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Dec 12, 2010 12:24 pm
Dec 12, 2010 12:24 pm
Subject: Re: 2 litre Thermostat
Hi Folks
Here’s my contribution to the debate on thermostats for Two Litres. The same comments also apply to Three Litres with separate radiators, but not to very late Two Litres, 16/80 and Three Litres with the ZMBS chassis which all have thermostatic slats.
First let’s consider the radiator. It’s actually in two parts, soldered together. The core is connected to the header and footer tanks. The by-pass is made up of the sides of the shell separated internally from the core by blanking plates. This provides a short circuit path for the coolant so that when mixed with water passing through the core, it will warmer than if it all passed through the core. Very useful when the car is cold!
The header tank has a separate area connected to the by-pass, also separated by a blanking plate. When the engine is warm, because the core is a high resistance path, the by-pass needs to be blocked off, so the thermostat acts as a changeover switch to divert water to the by-pass when cold and to the core when hot. An internal spigot on the thermostat housing passes through the blanking plate and you can see the little holes in it which allow the water through the by-pass. These are blanked off by the thermostat when the engine is warm, so that if a car is running without a thermostat, on a hot day in traffic it will overheat!
The Two Litre cooling system is very efficient and I suspect anyone who has fitted an electric fan either does not have a working thermostat or the core is very badly blocked up and needs de-scaling.
For early high chassis cars such as mine, I found a generic unit with bellows linked to a rotating vane which would act as a changeover. I made up a capsule out of thin brass sheet which slid into the early housing and works well. Ideally you should avoid the ‘plug’ type thermostat as used on a Mini. It will not block off the by-pass when hot.
Around 1930, Lagondas were fitted with a new kind of thermostat which has a vane and a spiral bimetallic spring. The vane spindle passes through the top to a little dial. This allows the user to vary the spring tension to set the temperature the engine runs at. This is an excellent arrangement but you might find that the spring has rusted through or the whole assembly has been removed. Thermostat units containing this vane can still be found at autojumbles, I paid £20 for one at Beaulieu this year.
I hope these notes have been useful.
Colin M34
Hi Folks
Here’s my contribution to the debate on thermostats for Two Litres. The same comments also apply to Three Litres with separate radiators, but not to very late Two Litres, 16/80 and Three Litres with the ZMBS chassis which all have thermostatic slats.
First let’s consider the radiator. It’s actually in two parts, soldered together. The core is connected to the header and footer tanks. The by-pass is made up of the sides of the shell separated internally from the core by blanking plates. This provides a short circuit path for the coolant so that when mixed with water passing through the core, it will warmer than if it all passed through the core. Very useful when the car is cold!
The header tank has a separate area connected to the by-pass, also separated by a blanking plate. When the engine is warm, because the core is a high resistance path, the by-pass needs to be blocked off, so the thermostat acts as a changeover switch to divert water to the by-pass when cold and to the core when hot. An internal spigot on the thermostat housing passes through the blanking plate and you can see the little holes in it which allow the water through the by-pass. These are blanked off by the thermostat when the engine is warm, so that if a car is running without a thermostat, on a hot day in traffic it will overheat!
The Two Litre cooling system is very efficient and I suspect anyone who has fitted an electric fan either does not have a working thermostat or the core is very badly blocked up and needs de-scaling.
For early high chassis cars such as mine, I found a generic unit with bellows linked to a rotating vane which would act as a changeover. I made up a capsule out of thin brass sheet which slid into the early housing and works well. Ideally you should avoid the ‘plug’ type thermostat as used on a Mini. It will not block off the by-pass when hot.
Around 1930, Lagondas were fitted with a new kind of thermostat which has a vane and a spiral bimetallic spring. The vane spindle passes through the top to a little dial. This allows the user to vary the spring tension to set the temperature the engine runs at. This is an excellent arrangement but you might find that the spring has rusted through or the whole assembly has been removed. Thermostat units containing this vane can still be found at autojumbles, I paid £20 for one at Beaulieu this year.
I hope these notes have been useful.
Colin M34