Lotus Elan

Accidentally overheated my engine!

PostPost by: 69S4 » Tue Jun 11, 2019 6:27 pm

I’ve always had a manual override switch for the fan as I prefer to keep on top of the cooling. Leaving it to the ( adjustable) automatic system means either waiting until the temperature is higher than I prefer before it kicks in or having it come on at a lower temperature and run endlessly. The switch enables me to decide when it should be on with the auto system there as a backup if I forget/ get distracted. The switch itself is a simple latching push switch with an internal light so I can tell at a glance whether the fan is on or off.
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PostPost by: disquek » Tue Jun 11, 2019 8:35 pm

Honestly, automatic cooling fan switches have been around for 50+ years now. What's the issue? If you dont like the on/off point, pick a different switch. They come a variety of points.

I installed redundant fans and switches/controllers to be safe. But I would never rely on my remembering to switch on a fan manually.

-Kyle
'70 S4 Elan - Cosworth BDP & Spyder Chassis
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PostPost by: prezoom » Wed Jun 12, 2019 2:25 am

The original Otter switch on my Sabra gave up the ghost many years ago, and there is no longer an original replacement. A manual switch was installed, and I have no trouble thinking about switching it on when needed. The only problem is, the old Ford Consul 204E engine does not make enough horsepower for the engine to overheat even without the electric fan on summer days here in SoCal.
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PostPost by: Andy8421 » Wed Jun 12, 2019 4:39 am

As pointed out above, if the coolant remained in circulation and didn't boil dry, you haven't 'overheated' your engine in the sense of having done any damage.

When the car is moving at a reasonable speed, a fan is redundant - the amount of air blowing through the rad because of the forward motion of the car will exceed the air from a fan. The fan is only necessary when the car is stationary or moving slowly. When racing MGs in the 90s, a common trick was to remove the mechanical fan blade to save a few HP. Conversely, my old Landy Defender has a fan the size of a windfarm turbine - I guess the expectation is that it will be plugging through mud in low range with little forward speed and has to rely on the fan for all its cooling airflow.

If you don't want to rely on a thermostat, there is nothing wrong with running an electric fan 100% of the time, although it will sap a little performance from the engine via the alternator, shorten the life of the fan, effect warm up time - and depending on the fan can be noisy.

One final comment not mentioned above, under bonnet temperature on an Elan are high, and the exhaust manifold is damn close to a flammable passenger footwell wall. Irrespective of the benefits of the fan keeping the coolant cold, I like the idea of it blowing a bit of air around the engine bay when stationary.
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PostPost by: monkeyodeath » Thu Jun 13, 2019 11:20 pm

The radiator fitted to my Elan doesn't appear to have any type of temperature switch, nor can I see a sign of one anywhere else in the tubing.

For now, I think I'll just default to driving the car with the fan always on, but I would eventually like to add some kind of thermal switch. No sense running the fan when it's not needed, especially since it seems like the cooling setup (at least with whatever upgraded radiator is on my car) is adequate to keep things cool.

I like the idea of the in-line temp switch spliced into the hose at the bottom of the radiator.

I also like Andy's point about getting a little airflow in the engine bay. I wonder if I could add a second switch that activates when the ambient air temps in the engine bay exceed a certain level. I know that in many cars I've worked on, the fan clutch simply goes off air temperature.

I'd rather just have something that works automatically. Driving this car is so fun and involving that I'd rather not have to think about engine cooling while I'm having fun!
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