Tech Tips: Letters

From Moss Motoring 1985


Pg4-1Just a couple of things I figured out the hard way. First of all, on overheating. If the heater is on when the engine is running hot, and the condition of the heater valve is at all questionable, it is not advisable to turn off the valve. As long as the heater core is included in the coolant’s flow, the car will run cooler, but if there is hot coolant in the heater core, and the valve is shut off, the coolant in the heater core will contract, while the coolant in the radiator expands. This can cause the heater valve to leak onto the distributor, shutting down the engine. The solution is to replace the valve, or install a distributor waterproofing kit (#282-665), both of which are preferable to being towed home on the nicest day of the summer.

Steve Close San Francisco


A blocked heater core is often responsible for poor coolant circulation. It is easy to flush the heater core without removing it from the car. This is most easily done in conjunction with an engine compartment wash or a cooling system overhaul, as everything gets pretty wet.

Disconnect the hoses to the heater and back flush the core with a garden hose. On cars that have the nipples in tight places, leave the hoses on the core and flush through the hoses. Flush in both directions until the water runs clean. Stand back, the water will really shoot out of the core carrying with it an amazing amount of rust and scale.

Carefully inspect the hoses and clamps. Any questionable parts should be replaced at this time while it is easily done with parts at hand.

In the good old days the dealer would supply you with a touring kit that included, among other spares, a set of hoses. This is still a good idea especially if your trip will take you through areas of the country where the corner parts store is not likely to stock parts for your car.


Many MGA owners seem to be experiencing problems with the brakes ‘binding’, especially right after a brake system rebuild. The common complaint is that the brakes begin to drag as the car is driven, which creates tremendous heat and eventually stops the car possibly damaging your new linings, pads, disc, etc.

The Factory Workshop Manual (Moss part #210-410) gives explicit instructions on setting the master cylinder pushrod which sometimes cures the problem. However, even with the proper free play in the pedal, the brakes can still bind up. The problem is that the master cylinder piston is not coming far enough forward to uncover the bleeder orifice that allows the expanded fluid to bleed into the reservoir.

Solution: Add a shim between the master cylinder block and the cover plate. This shim allows the piston to come a little further forward thus uncovering the bleeder orifice.

I cut my shim from .020″ brass shim stock, using the gasket ( Moss part *180-020) as a template but allowing a 1.00″ diameter clearance hole for the brake piston. I used two 180-020 gaskets, modifying one to include the 1.00″ diameter hole, but leaving the other one standard.

S. Mark Palmer Lansdale, Pa

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