Nigelw Posted March 9, 2014 Share Posted March 9, 2014 Need to start getting a few of my other jobs squared away and as the old viscous unit was just spinning round wildly I knew it had expired. Originally planned an electric fan install but after much learning this past 2yrs I realized that I needed the viscous fan to ensure the intercooler was working efficiently, I digress. Need a new viscous coupling, options and choices are few and far between. Genuine LR @ £250 Bearmach @ £55 All Makes @ £18 Britpart @ £18 Who has experience of what and what is best to avoid? Really wanted to buy a genuine one but F**K me can I afford £250 Mnd you, still cheaper than replacing an engine after it over heated Quote Link to comment Share on other sites More sharing options...
Tetsu0san Posted March 9, 2014 Share Posted March 9, 2014 For that choice I would try AllMakes. They are based on the business park where I work and I have never had an issue with their stuff before. Quote Link to comment Share on other sites More sharing options...
JimDay Posted March 9, 2014 Share Posted March 9, 2014 Could always fit an electric one lots of universal ones on e bay Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 10, 2014 Share Posted March 10, 2014 I had a bad experience with an electric fan, after a creek crossing it burnt out, not immediately but some time later when the fan was needed and never worked and the water temp went through the roof. Lesson learnt, electric fans are okay for road cars but not for off roaders, stick to the viscous coupled one, I also carry a small flat plate thas a hexagonal cut-out in it and four holes to correspond to the 6mm fan mounting bolts so I can "lock" the coupling so its permanently driven for very hot conditions Quote Link to comment Share on other sites More sharing options...
steve b Posted March 10, 2014 Share Posted March 10, 2014 That's a great idea Iain might have to knock one up for myself I've used Allmakes and Bearmach fan VC's and have both been fine cheers Steveb Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 11, 2014 Share Posted March 11, 2014 There are two ways of making the plate. The hard way is to drill a 1" diameter hole and file out the hexagonal shape, the easy way is to buy a cheap tube socket, cut it down to no more than 3/16" and weld it into the plate, this gives you adequate space on the left handed thread fan nut for a spanner to unscrew the fan nut, then drill in the plate matching holes for the four 6mm bolts that locate the fan. Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 11, 2014 Share Posted March 11, 2014 Boydie, that sounds like an excellent idea. Could you post up a photo, please? Nige, don't fit an electric fan - they don't have anywhere near the effectiveness of the big engine driven fan and are less efficient. As a short term bush repair, a failed-open viscous coupling can be "failed-closed" with a couple of cable ties wrapped around the viscous unit and fan hub, but a proper repair is better as it will allow the engine to run at a better temperature and warm up faster. I don't trust Britpart, and much of Allmakes stuff comes from the same place. I've not had any trouble with anything Bearmach, but I couldn't definitively say that they don't all use the same supplier... Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 12, 2014 Share Posted March 12, 2014 Will do, give me a couple of days please as the plate is currently on the fan. By the way, excuse possible old age dementure, the 25mm hole is for the welding in of a portion of a cheap box very thin wall box spanner, if you are going to file out the 23mm hex, (30mm across the flats) I would advise you drill a 20mm hole after very carefully marking out the profile of the hexagonal with a scriber. BTW its a LOT of filing !!!! Initially I did the former, then perchance I came across a second hand box spanner of the right size in a garage swap meet (possibly for a very large spark plug???) and made a "proper" job of it. Either way you will need to turn up a 130mm diameter plate in order to cover the four 6mm bolt holes, ideally softish steel material and drill your prefered hole in the centre. My plate fits over the top of the fan, not under. Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 12, 2014 Share Posted March 12, 2014 Nige, BTW if your doing a LOT of fording, obtain a differential bango fitting and drill and tap the top of the timing cover to give it a breather once the fording plug is fitted, the instant cooling of the cover once you enter the water can result in water being sucked into the cover through the front seal. Quote Link to comment Share on other sites More sharing options...
Nigelw Posted March 12, 2014 Author Share Posted March 12, 2014 Nige, BTW if your doing a LOT of fording, obtain a differential bango fitting and drill and tap the top of the timing cover to give it a breather once the fording plug is fitted, the instant cooling of the cover once you enter the water can result in water being sucked into the cover through the front seal. Been pondering the breathing of the timing case as have only seen the extended breather that fits the circular plate for the FIP and as this is where the tension/idler pulley for the A/C goes I was wondering what to do about a breather? Worry not Snagger, I went off the idea of electric after the steep learning curve of intercooler efficiency and how the intercooler needs the extra air drawn through it at all times to reduce intake temps! While the viscous coupling is off I will be sure to make the locking plate up to go in my spares box along with the plate for removing the steering wheel. Good call there Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 13, 2014 Share Posted March 13, 2014 It's not just the loss of the intercooler effectiveness. If you look just at the sheer size difference between electric and viscous, it gives you an idea of the difference in cooling ability. As for efficiency, electric fan manufacturers' statistics about bhp and economy reductions of mechanical fans are based on fixes fans on engines running at high rpm with no airflow from vehicle movement, so the blades are working at a high angle of attack. The real world is a little different - if the engine is spinning at high rpm, it will either be at high road speed, meaning that the fan will be windmilling even at hgh rpm, or if at low vehicle speed, will need more cooling than the electric fan can provide long term. Furthermore, an electric fan needs energy to be transferred from engine kinetic energy, losing a large fraction of total energy in the process, through the alternator into electrical energy, transmitted along the wires with associated resistance and losses, to suffer another set of losses as the electrical energy is converted back into kinetic by the fan motor.An engine driven fan doesn't suffer those energy transfer losses. Nor does it drain your battery when parked or eat your rad when its dodgy mounting kit goes awry! Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 18, 2014 Share Posted March 18, 2014 The other point to consider is the required airflow. With an after market fan, the airofoil blade has been designed to give a maximum flow for a given size electric motor at arround 85% of the total motor capacity, this gives a certain design leeway and prevents the motor from blowing fuses from drawing excess current, over the design max cubic litres per second the blades simply cavitate reducing the driving load on the electric motor. The buyer has no idea really just how much air flow his vehicle needs to maintain temperature, these figures simply are never published. specific The design of a mechanical airfloil blade is far more complex. The fan designer will be given criteria to work to in that they will know how much airflow is required for various water temperatures at the radiator, they will also know from the manufacturer the surface areas of the radiator and its efficiency, the complexity comes in at what engine revolutions this design has to allow for; example, you may be doing 100kph in 4th gear at 2500rpm and your engine cooling system needs "X" cubic meters per second for satisfactory cooling while an identical vehicle along side you is in 5th gear and while needing the same CMS is only reving at 2000rpm. It could be argued that the 2500rpm motor is working harder than the one in 5th gear and would need greater cooling but thats not always the case and that variable is only part of the problem and equasion. Consequently engine driven fan blades are designed for a far greater efficiency over a greater rev range. Yes, they do draw greater power from the engine than an after market electric fan will require but the electric fan will never be able to move the same amount of air as the driven fan will. The solution to this loss of power is the viscous coupling, its only in operation when its needed, that said I have a locking plate to give permanent drive to mine as I know that on over 45 degree C days if I use the A/C system my engine will experience a 15 degree temperature rise, with the fan locked and running full time this rise is reduced to a more acceptable 5 degrees, I can only put this abnormality down to the condenser fans inadvertantly cooling the bi-metalic coil on the viscous drive Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 18, 2014 Share Posted March 18, 2014 That's an interesting point about the effects of the ac. I am retrofitting ac from a Vogue Se to my lower spec RRC as I rebuild it (got all the parts from a few scrapped vehicles). The two electric booster fans on the condenser are fairly substantial, but the whole assembly has the effect of partially blocking the rad. I know ac activation raises the engine temperature (and fuel consumption) on most vehicles, but had never thought about it beyond the energy required by the ac pump. The airflow from the booster fans could be cooling the viscous fan hub a little and causing it to engage later. I'll keep and eye on that, and if needed I'll fit a plastic cap over the hub to deflect the booster airflow so the viscous fan behaves normally. There are two extra sensors in the thermostat housing elbow of a 300Td, and I presume other engines, when ac is fitted (200Tdi thermostat housing have two blank holes in their tops for these). The lower threshold switch will activate the booster fans as engine temperature rises and the higher threshold switch will deactivate the ac to protect the engine. Some aftermarket kits don't have these switches or logic. I don't think the booster fans should switch on with the ac, though - I think they're only meant to be triggered by raised engine temperature. Quote Link to comment Share on other sites More sharing options...
Nigelw Posted March 18, 2014 Author Share Posted March 18, 2014 The other point to consider is the required airflow. With an after market fan, the airofoil blade has been designed to give a maximum flow for a given size electric motor at arround 85% of the total motor capacity, this gives a certain design leeway and prevents the motor from blowing fuses from drawing excess current, over the design max cubic litres per second the blades simply cavitate reducing the driving load on the electric motor. The buyer has no idea really just how much air flow his vehicle needs to maintain temperature, these figures simply are never published. specific The design of a mechanical airfloil blade is far more complex. The fan designer will be given criteria to work to in that they will know how much airflow is required for various water temperatures at the radiator, they will also know from the manufacturer the surface areas of the radiator and its efficiency, the complexity comes in at what engine revolutions this design has to allow for; example, you may be doing 100kph in 4th gear at 2500rpm and your engine cooling system needs "X" cubic meters per second for satisfactory cooling while an identical vehicle along side you is in 5th gear and while needing the same CMS is only reving at 2000rpm. It could be argued that the 2500rpm motor is working harder than the one in 5th gear and would need greater cooling but thats not always the case and that variable is only part of the problem and equasion. Consequently engine driven fan blades are designed for a far greater efficiency over a greater rev range. Yes, they do draw greater power from the engine than an after market electric fan will require but the electric fan will never be able to move the same amount of air as the driven fan will. The solution to this loss of power is the viscous coupling, its only in operation when its needed, that said I have a locking plate to give permanent drive to mine as I know that on over 45 degree C days if I use the A/C system my engine will experience a 15 degree temperature rise, with the fan locked and running full time this rise is reduced to a more acceptable 5 degrees, I can only put this abnormality down to the condenser fans inadvertantly cooling the bi-metalic coil on the viscous drive Always when I read a post like this I feel like such a novice even though I have been spannering on Land Rovers for almost 20yrs Quote Link to comment Share on other sites More sharing options...
Maverik Posted March 21, 2014 Share Posted March 21, 2014 Just to add, a limitation to a viscous fan is that they only work with a correctly fitted cowling, if the fan clutch isn't getting the hot airflow over it from the radiator, then it pretty much always operates in open clutch mode and doesn't do its job properly... embarrasingly it took a little while for this to sink in with me... I have an old Mondeo fan fitted to the 90 with a manual switch, not really had a "hot" day to test it on, but with a new radiator and thermostate up to now just driving around she manages her own temperature without a fan perfectly - horse box towing too didn't really do much to alter the situation, but I put the fan on anyway for good measure. When I eventually put an genuine 200 in it, I'll be converting it back to viscous. Quote Link to comment Share on other sites More sharing options...
elbekko Posted March 21, 2014 Share Posted March 21, 2014 Need to start getting a few of my other jobs squared away and as the old viscous unit was just spinning round wildly I knew it had expired. Originally planned an electric fan install but after much learning this past 2yrs I realized that I needed the viscous fan to ensure the intercooler was working efficiently, I digress. Need a new viscous coupling, options and choices are few and far between. Genuine LR @ £250 Bearmach @ £55 All Makes @ £18 Britpart @ £18 Who has experience of what and what is best to avoid? Really wanted to buy a genuine one but F**K me can I afford £250 Mnd you, still cheaper than replacing an engine after it over heated I would't go for the Allmakes/Britpart one (same price, so most likely the same part), the bearings fail and can take out your rad... I fitted one I got from BCP, it certainly wasn't £250, but was definitely a proper OEM, if not genuine part. Quote Link to comment Share on other sites More sharing options...
Nigelw Posted March 21, 2014 Author Share Posted March 21, 2014 I would't go for the Allmakes/Britpart one (same price, so most likely the same part), the bearings fail and can take out your rad... I fitted one I got from BCP, it certainly wasn't £250, but was definitely a proper OEM, if not genuine part. I have to go to the university of Ghent so will callin and see Joachim on my way round on Monday Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 21, 2014 Share Posted March 21, 2014 Maverik does have a point, ideally the viscous fan drive would be off the water pump and the temperature sensor would be in the water from the thermostat to the radiator, normally this would be in the form of a wax bulb that controlls the silcon fluid drive although on some engines, (Cattapillar I believe are one, it is a bimetalic coil) . This simply isnt possible on the Land Rover 300 and 200TDi engines so the lesser efficient bi-metalic coil in the air flow has been used. This is less than ideal as it can be affected by ill fitting cowls, extream moist air, and high temperatures being discharged from the air conditioning condenser. A solution would be a remote bulb but I dont and have never heard of a viscous drive with a remote sensor, if anyone knows of one I'd like to hear of it. Quote Link to comment Share on other sites More sharing options...
Daan Posted March 21, 2014 Share Posted March 21, 2014 I had a bad experience with an electric fan, after a creek crossing it burnt out, not immediately but some time later when the fan was needed and never worked and the water temp went through the roof. Lesson learnt, electric fans are okay for road cars but not for off roaders, stick to the viscous coupled one, I also carry a small flat plate thas a hexagonal cut-out in it and four holes to correspond to the 6mm fan mounting bolts so I can "lock" the coupling so its permanently driven for very hot conditions I just drilled the heads of the bolts of the fan and the bolts of the pulley, so I can lockwire the fan in the fixed position. I think you can even undo 1 bolt, so its interlocks with the 4 bolts for the puley, and than it is fixed as well. Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 26, 2014 Share Posted March 26, 2014 I would'nt be doing that (undoing one bolt so it interlocks with two of the four pulley bolts) for anything other than a short distance low rev emergency as the driving flange those 4 bolts tap into is urine weak !! Quote Link to comment Share on other sites More sharing options...
Daan Posted March 26, 2014 Share Posted March 26, 2014 I would'nt be doing that (undoing one bolt so it interlocks with two of the four pulley bolts) for anything other than a short distance low rev emergency as the driving flange those 4 bolts tap into is urine weak !! wasn't suggesting it to be a permanent fix... Quote Link to comment Share on other sites More sharing options...
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