Guide to the Se6a Cooling System

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Roger Pennington
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Guide to the Se6a Cooling System

Post by Roger Pennington » Fri Oct 05, 2012 1:32 am

This seemed to have disappeared into the archives, and I think it really belongs in here, so I've moved it to a new topic. It's the guide to maintaining the standard Se6a cooling system, which I wrote a while ago to ensure that the knowledge was not lost.

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MAINTAINING THE Se6a COOLING SYSTEM
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Here is my guide to maintaining the cooling system on an Se6/6a in good working order.
I have followed this method for nearly 30 years (since early 1983) with no problems. I can't claim total
authorship of it as the bones of the method were set out in the original Reliant Owner's Handbook, however
I have fleshed it out with extra tips picked up over the years. I hope you will find it useful, and that it will help to banish the myth that Se6a's inevitably overheat.


First, the upper/outer seal on the pressure cap. This needs to be in good condition. There should be a flat rubber washer under the rim of the cap - if it is missing or perished then it's worth replacing (old inner tube should do the job). Also check that the rim of the thermostat housing is not corroded - if necessary true it up lightly with a file. Check there are no holes or splits in the overflow pipe (especially at the end where it's clipped onto the thermostat housing).
Next, Fill the system up right to the brim of the thermostat housing (ie. so that it is up to the overflow pipe). Make sure any air is dispelled by manipulating the hoses to force it out. Then replace the cap and run the engine until it is thoroughly hot (the cooling fan should be cycling on and off). Water will have expanded into the overflow bottle. Top up the bottle until it is full to the brim. (you don't need any more expansion space, as the engine is currently fully hot).
Now leave it to cool until stone cold. Water will be drawn back into the engine as it cools. When cold you should find that the overflow bottle is about 1/3rd full - mark the level on the side of the bottle. This gives you your "cold level". (if the water isn’t drawn back, check if the pipe from the expansion bottle to the thermostat housing has perished where it joins the housing).

It is now easy to monitor the level, as you have a "Hot Level" (overflow bottle brim full) and a "Cold Level" (the mark you have just made). If the water level should fall slightly, due to slight weeps from one of the many hose connections, or evaporation over time, then it's easy to top it up, hot or cold at the overflow bottle. Also, because the overflow bottle always contains water, then you are not going to get air
drawn into the system, and leading to yet more air locking problems. There is normally no need to remove the pressure cap, disturbing the seal, as you can monitor the level in the overflow bottle.

Also worth adding as a general point - use a 50/50 mix of antifreeze for good protection against both freezing and corrosion.

-----oo00oo------


....Roger

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Guide to the Se6a Cooling System

Post by upstart8s » Mon Jan 14, 2019 6:09 am

Roger,
I am just about to fit a new coolant expansion tube (recently supplied by QRG) to complete my overheating saga. When I look at the plug which fits into the expansion bottle, I notice that it is solid and a tight sliding-fit over the tube. My memory fails me regularly, but do I need to drill a small hole in this bung to allow air to escape? I seem to remember another contributor suggesting this some time ago and it seems to make sense (to me, anyway).
Stu


current...
1977 Reliant Scimitar GTE SE6a (VHI registered) 3000 automatic/pas UUV***S
1991 Mazda Eunos Roadster (import on classic insurance) 1600 automatic/pas J***XAN
2006 Vauxhall Astra Estate 1800 automatic/pas FM***TLO
previous...
1977 SE6a automatic VOH***S
1994 SS1 1600CVH manual B***RWK (#54)

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Guide to the Se6a Cooling System

Post by Roger Pennington » Tue Jan 15, 2019 12:51 am

The original bungs did have a small hole to allow air to escape as the bottle fills (and re-enter as it empties), due to the warming-up and cooling-down of the engine. The bungs were a fairly tight fit in the bottle but I guess they would pop-out if they didn't have a bleed hole, as the bottle filled and the pressure rose. If they are now being supplied without a hole, I would have thought it was a good idea to make one.

Strictly speaking, you don't actually need a bung at all for the system to work, as the bottle is unpressurised, so as long as the tube is below the surface of the water at all times it will work correctly. The major value of the bung is that it ensures that the tube *is* actually held under the surface of the water, and doesn't "escape" into engine bay! :wink:


....Roger

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"Condition can be bought at any time; Originality, once lost, is gone forever" - Doug Nye

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