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Standard OEM radiator with plastic end tanks
Drivers side plastic end tank leaking under pressure

The standard OEM Elise radiator is another weak point in the cooling system. Although it is lightweight, it has plastic end tanks which are prone to expanding and leaking under pressure (possible manufacture problem where the main core is bonded to the top/bottom - but no reference). This is the most common fault and the first signs of failure are drops of coolant on the windscreen, either drivers or passengers side, but catastrophic failure of the end tanks has been known.

Unfortunately you need to Remove S2 front clamshell before you can replace the radiator.

A upgraded radiator is pretty advisable when going for Honda/Audi/Duratec engine upgrades. Most converted cars on the original radiators seem to blow them up pretty soon after conversion.

Aftermarket Upgrades

There are basically three options available when it comes to after market radiators that will fit an Elise/Exige. All three are 'all aluminium' and none have the dreaded plastic end tanks. There appears to be only two manufacturers that are making these radiators. The 42mm single row is made by ??? and the 45mm twin row single pass is made by Pro Alloy. All on-line retailers sell the same radiators, they just badge them with different names to confuse you. Hopefully the following table will help when making your choice for purchase:

32mm Core/Single Row
Manufactured by ???
42mm Core/Single Row
Manufactured by ???
45mm Core/Twin Row
Manufactured by Pro Alloy
Eliseshop Not available Aluminium High Pressure extra capacity Radiator Pro Alloy Full Aluminium Race Radiator
Pro Alloy Not applicable Not applicable Alloy Race Radiator
Seriously Lotus High Pressure 32mm Radiator High Pressure 42mm Pro-Alloy Radiator Single Pass 45mm

The radiator fitted by Lotus with the plastic end caps is a 32mm single core, single pass, manufactured by PMA Group. The direct replacement for this radiator, maintaining the same coolant volume in the system, is in column one. Columns two and three offer greater capacity. Other variations are available but the above three will cater for 99.9% of people on road and trackdays.

The following video will help you understand some of the terms used in radiator speak, like twin rows, dual cores, triple pass etc:

Triple Pass

The triple pass radiators are only intended for motorsports and are not recommended for road use. The reason being there is not enough coolant flow at idle (sitting in traffic) to force the coolant through three passes of the radiator. Road users who have fitted triple-pass radiators have resulted in increased engine temps. This advice holds for heavy trackday heros that drive their cars to/from circuit; the car is still liable to be stationary in traffic.

Manufacture Model Retailer(s) Notes
ProAlloy 42mm Core / Single Row / Triple Pass EliseParts
Elise Shop
Seriously Lotus
ProAlloy 45mm Core / Twin Row / Triple Pass Hangar111
Elise Parts
Seriously Lotus
Unknown 50mm Core / Twin Row / Triple Pass Seriously Lotus
Koyorad Racing 48mm Core / Twin Row / Triple Pass
P/N# HH652890N
Options Auto
Denso F1(bespoke) 27mm Core / unknown / unknown Blackwatch Racing 21 fins / inch, .25 tube spacing, 2.5lbs empty

"bespoke" denotes limited supply radiators specially created by race shops / tuners for high-performance cooling

Indication of HGF

Its been suggested in the past that a blown radiator can indicate imminent HGF. The header tank cap is normally the first to vent when the system is pressurised since it only requires approximately 1 bar. The radiator is designed to operate at pressures a lot higher than this and the cap acts as a fuse. However, the header tank is on the lowest pressure point of the circuit and this allows high pressure peaks on the high pressure side (which is from the engine to the rad). Therefore it would be prudent to have a petrochemical test (sniff test) performed on the coolant fluid if the radiator fails to rule out possible HGF.