Vertical-flow to Crossflow Radiator Conversion
Austin-Healey Sprite and MG Midget, 948cc-early 1275cc
Cooling problems have long been a part of the lore of British cars, and anything that can be done to relieve the situation is a welcome thing. The conversion discussed here can be accomplished in an afternoon, requires no special tools and no new holes need to be drilled! As with any successful repair or modification, care and attention to detail will yield a satisfactory result. Read these instructions thoroughly BEFORE proceeding!!
For purposes of this conversion, "late" means 1275 from AH(c)72034 and MG(c)60441. Cars with numbers earlier than this have non-crossflow shrouds.
You will need the following parts:
Part No Description Quan
AHA8732 Radiator shroud, Crossflow (LATE 1275) 1
AHA8731 Cross-over Tube 1
ARA1618 Cross-over tube Drain Plug 1
ARA2404 Radiator Filler Plug (should come with radiator) 1
TRS1418 Filler Plug Seal Washer 1
ARH250 Expansion Tank 1
GRC110 Radiator Cap 1
AHA8739 Expansion Tank Mount 1
GRH1002M Overflow Hose 1
ARA318 Radiator 1
RH1130 Top Hose 1
RH1131 Lower Hose 1
RH1512 Bottom Elbow 1
12G1902 Thermostat Housing (1275 Only) 1
12G1597 6-bladed Fan (not required but recommended) 1
Most of these parts are available either used or new, with the only problematic one being the radiator shroud. Be careful at the used parts dealer! The earlier 1275 (and the 1500, for that matter) shroud is similar but will not fit the cross flow radiator!
1) Remove the old radiator and hose. NOTE: Now is the time to look for the British car disease (rust) and clean up any corrosion you might find with a wire brush and emery cloth. Be sure to repaint to inhibit further corrosion. This is also the ideal opportunity to change your water pump. At the very least, check the old one for play in the shaft and for any sign of leaks. Also consider changing the bypass hose between head and pump.
Environmental note: Ethylene glycol (antifreeze coolant) is sweet-tasting to animals, who will often readily drink it. It is a deadly systemic poison for them, so please be careful about leaving it on the ground or in a pan where Fido or Tabby can get near it.
2) Mount the crossover tube on the steering rack mount bolts, making sure the ends of the tube are facing forward.
3) Install the lower radiator hose between the crossover tube and the engine.
4) Install the 6-bladed plastic fan.
5) Install the radiator in the shroud (all nicely cleaned and repainted, of course, if a used one). CAUTION! use only the short bolts supplied or test fit what you have to be sure the ones you use don’t bottom out and destroy the radiator!!!
6) Install the radiator and shroud, making sure to mount the new shroud as low as the mounts will allow.
7) Install the lower elbow hose between the radiator and the crossover tube.
8) Install the upper radiator hose. You will have to change to the 12G1902 thermostat housing from the late 1275, as the existing one will not “clock” correctly to line up with the hose. Be sure to use a new gasket and a good sealant (Gaskecinch is recommended).
9) Install the overflow tank assembly. Use the stock 1275 crossflow-type tank and mounting strap. Mount this as high in the engine compartment as you can, as the cap must be mounted above the highest point of the system do you will trap air when the system is filled. The best location, depending on the size of the tank, is on the inner fender above the left-hand shock absorber. In a pinch, it may be possible to use an aftermarket "generic" tank assembly available in a parts house, but be careful to get the "pressurized" type and get the smallest you can.
10) Refill the system. A water pump lubricant is recommended (if not using coolant) to lube the pump and inhibit corrosion.