Electric Fan

[Eddie.]

I'm a good way through the M20 engine swap now, but I've run into a bit of snag.

I measured the engine with the fan on and compared that measurement to the space in the engine bay, as predicted, it won't fit with the radiator I've got.

So I cut the slam panel out to move the rad forward, I then noticed that the radiator sits very high, because of the lower crash bar, I believe it'll be too high for the bonnet to close.

So I figured I could just run the car without the engine driven fan and fit an electric one, but actually finding a decent kit seems tricky?! Are the eBay ones okay? Also, what sort of amps does the M20 produce, will it be sufficient to run a decent size fan?

Cheers,

[nas80]

you want a spal fan that is a "pusher" mate and then mount not in the bay but on the other side of the rad.

Id leave them ebay things alone - its all about the CFM the ebay ones I saw when I was last looking don't really push out the CFM so will have to run for longer..

Your electrics can handle it as long as you stick a separate relay (and fuse) to the fan

Your problem is that you will need a fan switch. your new rad wont have that but you can get a pipe joiner which allows a fitment of a sensor in the middle.

[Eddie.]

Well, the rad that I have does seem to have a small thread at the bottom of it, about M14, could that not be suitable for a switch?

Worth bearing in mind, that my E30 engine, is the PFL one, which has a different cooling system to the later ones.

[nas80]

yeah that would work.

[Eddie.]

Any idea what temperature the M20 system should turn on at?

[nas80]

depends on the thermostat - you want a switch that opens a couple a few degree higher and turns off 1 or 2 degrees lower. you can get variable fan controllers though.

[Eddie.]

Right... I'll whip the 'stat out and see if it's an OEM BMW one or not, try and work it out from there.

[mr edd]

pre facelift 6cylinder cars had a two speed eletric fan ..slow at 91 deg full speed at 99 deg

http://www.bmwmobiletradition-online.co ... g=11&fg=60

[luke]

My 323i was a pre-facelift with the cooling system pictured.

I ran a 16 inch e28 Aux fan, which cooled the car fine (the 3 row behr has lots of capacity compared to the later radiator) but it was very loud. If you want something factory that is quieter, look at an e32 / e34 16 inch aux fan. They have curved blades so they're quieter, and move plenty of air (I currently run one on the e30, and it works well in traffic).

You can get an e28 thermo switch that will switch the fan on at 82 degrees (ie. just above thermostat temperature). If you're going to run a two speed setup, I'd run an 82 degree switch for low speed and a 91 for high speed. I just run mine on high speed at 82 degrees to keep it simple.

[jls7]

I can give you a couple of tips on how NOT to do it...

I replaced my engine driven fan on my m10 with a $50 electric fan from eBay. I had it running through the original wiring circuit from the aux fan (which is linked to both the aircon switch and the temp switch at the bottom corner of the radiator), only the wiring to the temp switch was re-routed to a manual switch in the car. I ended up leaving it switched on the whole time, in case I forgot to turn it on when needed.

It seemed to work fine until the fan died a few weeks ago. The auto electrician decided that it was a combination of being a cheap fan and being on so often that lead to the brushes inside the fan motor wearing out.

His recommendation was to buy a good quality fan, and wire it from a temperature switch on the top hose so it would only go on when needed. (which is what I know I should have done in the first place, but I was being cheap and lazy).

If you do use the temp sensor in the bottom of the radiator, be aware that it is at the coolest part of the radiator, and you should adjust your temp switch appropriately.

And yeah, as Nas said, mount it on the side of the radiator out of the engine bay. You'll have loads more room. I spent aaages trying to find one thin enough to fit inside, and still had to trim it a bit.