Viscous fans - a few quick checks to prevent overheating

Another cause of Land Rovers overheating is viscous fans failing
Here are some things to watch out for to prevent overheating!
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[@allanhughes7859]

Bloody hell just left an old bus standing for 5 years and yes the stuff did go all over the place bought a new unit at cost to find once I drove the old bus for a while it all came good again so another god dam lesson learnt !!!!!

[@ForceBuilt]

Autos sit for long periods of time with the clutch vertical with no option to store flat. Great video explanation. Thanks

[@BritannicaRestorations]

Thanks for watching!

[@Trenial]

old thermostats in US housing from like the 80's and back had this same thing on the inside, as you pushed the lever to adjust the temperature.

[@BritannicaRestorations]

Thanks for sharing

[@bimble7240]

The other advantage of the Viscous fan (compared to solid) is that the engine warms up faster as the fan isn't doing much, until the engine gets a bit too hot, e.g. Idling in traffic or towing etc.

[@MrRobmellor]

Hi Mike, once again a brilliant video on a subject that is not very well understood. After a life time on the spanners you have taught me some thing that I knew little about in a very straight forward manner. Credit to you Mike, I am looking forward to you raveling more hidden mysteries soon. Best wishes from Yorkshire Rob.

[@BritannicaRestorations]

Hi Robert! I don't know what it is, but these fans last better on every vehicle except for Defenders I guess we are just lucky that way! Mike

[@tomnscrubs]

Been nice to know how many CFM's they pull vs Electric fans. Thanks for the Good Lesson on these, gonna get a new one.

[@BritannicaRestorations]

Any time!

[@d4jmo]

Great info mike cheers bud 👍

[@garthrichert5256]

Just to say thank you for your fast replies and all the videos , all of which are so useful. Garth Richert

[@BritannicaRestorations]

No problem but I have to ease back on replying to all comments ( as there are quite a lot now) and try and reply to good questions so that others can learn

[@Jottingsfrom]

Another great video. Thanks Mike. Overheating is my biggest nightmare living in Western Australia (it gets really hot). I fitted an Engine Watch Dog TM2 and it’s already paid for itself. Traveling down the freeway it went off - I pulled over straight away and found the serpentine belt had come off. A new belt and everything was good. Cheap peace of mind. Thanks again.

[@BritannicaRestorations]

I was in central Australia 20+ years ago and indeed it does get a tad warm - in fact I had to undo my top button on my shirt! LOL! This is the second time I have read in my comments about the Engine Watch Dog - I may have to investigate further. Thanks for the comment! Mike

[@rockystonewolf]

On my Td5 the fan is removed altogether! No issues with overheating at all. In fact, I have only ever felt here on half the radiator. I re-asseble the fan when using the PTO for hydraulic power. I run a log splitter that occasionally need to be operating for a whole weekend.

[@juanweigel1057]

Thumbs up for the info Tucson Arizona

[@BritannicaRestorations]

Thank you Juan Mike

[@fionanokelly]

Hi Mike !! I've had my Disco1 for 20 years; it's just getting to 400,000 Km on the clock, and only once did I have an overheated engine. It was on a very hot afternoon at about 30C and I was belting down the highway. It never happened again, and till today the viscous fan is working just fine. By the way, you have a great sense of humor. Keep it up. It made me have a great laugh !!

[@BritannicaRestorations]

Thanks Fionàn! But at £31 it is cheap insurance for a new unit! Mike

[@timjames69]

I've not ran a fan for about 2 years. Interesting video on how the work, I have recently just fitted one of the aircon fans to the front (grill side) of my intercooler and found it helps keep the radiator cleaner as it pushes with water and grit out. Also I have used the original aircon wiring (poles reversed to change direction) that way I can control it with the switch but it also runs automatically

[@BritannicaRestorations]

Thanks for sharing

[@raygale4198]

A problem with fixed fans is that at high RPM and high road speed they block ram air flow as they start to behave like a solid metal disc spinning behind the radiator. Nearly all modern cars now have electric fans. I have learnt a lot watching your channel, I adopt a British MoD 110 that found it's way to Australia tomorrow. Wish me luck.

[@sukottora]

I tend to take them off my TD5 110 in the winter unless I'm towing something heavy - which is rare. Thing is, it seems to have been breading over winter I found 3 in the back of the garage when I put it back on a couple of months ago... I'm not sure what it was breading with though. That said, if it's been breading I suppose it means It's definitly F**ked. I digress.. Another great vid from the archive - thanks.

[@vitessetube]

Mike, excellent video and most amusing humour too! :-) I have been toying with the idea of fitting a revotec electric fan to my Puma 90, but to be honest I am not sure its worth it if the viscous is in good order and if used in comjuntion with a decent radiator, I am sure its perfectly up to the job... especially in the not very weather testing South East , UK!

[@BritannicaRestorations]

Thanks I fitted a twin fan system to my 3.9 Isuzu in the Defender as I was running out of space - works well and I got the override switch with the kit But at only £31 for a new viscous unit, electric fans are quite a luxury Mike

[@erhardt1477]

Learn something every time 👍🥳🖖 Greetings sir from Germany 🇩🇪

[@BritannicaRestorations]

Thanks for watching!

[@erhardt1477]

@@BritannicaRestorations Well... I have a strong motive ... I’m getting a Landy here in Germany, but lucky me... I watched your videos sir 😜👍🥳

[@allanhughes7859]

As all the others have said thanks so much for your time Just found your channel and have subscribed being a Land Rover hater/lover I need all the help I can get trust me !! I know folk make money doing these things but who cares the more you make the happier I will be because its work at the end of the day and you deserve every penny you get You also do it in such a way that I understand which also helps Me Mam said if I had brains I would be dangerouse So as I said thanks again Will now re cap on what you have done!! Dont worry about the pricks with thumbs down they are just MORRONS Cheers !!

[@BritannicaRestorations]

Thanks Allan! Mike

[@theredneckpirate5792]

Hows she going Mike, great info on your videos, I’m ripping mine out and replacing with an electric fan that I can control via the cab and a stat 😄😄 Big hello from Northern Ireland 👍🏼

[@BritannicaRestorations]

Sounds great!

[@schoolandstuff7128]

Great video. I have a a V8 Discovery 2 that I recently acquired. When I am driving the temperature stays between 188-194°F, but once I stop the temperature jumps almost instantaneously to about 210-215 and continue upwards until I start moving again. Your video is helping me to troubleshoot the problem.

[@BritannicaRestorations]

Thanks for sharing

[@lr_discostu]

Get an genuine hot temperature thermostat which will not only open at a lower temperature but also open at lower pressure. The original is designed to provide lots of cabin heater performance at the expense of engine cooling performance at idle. You want the genuine pel500110 part. The correct part is grey and not white or black. Don’t bother with any of the aftermarket units. I changed mine five times before I found the right solution.

[@ruaidhriobriain]

A few years ago I bought a 200TDI Discovery 1 with the viscous fan in the boot and an electric fan wired to run continuously as soon as you turned the ignition on. If you went over 60mph the temperature went above normal and if you slowed down it would go back to normal. I was washing it one day when it was hot and I noticed the water only evaporated off the top part of the radiator. Fitted a new radiator and I put back on the viscous fan and I never had overheating problems again

[@BritannicaRestorations]

I have lost count of the number of radiators with little or no fins - but do not leak!

[@bigbill74scots]

REALLY good video.

[@BritannicaRestorations]

Thank you - glad it was informative! Mike

[@corhendriks1755]

Hi Mike. Saw this video of yours just now. Extremely interesting as the principle of the viscous fan is barely understood (even by professional mechanics). Worked in the seventies and eighties as a Landrover mechanic and the Raro ones broke down regularly. When starting to work in the nineties with Landcruisers i was a bit biased. Turned out that the viscous drives on a Landcruiser never break > have seen examples with 750,000 kms and still the original and you can even repair them. To me they seem to be a more sophisticated (better and far less temperature fluctuation) solution compared to the fixed fan and much more reliable than any electric fan i've seen. Just my 5 Kenyan Shillings....

[@francismwangi7329]

Hey. Naeza get wapi hizi viscous coupling clutch ya navara

[@carlossaenz4075]

That's what would say !!!! old fashion fan they hardly go out they run on the motor. So if they do go out u know there some thing to do with ur motor or the fan belt. Easy

[@juliofernandez2442]

Hi Mike It's Julio from Miami My Landy still stranded in Europe but soon it will be here I live in Miami so my only concern is overheating ( already I lost one car last summer,booth heads blown up ,my lady was driving and she don't pay attention to the vapor under the hood , but please don't tell anyone) My acquisition is coming from Italy and I don't believe they have over 80f for eight months a year I'll take all warnings and recommendations you give and at soonest I apply your knowledge in my Landy I subscribe to patreon to pay for your knowledge , some people I know call all time for instructions on my field Keep teaching for the old guys and the new wannabe mechanics

[@BritannicaRestorations]

Julio - if the cooling system is in good order then you should be fine - but pay attention to the radiator core -- it may not leak, but the fins get all rotten and thus will not cool Mike

[@zitotomas1526]

Great lesson. I got a land rover Defender 130 its overheating. I already repaid the cylinder head and changed the head gasket but it still heating. I don't know what is happening.

[@BritannicaRestorations]

Thermostat? Water pump? Bad radiator?

[@JCO2002]

Having problems with mine on a 200tdi. Tempted to try to drill and bolt so it runs all the time. I'm in Jamaica, where it's always warm.

[@BritannicaRestorations]

That would not be the first time someone has drilled it!

[@harrisonbowie829]

how fix a free spin fan .Thums up.

[@stephenwagg9683]

Yes good stuff Mike, viscous coupling hubs on vehicle fans have been fitted for centuries, and really they have been pretty good ?? so given what you have said about crud in the hubs................how do you clean them out? plus if you had to replace one would it be cost effective to buy a new one or go electric, all modern car type vehicles use electric and are reasonably reliable? I used to fit Kenlow fans on most of my watercooled , breathed on engines back in the day and they were pretty fab, no wasted horses, but pretty noisy on some of my "hot"motors.

[@BritannicaRestorations]

you should be able to power wash the bimetallic spring when it is of the vehicle I have used this style fan on my Defender conversions www.revotec.com/

[@BritishBeachcomber]

You use a laser stroboscope, that's why you need reflective tape.

[@Simonandisla]

Very interesting tutorial. I recently had my TD5 chipped and turbo tweaked and ever since, the temp gauge creeps up particularly under load i.e. going up a long drag hill. Chap that did the remap says I have a more sensitive gauge and offers to re set the gauge for me back to the factory setting. I replaced the Intercooler and replaced Intercooler hoses with new silicon hoses. The gauge never moved before the remap. Round town etc no probs at all. Any thoughts ??

[@BritannicaRestorations]

To be honest I have not that much experience with Td5 here in Canada as all vehicle have to be over 15 years for import and those that do import usually bring in 300Tdi Have you got an EGT sensor and gauge fitted? If the vehicle is old I would check the fan is working - the couplings are cheap, but if not locking up can cause overheating as air flow can be reduced when slowly pulling hard up hills - just when you really need max air flow Around town, there is low airflow, but the engine is not working hard Just a thought Mike

[@fonso1961]

Interesting video Mike I have little knowledge in this subject lol. Mine has an electric fan with a capillary thermostat with the sensor running into the top radiator hose. This was fitted before I purchased it . Is this the normal set up for a electric fan.

[@BritannicaRestorations]

Yes quite normal - sounds as if you have a Kenlow fan system Mike

[@simonparsons5992]

Another great video Mike! On the subject of cooling 300tdi engines I've just fitted a range rover classic coolant level sensor to my expansion tank there's a transmission temp warning lamp on the dash of Euro spec defenders I've wired through this as a tell tale, only problem is it works the wrong way around! it's on when I'm ok and goes out when I'm running low on coolant buy it's about more piece of mind thanks again for passing on all this knowledge

[@BritannicaRestorations]

I saw this the other day www.landroverexpedition.com/technical/300tdi-low-coolant-alarm/ Mike

[@simonparsons5992]

Britannica Restorations thanks mine didn't have the resistor that might make it work the right way round!

[@BritannicaRestorations]

Did you use the circuit as in the link I sent you? Mike

[@simonparsons5992]

Britannica Restorations I hadn't seen this till you sent it I didn't included a transistor in mine so I couldnt get the relay to trip I'll be modifying my set up to match the link

[@BritannicaRestorations]

I think I will make a couple - seems easy enough And the sensors have come way down in price - but the are $170 each in the US! About £17 in the UK Mike

[@adl2005]

You mention storing the fan laid flat and not upright as the fluid will go to bottom of fan.What's the difference to leaving your vehicle stood for a few weeks if it's not a daily and just used for offloading surely it will have the same effect and damage the water pump.

[@garthrichert5256]

I wonder why the aircon condenser is in front of the radiator. Maybe it puts warm air into the radiator and makes the engine cooling less efficient.

[@BritannicaRestorations]

Big US pickup trucks have massive radiators but always at the back if the transmission cooler, A/V condenser, Steering cooler and engine oil cooler, so you are right the rad picks up all the heat exhausted by these other coolers - but the rad is very large to compensate, where a 300 Tdi is stil the same rad As an interesting foot note, the HS2.8 conversion retained the 300Tdi rad, but it was too small for towing or mountain work - I used to put stationary engine cores in which had an extra row of tubes and that worked fine Mike

[@bushratbeachbum]

Great video, nice one! I've got a fan doing odd stuff, the motor was overheating so I checked the fan and it was near to free spinning when hot. I changed the silicone oil in it and put it back on. Still the same, free spinning when hot, some resistance when cold. The bimetallic spring is reactive to heat, when open, i could see the valves open and close with the springs movement. Am i losing my marbles or am i missing something?!! Any input greatly appreciated!! Cheers!

[@bushratbeachbum]

@Britannica Restorations Ltd do you replace the oil in the fans or just replace the hub?

[@BritannicaRestorations]

Get a new unit - they are pretty cheap now

[@bushratbeachbum]

Cheers. Id rather investigate further to see what's going on. I've put a spare one on for now. Im not fond of leaving mysteries unsolved haha!

[@jtotheb1993]

bought a v8 parts car for my td5, the last owner of the v8 locked the visco fan up with a bolt it exploded on him at 120kph wiped out the radiatior, all the hoses, transmission lines, smashed the battery box and wrecked the bonnet and subsequently destroyed the motor as he didnt stop when it happened. all for the sake of a $60 part fitted twin thermo fans to my d1 v8 turns out the electric fans out of a mid 1990's falcon fit the radiator almost perfectly with a few modifications with a dremel it looked factory

[@BritannicaRestorations]

Saw someone do something similar with a Roll Royce Shadow 2 many years ago - sat in the drive revving it up listening to the motor - then snapped the fan pulley - the bonnet was open - but that WAS expensive to fix - if I remeber the 2 x matching fan belts were well over £100 a pair 30 years ago!

[@JCO2002]

Hmm - guess I'll forget about trying that on my Disco 1.

[@RangieNZ]

So 'store them flat'? How are they stored on the car?

[@vincea1401]

Hello Mike, Nice explenations. When i broke my vm (2,5), i had à New visco before And i was wondering if it was same has 300 tdi has, since they look like thé same, just for thé visco, not thé fan that looks different.

[@BritannicaRestorations]

I'm not sure

[@scotturquhart5454]

Hi Mike, Great explanation of the viscous fan clutch. Have you had any luck replacing the bearing in one? My V8 disco fan clutch just seized in minus 40 BC weather. And boy does it ron HP on the highway. Sounds like an airplane taking off when I get on the gas to pass someone. I have rebuilt some toyota fan clutches over the years, but I cannot find how to take the rover fan clutch apart. FYI, the fluid in the fan clutch is a specific high viscosity silicone oil. I know toyota sells it. Cheers Scott

[@BritannicaRestorations]

You cannot get them apart with out destroying them

[@scotturquhart5454]

@@BritannicaRestorations Well that sucks. Oh, well, off to buy another one. Once I get a new new one, I guess I will destroy this one.

[@BritannicaRestorations]

They are not all that expensive - I throw all mine in the scrap furnace!

[@kazman500]

Would you recommend replacing the radiator and/or the fan with OEM or are there after market that is better?

[@BritannicaRestorations]

OEM is always the best choice, but I believe for the radiator it is copy (China) or genuine - and Genuine are very expensiveAs for the fans - the copy ones are made in Taiwan, the OEM in the UK Mike

[@markleriche6942]

Interesting about storing them horizontally. I get boxes of new ones made for Mercedes and the boxes indicate storing vertical. I'm unsure which is right or wrong but I guess they spend all their working life vertical. I'm interested in any further info on the pros and cons.

[@BritannicaRestorations]

That's the way it said on my boxes - funny old world!

[@scott196464]

@@BritannicaRestorations maybe when new it cant or doesn't flow out of the reservoir .When it's been used its all out in the clutch

[@hurleylfd]

If it is not a good idea to store a fan vertically, should a fan be removed from a vehicle that is being stored or not driven often since the fan would be vertical? Love the videos.

[@BritannicaRestorations]

Good question! I know they have to be stored horizontal, but didn't give it much thought as to being on the vehicle a long time! I will think about that! Mike

[@spgtgb]

@@BritannicaRestorations I hav been told that a new fan van be stored any direction, BUT a used one should be stored vertical .

[@mjsniper8247]

Hi didi happen to refill the silicone fluid if so you recon how much fluid needed? thanks

[@BritannicaRestorations]

Not possible to repair

[@teameliteuk2023]

Hi mike great videos what happens if your viscous fan starts spinning asoon as you turn your engine on hot or cold on a defender td5 1999? Cheers

[@BritannicaRestorations]

If it does not 'lock' when hot then it is done = try a hot air gun on the bimetallic spring and see if there is a difference in resistance

[@bushratbeachbum]

It'll take centrifugal force to move the silicone oil in to place surely? To test it that way you'll have to heat it while it's running

[@scott196464]

if you start it cold and rev at 2000ish it should be quite loud and blow heaps then after 30 second or a minute it should go quiet.

[@malliadan1]

hi my 300tdi overheats only when going uphill in hot summer days and cools back down when i'm going downhill. Normally it stays middle (normal) or even a bit less New Alu radiator and new Turner performance head.

[@BritannicaRestorations]

is the thermostat ok?

[@malliadan1]

@@BritannicaRestorations just ordered a new one. i will remove the old one and test it in a pan and replace if necessary. will probably replace it anyway. Also my tdi300 was fitted aprox. 2 inches towards the rear of the vehicle so the fan is not actually inside the cowling. do you think this might affect?

[@Secker9]

Can I test my fan by spinning it by hand on a cold engine and then compare it to spinning the fan by hand on a hot engine? If it feels the same then surely my viscous coupling is faulty? Thanks.

[@BritannicaRestorations]

Sounds like it!

[@paulhunter123]

my car has this fan and overheats at idel - i can easily stop the fan turning with a piece of wood does this mean its bad?

[@BritannicaRestorations]

If you can stop it when it is hot with a bit of wood then it is bad - they usually are

[@ivankvaka8153]

My def td5 when is cold outside when not moving engine temperature drop off what is the cause? Thanks Ivan.

[@BritannicaRestorations]

Could be a bad thermostat

[@johnpayne3953]

The Peugeot 504 electro mechanical clutch fan never seemed to give problems I wonder why it died out ?

[@BritannicaRestorations]

Cost?

[@forenamesurname4576]

The iveco daily uses an electro mechanical clutch also, works really well

[@canamsteve]

I actually have a spare viscous coupling in my parts box. You don't Kevin it as a part separate from the fan? It does say This Side Up on the box, but if having them sideways is a problem, how about sitting vertically on a car stiored for months? Why isn't that a problem?

[@BritannicaRestorations]

I don't know I always lay them flat

[@irishlad7458]

My viscous fan is spinning all time my radiator is cold all the time my bottom stat only stays open for 10 seconds because my rad is cold all time the I have bursted 5 radiators in 10 years b4 some one actualy exspained how they work there is a viscous liquid inside the fan is not supose to operate until rad is hot so if there spinning all time the rad is too cold

[@irishlad7458]

U have got me all confused there not supose to spin till rad is hot so if there spinning the rad will never get hot and stat won't stay open

[@nzrestoration9486]

Why is it Mike that Land Rovers have this habit of getting hotter on the temperature gauge and then reverting to the mid point, when worked they all do this, from the series to disco and Range Rover, it’s always puzzled me? Jump in a Toyota and no matter how you drive it the temperature gauge always stays the same! Maybe they have better viscous fans??? Jeff

[@BritannicaRestorations]

I think Land Rover rested on their laurels back in the 60's with the success of the original Land Rover and just churned out vehicles as there was no competition. When the Japanese came along, LR were playing catch up and they churned out vehicles which the public test drove - that never happened with the Japanese - they made 100% sure they had a cheaper, more reliable product. I cannot understand how LR has not had major class action law suits against them for problems the KNEW existed for years The Japanese vehicles did suffer from high corrosion, but they were cheap, and nothing left the factory with a known issue hoping it would go away But then again - maybe it was deliberate, keeping 1,000s of mechanics in employment all over the world -you never know. LOL! Mike

[@jonathandosser]

Belgians make decent beer and chips - oh and chocolate!

[@BritannicaRestorations]

Nice beer - but not 'guzzling beer' like us Brits are used to! LOL!