By Andrew Turvey of CMC

It’s the time of year when the cooling system on your E-type is working at full stretch. Often those of you who are running strictly original examples are driving with one eye on the temperature gauge and the other on the road. However, some of you have fitted an extra electric fan and drive with a watchful eye on the ammeter instead. With this article I do not wish to contradict anyone’s personal experience, I will merely add my own ingredients to the cooking pot!

Unless you are blessed with infra-red sensitive vision, you will be relying on the dash-board temperature gauge to tell you that all is well under the bonnet or, as our American friends say, hood. The first thing to note is that the ‘Temperature’ Gauge is not always strictly accurate. We are, in the main, talking about electric units. It is often the case that a gauge will read +/- 10 degrees C, and 10 degrees is a critical amount.

The only way to check it is to put a digital probe on the radiator or thermostat. ‘Knowing’ the gauge is reading high or low by X degrees is a huge step forward. It may even be correct! Generally speaking, the earlier the E-type, the higher is the likelihood of an inaccurate reading.

This is often due to a variety of causes. It can be the result of an alternative temperature sender being fitted to the engine at some stage, faulty or incorrect gauge calibration or a faulty instrument voltage stabilizer.

Having a slightly inaccurate gauge can be a problem if you are unaware of it. But if it is consistent, and you can mentally compensate X degrees, then you could stick with it.

Temperature sensors are colour coded to get you into the right ball park. But individual sensors do vary when it comes to the gauge reading. Buying a replacement gauge and sender as a pair is one option, or, better still, replacing your electrical gauge with a non-standard capillary temperature gauge.

On the road

Once we have a tangible reading from the

Engine temperature readings can be split into two categories: on the move at 35mph plus and idling-stationary but not parked against the garage door.

Whilst the car is doing 35mph, the wind speed through the radiator should be more than enough to keep the engine at a stable 70 degrees (the electric cooling fan should not be running). If not, your radiator/cooling system is not behaving efficiently enough. This may be due to a lack of water circulation through the radiator and block. Air not flowing through the radiator correctly is another possibility. Other contributory factors are: retarded ignition timing, weak mixture and even sticking brakes. Modified engines are also big heat producers.

Like most designs of purpose the E-type was not intended to stand still! It was so conceived to shed its heat with forward movement. All versions have air outlets in the top of the bonnet which allow a lot of the heat radiated from the block and exhausts to escape, along with hot air from the radiator.

Whilst idling in traffic we need to push as much air up through the bonnet vents as possible. So an electric fan has two jobs: pushing air through the radiator and blowing air around the engine and out again. Later E-types, such as V12 or S11, are ahead in the electric fan department. They have two good fans that are capable of moving plenty of air.

Switching from Otter

Their only shortcoming is the unreliable Otter switch that controls the fan. In the V12 it is located in the bottom radiator hose. These switches are often replaced by a more reliable alternative from Renault or Kenlowe. Also, during the summer these fans can be wired to run constantly with the ignition on or through a redundant dashboard rocker switch. This keeps the under-bonnet temperature down very effectively. On V12s do not neglect to keep the rubber flaps on the radiator cowl in good order. They act as a one-way valve to stop air being drawn backwards into the cowl when the car is stationary.

The 16in Kenlowe (puller) fan fitted on the inside of the radiator is a solution for S1 cooling problems. Fitted in place of the standard electric fan, and coupled with a 55 amp alternator conversion, this will indefinitely draw considerable quantities of cooling air into the engine compartment. The standard radiator cowl should also be removed at the same time; this allows greater air flow on the move.

The Kenlowe thermostatic switch also proves to be very reliable if fitted correctly. Remember to get your big electric fan wired through a relay. Some of these fans have a 50 amp start-up current. This is where the ‘competent auto electrician’ comes into his own.

Setting the electric fan cut-in temperature

Set your electric fan to come on as early as possible, that is to say 75 to 80 degrees centigrade. Once the engine pushes over 85 degrees C, it becomes increasingly more difficult for the fan to bring the temperature back down. 85 degrees is only fractionally past the normal 70 reading on a standard gauge. Also very important! Check that the fan is blowing towards the engine.

I often see small electric fans fastened to the stone guard in front of the radiator which can present two problems. Firstly, the fan blocks air flow to the radiator on the move. Secondly, the stone guard is one inch away from the radiator, a gap which allows the air to disperse in front of the unit. Only a small amount of air passes through. What we want is positive air displacement through the radiator and also to push all the hot air out of those bonnet vents.

The right radiator?

As for the radiator itself, the existing core can be replaced with a ‘tropical core’ which retains a standard appearance and improves cooling.

Another popular solution is the aluminium radiator. So E- type radiators have come full circle. They are costly though, ranging from £350 upwards, but do give very reliable results, are stronger and more thermodynamically efficient than the originals. Running temperatures often fall by as much as 10 degrees centigrade, when compared with a copper radiator.

But heed a word of warning when buying an aluminium replacement radiator. Make sure you check the dimensions and bolt holes carefully. The people who make the radiator have no idea how tight a fit it is! If you are having one made, ensure that the dimensions you supply are five mm smaller throughout. You can be sure it will fit and the cooling will still be fine.

Before you fit your new radiator take the time to flush the rest of the cooling system out with a hose pipe. Ideally you should remove the core plugs prior to cleaning sludge from a six cylinder block. But that’s a job for an expert.

Capping it

Then there’s the radiator cap. The E-type one should generally have a 7lb yield pressure for a S1 and 11lb for a V12. I often see caps set to 15lb fitted but this is demanding on older water hoses

A higher pressure cap will allow the engine to run hotter without boiling over, but be vigilant. I would also recommend carrying a can of Bars Leaks in the spares box; this will seal many Jaguar engine weeps and not block the radiator.

Above all, keep your eyes on those gauges!

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