reb78 Posted June 5, 2017 Share Posted June 5, 2017 After a motorway run the other day, I decided to 'test' my viscous fan. The engine was hot, but the fan could be stopped with a piece of card. I took this to mean that it had failed and ordered a new Borg Warner branded one online. I can hear the fan the whole time now, but even when the engine is cold from first start. I 'tested' this with the same method, so a minute or so after starting with a piece of card, but could not stop the fan turning at all. Is this seized out of the box and should I return it? Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 6, 2017 Share Posted June 6, 2017 It sounds like the second unit is faulty. The first might be fine - the fan should not lock up when the engine is warm, only when it becomes overly warm. If the engine is within normal operating temperatures, I don't think the fan should be locked, otherwise it defeats the object and you may as well have a fixed fan. Quote Link to comment Share on other sites More sharing options...
Maverik Posted June 6, 2017 Share Posted June 6, 2017 other than a bout of curiosity... did you have any need to change it? i.e. have you been experiencing high water temps etc? Quote Link to comment Share on other sites More sharing options...
reb78 Posted June 6, 2017 Author Share Posted June 6, 2017 Ok. Thanks Snagger. I have requested a return and refund from the seller. What you say about lockup temps makes sense. Out of interest, do you know of any way of testing the viscous that was fitted to ensure it will lock up at higher running temps? Mav, my reason for testing was because of the potential hot under bonnet temps leading to clutch hydraulics issues the other weekend. I just wanted to ensure that cooling under the bonnet was as good as it could be to avoid under bonnet temps being hotter than they should be. No high water temps or anything like that thankfully (but i do only have the standard temp gauge fitted so that would be hard to judge). Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 6, 2017 Share Posted June 6, 2017 You have checked that there is nothing wedged between the pulley and viscous unit, or overly long bolts, that are binding it, haven't you? I can't check because my cars are several thousand miles away, but as memory serves, the bolt heads should be towards the engine side as they're the "slim end", the nuts and expose threads rad end where they wont bind on the pulley. As for testing, the method that comes to mind is to run the vehicle to get the temperature up and then leave it revving a bit while stationary to try to get the coolant temperature above normal. I'm not sure if it's the coolant temperature being conducted through the pump and shaft to the viscous unit or whether it absorbs heat passed from the rad through the airflow and direct radiation, but the latter seems unlikely. So, if you can get the temperature above the normal running level, you should soon see a lock up. Perhaps a little (cautious) direct heat from a paint stripping gun or a plumbing torch would work without running the vehicle. Quote Link to comment Share on other sites More sharing options...
V8Pete Posted June 6, 2017 Share Posted June 6, 2017 When the engine is not running the silicon fluid in the viscous fan settles at the bottom at fills both chambers. So when you start it, for a short time, the fan will run as if the engine is hot as the fluid provides drive. Once centrifugal force has pushed the fluid into the correct chamber it will lose drive. To test it you need to leave the engine running for a few minutes before trying to stop the fan with a piece of card. It could be that your replacement unit was fine. Quote Link to comment Share on other sites More sharing options...
reb78 Posted June 6, 2017 Author Share Posted June 6, 2017 I pretty much did this. Started up, got the car out and drove up the drive slowly on Sunday (would have been 2 minutes or so) and then I popped the bonnet and tried to stop it, but no joy. The other thing that made me think it was seized (hence the thread) is that I can hear it whirring up the whole time, so on my ten minute drive to work, I can hear it whirring every time I pull away - the engine is only just up to temp by the time I get to work normally, so the fan shouldn't be kicking in I guess? Quote Link to comment Share on other sites More sharing options...
Hazza Posted June 17, 2017 Share Posted June 17, 2017 I also bought a replacement viscous unit (the original had seized to the water pump and had to be cut off) and found that it was locked all of the time. I've never managed to get the 200tdi hot enough to lock up the new unit. On a previous TD5 I found (accidentally) that leaving a radiator muff in place then driving along the motorway soon locked up the fan... Maybe try a covering the radiator and going for a drive? Keep an eye on temperatures obviously! Quote Link to comment Share on other sites More sharing options...
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