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MG MGB Technical - Kenlow fan

Hi guys, when in France last year sitting in traffic temp was going up all the time, so before going to France again this year I thought I would fit a kenlow fan, got a bargain one second hand but never fitted, I need some info, a friend told me I should take off my fan on the engine as I don't need it when I fit the electric one has anyone done this?
Also I want to fit it directly operated by an on off switch on the dash, don't want to connect it to the temp.
So I was going to leave my fan on the engine and just switch on the kenlowe when required does this sound ok?
Would be pleased to hear your thoughts.

Cheers Jack
Jack New Forest

No real point in taking the mechanical one off if you can fit the electric without, although it would save a gnat's HP and some noise. You will probably need shorter bolts for the pulley on the pump if you do. I can't see why you only want it manual operation, unless it is only for emergency use, which would need the mechanical fan to be left on. But unless it is regularly used you won't know it is going to work when it *is* needed - which is probably another argument for removing the mechanical, so I'd definitely say to fit the thermostatic switch, with a manual over-ride if you like. However the manual over-ride is only going to be of use if the thermostatic switch should fail.
Paul Hunt

Jack,
Take the mechanical fan off. It really is there to shift air when the car is not moving fast enough to push enough through. Below about 5mph. An electric will flow more air at low speed. Use an over-ride switch, the advantage is that, if you use it as soon as the traffic slows or stops, it stops the temp getting to a critical point which is then harder to lower, especially if air temp is high. But put a thermo switch in, just in case you forget!
Allan Reeling

Jack,
if you feel you need to be in control then just do as you suggest and use the electric fan as a back up for when the engine fan isn't enough

a thorough clean and flush of the cooling system and check over might help with prevention rather than later cure

personally I'm fully committed to an electric fan only that works itself off a thermoswitch (without any override switching) - as we all have for the last 20 years with modern without giving it a second thought

the engine driven fan works in reverse to its requirements, it's on when not required and going slow when it needs to go faster

if you use the car in winter too then take the engine fan off, if not you could leave it on but either way I'd too suggest you put it on a thermoswitch - I like the Revotec one that splices into the hose rather than the Kenlowe probe under the hose end
Nigel Atkins

Always the one to play devils advocate.

We fitted a Kenlowe to the road midget with a thermostat switch. All worked fine until one very hot summers days when I was heading over to the coast to meet my wife and kids who were holidaying whilst I was still working.

I got half way there and the temperature was rising quite high and I could hear the fan going. It turned out the thermoswitch had failed and as I'd removed the plastic fan there wasn't a lot I could do.

I recall I bypassed the switch and ran it live permanently just so I could get to the coast in the Midget and not have to return home for the boring car.

We've built the BGT with an electric fan on a manual switch only. I've just kept it simple, one eye on the temp gauge, it warms up to a point I switch on the fan. Simple as pie. It's connected to the purple section of the loom so can still be running when the engine is off.

So far it's worked fine.

Andrew
Andrew McGee

I hate Kenlowes!

Mostly because people bolt them in and wire them up without unpluggable connectors so that taking the rad and its support panel out to do an engine change or clutch is a pain.

The other reason I am not keen on them is that they only switch in once the temperature is already rising and have to stop the rise before pulling it down - the mechanical fan is fighting the temp all the time.

Yes, I know the late cars had electric fans - my V8 has two and still struggles to keep cool on long fast climbs up the mountains in sunny France! I am actually looking at a way to get a mechanical fan on the V8!

As a matter of interest - a windmilling (ie not powered) Kenlowe fan actually restricts airflow through the rad, so at speed the cooling is worse than without it. Also at speed a mechanical fan is not absorbing much power as the airflow is boosted by the ram effect. So you are not saving 3-5 bhp as often quoted. At stationary idle when the cooling air is really needed I doubt there is anything between electric and mechanical fans.

Oh and finally they are not free cooling - they take power away from the engine via the alternator ...

Chris at Octarine Services

each to their own and whatever floats yer boat is fine

I just wonder if all those that fit override or manual switch to electric fans have also been doing this on their modern cars for the last 20 years too

Andrew had a thermoswitch go wrong , fair enough, possibly the exception that proves how reliable they normally are, I know someone who had a Kenlowe fan motor stop working in his classic but the fan motor was over 20 years old on a car that saw use but not frequent use

I agree with Chris about plugable connectors and that makes sense with any removable electric item fitted and that an electric fan doesn't save you that much power when the weather is warmer and/or you're not on the open road (well able to do a constant 40+ mph anyway)

I'm not sure (I have no evidence to prove it) that a a windmilling electic fan would make much difference to the cooling and from my personal experience of a few electric cooling fans fitted to a few different classics (not a regular B/GT though to be fair) I can say the electric cooling fan is better than the engine driven at stationery

as I put earlier I feel, regardless of type of fan fitted, that most cooling/heating systems on classics are not working at their bests because of the systems not being fully clean (including the engine block) and possibly not all components and sealing foams/seals being in good condition (or missing)
Nigel Atkins

ETA: not having the engine fan unnecessarily cooling a cold engine is very useful too especially for those of us that use our classics in the winter (which included when I had them my BGT and after that my V8 roadster)

(the V8 roadster also had no choke and was used during the winter but that's another story)
Nigel Atkins

" I could hear the fan going. It turned out the thermoswitch had failed ..."

*Couldn't* hear the fan going? That would make more sense.
Paul Hunt

Paul... you are correct. Just spotted my fingers weren't typing what my brain had told them to do.... quite normal for me then :-)

Couldn't hear the fan even though the temp shown on the gauge would have meant it should have been working.

Anyway, the Midget has since been reverted back to the mechanical fan and that Kenlowe is currently sat in one of my storage boxes for just in case in the future.

I've not had any temp problems in the Midget since, well apart from blasting back from Scotland a few weeks back and then hitting Leeds at rush hour where it climbed a bit too high in stationery traffic.

Nigel has a point (goodness I'm agreeing with Nigel again shock horror :D ) with his comment about not cooling a cold engine. My previous BGT was an all year round car with a mechanical fan, I could never get that to warm up enough. It should be an interesting comparison this coming winter. Currently the engine warms up nicely and is maintained just to the left of N on the temp gauge by the use of the manual electric fan.

Andrew
Andrew McGee

Andrew,
I think the you agreeing with me is a first but all is safe as long as it's kept to B forums only

I once used black Hammerite painted corrugated cardboard panels as external rad grille blinds on my BGT one winter so someone lent me a proper rad grille blind, it was then I discovered the car had the wrong pressure cap on it when the temp gauge went high

I keep meaning to make a rad grille blind for the Midget but I might just use a rally plate cable tied

Paul,
you missed the missing 'e' :)
Nigel Atkins

I can't remember not having an electric fan on a classic. Because I'm Northern and therefore "careful" with dosh, I've never actually bought a Kenlow, or similar. Most of them have been off modern cars in the scrap yard, or made using heater motors or similar. All worked perfectly without a failure.........to date!! But ~I'm a Northern engineer and having something turned by the engine, making noise, and only of use for a small proportion it's operating time, seems daft. Especially when you consider when it's really needed it's running at it's slowest and it's running when you definitely don't need it, as Nigel said, when cold starting.
Hell why not go back to leaning out of the window to squirt water on to the screen, from a squeezy bottle and have manual wipers, nothing running off that troublesome electricity there!!!
Allan Reeling

Allan you've added what I meant to but forgot - how some use fans from the scrap yard that have already worked for a car's lifetime and still have no problems (I could never do this with my car luck) but it shows how long lived these components can be

(and that possibly those in regular use may be better than units not in regular use?)

of course now one of our fans will stop working or thermoswitch !
Nigel Atkins

Thanks for all your comments lads, good discussions as usual, but as usual a 50/50 split so I'll have to digest all the info and make a decision !
Cheers

Jack
Jack New Forest

>but it shows how long lived these components can be

They're all crap. I've just had to replace the one in my 1991 Honda after a mere 250k miles. Total rubbish. ;-)

Not to pile on but as far as the fan using electricity & therefore not saving anything, I did the sums once and calculated that the fan draws I think 0.7 hp (assuming about 20 amp draw and also assuming the alternator being 50% efficient). That's certain be less than a mechanical fan. When not running (i.e. most of the time) it uses no power at all.

I don't like the idea of having the electric fan manually controlled for two reasons: 1. Are you ALWAYS going to be attentive and turn it on when needed? I still leave my O/D engaged at times at stoplights even though I intend not to... 2. Do you trust someone else to ALWAYS be attentive and turn it on if they have to drive your car? I once had to drive home a car belonging to a friend who fell & broke her leg. She was unable to drive so the choices were to find someone to drive it (me in this case) or have it towed the 2 hrs home. Of course you could just leave it on all the time but then what's the point?

I forget the brand that I installed on my B (not Kenlow) but I've seen other brands and they appear identical to mine. It would not surprise me in the least if there are only a small handful of manufacturers of aftermarket fans that supply the different brands. I think the next one I do may I may use a junkyard part....

Last comment -- I do think folks worry too much about keeping the temp down. I'm of the opinion that most people end up overcooling the engine and more harm is done running it too cold than too hot. Too cold and contaminants in the oil (water from combustion, fuel washed down the cylinder walls) don't get driven out as quickly and thus can cause accelerated wear. Also, burning fuel releases energy that either turns the crankshaft or gets dumped into the cooling system. I'd rather use it to turn the crank. The colder you try to keep the engine, the faster the energy goes into the cooling system and is lost....
Rob Edwards

All modern cars use electric fans and I am sure they give little problems. I admit I am no expert, but the BGT I bought had a Kenlow fitted controlled by an adjustable thermo switch. It has an override switch with a pilot lamp incorporated which also comes on when the thermo switch triggers the fan. So far, the system has worked perfectly with no need to use the bypass switch. I do not like anything which I need to monitor and switch on manually as I am sure to miss it when it is required.

Ronnie
RA Potter

Rob,
I'm with you on the over cooling at certain times but IIRC don't different engines have different 'optimum' running temperatures, then you have to allow for possible inaccuracies of gauges, still best to have a clean system in good condition so it's efficient and then let it warm up more if required than an unclean system and/or not in good condition that struggles to maintain a safe margin

Ronnie,
if you don't want to monitor it why not remove the override switch and light and make the wiring more direct (usually less to go wrong with less joints and components)
Nigel Atkins

Ronnie said "I do not like anything which I need to monitor and switch on manually", he isn't complaining about the override switch and pilot light. I added the same to my V8, but I haven't ever used the override, except to turn on the fans when they weren't supposed to be on. I've never added an electric fan to a car that had a mechanical, and never found I needed one. The roadster did get up to the edge of the H zone once, but ran normally and didn't lose any coolant. On runs with a rally plaque that goes in front of the grille, and even on the hottest runs the temp gauge never got more than a third of the way from N to H. If you can't get your MGB to run near N on the gauge, in anything except the coldest winter weather, than something is wrong with the stat or gauge.
Paul Hunt

Paul,
normally I agree with you but not this time - the way I read it is that Ronnie is saying that he doesn't like (not necessarily moaning) to have to monitor so that's the pilot light and doesn't like the manual switch

I agree there shouldn't be a need to add or change to an electric fan especially for car that are not in regular or frequent use and next to no use in winter

otherwise it's just a want or upgrade for more frequent or daily use throughout all the year and seasons
Nigel Atkins

Hmm, I can't help feeling that it is one of those "improvements" that actually are not much of an improvement except to someones profit - how much are Kenlowes now?

As to temperature then I always run an 88 degree thermostat - the hotter the engine runs the better for economy and long life - the scale on the gauge is misleading, the WHOLE of the centre black bit is NORMAL, not just the N and actually with a 4lb rad cap fitted and 25% antifreeze in the coolant the boiling point is around 105 degrees which is almost out of the H section of the gauge.

In short, if you aren't steaming or losing water then you don't have a problem - if there wasn't a gauge on the dash you wouldn't worry about it! Same as oil pressure - if you only had a light then you wouldn't worry about that either till the light came on!
Chris at Octarine Services

Those of us who run Rover V8's prior to cross bolted main bearing caps, can get a little neurotic about temp. The cast iron caps obviously have a different coefficient of expansion than the aluminium block. Running at the upper end of temperature can cause the caps to "fret" in the block. Not good and a potential wrecker!
Allan Reeling

Yes I run an early V8 and worry not about water temps around 100 degrees - there is no water passage near the main caps - the whole bottom end is cooled by the oil which is why I run a 13 row oil cooler.
Chris at Octarine Services

Hi

I may have not been clear in my post. What I meant was I am more than happy to have the fan run automatically. I reckon many of the problems with overheating or running very hot are caused more by the general condition of the cooling system. When I rebuilt the motor last year the water jacket around the front 2 cylinders was blocked with sludge that was as hard as concrete. I do not believe any amount of cleaner or flushing would have made any difference to the cooling system. I also renewed the radiator at the same time and I can see a marked difference in the way the fan now runs. I need to be in very slow traffic for it to run.

Ronnie
RA Potter

Ronnie,
your engine might have been too crudded up but it proves the necessity of the part of my thorough coolant system cleaning to remove the engine (water) drain plug and whilst draining old coolant and flushing out use a piece of thick wire to clear out the crud that then collects at the engine block drain hole or perhaps more if its really bad

when the system is cleaned and flushed the engine part is usually forgotten about so is more likely to need doing as it's been neglected before
Nigel Atkins

I've always fitted an electric fan in place of a mechanical fan on cars in the past, sometimes bought from a scrap yard.

My B has an electric fan with an override, and rarely needs turning on, even when climbing in the Pyrenees. I'm also quite happy to remember checking the temp. gauge.

I don't have a problem with the fan windmilling and restricting the airflow through the rad.

Mine sucks.
John Bilham

When I bought my B, it had a manually controlled electric fan.

I forgot to turn it on twice, the second time being terminal.

When the car is back together, I haven't decided whether to fit a mechanical fan, or refit the electric one with a thermoswitch and over-ride.


Dave O'Neill2

I am trying to help sort my brother-in-laws MGB which recently overheated very badly in a 4 hour motorway traffic jam.

This has resulted in a cracked head which we are in the process of replacing.

Its a 77 roadster (rubber bumper converted back to chrome bumper),it has a tiny electric fan ( 7 or 8 inch) that just covers the Rt half of the rad but no mechanical fan. I would have thought that at least a 12 inch fan would be needed to cool this rad.

It has always run with the temp needle in the middle of the gauge until he hit the super traffic jam.

Was the 77 roadster originally fitted with a mechanical fan? If so, I may persuade him to fit one until he can get hold of a bigger electrical one.

Cheers
Colyn Firth

Hi Colin,
I'd suggest you start a new thread for this to get all the info you require

'77 roadster would have an electric fan, I don't know the fan size but it need not be 12" you're confusing size with efficiency

the MGB must be the classic with the most parts and information about the car available by some way so there's loads to be found out if required

what you need to establish is why it it overheated - was it that something was/went faulty or broke on the car, driver error (lack of past and/or present maintenance, lack of proper set up)

sitting in a traffic jam during warm weather might get the engine hot but it shouldn't cause it to overheated badly and cause a cracked head

especially as you put the gauge usually shows normal

and apologises if I'm wrong but with respect I think possibly you and/or he may need to learn more about the car by asking questions as you have and IMO to (buy if required) and read the relevant Driver's Handbook - (Ref: 0053) - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

(also available elsewhere)
Nigel Atkins

Hi Nigel

The block was so bad I could not clear the drain on the side of the block even with compressed air. I eventually cleared it when the head was off with a long screwdriver through the coolant holes and a hammer!!!. Here is a pic of the fan.

Ronnie


RA Potter

yes it seems a lot of the B engines need a 'hammer 'n' chisel' approach make you wonder about past maintenance and 'hotspots'

er, that's a big fan, when it boots in do your lights dim and steering go light :)

especially living where you do I hope you've got a thermostat for the oil cooler

- or perhaps a remote controlled rad(s) blind
Nigel Atkins

Dave - I appreciate what you're saying, but knowing when my fan will need turning on has become second nature after about 40 years' use in different cars.

Now I really have tempted providence...!

Best wishes
John Bilham

Hi Nigel

At idle the fan drops the revs by 100rpm, and unfortunately it does not have enough power to reach take off speed!!. The oil cooler is blanked off with vinyl and cable ties.

Ronnie
RA Potter

Ronnie,
considering it's size the 100 drop sounds fine compared to mine, I have a 10" slim Revotec fan on my Midget and an over-sized alternator and you can really tell when the fan is working at idle

make you wonder how power the electric drag takes

I think I've only seen in a Haynes (Spridget) (a book I don't normally like) about blanking off the oil cooler

I've always fancied a roller rad blind like on the Volvo Amazons(?)

personally - and I don't want to start another debate about it here now - that road going Bs (and Spridgets) don't need an oil cooler, perhaps if they regularly do heavy towing, and the oil gets over-cooled 95% of the time
Nigel Atkins

"Was the 77 roadster originally fitted with a mechanical fan?"

Yes, and it sounds like you have the standard fan. All V8s and 4-cylinder export cars from 77 on had twin fans of the same type. They are not particularly efficient, but then they were always adequate. Some 76,000 cars were produced with these fans, if there were a fundamental problem with their cooling abilities we would know by now.

What did the temp gauge do when this overheating occurred? If it went right up into the H zone you should have had more than enough time to switch off and save the engine. Was it losing coolant? It would have to have boilded over and nearly dry to do that much damage I would say.

There can be many reasons for running too hot, broken into two main categories - the engine producing too much heat, and the cooling system not being able to get rid of it as it should. The design of the electric fan system is such that even if it normally runs on N on the open road, in traffic it should always go up to about 1/3rd the way to the edge of the H zone before the fans switch on, then come down a little from that before they switch off again. It should only come back to N when you get on the open road again.

Before spending money on a new fan you need to find what is wrong with your friends system, and put that right. If the problem is the rad partially blocked or the coolant not circulating correctly then the biggest fan in the world isn't going to make much difference.
Paul Hunt

This thread was discussed between 02/07/2013 and 06/07/2013

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