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MG MGB Technical - Cooling fan upgrade


Can anyone recommend the correct size and brand of aftermarket cooling fan for an '80 LE? Should I do this rather than replace the small fans in front of the radiator? Would the fan need to have a shroud made for it?

Many thanks,
Dave
David Plantz

David,

Recommend you stick with the two small fans. I also have a 1980 LE. I did have one fan fail and replaced it. Also, when I replaced the fan, I removed the radiator and had it serviced and now the car runs cool and never goes above the thermostat rating of 180 degrees. Fans show up at good prices on Ebay and on the classifieds on this site. Good luck.

Chuck
Chuck Hassler

David-
If you're considering an electric fan, Brit Tek sells a kit with high capacity units in both 10" and 12" that can be used to replace your Original Equipment items. You can even adjust them for the temperature at which you want them to switch on and off. Be sure to fit them behind your radiator so that they wont block airflow. No, you won't need to fabricate a shroud. Click on this: http://www.brittek.com
Steve S.

One 10" will fit. If you use 2, a 10" lize will be a little too wide (I have 2 10" fans). If 2 fans are in your plans, try a 9" or an 8".

The hub for the fan on the engine sticks out pretty far and is pretty wide. I have not figured out how to get two puller fans in there, so I think you must mount them on the outside.
Frank Baker

Kenlowe make a suitable fan that comes in a kit to fit to a B, with mountings and thermostat that allows you to vary the temp it cuts in at. Not as cheap as a junk yard option though. In the UK the kit is about £100 GBP.

Iain
I D Cameron

i took my 1980 mgb to Texas for a 3 year work transfer and being black i upgraded to the V8 spec dual fan set up...i ran both units through a relay to reduce the load on the rad swicth and have had no probs (touching wood quickly). Now back in the UK with a cooler T'stat it runs at fractionally below halfway on the gauge and the fans rarely cut in. for me it was a more "original" look than the aftermarket add on fans, easy to get the bits, the mounting points are all there and easy to fit to original wiring (with add on relay)
J K C Whitehead

You shouldn't need to change them to get correct running temps. Be aware that the MGB temp gauge goes up and down according to actual engine temp, and this varies quite a bit from running in free air (i.e. 40/50 mph or so and not in a line of traffic or even worse stuck behind a lorry) which should show around N on the gauge and stopped in traffic just as the fans come on which can go as high as mid-way between N and H. Modern cars by comparison control the gauge from the ECU and *don't* send the normal engine temp changes to it, i.e. it should stay close to N at all times, only temp changes that are considered (by the ECU) to be outside the normal range of variations.

In high ambient conditions it can run at higher than N. Unless it is losing coolant or steaming it isn't overheating.

Make sure your fans are operating correctly, I found mine were losing about 3v in various connections, and in long idles on high ambients the temp gauge was getting very close to H, but still not 'overheating'. The relay (standard on factory V8s) was losing a bit (and getting very hot in the process) but the biggest problem was the factory ground, which both fans have to share with each other and the headlights, via a standard gauge wire, all the eway back to a grounding point by the fusebox. I *added* a local ground for each fan under its mounting bracket and these (and changing the relay) made a huge difference to the voltage and running speed of the fans, and hence the temps seen on the gauge, which now don't get above mid-way between N and H even under test conditions of about 40C ambient.
Paul Hunt 2

What is the problem you are having? Are you running hot? Or have the fan motors failed?

Moss sells replacement fan motors for about the same cost of converting to a Hayden set-up.

<http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28984&SortOrder=25>

<http://www.mossmotors.com/Shop/SearchResults.aspx?SearchText=fan&WebCatalogID=8>

I had overheating problems that was caused by a clogged radiator.
Kimberly

FWIW, when I built my Rover 3.5 roadster, I tried to get a fan to fit behind the rad but due to long-nose water pump, couldn't get one to fit.

I'm using two original MGB electrics mounted in the stock location. I've got them on a thermo-switch set to come on when temp reaches just above N (but can vary this if required). These are wired with a relay as well.

My point is that these two fans have been doing a great job of cooling the 3.5 even in traffic. If temp gets halfway between N and H, the fans will cool it back down. Don't give up too quickly on the original design!
Simon Austin


Well, I've already replaced one fan motor. I just need to order one more. My thinking was that a single puller fan might do a better job, but it sounds like the twin fans work well from the info here. My car doesn't overheat.

Many thanks,
Dave
Dave Plantz

Dave,

You may have made your mind up by now, but I have the Flex-a Lite 15 inch 110/120 fan. This puller fan cools the car in 1 minute. After I removed the two fans that seemed to me as blocking the air I noticed immediately that is what it does. The air goes right through the radiator now with no obstruction and when driving my fan does not come on at all. With this puller fan fitting accross the whole radiator it surely does what it is supposed to. I can sit in traffic all day if I want and it will keep my temperature at an even 180* if I want.

Still your choice,

Ray
Ray 1977mgb

IMO, 180º is too cold. For maximum power, efficiency, and engine longevity, you want to run the engine as hot as is practicable. Both Peter Burgess and Smokey Yunick recommend hot thermostats -- Burgess says "The ideal 'stat is 88 degrees Celcius (190ºF) ." Yunick says:

Quote:
" It is easy to see how overheating can be a problem, but I think some racers overlook the fact that it is possible to 'overcool' the engine. Some guys go to great lengths to keep the engine temperature down to 180 degrees. And, though the engine doesn't overheat, they don't realize that they're putting energy (heat) into the cooling system that could be used to produce power at the crankshaft.
Running the engine at 180 degrees will drop the overall horsepower by 2%-3%. For max power the cooling temp should be at least 200 degrees...."

I run a 195ºF tstat year-rond in North Carolina, where the boilerplate weather forecast from June to September is "Upper 90s, with a chance of afternoon thunderstorms." Sometimes the weathermen are wrong though -- sometimes it's hotter than that... ;-)
Rob Edwards

Rob,

I stated above "If I want" I can keep my temperature at 180*.

I agree with you 100% that you should not use 180* as it is to cool and you lose hp. I set mine at exactly 200* which is dead center on my VDO temperature gauge.

Ray
Ray 1977mgb

Sorry, I assumed that by stating "If I want", you were saying to wanted!
Rob Edwards

Hi Folks,
I replaced my stock 8" thermo fan with modern 10" unit. I later removed it and fitted a 14" puller fan.
I found that the puller fan kept the HIFs cooler while sitting in traffic in the summer time.

Sitting traffic on a 100f day, the carbs became too hot - to the point where I'm sure I was starting to suffer from vapourisation [?]. Fitting the 14" thermo fan generated significant airflow around the engine - particularly over the carbs, keeping them cool.

We're in winter here now, and the fan almost never operates in the colder temps. I run the 190f thermostat.

regards,

Rod A
Rod A

Rod,

I just finished explaining this to someone on the supercharger forum. It is amazing how much air these fan pull in and circulate in and out the engine bay especially over the carb area.

Ray
Ray 1977mgb


Hmm...well now I'm thinking of doing what Ray did to his ' 77. I'd like to keep the car as original as possible, but if the Flex a Lite fan works that well I'm all for it. Also, I wasn't aware that I need a 190 degree thermostat. I'm pretty sure that the car has a 180 in it now.

Many thanks for all of the help.

PS: Great-looking B, Ray. I've looked at your website. Quite impressive.

Dave
David Plantz

Dave.

Thanks for the comment about my MGB. I use a 180* failsafe thermostat from Moss Motors. In my view the 180 and 190 degree thermostat is opening up at those temperatures. Once it is up that high they usually stay open as my engine is not going to cool down enough to close them. I like using the 180* to open up early and get the radiator up to temperature faster than waiting until 190* to open. Once open it doesn't matter because my adjustable thermostat will take care of the rest and keep the temperature at 200* and shuts off at 195* kicking on and off the fan. I also like the failsafe thermostat just in case anything did happen these thermostats will lock in the open position to prevent engine damage. Being safe to me is better.

Ray
Ray 1977mgb

This thread was discussed between 16/06/2006 and 26/06/2006

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