Bmc Captain

[Mark Walton]

My 1.5 bmc s are prone to running hot.

Changed usual stuff and port has a new heat exchanger.

Any tips oh and how full should the heat exchanger be when cold?

[Linda Nixon]

The heat exchanger should be full. Have you replaced the pressure caps on the heat exchanger? Have you checked/replaced impellers? Are the inlet filters all clean? Is all clear where the water is injected into the exhaust pipes? Is there plenty of water coming out of the exhausts? Have you checked the thermostats in the engines?

If all this is okay and water is coming through nicely, it could be leaking cylinder head gaskets or as the engines are 40 years oldish, the engines could just be clogged up or simply worn out.

Chris – Technical Officer

[Bob & Freddy Tuffnell]

It could be corrosion on the impeller on the primary water pump (the one on the engine block, which is driven by the same belt as the alternator).  I assume that basic ideas like thermostat operation and specifications have already been checked? Otherwise you could suspect scaling up of the water galleries, especially if repeated overheating has encouraged topping up with tap water instead of antifreeze solution.
On my BMC1.5, I have fitted a pressurised overflow tank, so the heat exchanger stays 100% full at all times. The spring loaded pressure limiting cap is on the remote tank. I found one that was originally made for a Rover 2600, but the same thing was installed on many other cars.

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[Mark Walton]

Very good info thanks everyone. I like the expansion tank idea makes a lot of sense.  My M27 has one on the lister LWPS2! What pressure on your caps please?

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