As space will be at a premium under the bonnet on my car due to the large engine and dry sump system and intercooler etc to fit in, I have been considering fitting the radiator at the rear of the car and run pipes down the tunnel, has anyone ever done this? any major drawbacks to my plan? I know obviously airflow to rad will need to be considered but I think that could be sorted relativly easily. Would also allow me to run a significantly bigger rad which is preferable, and moves a little bit more weight over the rear wheels... Your thoughts?

Airflow is your enemy. Strange things happen at the rear of cars like the air turbulence and negative pressure.
Side mounted or ducted would be a better option.
I used to race imps and a rear rad was crap. Front rads were best

How about fitting some ducts in the rear panel at the sides just above the arches to catch the airflow?

Edit - Another option that i was considering was to mount 2 small radiators in the front side panels to catch the air just behind the front wheels.

[Edited on 14-5-10 by speedyxjs]

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Originally posted by speedyxjs
How about fitting some ducts in the rear panel at the sides just above the arches to catch the airflow?

Edit - Another option that i was considering was to mount 2 small radiators in the front side panels to catch the air just behind the front wheels.

[Edited on 14-5-10 by speedyxjs]

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Don't worry too much about increasing the rad size (assuming the airflow works) as the long pipes in the tunnel will also act as radiators helping the cause. B&Q sell aerial poles made from aluminium that are long enough and and the right diameter iirc. You may have to think about the water pump though if the existing one isn't man enough.

Overall weight (there's a lot more water in the system) is a downside.

It is easy to get air locks, you need to carefully plan the route for success.

I would advise you fit an electric pump to help push the water around, boat bilge pumps are cheap with high volume, no need to spend hundreds here.

Regards Mark

There is a lot you can do before putting the radiator in the back.
Multiple rads, 2 smaller rads one behind the other, extra heater matrix in the engine bay side panels, horizontal rads etc.
You could reduce the passenger foot well and use the space for other engine bay stuff as the passenger foot well does not need to accomodate a pedal box.

if you had to remove 1 from the front i would have the rad at the front and worse case fit intercooler elsewhere ie rear or top mount or charge cooler etc,

My problem is I am trying to cool 300HP and I think the rad that is on at present would not stand a chance tbh it is substantially smaller than the volvo item.

Top mount for cooler isnt really an option due to engine height, this will be reduced by dry sumping but still remains a tall block. Horrizontal rads are definatly worth considering though.

Good idea about using a bilge pump if I do go down the route of a rear rad.

I shortened the sump on my 6 cylinder whiteblock, i have a lot more ground clearance than i had with my pinto. I.d go for a custom intercooler/radiator in one that will fit under the nose cone.

Ran water cooled beetles for a few years and we had a lot of success putting in an oil cooler at the rear but the rad had to be front mounted to stand any chance.
As for cooling the 300 hp engine caterham get a custom triple core rad that fits into the nose. not cheap at 200 od quid.
The long water pipes to move the water round are a pain and they have a problem with clearance.
I used to knock the one hose off regularly when we bottomed out on bumps.


The other thing to remember that having a marginal cooling system is a right pita cause if it does get a bit warmer you have problems on the very days you should be enjoying it.

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Originally posted by Benzine
I shortened the sump on my 6 cylinder whiteblock, i have a lot more ground clearance than i had with my pinto. I.d go for a custom intercooler/radiator in one that will fit under the nose cone.

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Originally posted by mark chandler
It is easy to get air locks, you need to carefully plan the route for success.

I would advise you fit an electric pump to help push the water around, boat bilge pumps are cheap with high volume, no need to spend hundreds here.

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You could always mount the radiator in the rear and then drive around in reverse.

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Originally posted by Irony
You could always mount the radiator in the rear and then drive around in reverse.

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Dunno if it helps at all, but the engine is in the rear of my Mojo (the correct place) and the rad is at the front. I am using the standard water pump and I have never had any particular problem with airlocks or coolant flow given the extra length the water has to flow. I've used 32mm hoses, both rubber and silicon, and 32mm aluminium tube to extend the flow, and these are run down the tunnel which is quite easy for me as I don't have a propshaft in the way.

For comparison, I'm running 120-130bhp with a standard Polo rad, and the engine sits at 90 degrees all the time now. The water temperature at the exit of the rad is about 60-70 degrees depending on traffic and type of driving so there's a bit of spare capacity for warmer days.

Hope this helps,
Ed.