I tried to get a mechanical (ie float switch) loss of coolant detector as recommended in the FAQ, but a very small float switch is needed to fit in a 240 shallow expansion tank. (Yes, BBoarders "Oleseahorse" and "Randy Starkie" have posted they have successfully installed a float switch in a 240 tank).

However, McMaster-Carr will not export these miniature float switches recommended in the FAQ to persons outside USA due to US Export Control Regulations - seriously - my order from Australia was rejected for this reason. Such miniature float switches are not available in Oz.

So I installed an electronic detector instead. These simply check for some conductivity (ie coolant present) between a stainless steel electrode inserted in either the top of the radiator (drill at your peril into plastic Blackstone!) or in the expansion tank (I safely drilled and tapped 1/8" NPT into the nylon tank).

For the the detectors to work maybe they require high coolant conductivity due to either (a) use tap water instead of demineralized water in radiator or (b) use antifreeze/anticorrosion with ionic (ie borate, silicate, etc) additives. But now long life antifreeze/anticorrosion uses non-ionic (ie organic) additives (also for environmental reasons) & Volvo mandates demineralized water.

(With demin water + long-life organic antifreeze/anticorrosion there is a very high resistance between a probe in my expansion tank and the engine block of 4 megohm, so if the detector puts 4 volts on the probe, it must sense the presence or absence of a microscopic 1 microamp current!!??)

These types of aftermarket loss of coolant detectors must be common worldwide so has anybody had this problem?

(detectors are at Oz made at www.redarc.com.au (model LCA1224) & www.enginesaver.com.au - they have no comment on coolant composition!). (I'm not going to put tap water, or inferior coolant, or a teaspoon of salt!! into my cooling system to get conductivity for this detector. Maybe this is why new Volvo, BMW, Ford, etc use float switches (in deep tanks!) to detect loss of coolant!)

sutherml @ Adelaide, Australia
1979 244GL @ 500,000 km