degrees in kruger with the aircon on?
Faulty guage maybe?

Opinions would be appreciated.

[Kagiso II]

I M O - the visous fan ALWAYS runs, in tune with the engine revs (as soon as the engine has reached operating temp]
- Electric fans switches on & off as per the temperature of the water [wherever the the sensor is positioned]

At least, all of my vehicles have viscous fans - and they run forever [and on none of them will I ever switch from viscous to electrical fan .. it just does not work effectively off road]

BUT Peter & Frans would know best [better at least] (ek prik net hier dat jou thread nie doodgaan nie]

[JG Shields]

Maniac, if a Viscus fan is in good working order, it will only engage when "cooling" is required from the cooling system. If I was in you position, I will remain suspisious of the cooling system and less so about the Viscus. I suspect that your Vicus is doiing exactly what it is made for...... The temp guage inside the car is not an accurate indication of the cooling system's efficiency. In fact, it is possible that the Viscus is indeed keeping the temp down within normal spec. Have your radiator, thermostat and waterpump checked out.

I had the exact same symptoms on my 4.8. I replaced the radiator after a proper inspection which revealed serious blockages in- and outside. With the new radiator, my viscus was perfectly fine and only kicked in under extreme conditions.

[AndriesS]

In my limited experience, I've never seen a viscous fan standing still-the ones on my cars have always turned while the engine is running. Normally spins after the engine is stopped as well. In theory should stop quicker when hot.

I've not seen one that has an on/off operation and my gut feeling tells me the following:
When the air temp being pushed through the radiator at speed is below a set limit (the front of the viscous will sense/measure the air coming through the radiator which will give an idea of the water temp ), the fan will freewheel in the air , when the air temp reaches a certain temp the oil will heat-up /clutch will engage from a bi-metal strip and the fan blades will start to turn at a similar speed to the fan pulley speed.
When the car is stationary there is still a limited dragging / resistance in the viscous coupling and of the fan blades will turn (but not at the pulley speed), again sucking in air/ measuring etc as above.
If you try and grab it when it is cold you should be able to hold it, but when it is hot(above the limit) (I won't suggest the exercise as you might hurt yourself) as viscous coupling should now have maximum drag/resistance to speed difference and the fan speed should meet the pulley speed.

This is the main reason why it is so difficult to tell if a viscous is working as it always looks like it's turning the fan. That said if you measure the fan rotating speed vs the pulley rotating speed at different temp you should be able to test it.

I used the limit word as the temperature reference point where the viscous will kick in.

Finally, some people suggest to pour cold water onto the coupling when planning a water crossing, this will drop the temperature the viscous feel and thus it will get back to the stage where the fan is dragging from the build in minimum resistance and the water from watercrossing will make it effectively stop.


Recap
If one looks at a viscous coupling/ clutch - it will have an input side ,i.e. where it bolts to a pulley and then an output that bolts to the fan. if you turn the input and hold the output you will feel that there is resistance - hopefully you did it at room temperature and this will give an idea that even then it will turn the fan but there will be slippage as the fan does have an amount of resistance.
Now if could throw boiling water over the coupling, and hold the output and try to turn the input at 1000revs you should find the resistance changed drastically and they are nearly "locked" together.
The black magic inside the coupling is normally activated by some temperature sensitive method , i.e. special oil, bi- metal spring (front of coupling looks like it has a wind-up toys spring) etc

[JG Shields]

Andries, I agree with you. My explanation of the viscus' "engage" action is suppose to mean the same as your better explanation....ha...ha..

Short and sweet.....if a viscus fan sounds like an aircraft prop in motion, the viscus clutch is engaged. If the viscus clutch is in good working order, it engaged because it senced temperature levels which requires cooling...high temperatures! Those temperatures comes from the radiator(cooling pack) ,situated to its front, only. Therefore, IF THE VISCUS IS IN GOOD WORKING ORDER, start looking for overheating causes somewhere in the cooling system and DO NOT RELY ON THE CABIN TEMP GUAGE to base any findings on.

[Maniac]

Any ideas / suggestions on where to go in Cape Town for cooling system faultfinding? The car has been for a service recently, and a Dino, and at the service I asked them to test the coolant , suspecting blown headgasket, but all test came up clean.

Cooling system pressure test done as well as radiator flush.

Thanks for the replies.

[tour de frans]

Good day
JG and Johndough are spot on.The fan are doing its job.Maybe the temp through the radiator are on the edge to keep the fan kicked in.Blocked core or tubes?
Just one thing:Johndough said:when cool the fan are free and you can catch it.Very true,but do not try to catch on the first start-up when cold.The fan are locked for the first min. or two.The fan will blow and then die after a while.The fluid need to relax the clutch first and then when hot it will lock again.
Visit any CHE in Cape town,they will check out your radiator.
Rdgs
Frans

[Maniac]

Frans CHE?? Please explain. I have dealt with a few radiator places, and results have not been that good.

[tour de frans]

Cape Heat Exchange,go to the Paarl branch,they are very clued-up.

[Maniac]

Had a look today with the engine bay open and the engine on. The suction hose from the radiator (top) is pulled FLAT from 2000 rpm .... will be looking for a replacement on Monday morning.