The standard MGA radiator is a copper-and-brass construction with soldered joints and an integral header tank at the top. It is mounted in the front of the chassis between the front wings, secured to the chassis by mounting brackets and isolated from vibration by a rubber packing kit. The radiator core provides the heat exchange surface where hot coolant transfers its heat to the airflow passing through the fins. A corroded, blocked, or leaking radiator is the most common cause of chronic overheating on the MGA.
Internal corrosion restricts coolant flow through the core, reducing the effective cooling surface area; external damage from road debris or poor storage crushes the fins, similarly reducing airflow. Original-specification new radiators and reconditioned exchange units are both stocked, together with the packing kit that sits between the radiator and chassis mount.
Pushrod vs Twin Cam Radiator
The pushrod radiator fits all 1500, 1600, and Mk II models. The Twin Cam radiator is a different unit positioned further forward in the chassis, connected to a separate aluminium remote header tank mounted on the left-hand side of the engine bay above the exhaust manifolds. The two radiators are not interchangeable, they have different mounting points, hose connections, and overall dimensions.
When ordering, specifying pushrod or Twin Cam is essential.
Radiator Cap
The radiator cap controls system pressure and must be the correct rating. Early 1500 cars (before chassis 71832, July 1959) used a 4 lb cap. From chassis 71832 onwards, which covers the vast majority of 1500 cars, all but the very earliest 1600s, and every Mk II, a 7 lb cap was fitted. Both ratings are still stocked and are suitable for the original-specification radiator.
The cap also incorporates a vacuum valve that prevents the hoses collapsing as the system cools; a stuck vacuum valve will cause bottom hose collapse and restricted flow. The Twin Cam uses a different arrangement, a non-pressurised cap sits on the remote header tank, with a 7 lb relief valve fitted to the overflow pipe (added at chassis 652 in September 1958). A pressurised cap should not be fitted to the Twin Cam header tank.
Coolant Hoses
The top hose carries hot coolant from the thermostat housing at the front of the cylinder head to the radiator header tank. The bottom hose runs from the radiator to the bottom-hose elbow; a short connecting hose then runs from the elbow to the water pump inlet. On the MGA, the bypass function is handled internally by a port in the thermostat housing, there is no separate external bypass hose between thermostat and water pump as found on some later B-series installations. When the heater is fitted, a heater hose connects the rear of the cylinder head to the heater matrix through the bulkhead, with a second return hose completing the circuit; when the heater is not fitted, the cylinder head outlet is blanked off with a plug.
An overflow hose runs from the radiator cap outlet down past the radiator. Hose profiles and lengths differ between pushrod and Twin Cam installations owing to the different radiator and engine positions. Hoses deteriorate with age regardless of whether they appear externally serviceable, and it is good practice to renew the complete hose set during any major cooling system overhaul, a burst hose at speed will empty the cooling system within minutes and can cause serious engine damage before the driver can safely stop.
Hose Clips
Hose clips are available in two styles: the original wire type, which is period-correct for concours restoration, and the modern Jubilee type, which provides more reliable sealing and easier adjustment. Different sizes are stocked for the main cooling hoses and for the smaller-diameter heater hoses.
Ordering Notes
Specify pushrod or Twin Cam when ordering any radiator, hose, or cap component. For the radiator cap on pushrod cars, confirm the chassis number to determine the correct pressure rating, 4 lb for chassis before 71832, 7 lb for all subsequent cars. For Twin Cam cars, the header tank uses a non-pressurised cap. The radiator drain tap and its sealing washer are stocked as individual service items, and the rubber packing kit that isolates the radiator from its mount is also available as a restoration consumable.
Complete hose sets are a practical alternative to individual hose purchases where a full cooling system overhaul is being undertaken.