Engine cooling 3.9lt V8 + Viscous Fan
Posted by Dave Connaway on April 19, 1998 at 10:42:17:
Although I don't tow caravans, similar overheating problems to the messages posted recently, have plagued my NAS Defender 90 with 3.9lt Efi V8 and standard LR viscous coupled fan (VCF). Like other correspondents my vehicle is more than happy to cruise all day on the roads with the temperature guage just below half-way with no mud in the radiator cores! HOWEVER, give him a jolly good pasting offroad then go through a nice deep water splash and the temperature gauge hits the roof! AND the noise from the fan changes to a squeel (NOT belt slip) with negligable air flow felt from behind the VCF.
Having examined the VCF, there is a small coiled spring on the radiator side of the unit when fitted to the engine and I bet a few Quid that it's bi-metallic and sensing radiator air temperature. Therefore having got the engine nicely hot in Low 3 and then "foot to the floor", to then submerge him in a big puddle of cold water / slurry has the effect of splashing / cooling the spring (which the VCF assumes that radiator air is now cold) and disengages the VCF drive and the engine temperature hits the roof!
Perhaps someone with insider knowledge could agree / disagree?
Having almost boiled the engine on a number of off-road occasions and fortunately had a cordless drill and self tapping screws available the VCF has become a screwed coupled fan (SCV)! Fortunately my local dealership have replaced the SCF with a new VCF on a few occasions under warranty, but still cannot tell me how the unit functions and whether my water cooling theory is correct.
Apparently LR are more than happy to replace VCF's but won't shell out for a nice pair of electric fans (EF) because the replacement has to be like for like. Expert (UK) off roaders are about equally divided on the attributes of VCF against EF - anybody got similar stories views??
Is it true that all RR / Disco / Defenders whether V8 or Tdi are fitted with the same VCF as standard?
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