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Oct 19, 2016 15:54:42 GMT
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from the e39 running like a bag of spanners thread there is some mention of viscous fans as a couple of us said that the OP water pump bearings might be noisy.
anyway.
ive just received a viscous coupling from a parts company in germany and its a german manufactured product.
theyve just sent me this coupling as ive pointed out to them that the previous one that they sent me isnt working so they have kindly sent me another free of charge and don't even want the other unit back.
this is my understanding of how a viscous coupling works.
with a cold engine, at idle even, the clutch isnt engaged. it allows the fan to move freely and independent of the fan pulley as there is no need to have a fan running when the engine is cold and it were it running it would make the engine take longer to warm up. so basically the fan pulley is whizzing around as normal at engine speed and the fan just lags behind in a dossy manner doing very very little. essentially with the engine not running the fan should be able to move with ver little resistance, just by coughing on it!
when the fluid in the coupling is heated up by the engine temperature then the clutch engages, the fan is locked and will spin in order to cool the radiator.
that is my understanding, that has always been my understanding and will always be my understanding lol
it seems that the people that make these couplings that i have been buying from think that they should be stiff(engaged)when cold and ease up as the engine warms because they keep supplying me with couplings that do just this and I'm starting to become a little confused as to how the world operates at large when people bend the rules so dramatically and spread their misunderstnadings-i know some are going to say that that is what i am doing or victim of : /
I'm begining to think that these fans need a little time to bed in or something but after 10 days of use it isnt behaving any differently.
if you think that your fan is supposed to be stiff when cold-please do some simple googling before telling me ive got it back to front lol
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Oct 19, 2016 16:24:24 GMT
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Hi, In the early days of viscous fan couplings the fluid in them were able to transmit the drive through from pump to fan at low speeds and would usually not go above a set speed because of 'slip'. The reason being that when idling in traffic you got air movement through the rad, when on the open road the air movement was not needed from the fan. If one failed by seizing up you certainly noticed the effect on noise and economy. Many modern ones are usually thermostatically controlled as you describe. Perhaps you could investigate which type you have.
Colin
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Oct 19, 2016 16:38:41 GMT
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sticking to what i said, surely if your car is sitting in traffic and starts to get hot then the viscous fan would lock and provide cooling.
i don't think that there is any application of viscous coupling that functions to engage the fan blades while the engine is still cold.
ive never heard of 2 different types of viscous coupling either.
just have this issue that they keep supplying me with stiff couplings
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Oct 19, 2016 16:45:39 GMT
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And sticking to what I said, they may not all be thermostatically controlled.
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Oct 19, 2016 16:53:00 GMT
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how does it engage if its not thermostatically controlled?
i understnad what your saying but that would work against the interests of the engine lol
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Oct 19, 2016 17:05:39 GMT
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Hi, It's partially engaged all the time up to certain speed when the drag of turning the fan is to much for it to go higher. This helps by providing air movement at lower speeds, like when stationary in traffic, and not when on the motorway when the cars speed will provide it. This helps with the engines fuel consumption by not having to power a usually quite large fan at high speed.
Colin
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Rich
Club Retro Rides Member
Posts: 6,302 
Club RR Member Number: 160
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Oct 19, 2016 17:08:07 GMT
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I explained that in the previous thread. The fan will run at a constant speed regardless of engine speed. That is what a viscous fan should do. Not 'engage/disengage' dependent on heat. If anything they drive worse when hot due to the fluid loosing its viscosity from experience.
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Oct 19, 2016 17:16:20 GMT
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i know that you explained that but that is the opposite of my understanding of how they work whichis why i started the thread.
i replaced a coupling that is stiff with another that is stiff.
you say that they are constantly engaged and run according to engine speed, so you have created a third way that they work that differs from what me and from what colin have said.
professional mechanics write up stuff all over the net about this but you can find as many articles that conflict with each other as thise that agree.
by your example though, if the viscous coupling was 'fixed' then why bother with this viscous element at all? so that doesnt make sense to me. no offense to you of course.
everyone thinks that they have the correct answer-including myself but there is no definitive answer out there that i can find.
for example you say that its not about heat but to meet heat is the prime reason a viscous fan exists, activated by heat to evacute heat.
engine speed isnt a consistant way to determine engine heat. a car can be hot when driven hard but can be hot when sitting in traffic.
thats why I'm agreeing with everything that i had read or seen that demonstrates heat as the aspect that triggers the function.
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Oct 19, 2016 17:30:19 GMT
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excerp from wiki for whatever that is worth...
When the engine is cool or even at normal operating temperature, the fan clutch partially disengages the engine's mechanically driven radiator cooling fan, generally located at the front of the water pump and driven by a belt and pulley connected to the engine's crankshaft. This saves power, since the engine does not have to fully drive the fan.
However, if engine temperature rises above the clutch's engagement temperature setting, the fan becomes fully engaged, thus drawing a higher volume of ambient air through the vehicle's radiator, which in turn serves to maintain or lower the engine coolant temperature to an acceptable level.
...and you can find the same story all over the net.
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froggy
Posted a lot
Posts: 1,099
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Oct 19, 2016 18:36:12 GMT
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my understanding of viscous couple fans is limited to shoving s hammer handle against the fan blades and starting the engine . If it spins up pretty quick it's good .
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frag
Part of things
Posts: 336
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Oct 19, 2016 21:08:45 GMT
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Surely,the bi-metallic strip that is coiled up on the front of the unit,reacts to the temp of air flowing over it (which is blown thru from radiator) and then locks or unlocks the amount of 'drive' by altering hub internals. ?
In my experience,they lock up more when hot,freewheel when cold.
Better warm up,more bhp and better economy.
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'69 Holdsworth bay
'88 T25 Panel van
‘72 beetle
‘78 vw champagne T2
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frag
Part of things
Posts: 336
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Oct 19, 2016 21:19:07 GMT
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Oh,and regarding the locked up while cold scenario.
I don't think that's necessarily a fault.I suspect that on start up,some centrifugal action is needed to 'sort itself out'
Ford rangers,when started and revved from cold,the fan can be heard and is very noisy,if you hold revs on,within a very short time (prob less than a minute) the fan can be heard to fade out,the very loud noise stops.
They all do it,and never had a problem with any of them.
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'69 Holdsworth bay
'88 T25 Panel van
‘72 beetle
‘78 vw champagne T2
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My understanding is that of Stinkynails and the new BMW and Sprint units I have are both freewheeling when cold.
And according to BorgWarner youtube videos they work as Stinkynails states. i.e free spinning when cold, fluid heats up and locks the fan so its spins at engine speed.
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Last Edit: Oct 20, 2016 0:51:00 GMT by Deleted
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ChasR
RR Helper
motivation
Posts: 10,244
Club RR Member Number: 170
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i know that you explained that but that is the opposite of my understanding of how they work whichis why i started the thread. i replaced a coupling that is stiff with another that is stiff. you say that they are constantly engaged and run according to engine speed, so you have created a third way that they work that differs from what me and from what colin have said. professional mechanics write up stuff all over the net about this but you can find as many articles that conflict with each other as thise that agree. by your example though, if the viscous coupling was 'fixed' then why bother with this viscous element at all? so that doesnt make sense to me. no offense to you of course. everyone thinks that they have the correct answer-including myself but there is no definitive answer out there that i can find. for example you say that its not about heat but to meet heat is the prime reason a viscous fan exists, activated by heat to evacute heat. engine speed isnt a consistant way to determine engine heat. a car can be hot when driven hard but can be hot when sitting in traffic. thats why I'm agreeing with everything that i had read or seen that demonstrates heat as the aspect that triggers the function. Even if they are fixed to 'slip' that serves as an MPG aid while still providing some cooling for the engine. The Stag Viscous Couplings went under another name for this reason, like Torquadrol, referring to them not sapping loads and loads of power. On the M3 I went from a coupling that was audibly noisy ; it sounded like a jet under the bonnet! The last owner moaned about how the car would only see 19MPG! With me in that state the car saw around 22MPG. With the new OE spec coupling you cannot hear it at all, even with the fully warmed engine. The MPG has not gone up loads but it has gone to 25+MPG. In addition the oil temp has dropped a good 10-15 degrees and the engine does now seem more responsive than when I bought it, and that comes from someone else driving the car. Mine does however seem to go from freewheeling near enough when cold to spinning at a quicker rate when warm  . I have not seen it lockup myself, but I do also have a secondary fan. Maybe the engine has to get very very very hot for it to permanently lock, I.E, about to overheat. If it's a good quality coupling you have (like Hella/BEHR on a BMW) and not the cheapest thing you could get your hands on I wouldn't worry about it if the rest of the system is working. A fully locked viscous coupling will have quite an effect on MPG and response, not to mention power. In worst cases the blades of the fan can bend and destroy a radiator. I have seen the latter a few times on cars with iffy couplings. |
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Last Edit: Oct 20, 2016 4:58:28 GMT by ChasR
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On my E38 the viscous fan would match engine revs upon first cold starting (which never made any sense to me), it would then slow itself down shortly after and not really track engine revs until it heated up and then you would hear the fan accelerate up to engine speed again then slow down again a while later so it certainly seemed to be properly temperature controlled. When cold the clutch was quite stiff, when warm it was really loose and when hot it was stiff again. It never completely locked though so it may have reached a max speed when engaged but certainly sounded like it was tracking with rpm up to 6k creating a near hurricane under the bonnet.
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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Guys. Just stop for a second and think about it.
The reason youre confused is that not all fan couplings are the same, work the same way or are trying to achive the same outcome.
Some will transmit drive when cold and slip at higher rpm to save power
Some will free wheel when cold and lock up when hot for better cooling.
I dare say some do both.
Some work with viscous couplings
Some have a bi-metallic strip in them
They are not all the same.
What you need to do is be sure what the one on your car is supposed to do before you go complaining. They may be right and it is supposed to be stiff when cold.
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Oct 20, 2016 23:51:13 GMT
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On an M50 engined E39 the viscous fan should spin slightly at cold, and the clutch should engage and spin the fan (with torque) once the engine is up to the correct temperature. A quick test is that you should be able to stop the fan with a cold engine with a rolled up newspaper.
The reason why the fan shouldn't be fully engaged at all times is because it will constantly cool the engine, which will send a signal to the ecu via the temp sensor to map the engine as if it is cold - increase the fueling; hence why it will kill the MPG, and potentialy cause bore wash, which isn't good for the engine.
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ah ha! this is the main why i started the thread and why ive just had to change my coupling!
on my m20 i thought i had an issue with the temperature sensor and changed it even though showed it had the correct resistance but the car was behaving like it was over fuelling because of it being cold.
it was running from one extreme of being too rich to too lean because of the way its been set up to compensate for the interference of the defective viscous coupling.
i do have an oil leak from the cylinder head gasket and I'm going to change it next week so ill be able to take a look at the bores.
ill post some pics of the the car burning once ive put a match to it after : /
they still keep sending me viscous couplings-stiff as a porn star.
explains why the car was running seriously lean when i bought it.
time for an electric fan me thinks because the coupling producers don't seem to get how they are supposed to work...
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Rich
Club Retro Rides Member
Posts: 6,302
Club RR Member Number: 160
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Oct 21, 2016 12:36:50 GMT
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ah ha! this is the main why i started the thread and why ive just had to change my coupling! on my m20 i thought i had an issue with the temperature sensor and changed it even though showed it had the correct resistance but the car was behaving like it was over fuelling because of it being cold. it was running from one extreme of being too rich to too lean because of the way its been set up to compensate for the interference of the defective viscous coupling. i do have an oil leak from the cylinder head gasket and I'm going to change it next week so ill be able to take a look at the bores. ill post some pics of the the car burning once ive put a match to it after : / they still keep sending me viscous couplings-stiff as a porn star. explains why the car was running seriously lean when i bought it. time for an electric fan me thinks because the coupling producers don't seem to get how they are supposed to work... Are they still stiff after being ran up and then left to cool? The Borg Warner one I fitted to my E28 had a leaflet with it saying they won't work properly directly out of the box due to storage allowing the fluid to require distributing internally. Just a thought. |
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bortaf
Posted a lot
Posts: 4,549
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Oct 21, 2016 15:37:36 GMT
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On an M50 engined E39 the viscous fan should spin slightly at cold, and the clutch should engage and spin the fan (with torque) once the engine is up to the correct temperature. A quick test is that you should be able to stop the fan with a cold engine with a rolled up newspaper. The reason why the fan shouldn't be fully engaged at all times is because it will constantly cool the engine, which will send a signal to the ecu via the temp sensor to map the engine as if it is cold - increase the fueling; hence why it will kill the MPG, and potentialy cause bore wash, which isn't good for the engine. ? err no, it will constantly cool the RAD the stat will keep the engine at operating temp and close if it gets too cold, if a locked fan is overcooling the engine to the point it's running on a cold map the stat is faulty, the higher fuel usage is due to the extra drag from the fan constantly pulling air through the restriction of the rad core. There are differant types of "viscous fan" as said www.haydenauto.com/featured%20products-fan%20clutches%20and%20fan%20blades/content.aspxthe normal type used in RWD fords pretty sure it's the same as BMW style as i have used ford ones in BMWs in the past ? www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Hayden/Fan_Clutches_How_They_Work.pdfAnd lastly why they spin faster for a while after first started www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Hayden/Hayden%20Fan%20Clutch%20Design%20Types.pdfAnd finaly taken from the ford factory manual descibing the viscouse fan operation PRINCIPLE OF OPERATION Temperature Sensing Viscous Fan The temperature sensing fan drive operates a shear type fluid coupling which controls the fan speed by transmitting the drive through a film of silicone fluid and has the ability to idle the fan at all engine speeds, whenever the engine cooling requirements are low. The interior of the drive is divided into two chambers. The rear chamber contains the rotor (K) whilst the front chamber forms the fluid reservoir (Ll. Fluid is pumped into the reservoir by the rotating action of the rotor and the use of a ram pump (C). This pump consists of a hole (called the discharge port (A), and a "weir" (B), which is a depression in the pump plate designed to cause a pressure rise in the fluid. This has the effect of transferring the fluid from the rotor chamber to the reservoir while the engine is running. The ram pump is located near the circumference of the pump plate (P). The rotor is directly 1inked, via the drive shaft (M) to the engine and with the engine running the rotation of the rotor retains the fluid in the reservoir. As the engine cooling demands increase, a bi-metallic element (E) senses the air temperature behind the radiator, and operates a control valve (G) which progressively (as demand increases), opens the intake port (H). This allows fluid re-entry into the rotor chamber, which in turn increases the fan drives' torque capacity. Hence, as the engine coolant temperature increases the fan rotor chamber fills with more fluid, increasing the friction factor, which increases fan speed (within its design parameters), thereby increasing the air flow and cooling capabilities. As the above description explains, the speed of the temperature sensing viscous fan is related to engine temperature and not engine rpm.  |
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Last Edit: Oct 21, 2016 15:58:20 GMT by bortaf
R.I.P photobucket
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