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mcramsay 10th March 2017 14:02

The race aluminium polo rad I'm running seems to just be only coping with the m3 lump feeding it. At higher speeds its fine, but at low speeds the cooling fan is doing most of the work. I'm going to try and duct above the nose cone to force air through the rad rather than over the top.

If this fails what radiators are others using? The polo rad was the only one I could find that would fit!

Patrick 10th March 2017 19:30

What size fan do you have? I had issues with the stock rad and fan. I initally put an Northern ali ran on there with my M20B28. Even with the and a 12" fan it was border line on hot days, I put a 16" on and it has been fine since.

It now sits at 75C until it gets hot to the point where the fan kicks in around 80C - doesn't move from there anymore.


12" Fan

16" Fan


The rad is branded northern, I got off ebay:

Comes like this so you can put the connections where you need them:

mcramsay 10th March 2017 19:59

I have a big 16" kenlowe fan, it keeps things cool but it comes on and off more than I would like,. It pulls 25A running aswell which was giving battey & alt issues as I'm running a tiny pc680 battery and the alternator wasn't giving out enough amps at idle... but that is sorted now

The temp sits at 90 when going along at a good speed. Creeps up at lower speeds though and the fan cuts in.

Any idea where your rad came from or what to search for to find it?

Personally I would like to go larger on the rad, I'm just struggling to find anything that will fit!

Patrick 10th March 2017 20:38

I found the original email from the ebay order! It was listed under:

Northern 19x22 blank radiator, hot rod,kit car

The shop in the UK where I bought it doesn't exist any more but this looks very similar, located in the US so there'd be import VAT/Duty:

I had to shape the top edges a little so the nose cone would fit over it:

I can't find the images of the brackets, but each side it two metal strips bolted together with some rubber between to act as a vibration damper.

Mike 10th March 2017 22:55

I bought my rad from a local company that make them for F1 stock cars - big American V8s!

The guy there suggested having a bespoke radiator made from standard components.
We established a Landrover header tank was the optimum depth in the Cabrio nose cone (same for Sportster?). Then he said he could fit a 3 core to virtually any width I wanted). This was the result:

I fitted a 16" Spal pusher fan with a sealed shroud.

I was able to have the fittings angled to best suit the pipes on my engine, and have auxilliary fittings for the temperature sensor, and top bleed hose return to the header tank added.

And all for the same price as a standard tank - £150.

It is important to close off the areas around the radiator to prevent air going over it rather than through it. I glassed in a sheet of GRP to the nose cone and then trimmed to suit with the radiator installed.

MartinClan 11th March 2017 14:10

I used a stock e30 325 rad. Early model as I recall. Mounted as high up as I could get it so it wasnt obscured by the front crossmember. 12" fan. Never had any overheating even when stuck in a 2 hour jam on the m3 in the middle of summer. I do have an oil cooler as well.


mcramsay 12th March 2017 11:32

Cheers for that robin, have you got any pictures?

Patrick 12th March 2017 12:04

Robin is your stock rad mounted so that the water flows across rather than up/down ? I've read that can make a difference.

mcramsay 12th March 2017 18:31

So today I moved the radiator as far forward as possible, this has allowed me to fit the fan behind the rad, I'm going to duct the radiator on top bottom and sides so all air entering the nosecone has to go through the rad. I'm also going to pop down to marlin and have the bonnet louvres done sooner rather than later.

I notived the rap cap didn't seem to have much bite when tightening up, so I gave a little bend on the tabs to make it seal firmer.. I noticed up run up today that the silicone rad hoses got quite hard... harder than I've felt before which leads me to two thoughts, has my rad cap not been sealing and my system has not been pressurising properly and should the hoses get hard at operating temp? The cap is set at 13 psi.

I did a quick little test with an electric air pump, I plugged into the header tank return ( 8mm from radiator) and plugged the pump into this. And then caped the return line from the rad. This allowed me to pressurise the system without running the car, the cap lifted at 13 psi on the dot and the hoses felt hard with pressure in the system so I'm guessing this is normal ?

Jaguartvr 13th March 2017 07:48

Hoses should be hardish but you should be able to squeeze them a bit.
I have an old MK2 jag and the cooling can be a bit marginal in modern traffic, it does have a kenlow but it does run just the hot side of the temperature gauge. I added "water wetter" and it now runs on the cool side of the middle of the gauge.
I do intend at some point to swap over to Evans waterless coolant, bit pricey but it's big advantage is that it doesn't expand with heat so there is no pressure on the cooling system which has to be goo in the long run.

Patrick 13th March 2017 08:25

Something else worth looking into:

Jay Leno is a big fan

MartinClan 13th March 2017 11:46

A couple of pictures from my old build website which still seems to exist even though I stopped my Tiscali account years ago...

You can see that the rad is squeezed up as far as it can go to the top of the cowl. All of the cooling matrix is exposed - only the bottom tank is hidden by the crossmember. As I remember, if you used Marlin's "standard" position at least 25% of the matrix is obscured.

I was even able to use the standard BMW hoses - always a bonus if you ever have to replace them.

And to answer Patrick, its a standard up/down flow - not a crossflow.

Cheers, Robin

mcramsay 26th March 2017 11:38

So I've moved the radiator, completely ducted the nose cone & moved the fan and on a test drive yesterday it was better but the engine is very close to overheating. The rad fan is still on most of the time and it depends if I'm driving into the wind or not!

Doing some sums the northern alli rad above has almost double the core surface area of mine, 688 cubic inches versus my 346 cubic inches. (The 688 is very close to the CI of the original m3 rad size) so I think my answer is despite all my efforts I need a larger radiator. It's no fun driving the car with my eye on the temp gauge constantly.

On another note I gave it some stick yesterday the power from 3500 rpm onwards is insane. The noise is also addictive.

Does any one know a company in the U.K. That could manufacture that radiator without having to import from the states?

Mike 26th March 2017 15:24

Are you set on having an aluminium rad?
There will be a number of local radiator companies that can make you a bespoke one in copper.

My local was Boston Radiators, Maud Street, Boston Lincs, who make radiators for a lot of the Formula 1 Stock cars.
They can make you anything you want and I believe in ally if you want it.

Tel: 01205 369555

Have a look on eBay at Stock car radiators

mcramsay 26th March 2017 22:35

Not set on ally at all, I never considered having one made of copper to be honest I will look into it! There is a local radiator shop around the corner might give him a shout tomorrow

mcramsay 27th March 2017 10:52

I emailed a company on eBay, who asked me to call, turns out it was the exact same number as above! Spoke to a really great bloke who told me exactly what I need to do and he could make one no problem, I've got to make a template and send then a drawing, he's been making radiators for 35 years, and copper is much better than aluminium! Expects the cost to be somewhere around £200 maybe a bit more depending on what I need done.

Sounds good to me!

Mike 11th April 2017 18:30


Originally Posted by mcramsay (Post 87039)
I emailed a company on eBay, who asked me to call, turns out it was the exact same number as above! Spoke to a really great bloke who told me exactly what I need to do and he could make one no problem, I've got to make a template and send then a drawing, he's been making radiators for 35 years, and copper is much better than aluminium! Expects the cost to be somewhere around £200 maybe a bit more depending on what I need done.

Sounds good to me!

Did you order a radiator from them?

mcramsay 16th April 2017 13:37

In the end no, I spoke to cool experts in Nottingham, they modified a ford cortina radiator for me, gone for a 70mm thick core 490 wide 470 tall. Been a bit of a pain to plumb in but I'm hoping to get out this afternoon. Hopefully all will be well!

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