The cooling system is one of the most clearly differentiated areas between the TD and TF. Both use the same fundamental layout, front-mounted radiator, belt-driven fan, engine-driven water pump, but the TD is non-pressurised and the TF pressurised at 4 lb. This single distinction affects the radiator, cap, hoses, and thermostat arrangement.
The TD Cooling System
The TD's cooling system followed the unpressurised pattern of the earlier TC. The filler cap on the header tank served only as a seal with no pressure valve. The radiator and header tank were painted black, with the chrome shell forming the visible front of the car. A temperature gauge adaptor boss on the header tank provided the connection for the water temperature sender, early TDs had a separate oil pressure gauge, but from chassis TD/13914 in February 1952 a combined oil pressure and water temperature gauge was fitted as standard.
The adaptor accepts either a temperature gauge pipe adaptor or a blanking plug depending on the instrument specification. The TD radiator is reconditioned on the customer's own unit basis and is not interchangeable with the TF. Mounting uses a lower bracket, chassis crossmember, and eight-bush mounting kit. On the TD the headlamp mounting brackets tie into the radiator mounting, this interconnection is unique to the TD's free-standing headlamp design and does not apply to the TF's faired arrangement.
The TF Pressurised Cooling System
The TF's pressurised system was a significant improvement over the TD arrangement. Operating at 4 lb through a pressure-rated cap, it raised the effective boiling point of the coolant, reducing localised boiling and coolant loss under hard driving. The TF radiator is a different design from the TD unit, necessitated by the lower bonnet line, the core is lower in height but thicker in depth to maintain cooling capacity. The filler cap is accessed under the bonnet; the external cap visible on the raked grille is a dummy decorative item.
The TF radiator is also reconditioned on the customer's own unit basis and is not interchangeable with the TD, owing to different core dimensions and the pressurised cap arrangement. The chassis crossmember and eight-bush mounting kit are shared between both models.
Water Pump and Thermostat
The water pump is shared between later TDs and all TFs from engine XPAG/TD/6483 onwards, when the integral-seal specification was introduced. The thermostat arrangement differs significantly: the TD uses an integrated thermostat-and-housing unit; the TF uses a separate Waxstat-type thermostat in a revised water outlet with a sealing plug. TF thermostats are available in three ratings, 74°C, 82°C standard, and 88°C. Full detail is covered under Water Pump, Thermostat & Fan within the Engine category.
Coolant Hoses
The top hose and water branch pipe are model-specific between the TD and TF, different lengths to suit the different radiator positions and outlet arrangements. The bottom hose set, comprising three hoses, is common to both models. Hose clips are available in period-correct Supergrip or modern Jubilee-type specifications.
Cooling Fan
The cooling fan is a four-blade assembly formed from two pressed-steel stampings, a front pair and a rear pair, bolted together through the water pump pulley with a fan spacer. The TD fan was painted black; the TF fan was painted red. Both share the same basic assembly and mounting.
Radiator Maintenance
The radiator is the single most critical component in the cooling system. Internal corrosion, blocked waterways, and deteriorated soldered joints progressively reduce cooling capacity, often without external signs. Reconditioning involves stripping the core, rodding or replacing tubes, re-soldering, and pressure testing. The drain tap should be operated periodically to prevent it seizing.
Radiator Slats and Finishing
On the TD, the chrome radiator shell carried painted slats matching the interior upholstery colour, a distinctive period detail. Late Mark II cars from chassis TD/C/22613 in December 1952 received chrome-plated slats as part of a special trim package, and all TFs had chrome slats as standard.
Ordering Considerations
The cooling system is a clear TD-or-TF split on most items. Radiator, filler cap, top hose, and water branch pipe are model-specific, as is the thermostat arrangement (TD integrated, TF Waxstat). The bottom hose set, crossmember, eight-bush mounting kit, and drain tap are common. The water pump and fan belt are shared from engine 6483 onwards.
Always specify TD or TF when ordering, the most common error is fitting a TD filler cap to a TF, or vice versa.