Cooling System

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3000M/3000S

The cooling system has always been a 'hot topic' for these cars, as the system was designed to fit under a much lower bonnet space than its Ford donors, with a smaller grille and in most cases a spare wheel to make things even less than perfect. However, despite a lot of problems, I've found that it copes without issue even in standard form with the spare wheel in place. I think the trick is to make sure the radiator has a decent pair of small cooling fans, in addition to the engine driven fan. Many owners remove the engine fan, but it can only help to increase airflow over the engine in traffic so I prefer to leave it in place, at least until the time I decide on a suitable replacement. Below is a list of the main components, each with some useful notes.

Radiator
The extra deep radiator was a TVR designed unit. Due to the lack of space, and directed airflow through the low shallow grille, they decided to increase the number of cores to increase the surface area of the heat exchange. The later M series cars had a higher "square" type radiator. More info on this soon.

Thermostat
The thermostat is found under the Alloy housing, on the front Left Hand of the inlet manifold. This joins the engine to the Header Tank (see below). The thermostat can be changed to various opening temperatures depending on climate/season, and they range from approx. 72ºC to 90ºC. The thermostat plays a part in coolant circulation, so removing it altogether isn't really a good idea. Instead, you could remove the centre section, but only if the thermostat is stuck shut & you have no other choice. A thermostat ring is available to replace the original - I've not used on but know they are used for the original Mini when a thermostat isn't used.

Water Pump
There are a couple of type of water pump for the Essex, one of them has an extra coolant take-off which needs to be blanked, the other type is already blanked off. If trying to plumb in the extra hose, you will come across odd overheating issues and even find the head can overheat. I use a MG Metro blanking plug if you can find one for this - here is a link to minispares

Heater Matrix
A small radiator fitted in the passenger footwell, high up behind the dashboard. Any leaks will be apparent by windows that constantly steam up, and a smell of coolant. Leaks when hot could scald a passenger's legs. The airflow is controlled via a heater fan mounted under the matrix, inside the footwell. Airflow was originally ducted via a wide bore air hose that was routed from the front grille area all the way to the matrix, providing airflow at any moving speed. 

Carburettor Auto Choke (DGAS Carbs)
The Weber 38 DGAS has an automatic choke, operated by a bi-metallic spring in a housing heated up by engine coolant. As the spring heats up, it changes shape & opens the choke flaps on the carb. The choke spring is also linked to a fast idle lever which gives the engine a higher idle while the choke is in operation.

Expansion Tank
Strapped to the Right Hand wheel arch, this is an essential storage tank for the main cooling system. The pressurised cap is fitted to this tank rather than the header tank (which should be a blank non pressure release cap). As the coolant heats up & the system expands, the Expansion Tank receives coolant, and allows it to flow back as the temperature cools. In this way the header tank should remained totally full and prevent any air lock in the cylinder heads/inlet manifold.

Header Tank
The TVR designed cylindrical tank, that provides a head of water (highest point) to ensure no airlocks are left in the cylinder head/inlet manifold. The top entry feeds the thermostat housing, the bottom runs from the left hand top radiator outlet. The only issue with this tank is that it's made of steel, and so corrosion is common. The tank cap should be a blank (unpressurised) type, and this cap is used for initial filling of the system.

Electric Fans & Otter Switch
The original low radiator had a single electric cooling fan (as far as I can make out), and was controlled by an early version of a radiator fan control switch known as an Otter Switch. The Otter Switch was a heat sensitive switch which was a press fit into the coolant, sealed with a special grommet. The switch is very reliable in itself, but beware any overheating eposide can result in the otter switch being ejected under pressure. This is to date the only scald injury I've ever suffered on a car, but I'll never forget it, despite wearing 2 layers of gloves at the time. If at all possible it would be wise to blank off the otter switch orifice completely and use a thermocouple type radiator fan/relay kit such as this Fan Controller Kit.

System Filling/Bleeding
The cooling system should be filled cold, using a mix of antifreeze & de-ionised water depending on your climate. 50%/50% mix is a common one here in the UK. In summer you could choose to use a coolant additive called Water Wetter (or similar), which when used with de-ionised water alone does reduce engine temps well - especially good for hot weather use. The only downside is the need to drain & fill with antifreeze mix once autumn arrives.

  

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2500M

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1600M

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