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John O's Scorp Insanity

Coolant Overflow Bottle

Water Pump Showdown
Overflow Bottle
Stainless Expansion Tank
Hood Release Cables
Tractor Seat Mod
Hardtop for Big
History of 1194
Original Condition Reports
Contact, Links, and Boilerplate

Good enough for a Spitfire...


The Problem

Scorps and Montes aren’t supplied from the factory with a cooling system overflow catch tank like most cars have.  When the cooling system is in tip-top shape, this really shouldn’t be a problem. The radiator cap acts like any two way pressure cap, expelling excess coolant volume and sucking in air (rather than coolant from a catch tank) until a good working coolant level is settled in.  However, when the cooling system is running hot or having a pressure problem, you might not know your cap has been venting coolant until the temperature gauges begins to climb and you’re in trouble.  The real problem is that, whether running right or not, coolant which is being vented ends up on the ground.  This seems pretty sloppy to me and makes it tough to diagnose what’s going on with the cooling system when there is a problem. Worse, in a cooling system like the Scorpion's (124, too!) which is highly prone to high spot air bubbles, why encourage ingestion of air at all when it can be avoided?

A British Solution
Since I’d figured out early on that the Scorpion’s cooling system was essentially that of the Fiat 124 just extended a bit (same rad cap, too), with an X1-9 radiator, I knew that adding an overflow reservoir would make the Scorp’s system (in theory) behave like the 124’s …or any cooling system with an overflow reservoir.  I needed to source an inexpensive overflow catcher to test it out.


While visiting a local British car show held every year near Mt.Vernon, Brits On The Green, a ready answer was on display.  While walking around the Triumph Spitfires and GT6s, I noticed their radiators were all equipped with a little plastic overflow cans.  In the British style of automotive engineering, the cans looked a bit cobbled on, like one step above a plastic mayonnaise jar with a hole drilled in the top, a hose stuck in it, duck taped and tie-wrapped to the frame.  I took pictures to remind myself of what I’d seen, and when I returned home, I hit the Moss Motors site and ordered up all the pieces I'd need for my new Scorpion coolant overflow bottleInteresting to me, it turns out the Spitfire and GT6 guys had the same idea I had because the bottle I saw in the cars on the show field is only native to the Triumph TR250.


With a little cobbling of my own, I easily mounted the bottle bracket to the back side of the right rear tail light tub.  I added a little hardware and some reinforced tubing for a better fit and appearance


Just as I’d suspected, the Scorp’s cooling system, at least at the pressure cap end of the deal, now behaves more like that of the Fiat 124.  When hot, the system pressure expels excess coolant into the overflow can, and when cool, it sucks only coolant back, nearly removing any possibility of air entering through the rad cap and contributing to air bubbles forming at the high spots in the system. Not only is this "proof of concept", but this works as-is without further modification needed!

John O.

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Created 17 Oct 2009