Cooling a rear engined, rear rad vehicle

Here you can see just how tight it is.

The theory is that the fan pulls air through the side vents into the rad.
This is then blown (by the same fan) through a small vent under the van



Visible hear on the right.

The engine bay is effectively sealed to help this air flow, however once sitting still (like in traffic) or under slow moving heavy load (like going uphill) the heat given off by the engine also has to escape through that little vent.

It appears to be a bad idea, poorly executed.

I guess anythings possible.
I believe the theory is to draw in clean, dry air but it still seems odd.

I'd agree, my MR2 is mid engined (with a front mounted radiator) also has a side vent to the engine bay.
The airflow in the engine bay is from underneath up through the engine bay and out through vents in the lid, on the move it's that strong it will lift an unlatched engine bay lid up. When stationary there's an electric fan that draws air in from the side vent across the engine and out of the lid. I have a vague recollection of reading about someone reversing the airflow on and imp to improve cooling (might have been on here)
It's all about airflow, the more air you get into and out of the engine bay, the cooler it will run, venting under the car isn't helping I.M.O.

bigger rad with a more efficient fan

when i used to help out grass track racing they used to run export fans on their mini’s that had different blades angled /bigger ? that pushed/sucked more air

or run a modern electric fan with a bigger rad change the air flow as per other posts

In engine cooling air flow is king. A mechanical fan generally shifts more air than an electric fan once you are on the move and the engine revs are up. It might be worth calculating your fan speed in relation to engine speed with those pulleys. Adding an electric fan to the other side of the rad will help low speed/idling.

Water flow is next. Is the pump working efficiently, getting the most flow for engine rpm. Darkspeed has done a lot of work on flow from different imp pumps. You might be able to use this information to asses your pump.

The radiator has to be of good design and in good condition. In a modern aluminum rad, it’s not having lots of fins that’s important. If you go too dense the air won’t want to go through it. A rad with less fins per inch (fpi) can often work better. Likewise, if you make the radiator too thick it will hinder airflow and reduce cooling. Once the air going through the radiator has picked up all the heat it can, the rest of the radiator is just reducing airflow. A thin radiator can work better than a thick one.

The fins have little slits or louvres in them the angle of these louvres is really important. A small change can make a big difference on the radiator’s cooling ability. If you buy a new radiator that is a reproduction, the chances are it won’t perform as good as an oem item as these are not developed to the same standards. The manufacturer doesn’t have the vehicle manufacturer scrutinizing everything and setting standards. The same goes for companies making bespoke radiators. They generally use old technology cores. All this isn’t so important when your rad is at the front with all the ram air, but you don’t have this luxury.

So I guess what I’m saying is get the biggest surface area, oem modern radiator you can. Make sure you can get as much air and coolant through it as possible